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By R. W. Woodward, G. K. Burgess

minum bronze. Nearly all copper-base alloys are improved by rolling processes, but the copper-aluminum alloys seem to possess equally good properties when cast or rolled; this is a remarkable metallurgical fact. Another important property of these copper-aluminum alloys is their resistance to alternating stress. Many tests indicate that their resistance is greater in this respect than that of some steels, and I have seen instances when cast aluminum-bronze bolts have outlived five steel bolts in foundation work subject to severe shocks. I mention these various instances to indicate that work originally started as research for substitution of one material for another frequently develops 212 article which has properties not possessed by the original metal or alloy. I have dwelt particularly on the aluminum bronzes because recently I have done more special work on them than on other alloys, but I believe that the use of aluminum itself, in many combinations of metals, is a very important subject for investigation. Undoubtedly, after the war, the cost of aluminum will be reduced from its present price, and considering its low specific gravity it offers a very interesting and important field for research in the non-ferrous business. Naturally, if combinations containing aluminum can be developed in view of a probably increasing supply of metal, the cost will be reduced. This will benefit the industry generally and will immediately conserve tin. Bronzes, Bearing Metals, and Solders G. K. Burgess* and R. W. Woodward,† Washington, D. C.— From a metallurgical standpoint, there are several ways in which a reduction of the tin consumed in commercial non-ferrous and white-metal alloys can be effected. First, a reduction of the tin content of the alloy; second, substitution of part or all of the tin content by some other metal; third, a substitution of a different type of alloy, which in some cases also involves a change in mechanical design. The Bureau of Standards has been studying these methods of conservation for tin alloys, particularly in regard to babbitts and bearing metals, bronzes, and solders. Much of the information sewed by the Bureau was obtained from answers to questionnaires sent to manufacturers and users of these materials, so that, in general, any of the following suggestions or recommendations can be considered as being practical and as having already been thoroughly tried. Bearing Metals There is no question that the tin content of nearly all bearing metals can be reduced to some extent, and in some cases actually eliminated

Jan 1, 1919

By A. J. Boyer, T. R. Meadowcroft

An experimental determination has been made of the efject of surface diffusion on the vapor pressure obtained in a Kwudsen cell. The results show that a knife-edge orifice in a molybdenum lid may give erroneous results for the vapor pressure of silver. when a correction suggested by winterbottom and Hirth is made, the results become meaningful. Experimental work with cylindrical orifices in molyhdenz~m lids and knife-edge orifices in ceramic lids shows that good vapor-pressure results may he obtained when the orifice is designed so that ejfusion is the only significant source of weight loss. THE Knudsen effusion cell technique has been used by many investigators to study relative and absolute vapor pressures over metals and alloys at elevated temperatures. As a result of this interest, some theoretical studies have been made of geometric factors affecting effusion from the orifice of a Knudsen cell. A review of these studies has been made by Margrave.1 Recently, Winterbottom and Hirth2 have suggested that a physical effect, that of condensation, surface diffusion, and re-evaporation, may seriously affect Knudsen cell measurements, especially when a knife-edge orifice is used. Inasmuch as many of the present vapor-pressure data have been obtained using knife-edge orifices. it was felt that an experimental evaluation of the effect of surface diffusion on Knudsen cell measurements would be of value both in the design of the cell orifice and in establishing realistic estimates of the limits of error for existing data. The experimental program was in two sections. Firstly, measurements of the vapor pressure of silver were made in cells with cylindrical and conical orifices in which the surface-diffusion contribution to the weight loss should be negligible. These results were correlated with existing data to give a reliable measure of the real vapor pressure of silver. Secondly, measurements made using knife-edge orifices were corrected using the surface-diffusion theory of Winterbottom and Hirth2 and were then compared to the real values. The experimental arrangement is shown in Fig. 1. The balance was an Ainsworth RV-AU-1 automatic recording microbalance capable of measuring weight changes of ±0.02 mg on a total load of up to 100 g. The temperature was measured by an optical pyrometer signted on the bottom of the suspended crucible. The temperature readings were calibrated in a separate experiment in which pyrometer measurements were made while at the same time thermocouple readings were taken of the temperature at the inside top and bottom of the crucible. The range of reproducibility with this technique was ±4°C. A constant voltage source maintained a temperature of ±2°C at 1200°C over 10 hr. Silver of 99.99 pct purity was used in nonporous alumina crucibles. Lids of molybdenum, tantalum, or magnesia were cemented to the crucible using a sodium silicate cement. Table I shows the characteristics of the lids used. The vapor pressure is obtained using the basic Knudsen formula:

Jan 1, 1965

By E. J. Eisenach, Edward Matsen

AT the present time the Climax Molybdenum Co. is the largest molybdenum producer in the world and the operator of the largest underground mine in North America. It has grown steadily and rapidly since its beginning in 1917. Only 250,000 lb of MoS2 were produced during the first year from 1917 to 1918 when the company was formed. Operations were suspended shortly thereafter because of the lack of a market and knowledge of the uses of molybdenum. During World War I it was used as a substitute for some rare metals and for minor chemical purposes. After 5 years of intensive research and sales promotion, Climax metallurgists succeeded in finding proper applications for the newly discovered metal and the mine was reopened in 1924. Demand for molybdenum increased gradually and in 1930, 3.5 million lb of MoS2 were produced. In the meantime, research work for additional uses of molybdenum continued until it had established itself as one of the most important alloying elements in producing high quality steels. After the start of World War 11, from January 1942 to October 1953, 43 million tons of molybdenum ore were mined and 484 million lb of MoS2 were produced. Climax mine is located in Colorado, 100 miles southwest of Denver and 12 miles northeast of Leadville on the Continental Divide of the Rocky Mountains. The principal mine workings range from 11,170 to 12,000 ft in elevation. Topographically, it lies in the base of a large cirque that is surrounded by Mt. Bartlett to the north, Clinton Peak and McNamee Peak to the east and Ceresco Ridge to the south. This cirque opens to the west and to the Ten Mile Valley.

Jan 3, 1954

By Luiz C. Correa da Silva, Robert F. Mehl

An experimental study of the movement of markers in the systems Cu/a-brass, Cu/Sna-solid solution, Cu/Ala-solid solution, Cu/Ni, Cu/Au, Ag/Au, employing many types of markers and a variety of temperatures. Marker movement is confirmed and undoubtedly associated with the manner in which atoms move during diffusion. EVERAL years ago Smigelskas and Kirkendall' •S reported measurements on the interdiffusion of copper and a-brass and on the movement of inert markers placed at the original join. These markers were observed to move toward the a-brass side of the join, and from this it was inferred that zinc diffuses in a-brass more rapidly than copper. Similar results were reported a little earlier for the diffusion of solvents into high polymer solids.' This has attracted much attention, particularly from those interested in the mechanism and the theory of diffusion: Seitz3 has employed it in supporting the vacancy theory of diffusion; from the data Darken4 has calculated separate diffusion coefficients for copper and zinc, developing a "phenomenological" theory of diffusion; and Bardeen5 has employed it in constructing a general theory, including therein the work of Seitz and Darken, as has Le Claire. These matters have recently been reconsidered in a sympo~ium.7 Some reason has existed for questioning the work of Smigelskas and Kirkendall.' Their technique consisted in electroplating copper on a-brass, upon the surface of which Mo-wires had been secured, and then diffusing, measuring the extent of diffusion along the normal to the join, and measuring the marker displacement in the same direction by a comparator determination of the distance between Mo-wires on opposite sides of the electroplated brass sample. It has been suspected that the copper plate might have been porous, and that the original interface might have been an imperfect join, both contributing to the transfer of the volatile zinc by vapor transfer;' it has also been questioned whether the marker movement might not in a measure be a property of the marker itself; etc. These legitimate questions require experimental answers; the present paper offers such answers. Moreover, Smigelskas and Kirkendall studied the effect only in the Cu-Zn system and at one temperature; the attention which the work of Smigelskas and Kirkendall has commanded recommends similar

