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By J. M. GARZA

The production of oil in Mexico during 1945 was 43,402,852 bbl., or a daily average of 118,912 bbl. In March 1938 most of the oil properties were taken over by the Mexican Government and since then have been operated by Petroleos Mexicanos, an agency of the Government. The variations in the production during the last 8 years have been due to- fluctuations in the export market demand for Mexican oil rather than to the productive capacity of the fields. Since 1937, yearly production, to the nearest hundred thousand barrels, has been as follows :

Jan 1, 1946

By N. Parlee, V. C. Kashyap

The solubilities of nitrogen in liquid iron and liquid Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys were measured by the Sieverts method. Measurements were made at 1600° to 1800°C on binary alloys up to 20 pet Ni, 10 pet V, 10 pet Mo; and on ternary alloys containing 0 to 3 pet V with 0 to 5 pet Mo. The results on liquid iron confirm that Sieverts' law is obeyed in the range 50 to 750 mm pressure. The measured solubilities and their temperature coefficients are in general agreement with other modern authors. The logarithms of the activity coefficients of nitrogen in the binaries are approximately linear functions of the pet of alloying element. A method suggested by Wagner, Chipman, and others for predicting gas solubilities in complex alloys from solubility data on binaries was applied to the Fe-Mo-V alloys. Reasonably good agreement was obtained between calculated and experimental solubilities. NITROGEN'S solubility in liquid iron has been studied by a number of investigators. It is reasonably well established that the solubility of nitrogen follows Sieverts' law at least up to 1 atm partial pressure and that the solubility increases gradually with temperature. The solubility of nitrogen in Fe-X binary liquid systems has been investigated in only a few cases. Only the systems Fe-Cr,3-5, 7 Fe-V,3 Fe-Mn,3, 5 Fe-Ni,3, 5 Fe-Si,B, H Fe-C, L, H and Fe-P4 appear to have received any study. The only work on liquid Fe-V was done by Brick and Creevy.3 This was limited to 13.5 pet and 26.5 pet V, but no exact temperatures were recorded. No work whatsoever appears to have been done on liquid Fe-Mo alloys and even work on Fe-Ni alloys is rather scant. The work on liquid ternary systems is still more limited, and the only publication available appears to be that of Wentrup and Reif,7 who studied the Fe-Cr-Mn and Fe-Cr-Ni alloys. Rassbach, Saunders, and Harbrecht17 have reported work on the solubility of nitrogen in stainless steel but this was not a systematic study of any particular system. Commercial alloys usually contain several alloying elements. Thus, it often becomes important to be able to predict the nitrogen solubility in systems containing two or more added elements without the necessity of making measurements. Wagner,14 Chipman," Darken and Gurry," and Morris and Buehl 14 have suggested means by which this may be accomplished, and Langenberg14 has recently applied one of these methods to nitrogen solubility in complex liquid alloys. This paper reports the results of nitrogen solubility determinations on Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys and compares calculated and experimental solubilities in the ternary alloy. Attempted measurements on Fe-Cr alloys were not successful by the experimental method employed. Experimental Method The general method of solubility measurement was that of Sieverts.' The apparatus and procedure were essentially the same as used by Liang, Bever, and Floe."' The equipment consisted of a small vacuum furnace heated by a 6 kw induction unit, gas measuring apparatus, and a gas purification train. The crucibles used were Norton Alundum with alumina sand around them for insulation. The crucibles were charged with 100 to 200 g of material, about 180 g or nearly filling the crucible being found most satisfactory. Hot volumes were determined with argon and ranged from 95 to 130 cu cm (stp). Temperature measurements were made with a Leeds and Northrup optical pyrometer which was calibrated periodically against the melting point of iron in the same apparatus."-'* Good quality nitrogen, hydrogen, and argon gases were further purified and dried in standard purification trains. The sources of the high purity iron and other alloying elements used were as follows:

Jan 1, 1959

By H. E. Hostetter

Grossmann'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 hardenadility 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 DI of the steel. The validity of Grossmann'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, 1947

By H. E. Hostetter

Grossmann'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 hardenadility 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 DI of the steel. The validity of Grossmann'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, 1947

