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By Alfred James

Some months since, in the Johannesburg gold-fields of South Africa, the attention of the author was directed to certain statements to the effect that the gold-contents of foul or extremely dilute cyanide-solutions could not be effectively precipitated in practice by the usual zinc-method. Such statements caused all the greater surprise, because it is well known that this difficulty is not encountered in other wellknown districts, as, for example, in New Zealand, where solutions containing less than 0.05 per cent. of KCy are regularly reduced in practice to below 1 grain of gold per ton, while in Mexico and the United States almost equally satisfactory precipitations are not uncommon. As a result of these representations, however, the author visited several plants at work in the Transvaal, and noted that while at some few mines the precipitation was really excellent, at others the effluent, after treatment, was much too high in bullion-contents. An investigation into the causes of these unsatisfactory results disclosed the fact that more attention to the close packing of the zinc-shavings in the extractor-compartments tended to improve the results, even with the most dilute solutions. The function of the zinc being one of surface, it stands to reason that a compartment well filled with zinc would be more effective than a half-filled one. Moreover, the quality of the zinc was inferior. This should be in long, tough, thin, light threads; light enough to ignite readily, and tough enough not to disintegrate easily into a slime. The coarse shavings too frequently employed appear to give the reverse of the best practice ; they are brittle, contain less surface, and take up more room. It is almost impossible to pack a compartment properly

Jan 1, 1898

By Newell G. Alford

Forecasts of future timber consumption in soft-coal mining are handicapped by the lack of adequate experience records for estimating properly the timber requirements of the industry. Data were obtained from plants where records are kept or from operators who collected the information and to these were added composite figures for the continental United States in 1905 and 19191 and for central and western Pennsylvania and for Illinois in 1922.2 The result, representing slightly over 928,000,000 net tons, is shown in Table 1. Some of the companies furnishing data were unable to segregate the timber into classes of use but for those who did, Table 2 shows the board feet of posts and cross ban used per ton of coal mined and the percentage of the total timber consumed that was used in roof support. The wide variation in amounts of timber per ton of coal mined is the result of

Jan 1, 1924

Sec. 1. This Division shall be known as the Institute of Metals Division of the American Institute of Mining and Metallurgical Engineers. Sec. 2. The object of the Division shall be to furnish a medium of cooperation between those interested in the metallurgy, fabrication and uses of the nonferrous metals and their alloys; to represent the A. I. M. E. in so far as nonferrous metallurgy is concerned, within the rights given in A. I. M. E. By-law XI., Sec. 1, and not inconsistent with the Constitution and By-laws of the A. I. M. E.; to hold meetings for social intercourse and the discussion of nonferrous metallurgy; to stimulate the writing, presentation and discussion of papers of high quality on nonferrous metallurgy; to reject or accept such papers for presentation before meetings of the Division. Article II—MembeRs Sec. 1. Any Member, Associate, or Junior Associate of the A. I. M. E. in good standing may become a Member, Associate or Junior Associate of this Division upon registering in writing a desire so to do, but without additional dues. Sec. 2. But no one who has been continuously indebted to the A. I. M. E. or to this Division for more than three months shall be entitled to vote or to receive publications to which, as a member of the Division, he would be entitled. Article III—Funds Sec. 1. The expenditure of the funds reccived by the Division shall be authorized by the Executive Committee of the Division. Article IV—Meetings Sec. 1. The Division shall meet at the same time and place as the annual meeting of the A. I. M. E., and at such other times and places as may be determined by the Executive Committee subject to the approval of the Board of Directors of the A. I. M. E. Sec. 2. The annual business meeting for election of officers shall be held within a few days before or after the annual business meeting of the A. I. M. E. Sec. 3. At any meeting of the Division for which notice has been sent to the members of the Division through the regular mail at least one month in advance, a business meeting may be convened by order of the Executive Committee, and any routine business transacted not inconsistent with these By-laws or with the Constitution or By-laws of the A. I. M. E. Sec. 4. For the transaction of business, the presence of a quorum of not less than 25 members of the Division shall be necessary. Article V—Officers and Government Sec. 1. The officers of the Division shall consist of a Chairman, two Vice-chairInen, Secretary and Treasurer. The office of Secretary and Treasurer may be combined in one person, if desired by the Executive Committee. Sec. 2. The government of the affairs of the Division shall rest in an Executive Committee, in so far as is consistent with the By-laws of the Division and the Constitution and By-laws of the A. I. M. E. Institute of Metals Divisiori