Jan 1, 1952

By AIME

Annual production of more than 4,000,000 tons of 0.74 percent copper ore and coincident handling of over 5,000,000 tons of waste at the open-pit mine of Castle Dome Copper Co. near Miami, Ariz. takes a lot of power. Manufacturers have ever co-operated with mining companies in providing the required equipment to suit the problem. Power equipment suppliers have done much to make possible the economic and profitable production of copper from low-grade ores. In the future, as mining operations will necessarily handle even lower-grade ores, the ability of the manufacturer to supply the power and mechanical equipment to produce more metal at a fair and reasonable price will be the good right arm of the miner. About 27,000 tons of concentrate is produced from the 4,000,000 tons of ore.

Jan 1, 1948

By William R. Rumbold

When I was in South Africa during the latter part of 1904, there were three known tin-fields, which may be called the Cape Town, the Bushveld, and the Swaziland fields. The Cape Town Tin-Field. This district is situated near Kuils river, 20 miles west of Cape Town, and 5 miles from Kuils River station on the Cape Town & Stellenbosch railway. The deposits are in granite, intrusive in the Malmesbury beds, which are supposed to be of Silurian or Cambrian age. The granite, resisting denudation better than the surrounding shales, has formed low-lying hills, the highest of which, the Bottlelary Berg, is 1,510 ft. above sea-level. The rock consists of quartz, orthoclase feldspar, and biotite mica; tourmaline is also present. The feldspar occurs in large crystals. The rock is generally decomposed on the surface, and the decomposition sometimes extends as deep as 100 ft. This formation—granite intrusive in Silurian shales— extends for many miles to the northeast, but so far as I know the Kuils River deposits are the only ones now known to occur in it, though probably further prospecting will reveal other deposits. This particular discovery was accidental; alluvial tin being found in the course of boring for oil. The Kuils River Deposit. This deposit comprises both lode and alluvial tin. The lode strikes N-S., and dips about 30' E. into the hill. It is 5 ft. wide, and composed of dense white quartz, in which pinkish-gray cassiterite is distributed in large crystals. The vein also contains considerable quantities of wolframite. Fig. 1 is a rough plan of the relative positions of the lode and the alluvial deposit, the latter, as shown, following the course of a stream, while the lode crops out on the hillside ,

Jan 1, 1909

By A. P., Svenningsen

ECONOMICAL handling of a minimum of 25,000 tons of minus 3/4-in. ore per day, grinding it to 2 per cent on 65 mesh, and effecting a high recovery of the copper at the lowest possible cost were the principal aims in the design of the new Morenci concentrating plant. Dealing with a tonnage of this magnitude, it is obvious that lost motion cannot be tolerated. When ore is carried on a conveyor an unnecessarily long distance or elevated to a greater height than necessary, or when pulp flows in a launder by a circuitous route thereby losing elevation and distance, we have lost motion which is always costly both from the standpoint of construction and operation. In addition to the 25,000 tons of ore which must be handled, 100,000 tons of water per day has to be carried through the plant in the treatment of the ore. Though water is not so difficult to handle as the ore, the combined tonnage represents a figure which could easily run into a considerable monetary loss per day if all phases of the design were not carefully followed with the idea of eliminating any unnessary handing of materials.