Silver ore was first discovered in 1866 at Manhattan, and a few ore shipments were treated in a mill at nearby Belmont. The district was abandoned from 1869 to April 1, 1905, when rich gold float was discovered on what was to be called the April Fool claim. By early 1906, 4, 000 people lived in Manhattan. The San Francisco earthquake, in April of 1906, caused the withdrawal of capital from Manhattan and most of the mines were shut down. Later that year and in 1907, however, more strikes were made. The camp prospered until the mid-1920s, but a steady production of several hundred thousand dollars per year was sustained even during the great depression. Then, in 1939, Nevada's first bucket-line dredge was installed below the town and operated until 1947, producing $4.6 million in gold. The Houston International Minerals operation at Manhattan was started in July of 1980 at a throughput of about 545 mt per day (600 st per day). In contrast to the early day underground operations, Houston's mine is open-pit and processes low-grade disseminated ores. The ore is a metamorphic schist containing 2. 7 g Au and 1. 03 g Ag per mt (0. 08 oz Au and 0. 03 oz Ag per st). Some coarse gold, up to 1 mm in size, is present. Mining and haulage is done by a contractor. Stockpiled mine-run ore is crushed in three stages comprising a jaw crusher and two cone crushers, with screens ahead of the cone crushers. Crushed product, at about 19 mm (3/4 in.) size, is stored in a silo. Grinding is by single stage ball mill with the discharge passing over two hydraulic traps for coarse gold removal. These traps will be replaced in late 1980 by a two-cell Pan American jig treating the cyclone underflow. The jig hutch product, along with the hydraulic trap product that has been stored, will be treated further for gold recovery. The gravity tails will then be cycloned with the underflow being recirculated in the ball mill and the overflow being treated by flotation. A rougher concentrate is made in twelve No. 48 Galigher cells with the float tails being cycloned. Cyclone underflow is refloated in another four No. 48 cells; the overflow is treated in sluice boxes for further gold recovery before being sent by gravity to the tailings pond. Bulk flotation concentrates are cleaned three times with the final concentrate being thickened. The thickener underflow is then batch cyanided in mechanically agitated tanks and washed with barren liquor

Jan 1, 1981

By C. W. Dunham

FROM the primary gyratory crushing plant, described in MacLeod's article, ore is delivered to a large storage or surge bin from which it is carried by two transverse conveyors to the secondary crushing plant. The bin has a useful drawoff of about 13,000 tons, this being slightly over one half of the initial daily capacity of the Morenci Reduction Works. This arrangement provides sufficient storage to permit intermittent operation of the primary and secondary crushing plants without too close a coordination between the two.

Jan 1, 1942

By Fredrick C. Kruger

Anthropological diggings have revealed that the American Indians carried on intertribal trade in flint, obsidian, ochre, and other mineral commodities, indicating that mining was practiced before the arrival of the white man from Europe Carbon datings from the native copper pits on Isle Royal and Keweenaw Peninsula, Michigan, have yielded dates as early as 5555 BC for this mining. As early as Pliocene time, Eolithic-man fashioned artifacts of stones probably found on the surface, but by late Quaternary, Neolithic man was sinking shafts and mining underground for flint. Because placer gold was easily recognized and easily worked, it was used for ornamental purposes by nearly all cultures before other metals were discovered The Chaldeans hammered copper objects approximately 4500 BC and copper was used in India and China about 3000 BC. An ancient trail from the Nile to the Sinai led to the mines of copper and turquoise Paintings and bas-reliefs of Egyptian tombs dating around 3000 BC depict maps, mining, and smelting in this area. It is interesting that despite this widespread and long history of mining, Agricola records that the first mining laws were developed by the Greeks at Laurium about 700 BC. All of the base metals are known to have been produced in small quantities during the Colonial period in America, but perhaps the first commercial production was the iron ore shipped from Virginia to England in 1608, followed by lead in 1621. Among the earliest companies formed in America that still survive (according to the standard reference yearbooks), were: the Jackson Mining Co., predecessor of Cleveland-Cliffs Iron Co. on the Marquette Range, Michigan, in 1844; the Sussex Zinc and Copper Mining & Manufacturing Co., fore-runner of New Jersey Zinc Co. in 1848 (although the Franklin-Sterling body was discovered in 1640); the five companies, Pittsburg and Boston, Quincy Mining, Pewabic, Huron Mining, and Minesota all formed in the decade (1844-1855) that followed the rediscovery of Keweenaw copper, were combined into Calumet and Hecla; and Vermont Copper Mining Co. in 1853 Although southeast Wisconsin lead-zinc was discovered in 1690, Mine La Motte in southeast Missouri in 1720, placer gold in California in 1848, Comstock Lode in 1859, Leadville in 1860, Cripple Creek in 1891, no surviving companies of those early mining periods exist. The first strong producer in the Mississippi Valley was St. Joseph Lead in 1864; Homestake and Pickands-Mather, were formed in 1877, Phelps-Dodge in 1881; Pittsburgh Reduction, the predecessor of Al-