Jan 1, 1931

By G. W. Josephson

VIRTUALLY every year inventors find one or more startling new uses for one of the varied products of the nonmetallic mineral industries. For example, in November a major step toward positive control of rainfall was made when an experimenter converted a cloud to snow by dropping a few pounds of solid carbon dioxide into it. Other examples of ingenuity in the development of markets and production methods are noted in the following pages. For most of the industrial mineral products one of the outstanding features of 1946 has been the high level of production. There are exceptions, such as quartz crystal and lithium, whose production capacity during the war outgrew current peacetime needs, but they are few. Some technical men point out that this prosperity is not an unmixed blessing to technologic progress, because so much effort must go into day-to-day production problems that relatively little opportunity is left for the pursuit of new developments.

Jan 1, 1947

By A. F. Bridge

IN order to show the need for gas reserves, their control, and conservation, in California, it is necessary to describe briefly the local conditions under which gas is produced and marketed, to point out the lack of coordination between supply and demand, and to relate the history of efforts to prevent wastage. There are now 24 fields in California producing a surplus of gas over field fuel requirements. They are usually grouped geographically into three divisions, as follows: (I) Los Angeles Basin (Los Angeles and 0 r a n g e Counties), thirteen fields, all casing-head gas. Total daily gas available for sale 125,000, 000 ?cu.ft. (2) Coastal (Ventura and Santa Barbara Counties). Seven casine-head and one dry gas field. total-avail- able daily, 165,000,000 cu.ft. (3) San Joaquin Valley (Kern, Kings, Fresno, and San Joaquin Counties). Four casing-head fields, five dry gas fields, and two producing casing- head and dry gas from different zones. Total available daily pro- ducticon, 475,000,000 cu.ft. Total all fields, 765,000,000 cu.ft. daily.

Jan 1, 1936

By T. W. Guy

The increased moisture due to water-spraying for coal dust control is of interest even for mines from which the coal is to be wet-washed before screening, because in many cases wet coal dust materially de- 20-mesh X 0 sizes as pct ROM average ............................... 6.3 pct Range 2.3 to 9.5 pct 20-mesh X 0 sizes as pct 3/8 X 0 sizes average........'...................... 18.9 pct Range 12.7. to 23.9 pct creases the loading efficiency of men and equipment at the faces. It also causes a serious increase in the normal wear and deterioration of all equipment with which it comes in contact. It is important to the consumer if it increases his as-received moisture. No attempt will be made in this paper to cover the entire subject of water-spraying of coal for dust control. It will be confined to discussion and data on (I) percentages of dust in bituminous coals, (2) moisture increases due to spraying for dust control in mines or plants by methods which have proved satisfactory for periods of one to five or more years, and (3) a few suggestions for research. Size and Percentage or Coal Dust The U. S. Bureau of Mines1 classifies as coal dust all bituminous coal passing a 20-mesh sieve (0.0328 in. square opening). The percentage of such dust to be found in ROM coal, of course, varies widely with the characteristics of the seam, and with the methods used in the mining and in the preparation of the coal. ROM screen analyses of 12 U. S. coals selected at random from personal files given in Table I show: A few other screen analyses examined indicating 40 pct or more of 20-mesh X 0 dust in 3/8 in. X 0 sizes were not included because of uncertainty that they were representative. The number of results in Table I is not sufficient to give a reliable estimate of the average, or of the range to be expected, but it indicates that in every case the coal dust is a relatively large percentage of the total ROM coal, and, of course, a progressively larger percentage of resultants as the larger sizes are separated for marketing.