Jan 1, 1942

By H. R. Stahi

THE ore of the Southeast Missouri lead district consists essentially of galena in dolomitic limestone. The galena usually is in a very finely disseminated condition. The experience of recent years in the concentrating plants of the St. Joseph Lead Co. has shown that dry crushing carried to a point where about 90 per cent of the ore passes a 14-mesh screen liberates the larger portion of the galena, and minimizes further necessary reduction in rod or ball mills. Concentration practice has attempted to carry size reduction to a point where economic unlocking of the galena is obtained, without causing undue sliming of the very friable galena. While 60 per cent of the tonnage of the district is treated by the flotation process, only 40 per cent of the total concentrates is produced by that means, as efforts have always been made to keep the grade and tonnage of flotation feed as low as possible. The milling practice of the district for some years has recognized the generally accepted idea of better selective grinding in rod mills as compared with ball mills, with the attendant decrease in production of fines. The function of rod and ball mills in the various concentrating plants is the grinding of table middlings and coarse tailings that carry lead values too high to be discarded. The simplified flowsheet in Fig. I illustrates the place of grinding mills in the circuit. The arrangement of classifiers, tables and mills constitutes a closed circuit within somewhat flexible limits. In 1937 experiments were conducted in replacing the ball charge in a 6 by 4-ft. ball mill with rods 2 in. in diameter and 51 in. long. This step was taken with some hesitancy, as it was easy to picture a mass of tangled and crossed rods. However, no difficulties developed, and after a short trial period, six more ball mills were converted to rod mills. These mills are of the spur gear and pinion, belt-driven type, using in most cases a 75-hp. motor and having a 9 1/2 -in. open trunnion discharge. As ball mills, they carried a charge of 16,000 to 20,000 lb. of balls, 2 in. in original size. The feed to the mills was dewatered by dewatering wheels and introduced at 70 to 75 per cent solids, with a single scoop feeder. One change in mill design was found advisable when rods were introduced. The existing end liners had an outward flare of 3 ½ in. in 12 in. These were replaced by linings having vertical interior faces, in order to prevent undue end travel of the rods. This change gave an effective working length of 5 2 ¾ in. inside the mill. No alterations were made in the shell liners, which are of the smooth type, made of manganese steel 2 in. in original thickness. The rods at present in use are 51 in. long and 1 3/4in. in diameter. The composition has been varied at times; at present they contain 0.70 per cent carbon and 0.70 per cent manganese. Some breakage and etching occurs as the rods become small, but this is considered preferable to using softer rods, which may kink and cause tangling of the charge. The mill charges are renovated occasionally, broken pieces being removed and the charge brought up

Jan 1, 1945

By L. Guttman, C. S. Barrett, J. S. Bowles

THE transformation from the face-centered cubic (Al) to the face-centered tetragonal (A6) structure in certain alloys of the indium-thallium system reported in the preceding paper1 exhibits many interesting crystallographic and metallo-graphic features, most of which presumably are similar to those of other cubic to tetragonal transformation such as, for example, the one which occurs in the chromium-manganese system,2 the one which, judging by microstructures and X-ray pat-terns,3 probably occurs in the copper-manganese system, the ones accompanying ordering in FePt,4 Copt,&apos; and AuCu,5 and the transformation near 115°C in barium titanate.6,7,8 If, as mentioned in ref. 1, the transformation is second order, the phases in equilibrium do not differ in composition, and it is both possible and likely that the mechanism is a diffusionless one. The present paper reports the results of a detailed study of the indium-thallium transformation and presents a theory for the atomic movements of the transformation which accounts for the observations. Experimental Crystallography of Transformation Markings The transformation from cubic to tetragonal in the indium-thallium alloys produces microstruc-tures of the type illustrated in fig. 1. These structures are observable either as relief effects produced on a smooth surface by the transformation, or after polishing and etching. These microstruc-tures are markedly similar to those found in copper-manganese alloys: iron-platinum alloys," and barium titanate,7,8 where it has been demonstrated that the lamellae are parallel to the (101) planes of the original cubic crystal. That the observed lamellae in indium-thallium alloys are also parallel to the (101) planes was proved by the following analyses performed on single grains in polycrystal-line samples containing 20.75 atomic pct T1. A study of the microstructures of a number of specimens revealed the fact that in many specimens the transformation markings continued unchanged in direction across the (111) interfaces of annealing twins. This at once demonstrates that the lamellae are parallel to a plane that is common to both parent and twin orientations, i.e., a plane in the zone <112>. This conclusion is compatible with the lamellae being parallel to (101) planes. To make a more complete determination of the habit plane of the lamellae, two grains were selected in which annealing twins ({Ill) twins) had been present in the high-temperature modification (cubic). The traces of the annealing twins, and of the transformation markings in both parent and twin crystals, were plotted together in stereographic projection, and a parent-twin pair of orientations was found that accounted for all lamellae as (101) planes. The projection of one of these twinned grains is reproduced in fig. 2. In view of these results the probability of there being another solution for the habit plane remote from (101) is very small, but to explore the possibility that the habit plane deviates slightly from (101), a more precise analysis was undertaken. In this, the orientation of a grain in the cubic modification was determined from a Laue back-reflection photograph taken with the sample at 90°C. The traces of the lamellae that formed in this grain on cooling were plotted in the stereographic projection