Jan 1, 1976

By NONE N

Jan 1, 1963

By J. W. Freeman, R. F. Decker

A microstructural investigation was pursued to establish the mechanism of the pronounced benefits of traces of boron and zirconium on creep properties of a 55 Ni-20 Cr-15 (20-4 MO-3 Ti-3 A1 alloy at 1600°F. The mechanism of improvement of creep properties was found to be a pronounced stabilizing effect of traces of boron and zirconium on the grain boundaries of the alloy. The alloy with low boron and zirconium was subject to rapzd agglomeration of M23 C6 and in the grain boundaries, followed by depletion of y ' and intergranular microcracking at the grain boundaries transverse to applied stress. Brittle fracture then occurred by linking of microcracks. However, additions of zirconium, boron, and boron plus zirconium decreased this tendency in that order, allowing longer creep exposure and higher creep defor.mations before fracture occurred. VERY little information has been published describing the mechanism by which trace amounts of boron or zirconium improve the creep properties of complex nickel-base heat-resistant alloys, although the effect is now well recognized.1-4 Because the phenomenon is so important to properties and the effects are so striking, a study was made of the mechanism in a 55 Ni-20 Cr-15 Co-4 Mo-3 Ti-3 A1 alloy. It was believed that such a mechanistic approach would increase knowledge in theory of alloying and give a more basic understanding of alloy design to resist creep. The basic premise of the study was that boron or zirconium would alter the microstructural characteristics controlling creep and fracture to the extent that the effects could be identified by light and electron microscopy and by electron diffraction techniques. Characteristic of the microstructure of the Ti + Al-bearing nickel-base alloys is the dispersed precipitation of the intermetallic compound Ni,(Al, Ti), the ? ' phase, which is generally con- sidered to be the major source of high creep resistance.5-7 In addition, carbide phases have been identified8-10 and these can alter creep properties markedly.11 Since both the ?' and carbide transformations have been found to control properties, careful attention was paid to the effect of boron and zirconium on these transformations.