Jan 1, 1949

By George Smith

IN the utilization of natural resources owner, operator, and consumer should share the attendant benefits. Development needs to be planned under terms recognizing fully the interests of all concerned, for any undue advantage given to any one of these participants is apt to involve even greater and disproportionate injury to one or both of the others. For this reason it is well to preface any consideration of needed reforms in legislation affecting the disposition of public land with a survey of certain fundamental principles that determine the general conditions of all land transfers preliminary to development, utilization, and production. The disposition of any undeveloped natural resource, whether timber, oil, coal, or water power, as a transaction to which hand owner and prospective developer are parties, must be based in theory upon a division of expected returns. Whatever the terms of such disposition, neither party can reasonably ask for anything other than an equitable division of the returns. Under this analysis three and only three questions need to be discussed ; namely, what are those profits, how is this division to be accomplished, and what is the equitable basis of division ? The answer to the third question should probably be found by applying to the problem the principles of theoretical sociology, and' the question need not be mentioned further at this time, inasmuch as it does not involve the practical considerations to be kept in mind in connection with the other questions, which are concerned with only the measure of returns and their division. That is to say, whether the land owner's equity is to be stated as 95 per cent. or as 5 per cent. of the profits attending the development of the particular resource, no change would be necessary in the method to be adopted of arriving at the closest approximation of the prospective total profit.

Jan 10, 1913

By Albert Sauveur

THE following experiments were conducted in order to study the influence of the rate of cooling through and below solidification on the dendritic structure (macrostructure) and microstructure of some hypoeutectoid steel. The steel selected was of commercial grade and had the following composition: C, 0.40 per cent.; Mn, 0.85; Si, 0.70; P, 0.099; S, 0.043. After melting in vacuum in an Arsem furnace, the various samples were allowed to solidify and to cool to room temperature as indicated in Fig. 1. Samples were thus obtained representing all possible combinations of slow and fast cooling through the various ranges of temperatures indicated, namely: (1), zone of solidification or primary crystallization, (2) zone of granulation, and (3) zone of secondary crystallization. The location of the different temperature zones in the iron-carbon equilibrium diagram is shown in Fig. 2. The authors adopted. Belaiew's notations. The designations of the various samples readily indicate their treatment, as will be apparent from Table 1.

Jan 1, 1930

By Clyde Williams

A MAN who is a first-class metallurgist, engineer, and scientist and an outstanding organizer, administrator, and executive and who, at the same time, has an innate ability to "make friends and influence people" everywhere he goes is an exceptional personality at any time. And if such an individual can retain this combination of virtues during a great war despite the fact that the Government loaded him with enough work and responsibility for three such men. he is a most exceptional personality. And if he can keep his head and maintain an unfailing sense of humor during the trying war years and, while dealing with hundreds of jittery metallurgists and metalworkers, with Army and Navy brass, and with red-tape-entangled war agencies by the dozen, he is a rare personality indeed. Such a man is Clyde Williams, director of Battelle Memorial Institute. who will be President of AIME in 1947. The Institute is fortunate in having him as its mentor during what may be a critical and important year.

Jan 1, 1947

By R. E. Ogilvie, N. L. Peterson

DURING the past few years there has been considerable effort devoted to the understanding of radiation effects on materials. The concept of the Frenkel defect and other lattice defects suggests that radiation may alter the rate of many metallurgical phenomena, especially those which are diffusion controlled. In 1953 R. R. Coltman and T. H. ~lewitt' found an appreciable effect on the ordering rate of Cu,Au due to fast neutron bombardment. Since then several rather comprehensive theories have been proposed on radiation enhanced diffusion in solids.2"4 If the energy of the radiation is above the threshold energy for the removal of atoms from their lattice sites, Frenkel defects will be produced. These defects can be produced uniformly throughout a relatively thick specimen by high-energy X-rays permitting bulk property studies without the limitation of sample dimensions. In this work high-purity arsenic containing 30 ppm of impurities was allowed to diffuse from the gase- ous phase at 700°C into single crystals of p-type germanium containing 0.1 ppm of indium. As the arsenic diffuses into the P-type germanium, an n-type layer will form in the diffusion zone. At the p-n junction the concentration ratio of the arsenic to the indium is constant. Experimental Procedures—The germanium specimens, 10 mm by 10 mm by 5 mm, were polished and etched to a mirror finish. The specimens were then sealed off in a vycor glass capsule at 3 x 10"5 mm Hg pressure with a sufficient amount of arsenic powder to produce a one-half atm pressure of arsenic at 700°C. Specimens were annealed at 700°C without radiation. The diffusion coefficient determined from these samples agrees within 8 pct of previous work done by Fuller.' Three specimens were given diffusion anneals at 700°C in a small tube furnace centered beneath the target of a 2-mev Van de Graaff generator. The specimens when in the furnace were 10 cm directly below the target of the generator. These specimens were irradiated continuously during the diffusion run with the Van de Graaff operating at 2 mev with a tube current of 225 to 250 pamp. The intensity of the x-radiation at the surface of the specimen inside the furnace was approximately 4.5 x l05 roentgens per hr. The temperature was controlled within m2°C by a chromel-alumel thermocouple throughout this work with no observed temperature change due to the radiation. By careful lapping, the samples were polished at an angle of 5 deg to the diffusion zone, giving a XI0 increase in the visible diffusion zone. The location