Jan 1, 1951

By Theron Wasson

The discovery of eight new oil fields, two of which may be of major importance, was the outstanding record in Michigan this year. These new fields have helped to support the declining production from old areas and place the total of 18,559,000 bbl. in line with the past six or seven years. Thus, it appears that Michigan is doing its part in maintaining the production of the country in the third year of the war. The new fields are in the central basin area where oil was first discovered in Michigan, thus tending to focus attention on the deeper part of the lower peninsula of the state. Through 1944 the state of Michigan has produced a total of 222,-641,580 bbl. of crude oil from 100 pools, many of which arc relatively small. Among the previous1y discovered fields Reed City is still the outstanding producer, with Fork, Headquarters, and Adams following in the order named. The Reed City pool produced a little over 5,000,00 bbl., which was more than one third of the state&apos;s total for the year. Almost two thirds of the year&apos;s total oil production came from fields discovered in the past five years. Maps A map of the oil and gas fields of Michigan in 1943, published in the A.I.M.E. report for 1944,* shows the main producing areas and should be referred to if information in regard to their location is desired. The producing zones are shown in the columnar section in the same publi- cation." The data in Tables I and 2 have been carefully &apos; checked and every effort has been made to show as complcte information as possible. New Discoveries and New Developments Eight new producing areas were discovered during 1944 which, in order of importance, are: Deep River Field.—The discovery well in the Deep River field was drilled by Don Rayburn and others, and should be listed as a chance discovery, as, from a geological standpoint, it was not considered favorable until oil was found at a depth of 2838 ft. in a dolomitic layer in the top of the Dundee limestone. The first well was completed in January 1944, with an initial production of 2500 bbl. By the end of the year 15 wells had been completed, proying an area 2 1/2 miles long and 1/2 mile wide. Coldttater Field.-The Coldwater field was discovered in August 1944, by the Sohio Oil Co. Production is from secondary dolomite at the top of the Dundee at a depth of 3703 ft. To the end of 1944 nine wells had been drilled on 40-acre spacing. Essexville Field.—Essexville field was discovered by United Drillers and Producers, Inc. Eight wells had been completed to the Dundee lime by the end of 1944, and prospects were good for further development during 1945. Hilliards Field.—Hilliards field was discovered by Cook and Fortney. Production is from the Traverse lime at an average depth of 1588 feet,