Jan 1, 1961

By J. J. Gilman

RECENT experiments have shown that the mar-tensite reaction in a standard tool steel is influenced by the history of the reacting austenite. The martensite reaction proceeds to a given extent at a higher temperature in austenite formed from an annealed spheroidal structure than it does in austenite formed from tempered martensite: that is to say, a prequench lowers the temperature range of the martensite reaction in this steel. Furthermore, a prequench alters the appearance of the martensite as compared to martensite formed from "virgin" austenite. The steel used for this work was a manganese nondeforming tool steel of the following composition: C, 0.85 pct; Mn, 1.43; Si, 0.23; Ni, 0.12; Cr, 0.59; and W, 0.59. A piece from a rolled bar was forged to Vz in. sq and annealed to a spheroidal structure. Disks 1/8 in. thick were used in the experiments. Several sets of the specimens were prepared and austenitized in lead at 1475°F. Three sets were held at 1475°F for 15 min, quenched in water, and immediately reheated to 1475°F. After this quench the three sets were held for 5 min, 30 min, and 3 hr, respectively, at 1475°F and then the individual specimens in each set were quenched in molten baths to 325", 300°, and 275ºF, respectively, and held for 15 sec. Immediately after the quenching treatments? the specimens were tempered at 600°F for 30 sec to darken the martensite and then were quenched in water. The holding times were short enough to avoid isothermal transformation. Three other sets of specimens were given the same final quenching treatments as the first three, but they were austenitized at 1475°F for 20 min, 35 min, and 3 hr and 15 min, respectively, without an intermediate water quench. The two individual specimens from each set were quenched together in order to eliminate quenching errors. Several experiments were run in this way but only the six sets referred to are described in detail because they all yielded essentially the same results. By means of the stated heat treatments the martensite reaction was investigated for: 1—austenite formed from an annealed structure, and 2— austenite formed from tempered martensite. The martensite reactions of the two types of austenite differed significantly. This is shown by Figs. 1 and 2. Comparison of the photographs on the left in Figs. 1 and 2 with those on the right shows that less martensite was formed by a quench to a given temperature from prequenched austenite than from austenite formed from an annealed structure, that is, the prequench suppressed the martensite reaction. The effect was observed for specimens austenitized 20 min, 35 min, and 3 hr and 15 min. A comparison of Figs. 1 and 2 shows that the martensite reactions in both sets of specimens occurred at lower temperatures with increased austenitization time. This was caused by the increased dissolution of residual carbides with time at 1475°F. However, the difference in amount of martensite formed in prequenched austenite as compared to virgin austenite was approximately the same for all three austenitization times. One further observation should be noted. The needles of the martensite formed from virgin austenite are somewhat longer on the average and show less of a tendency to cluster than those of martensite formed from prequenched austenite. This causes the martensite on the right in Figs. 1 and 2 to have a more acicular appearance than the martensite on the left. Since the sets of specimens used in this work were austenitized for identical total lengths of time and the effect of a prequench on the martensite reaction existed for specimens held at the austenitizing tem-

Jan 1, 1953

PRELIMINARY REPORT PUBLISHED FOR THE PURPOSE. OF INVITING SUGGESTIONS FOR, THE BENEFIT OF THE COMMITTEE 1 As a result of invitations extended by The American Society of Mechanical Engineers, a, number of associations of national scope have appointed representatives on a Joint. Committee on Standards for Graphic Presentation:- Below are the names of the members of the committee and of the associations which have co-operated in its formation. WILLARD C. BRINTON, Chairman,. American Society of Mechanical Engineers. [7 East 42nd Street, New York City.] LEONARD P. AYRES,Secretary, American Statistical Association. [130 East 22nd Street, New York City.] N. A. CARLE, American Institute of Electrical Engineers. ROBERT E. CHADDOCK, American Association for the Advancement of Science. FREDERICK A. CLEVELAND, American Academy of Political and Social Science. H. E. CRAMPTON, American, Genetic Association. WALTER S. GIFFORD, American Economic Association. J. ARTHUR HARRIS, American Society of Naturalists. H. E. HAWKES, American Mathematical Society. JOSEPH, A. HILL, United States Census Bureau. HENRY D. HUBBARD, United States Bureau of Standards. ROBERT H: MONTGOMERY, American Association of Public Accountants. HENRY H. NORRIS, Society for the Promotion of Engineering Education. ALEXANDER. SMITH,. American Chemical Society. JUDD STEWART, American Institute of Mining Engineers. WENDALL M. STRONG, Actuarial Society of America. EDWARD L. THORNDIKE, American Psychological Association.