Jan 1, 1960

By C. E. Jackson, E. C. Nelson, A. L. Christenson

Much information regarding the transfornlatio~lal characteristics of a steel as it cools in a known manner from the austenitic state can be obtained from dilatometric studies. This method has received more arid more attention because of its great flexibility, accuracy, and ease of interpretation. 'The method is entirely applicable to any rate of heating and cooling although the experumental procrdures for high rates of cooling have offered some difficulties. This paper presents a description of equipment employing cooling rates up to 500 °C. per secorld and the results of dilatometric observations on six commercial steels are included. French and Klopsch1 studied the cooling transformations of a serirs OF carbon steel, using the thermal arrest method. This was followed by the systematic investigatiol1 of Esser and co-workers on the effect of carhon2 and other alloying additions. in which the transforlnation temperature\ were determined by magnetic induction measurements indicated by a string galranoineter. Emphasis was placed on determining Ar' trailsformations and the critical cooling rates for these steels. The maglietic measurements wrere used in an effort to obtain more accurate data at higher cooling rates. Measurements of thermal arrest were made also to check the validity of the magnetic indications, and good correlation was found between the two, although Esser's,Ar' temperature measurements on iron-carbon alloys were about 200°F. lower than the measurements made by Fresnch and Klopsch. A notable contril~ution by Esser was the introduction gas quenching. wever and Rose4 used a moving-coil galranometcr in the study of the .Ar and Ar" of iron-carbon alloys by the thermal arrest method and obtained somewhat lover Ar" temperatures than those observed by Esser below I per cent carbon and considerably higher ahove. They concluded that the cooling rate had little influcncc on the Ar" temperatures above 0.4 per cent carbon, although Esser had observed a decrease in the -4r" temperature with increasing cooling rate with similar steels. Digges determined the .Ar" temperature4 for a scries of high-purity iron-carbon alloys, and close agreement with his results was obtained by Greninger. The thermal arrest method. together with metallographic observation used in both these studies, represents the latest investigations of this type. Any investigation by thermal analyses is dependent on the heat of reaction and the specific heat of the

Jan 1, 1945

By C. D. Ramsden

DURING the war years of 1941 to 1945, maintenance of mine locomotives and other mine equipment took the form of rebuilding rather than of renewing. Pur¬chase of new parts became increasingly difficult and mine operators found it necessary to maintain equipment by sal¬vaging old parts. Mine-locomotive wheels, although not representing a high cost per pound of material, contain a con¬siderable amount of steel and without rebuilding would have to be scrapped long before even a moderate percentage of the steel in the wheel is actually consumed. Many mine operators have been re¬building locomotive wheels for several years with automatic open arc-welding equipment. In 1927, the Pittsburgh Coal Co. started such a program, using a single Westinghouse automatic welding head. Since that time, many refinements have been added, until in 1944 the setup was operating very efficiently. A desire to increase wheel life and to hold down rising costs led the company in 1944 to investigate the possibilities of the under¬flux arc-welding process for wheel rebuild¬ing, although at that time, little or no work had been done on multiple pass or "build-up" welding with the underflux arc. Work with this process had been confined largely to welding together flat plates in a "down hand" position. Possibilities for savings were intensified by the fact that the company has 300 locomotives in operation, using actively or as spares 1200 sets of wheels. During 1942 and 1943, about 500 sets of wheels were sent each year to the company's maintenance shop at Library, Pa., for rebuilding. Based on having 800 sets in service (many of the company's heavy locomotives have three- sets of trucks), the average life of a set of wheels was approximately 19 months. Anything that could be done to increase wheel life promised sizable annual savings. OPEN ARC WELDING With the open arc process, a set of wheels could be rebuilt for about 40 pct of the cost of new wheels. Underflux arc welding gave promise of greatly increased welding speeds, more homogeneous, dense deposits and the chance for use of a wider range in welding-wire compositions. Against this was ranged the higher cost of materials and the cost of developing the process from the theory to a practical reality. Since 1927, when a single open arc head was placed in operation, fixed welding procedures had been gradually developed, a positioner for handling a set of wheels was built, and a second head was placed in operation in order to weld two wheels simultaneously. The fixture, or posi¬tioner, which was built to position and turn the wheels under the two welding heads, included a motor drive, controlled by a rheostat, which rotated the wheels through a double set of speed reducers and a removable jaw coupling attached to one end of the axle of the wheel truck.