Jan 1, 1945

By E. R. Morgan, J. C. Shyne, V. F. Zackay

NITROGEN used as an alloying element in steel has received increased attention in recent years. Its merit as an austenite stabilizer and hot strengthener has long been recojinized, particularly by European investigators.&apos; Recent work&apos; indicates that nitrogen contents of 1/2 pet or more allow the addition of several percent of ferrite-forming hot strengtheners, such as molybdenum, without subsequent austenite decomposition at elevated temperatures. The room temperature properties of such alloys are characterized by high yield and tensile strengths with excellent ductility, even after cold working, as shown in Tables I and 11. The 1350°F creep-rupture properties of Cr-Mn-Mo-N steels are comparable to those of commercial alloys such as Timken&apos;s 16-25-6, containing 16 pct Cr, 25 pct Ni, and 6 pct Mo, as shown in Table 111. Cr-Mn steel containing 1/2 pet N must be made under pressure if ingot gassing is to be avoided. However, there are difficulties attendant to this practice. Pressure melting restricts the ingot size, and the equipment required is costlier and more complicated than comparable air melting facilities. An effort was made, therefore, to determine more economical methods of adding nitrogen. The pressures generated in centrifugal casting usually range from 5 to 10 atm and are sufficient to prevent the gassing of high nitrogen Cr-Mn steels. A centrifugal casting was made of an alloy containing 16 pct Cr, 18 pct Mn, 2 pct Mo, and 0.73 pct N. A risk, 8 in. diam and 11/2 in. thick, was cast at 1000 rpm. It has been calculated that a pressure of 9 atm was developed at the periphery of the disk at this speed. Metallographic inspection of specimens taken from the disk revealed no gas holes or other defects. The elevated temperature properties of radial and circumferential specimens taken from this casting are given in Table IV. The creep-rupture life of this cast nickel-free austenitic steel was equivalent to that of the wrought Cr-Mn-Mo-N steels. Although centrifugal casting appears to lend itself to the manufacture of high nitrogen austenitic steels, its applicability is limited to relatively small sizes. A process applicable to the production of large ingots of high nitrogen steels is suggested by low carbon rimming steel practice. Gas holes formed during ingot solidification are not detrimental so long as they weld shut during hot rolling. An economic advantage of gassing ingots is the increased ingot-to-slab yield, especially if the ingots are mechanically capped. Also, it is probable that higher nitrogen levels can be achieved with mechanically capped ingots than with hot-topped ingots. A series of gassy heats was made under both atmospheric and higher pressures, as indicated in Table V. Several of the air melted ingots were mechanically capped by chilling the molten ingot tops with a steel plate. The ingots were allowed to freeze in steel molds without hot-tops unless otherwise indicated. A comparison of Table 111 with Table V shows no significant difference in the creep-rupture properties of the gassy and the nongassy ingots after hot work- ing nor between the gassy ingots produced under different conditions. References 1 F. Rapatz: Application of Stainless and Heat Resisting Steels Alloyed with Nitrogen. Sinhl and Eisen ( 1941) 61, pp. 1073-1078. &apos;V. I?. Zackay, J. F. Carlson, and P. L. Jackson: High Nitrogen Austenltlc Cr-Mn Steels. Trans. ASM 119551 48, PP. 509-523.

Jan 1, 1957

By Donald Markle

ANTHRACOAL is a mixture of small particles of anthracite coal and a matrix of practically pure carbon, formed from the distillation of coal-tar pitch or other suitable bitumen. It is a hard, dense, homogeneous mass, with a silvery luster and in color varies from silvery to grayish black. When pushed from the oven, it develops only partly the fingerlike structure of coke; but, unlike coke, it has a tendency to remain in blocky masses. When struck with a hammer or passed through crushing rolls, it breaks with an irregular fracture, similar to anthracite, but with very little fines. Due to its density, anthracoal is harder, tougher, and stronger than coke. The results of a test made by the blast-furnace department, of the Bethlehem Steel Co., on two barrels of anthracoal are given in Table 1. TABLE I.-Results of Shatter Tests on Anthracoal and Coke Anthracoal Test Good Blast-furnace Coke First Second Barrel Barrel Moisture, per cent 0.77 0.76 Under 5, variation not over 3 points Sieve test Through 2-in. screen, per cent 7.71 7.29 Under 40 Through 1-in. screen, per cent 1.37 1.56 Through ½ -in. screen, percent 0.93 1.08 Under 8 Over 2-in. screen, per cent 92.29 92.71 Over 60 Shatter test Through 2-in. screen, per cent 10.06 &apos; 12.40 1 Under 16 Through 1-in. screen, per cent 2.66 2.06 Through ½ -in. screen, per cent 1.80 1.26 Over 2-in. screen, per cent Hardness number 86.40 86.10 Over 81 Analysis Ash, percent 16.64 16.48 Under 11 Sulfur, per cent 1.17 1.10 Under 0.95 Volatile matter, per cent 0.77 0.27 Fixed carbon, percent 82.59 83.25 Over 87