Jan 10, 1915

By Barry D. Lichter, Pierre Sommelet

High-temperature heat contents of InAs and GaAs were measured over the temperature range 400°K to temperatures above the melting points using a di-phenyl ether drop calorimeter. Smoothed values of the thermal properties have been derived and tabulated at even temperature interuals . The heats of fusion of InAs and GaAs were determined as, respectively, 8790 ± 200 and 12,590 ± 300 cal per g-atom at the respective melting points of 1210º ± and 1513º ± 1°K, yielding entropies of fusion of 7.26 * 0.16 and 8.32 ± 0.20 cal perºK per g-atom, respectively. A general discussion of the thermal properties of III-V com-pounds is given. THE low-temperature heat capacities of InAs and GaAs have been determined by Piesbergen.1Using a dynamic temperature modulation technique, Miller2 has determined the heat capacities of the compounds as well as GaSb and Ge between room temperature and 650°K; however, it has been observed that values determined by drop calorimetry for GaSb3 and for germanium4 are consistently about 5 pct lower than Miller's results. Cox and Pool10 report values for the heat content of InAs and GaAs and the heat of fusion of InAs. No value for the heat of fusion of GaAs appears to have been previously reported. This paper reports results of high-temperature heat content investigations of InAs and GaAs measured in the range 400" to above 1500°K employing a diphenyl ether drop calorimeter. These results, together with our previous results on III-Sb compounds3 as well as heat-content measurements5 of solid InP and Gap, are used in a general discussion of these compounds. EXPERIMENTAL PROCEDURES High-purity samples of the compounds, stoichio-metric to ±0.1 at. pct, were supplied in the form of crushed crystal fragments by Dr. Carl Thurmond of the Bell Telephone Laboratories. The sample preparation, description of the calorimeter, and details of the heat content measurement have been previously described.3 Samples were sealed in evacuated silica capsules and suspended by a Pt-Rh wire in a Pt-wound vertical tube furnace, heated to temperature

Jan 1, 1970

By R. D. Barer, M. B. Bever

Age hardening alloys are quenched from the solution treatment to room temperature in order to retain a supersaturated solid solution. Some alloys age "naturally" in this condition but in most alloys aging is induced "artificially" by heating to intermediate temperatures. Cold working of the supersaturated solid solution accelerates the aging process and quenching strains have the same effect. The investigation reported here is a study of the progress of aging in specimens quenched directly from the solution treatment to various aging temperatures. This procedure reduces the temperature interval of quenching and the resulting quenching stresses. It also eliminates any changes which would take place in the undercooled sample at room temperature prior to aging at an elevated temperature. Isothermal aging is thus approached and its kinetics may be studied. An aluminum-copper and an aluminum-silicon alloy were chosen for this investigation. The aging mechanism of aluminum-copper alloys is complex while the aging of aluminum-silicon alloys is nearly ideal. As standards of comparison for the samples directly quenched to the aging temperature, specimens were also age hardened by the usual procedure in which solution treated samples are first quenched to room temperature and then reheated to the aging temperature. Review of Previous Work The mechanism of age hardening has been the subject of a controversy which has ranged from the theory of outright precipitation of an equilibrium phase to theories based on subtle changes occurring in the matrix prior to precipitation. A detailed critical review of the literature up to 1939 is available1 and contributions to the general theory of age hardening continue to be made.2,3 Age hardening, whatever its mechanism, involves the nucleation of a second phase within a supersaturated solid solution. Theoretical considerations4,5 indicate that the rate of nucleation reaches a maximum at an intermediate temperature below the temperature at which supersaturation sets in. Studies of precipitation at various subcritical temperatures have demonstrated that the largest property changes in a given time occur at such intermediate temperatures.6,7,8 The precipitation of a phase from supersaturated solid solution is accelerated by strains which may result from quenching or cold work. Phillips and Brick9 established that quenching strains are an essential condition for the age hardening of aluminum-copper alloys at room temperature, at least for aging periods of less than 30 days. They also found that on aging at 300°C the hardness increased faster and reached a higher maximum after quenching into water than after quenching directly to the aging temperatures. Fink and Smith10 observed preferential precipitation on slip bands and grain boundaries in aluminum-

Jan 1, 1950

By AIME AIME

THE Industrial Conference appointed by President Wilson has presented the following tentative plan for preventing or retarding strikes and industrial conflicts by proposing new Federal machinery for the adjustment of differences between employers and employees. Theplan is signed by William B. Wilson, Secretary of the Department of Labor, 'as chairman of the conference; Herbert Hoover, former Federal Food Administrator, as vice-chairman; Martin H. Glynn; Thomas W. Gregory, former Attorney Gen¬eral; Richard Hooker; Stanley King; Samuel W. McCall former Governor of Massachusetts; Henry M. Robin¬son; Julius Rosenwald; Oscar S. Straus; Henry C. Stuart, former Governor of Virginia; F. W. Taussig; William O. Thompson; Henry J. Waters; George. W. Wickersham, former Attorney General; and Owen D. Young.