Jan 1, 1946

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

By Paul D. Conatore

INTRODUCTION There are important reasons for a discussion of tungsten resources, reserves, and production in the Circum-Pacific area. First, the world's chief tungsten deposits, as well as most of the world's tungsten reserves and production, occur in this region. It is well known that the world's largest tungsten reserves are located in southeastern China and that for many years, the largest individual mine in the world was there. Although China still has the world's greatest tungsten production, the very high-grade scheelite mine of Canada Tungsten Mining Corporation in the Northwest Territories is the largest producer of tungsten today. There is certainly a great quantity of tungsten in Asia, but the strategic importance of this fact is now offset by the wide distribution of mines and production facilities throughout the world, especially in other parts of the Circum-Pacific area such as Australia, Canada, and the United States. In addition, much of the Circum-Pacific area is comprised of Mesozoic-Cenozoic orogenic belts. These global tectonic units are regarded as very favorable for additional tungsten deposits, particularly scheelite-bearing tactites, and consequently, prospecting and exploration will most likely be concentrated in the Circum-Pacific area. Second, tungsten must be regarded as one of the, most important metals of modern industry because of its very special properties. It has the highest melting point, the highest tensile strength at elevated temperatures, and the smallest compressibility of any metal. The metal also possesses a very high density, excellent corrosion resistance, good thermal and electrical conductivity, and a low coefficient of expansion. As a result, tungsten has found increasing importance in a wide range of industries. From the filament in an electric lamp, to cutting tools and drilling bits, to the exotic radiation shields that protect supersonic aircraft and spacecraft, tungsten plays an indispensable role in our daily lives. The primary objective of this paper is to present an overview of important facets of known and suspected tungsten in the Circum-Pacific area. Resources, reserves, current production, planned capacity expansions, and new operations, as well as an assessment of the probability for development of deposits in the Circum-Pacific area, are discussed. RESOURCES The average crustal abundance of tungsten has been estimated at 0.0015 kilograms per tonne. A comparison of the abundance of various metals in crustal rocks to that of tungsten is presented in Table 1, which shows that tungsten abundance is similar to that of its commonly associated metals, tin and molybdenum. Table 1. AVERAGE CRUSTAL ABUNDANCE OF VARIOUS METALS (Grams per Tonne) [ ] With careful thought, it can be realized that tungsten ore deposits result from the concentration of the metal, through normal geologic processes, to levels substantially greater than its average crustal abundance. The minimum technologically and economically workable tungsten concentration, or cutoff grade, is a function of (1) deposit tonnage, (2) mining and milling methods, (3) production tonnage, (4) capital and operating costs, (5) tungsten market conditions, and (6) value of associated recoverable metals. The tungsten cutoff grade that is currently exploitable at a profit varies from 0.09% W03 to 1.55% W03, reflecting concentration factors from 470 to 8200, as shown in Table 2. Table 2. CURRENT TUNGSTEN CUTOFF GRADES [ ]