Jan 8, 1921

R. W. Raymond, New Pork, N. Y.:—I think Mr. Bache has put his finger on the chief source of the danger of dust-, or gas-and-dust, explosions in collieries. 1 mean the persistent determination of the miners&apos; unions to increase their weekly wages by the excessive use of explosives. This would not be feasible if coal-miners were paid by the day; but this form of payment is, for many reasons, not economically practicable; and the universal practice is to pay for the winning of coal according to the quantity produced. If the miner, by using a large amount of powder, can throw down a large amount of coal without corresponding labor on his own part in undercutting and drilling, he will receive more money for less work, provided he is paid for everything—merchantable coal, worth-less dust, slate, and " bone "—resulting from such a method. My attention was called to this matter many years ago by an admirable report of Prof. W. B. Potter, a past- President of the Institute, on the conditions obtaining in this respect in the Illinois coal-field. It was made very clear in that report that considerations of danger to workmen or loyalty to employers could not be relied upon to prevent miners from employing this perilous and wasteful method of increasing their own immediate receipts. So far as I know, only three remedies have been attempted, namely: the enforcement of discipline as to the methods of mining; the refusal to pay for dust, etc., produced by the miners&apos;methods; and restriction upon the use of explosives, effected by requiring the miner to purchase them from the employer, at a price so high as to make it unprofitable for him to use them in excess. All of these attempted remedies have encountered the bitter opposition of the miners&apos; unions. The enforcement of discipline has become almost impossible, if discipline be (as it should be) understood to involve punishment for the violation of rules when no disaster has followed. I

Jan 1, 1910

By J. C. M. Li

The steady state shape of a shrinking cylindrical grain boundary of miform boundary energy is shown to be circular. This is based on the principle of either the minimum rate of entropy production or the minimum thermokinetic potential. The circular shape corresponds also to a state of minimum (not maximum) velocity. The steady state shape of a grain boundary moving between two inclined surfaces is a circular cylindrical arc whose position and curvature will be afjected by the nature of the surfaces. The minimum thermokinetic potential is the only valid criterion in this case. THE preceding paper1 reports an interesting experiment in which it is shown that a grain boundary moving between two inclined surfaces assumes a circular cylindrical arc whose axis nearly coincides with the line of intersection of the two surfaces. The driving force is well defined since it is the energy of the grain boundary itself. The velocity of the grain boundary is found not to vary linearly with the driving force. Several interesting questions arise: 1) What principle determines the shape of a moving grain boundary? 2) What is the effect of the inclined surfaces? 3) How do we understand the nonlinear velocity-driving force relationship? It is attempted in this paper to discuss the first two questions based on irreversible thermodynamics and in a following paper to discuss the third question based on dislocation theory. STEADY STATE SHAPE OF A SHRINKING LOOP (A CYLINDRICAL GRAIN BOUNDARY) In irreversible thermodynamics, there are two criteria for the steady state. One is the minimum rate of entropy production2 which is based on the symmetry of phenomenological coefficients and is applicable to linear force-flux relations with constant coefficients. The other is the minimum thermokinetic potential3 which is based on the integrability of a certain Pfaffian differential equation and is applicable to nonlinear systems with variable coefficients. In the case of a shrinking grain boundary loop (a two dimensional version of a cylindrical grain), the flux of atoms across the grain boundary can be taken as the local boundary velocity v measured perpendicular to the boundary (the number of atoms transferred per unit area per second is equal to the product of atom density and the velocity of the boundary). The local thermodynamic driving force can be taken as y/p with y being the grain boundary energy (invariant with respect to the orientation and curvature of the grain boundary) and p being the radius of curvature. Such driving force can be understood by considering the loop as an elastic string with tension y. As shown in Fig. 1, across a length ds along the loop, the direction of y changes by an angle d@ which is ds/p. Because of this change of direction, the tension exerts a force perpendicular to the curve equal to yd@. The force per unit length is then y/p. According to the experimental observation, the velocity v is a power function of y/p, where M is the velocity at unit driving force and &apos;n is a constant. The rate of entropy production per ds along the loop is vyds/pT, where T is the temperature. For a given length L of the loop, the total rate of entropy production is The thermokinetic ptentia13 has only a differential definition and its existence depends on the integrability of this definition. In this case, Eq. [3] happens to be a total differential and the thermokinetic potential can be defined as which turns out to be the same as the rate of entropy production, Eq. [2], except for a constant factor n + 1. Strictly speaking, since the flux-force relation is not linear, the rate of entropy production may not be a minimum at the steady state. However, because of the proportionality between Eqs. [2] and 141, the state of minimum thermokinetic potential happens to be the same as that of minimum rate of entropy production. The steady state shape thus can be obtained by minimizing either integral [2] or [4] for a given L.