Jan 1, 1920

By Sherwin F. Kelly

GEOPHYSICS may be considered a vice (albeit, I submit, a comparatively harmless one) whose career is aptly described by Pope's lines: Vice is a monster of so frightful mien, As to be hated needs but to be seen; Yet too oft, familiar with her face, We first endure, then pity, then embrace. Although there may be some that have not yet succeeded in emancipating themselves from the first stage of horrified contemplation, geophysicists may be duly thankful that there are mining men and geologists that have arrived at a state of apparently irretrievable damnation.

Jan 1, 1936

By T. M. Kegley, J. H. Frye, D. L. McElroy, M. L. Picklesimer, E. E. Stansbury

Measurements of rate of growth, thermodymmic quantities, and partitioning of Mn are reported for high-purity eutectoid Fe-C and Fe-C-Mn steels for the auistenite-pearlite reaction. Evaluztion of the cotnstants of a derived-rate equation with these data indicate that Mn additions cause the decrease observed by increasivg the activation energy and apparent activation entropy or the movenment of complexes at the interface. A diffusion-controlled mechanism is not required. Appreciable partitioning of Mn to cementite occurs entirely behind the austenite-pearlite interface for more than 30°C of subcooling. ThE growth of pearlite from austenite has been extensively studied over a period of years. but the rate-controlling step in the process is not known nor is the mechanisrn of the effect of alloying elements understood. A comprehensive review of the subject has been given by Mehl and Hagel. The present study has been concerned with further considerations of the effects of alloying elements on the rate of growth of pearlite. Analytical relatioriships for the rate of growth of pearlite have been considered by Zener.2 Turnbull,3 Machlin,4 Cahn.5 Frye,6 and Frye et a1.7 The derived expressions in each case involve the free energy of the transformation. the interlamellar spacing. and some rate term of the nature of the diffusion coefficient. mobility or frequency of occurrence of some rate-determining step. The treatments. of course. differ in detail. Further consideration is given in the present paper to the equation of Frye, Stansbury. and McElroy which was derived from modified absolute rate theory without in any way specifying the mechanism of the reaction. This equation is r=c ? T ? F exp -?E*/RT [1] where r = rate of growth in mm/sec c = a constant AT = equilibrium transformation temperature minus actual transformation temperature "C ?F = free energy per mol of austenite minus that of pearlite ?E* = activation energy R= gas constant ?F in Eq. [1] is computed from the following: ?F=?H?T/To - ?T' dT' ?T' ?CdT"/T" [2] To To where AH is the enthalpy per mol of austenite minus that of pearlite at the equilibrium temperature, To, and AC is the difference in specific heat between austenite and pearlite per mol. Subsequently, Darken, Fisher, and Galligan8 have reported that a layer of ferrite separates pearlite from austenite at the growing interface (i,e., the advancing face of Fe3C is in contact with ferrite, not austenite) and the ratio of the thickness of this layer to the spacing of the pearlite has not been found to vary with alloy content or transformation temperature. This observation does not require any alteration in the above equation: however, it may require that a different significance be attached to the factor, AT. The AT term appears in Eq. [I] as a consequence of a factor for the amount of growth per complex transformed at the interface.* It is based *This is not the sole reason for expecting such a relationship. See Ref. 7._______________________________________________________ on a l/2 ?T dependence of the interlamellar spacing. Zener2 has developed a theory which leads to Soa 1/?V where So = the pearlite interlamellar spacing. This relation is as consistent with the data on interlamellar spacing as other relationships, although, as pointed out by Mehl and Hagel,1 the data are not sufficiently precise to consider the relationship as confirmed. The work of Darken, Fisher, and Galligan8 requires that the above be written where f = the thickness of ferrite layer between austenite and pearlite. The present paper is concerned with iron-carbon-manganese eutectoid alloys and reports experimental measurements of the following kinds: 1) the effect of

Jan 1, 1961

By AIME AIME

THE graduating class whom I am particularly addressing are going into the world at least a month earlier than normal, because of the war. You have been free to choose your work. You have chosen to be mining engineers. The principal importance of your engineering education to date has been in teaching you how to think and how through books to have ready access to the accumulated experience of previous generations, as well as the current experience of the day. You should by now have acquired something of the engineering point of view, the open skeptical mind. the power to observe, experiment, and draw conclusions, form theories and test these by further experiment, and weigh the inherent probability of conclusions drawn by others. I am asking you today to consider certain facts and the conclusions I am drawing from those facts.