Jan 1, 1982

Jan 1, 1938

Jan 1, 1938

By L. C. Brown, S. K. Behera

The diffusion rate in Ag-Sb couples is sensitive to con~pressive load with the width of Ag3Sb, the only phase present in the diffusion zone, increasing with stress up to 800 psi and remaining constant above this. Kirkendall marker experiments show silver to diffuse much faster than antimony in Ag3Sb and incipient porosity may therefore develop at the Ag/Ag3Sb interfnce restricting the transfer of atoms from the silver into the diflusion zone. Application of compressive stress reduces the tendency for porosity to develop and so increases the growth rate. In a recent paper Brown et al.1 observed a significant increase in the thickness of Cu2Te in Cu-Te diffusion couples on application of a compressive stress as low as 20 psi. Similar stress effects have also been observed in the Fe-A1,2 Al-u,3 arid cu-sb4,5 systems. It has been suggested that the increase in growth rates of intermetallic phases in these systems is due to a decrease in the amount of Kirkendall porosity with applied stress. In the present paper, results are presented of the effect of compressive stress on diffusion in Ag-Sb, together with a detailed examination of the Kirkendall effect. The Ag-Sb phase diagram6 shows that antimony has a moderate degree of solid solubility in silver, 5.7 at. pct at 350°C, but that there is essentially no solubility of silver in antimony. There are two intermediate phases— (hcp7) from 8.8 to 15.7 at. pct Sb and Ag3Sb (orthorhombic8) from 21.8 to 25.9 at. pct Sb. EXPERIMENTAL Diffusion couples were prepared from fine silver of 99.95 pct purity and from antimony of 99.7 pct purity. Both the silver and antimony were produced in the form of discs 1/2 in. in diam by approximately $ in. thick, with surfaces ground flat to 3/0 emery paper. Diffusion anneals were carried out in the apparatus previously described.1 A compressive load was applied to the diffusion couple through a lever arm system, with a reproducibility estimated to be ±10 psi. All runs were carried out in a protective hydrogen atmosphere. Following the diffusion anneal specimens were sectioned and polished and the width of the diffusion zone was measured metallographically. Composition profiles were measured using an electrostatically focused electron probe with a spot size of 10 , counting on Sb L radiation. Corrections for matrix absorptiori and fluorescent enhancement9 were not required. S. K. BEHERA, formerly Graducate Student, Department of Metallurgy, University of British Columbia, is now Postdoctoral Fellow, Whiteshell Nuclear Laboratories, Atomic Energy of Canada Ltd., Pinawa, Manitoba. L. C. BROWN, Junior Member AIME, is Associate Professor, Department of Metallurgy, University of British Columbia, Vancouver, B.C., Canada. Manuscript submitted June 14, 1968. IMD RESULTS Fig. 1 shows an electron probe traverse of a typical diffusion zone. In all couples examined only one intermediate phase was observed and the composition of this phase, 23 wt pct Sb, was in good agreement with the composition of Ag3Sb, 23 to 28 wt pct Sb. The presence of this phase was confirmed by X-ray diffraction of filings taken from the diffusion zone. The probe traverses showed no detectable solid solubility in either the silver or the antimony although the phase diagram indicates that some antimony, up to 6.5 wt pct pct Sb, should be in solid solution in the silver. However the width of this portion of the diffusion zone would be expected to be very small in view of the low diffusion coefficient in the silver, 4 x 10-l6 sq cm per sec at 350°C, 10 compared with that in the Ag,Sb, estimated as 3 x 10-8 sq cm per sec in the present work, and this region would therefore not be expected to be seen in the probe traverse. Application of stress resulted in a significant increase in the width of the diffusion zone, Fig. 2. At 350°C, the thickness of Ag3Sb increased from 250 at 0 psi to 400 p at the limiting stress of 800 psi, indicating an apparent 150 pct increase in the diffusion coefficient. Similar behavior was also observed at 400°C, indicating that the stress effect is not characteristic of just one temperature. The growth of Ag3Sb at 350°C and at various stresses is shown in Fig. 3. In every case the growth rate was parabolic indicating diffusion control. The kinetic curves all passed through the origin showing that delayed nucleation of Ag3Sb was not responsible for the stress effect and that it was a real growth effect. A series of tests were carried out in which diffusion was allowed to take place at a lower stress following an initial high stress diffusion anneal. Speci-

Jan 1, 1969

By F. R. Milliken

EXPERIMENTS, in what has come to be known as flash roasting began some ten years ago. The principle underlying the operation was not a new one, but the experimental work started at that time was the first that was carried through to a logical conclusion, followed by construction and operation of a pilot plant, and then full-scale production. For a short working definition, flash roasting may he considered the instantaneous and complete oxidation of finely ground sulphide particles, partially suspended in air or gas, the oxidation reaction evolving enough heat to make the reaction self-sustaining, or nearly so.

Jan 1, 1937

By F. G. Jones, R. D. Pehlke, H. E. Gardner

The solubility of nitrogen in liquid Fe-18 pct Cr-8 pct Ni-0. 7 to 2.3 pct A1 alloys has been measured up to the solubility limit for the formation of aluminum nitride in the temperature range 1600° to 1700°C uszng the Sieverts' method. The solubility of nitrogen in 18-8 stainless steel increases with increasing aluminum content. Based on a nitride composition, AlN, the standard free energy of formation of aluminum nitride from the elements dissolved in liquid 18-8 stainless-steel alloys has been determined to be: ?G° = -42,500 + 20. IT in the range from 1600° to 1700° C. EVANS and pehlke1 have measured the equilibrium conditions for the formation of aluminum nitride, AlN, in liquid Fe-A1 alloys. The present study extends that work to the more complex solvent, liquid 18 pct Cr-8 pct Ni (18-8) stainless steel. Recent work by Small and pehlke2 has dealt with the effect of fourth-element additions on the solubility of nitrogen in 18-8 base alloys. They found the effect of aluminum additions, up to 0.74 pct, on the solubility of nitrogen to be small. The present study covered the range from 0.74 to 2.28 pct aluminum, and by extending the composition range may be used to better define the effect of aluminum on the nitrogen solubility in these alloys. EXPERIMENTAL PROCEDURE The Sieverts' method was used to measure the equilibrium solubility of nitrogen gas in liquid 18-8 stainless steel alloys containing 0.74, 1.49, 1.93, and 2.28 pct Al. The solubility was measured as a function of the nitrogen gas pressure at temperatures of 1600°, 1650°, and 1700°C. The apparatus used is the same as described by Small and Pehlke.2 The 100-g melts were made from Ferrovac-E high-purity iron, Crucible Steel Co.; 99.95 pct Cr, Union Carbide Corp.; 99.9 pct Ni, International Nickel Co.; and 99.99+ pct Al, Aluminum Co. of America. The aluminum was charged at the bottom of the crucible, surrounded by nickel and iron. The chromium was packed into the interstices to minimize vapor transport of the aluminum during initial melting. The hot volume of the system, measured for each melt with argon, ranged from 45 to 55 standard cu cm with a temperature coefficient of —8 x 10-3 cu cm per °C. The melt temperature was measured with a Leeds and Northrup disappearing-filament type optical pyrometer sighted vertically downward on the center of the melt surface. The temperature calibration of the system by Small and pehlke2 was assumed. Two problems are involved in determining the solubility product of a solid, metal nitride phase in liquid iron alloys. These are: 1) establishing the point of departure from Henrian behavior at the solubility limit of the metal nitride phase; and 2) determining the composition of the solid nitride which is precipitated. Determination of the solubility product of AlN was made by admitting small amounts of nitrogen into the reaction bulb until the deviation from Sieverts' law was clearly evident in the form of a pressure halt. To obtain the solubility product at several temperatures during one run the following procedure was used: 1) add increments of nitrogen to determine the Sieverts' law line at the lowest desired temperature; 2) continue to add nitrogen to precipitate a small amount of the nitride phase; 3) increase the melt temperature 50°C to dissolve the precipitated nitride; 4) repeat step 2 until either a nitride formed or the system reached ambient pressure; if a nitride formed at 1650°C, the sequence was repeated at 1700°C. The composition of the precipitated phase was checked by an X-ray diffraction pattern obtained from powder scraped from the surface of the solidified 1.93 pct A1 melt. RESULTS AND DISCUSSlON Solubility Measurements. Fig. 1 is a typical nitrogen-absorption curve obtained from measurements on a 1.93 pct A1 alloy. Since the initial absorption of nitrogen follows Sieverts' law the nitrogen solubility is plotted as a function of the square root of the pressure of nitrogen gas in the reaction bulb. The results of the solubility measurements for all alloys studied are summarized in Table I. The slope of the Sieverts' law line for each alloy was determined. Since this is also the solubility of nitrogen at 1 atm pressure of nitrogen gas, the latter designation is used for the data. It should be noted. however, that in most cases the value lies above the solubility limit for AlN. Fig. 2 shows the effect of aluminum on the solubility of nitrogen at this reference pressure and as a function of melt temperature. The solid portions of the lines represent attainable solutions; the dashed regions lie above the limit for precipitation of AlN.

Jan 1, 1969