Jan 1, 1942

By J. O. Mack, J. B. Russell

IN recent years, solders containing 20 per cent tin with no bismuth or cadmium have been developed by a few companies, and personnel have been properly instructed in their use. In addition, since the tin shortage, a number of solders containing less than 10 per cent Sn, and some with no tin, are being used in special applications; however, a solder of this type has yet to be developed that is satisfactory for general use. [ ] The purpose of this investigation was to develop an alloy containing a maximum of 15 per cent tin, with no cadmium or bismuth, having solder properties equivalent to or better than those of substitute solders now specified containing i8 to 20 per cent tin (Table I), or even approaching the properties of the standard 40 to 60 tin-lead solder. The wartime restriction of bismuth and cadmium, elements that have beneficial effects on fluidity, solidification range and strength, makes it increasingly difficult to develop a general-purpose solder containing a maximum of 15 per cent tin. In the course of this investigation, 11 elements were used in various combinations with the basic 15-85 tin-lead alloy. These elements were antimony, silver, copper, indium, thallium, lithium, calcium, barium, potassium, sodium and arsenic. In all, 116 low-tin solders were investigated, with the idea of developing a solder that will give satisfactory working properties, specifically in regard to "wetting" of copper, brass and iron, solidification range, capillarity and shear strength of a soldered joint. The relative importance of these various properties plays an important role in the search for substitute solders, since it is almost impossible to retain all of the desired qualities of a high-tin solder and still make drastic changes in the alloy composition. Because of the expected uses of a general-purpose solder, it is necessary that it have properties, especially in regard to wettability, that will enable it to be used on the metals in common use. BASIC CONSIDERATIONS The maximum liquidus temperature of a solder is determined by the particular application involved and the temperature that can be obtained by the source of heat.

Jan 1, 1944

By Archer E., Wheeler

COPPER operations in the Congo mean the operations of the Union Miniere du Haut Katanga, because there are no other copper industries there. There is a mine at Bwana M'Kubwa, a little way to the South, in Rhodesia, which has been operated on a small scale, and-another farther south, the Falcon mine, but in quite a different section of the country. This Bwana M'Kubwa mine has recently been reorganized financially and the Minerals Separation interests have taken an extensive share in it, so that it may come into operation. The Union Miniere's operations are in Katanga, the most southeastern province of the Belgian Congo, and the company's concession is in the southeastern part of that province. The usual route for going into the country is by way of Cape Town, thence over the South African Railways through Kimberly and Mafe- king to Bulawayo, then by the Beira, Mashonland and Rhodesia Railways to the Rhodesia-Congo border, passing Victoria Falls on the way, and finally by the Belgian road, the Chemin de Fer du Katanga, to Elisa- bethville, the African headquarters of the company. From Cape Town to the border it is about 2150 mi. and from the border to Elisabethville about 158 mi., making a little over 2300 mi. from Cape Town, by rail.

Jan 1, 1924

By James S. Baker

LARGER than continental United States but with only about one third the population, Brazil is a land of enormous potential wealth, waiting to be developed. During a recent visit to that country I saw Brazil at war and learned about some of the recent mineral developments. Many engineers and geologists have been sent to Brazil by various U. S. Government agencies to assist the Brazilian producers and co-operate with the Brazilian Government in producing needed war minerals. The Foreign Economic Administration staff of engineers has been active and through their assistance to the Brazilian producers, steadily increasing quantities of strategic minerals were provided to aid the United Nations' war effort. Mineral wealth has been found in almost every state of Brazil. Many mineral deposits have been discovered during the war period. Examples are: barite near Bahia; the tungsten and molybdenum deposits in Rio Grande do Norte; and corundum, beryl, and tungsten ores in Ceara.

Jan 1, 1945