Jan 1, 1970

By Lewis W. MacNaughton

The North Texas district, as herein defined, includes the counties of Archer, Baylor, Clay, Cooke, Foard, Hardeman, Knox, Montague, Wichita, and Wilbarger. This area covers generally the crest and south flank of a system of buried mountains known as the Red River uplift. The oil and gas accumulations along this feature arc in traps, which, although localized by structures incident to the regional uplift, are usually modified by stratigraphic changes in the sediments. Excepting the fields in southeastern Baylor, southern Archer, and southwestern Clay counties, all the fields within the district are on this Red River uplift. These exceptions, which have the same type of oil and gas accumulation as the other fields, are on the extreme north end of the Bend arch, which is a broad anticline plunging northward from the Llano uplift in central Texas to Archer County. The larger part of past oil and gas production has come from Pennsylvanian strata, with less important amounts from the Permian, and minor but increasingly important quantities from the Ordovician. Developments during 1939 With the later stages of development being reached in the K.M.A. field during the first half of the year, some 400 fewer producing wells were drilled in North Texas in 1939 than in 1938, when some 1750 wells were drilled. Despite this decrease in activity, production in 1939 increased about 3½ million barrels over 1938 figures, and at the end of the year the oil reserves were somewhat larger than on the first of the year. As is usually characteristic of the district, this resulted from the discovery of a large number of relatively unimportant fields. Owing principally to no appreciable abatement in wildcat drilling, more new fields and extensions to old fields were discovered this year. Although none of these discoveries was of such magnitude as to be important to the oil industry, the new developments in Montague and Cooke Counties portend greater and probably more important operations in these areas.

Jan 1, 1940

By Lewis W. MacNaughton

The North Texas district, as herein defined, includes the counties of Archer, Baylor, Clay, Cooke, Foard, Hardeman, Knox, Montague, Wichita, and Wilbarger. This area covers generally the crest and south flank of a system of buried mountains known as the Red River uplift. The oil and gas accumulations along this feature arc in traps, which, although localized by structures incident to the regional uplift, are usually modified by stratigraphic changes in the sediments. Excepting the fields in southeastern Baylor, southern Archer, and southwestern Clay counties, all the fields within the district are on this Red River uplift. These exceptions, which have the same type of oil and gas accumulation as the other fields, are on the extreme north end of the Bend arch, which is a broad anticline plunging northward from the Llano uplift in central Texas to Archer County. The larger part of past oil and gas production has come from Pennsylvanian strata, with less important amounts from the Permian, and minor but increasingly important quantities from the Ordovician. Developments during 1939 With the later stages of development being reached in the K.M.A. field during the first half of the year, some 400 fewer producing wells were drilled in North Texas in 1939 than in 1938, when some 1750 wells were drilled. Despite this decrease in activity, production in 1939 increased about 3½ million barrels over 1938 figures, and at the end of the year the oil reserves were somewhat larger than on the first of the year. As is usually characteristic of the district, this resulted from the discovery of a large number of relatively unimportant fields. Owing principally to no appreciable abatement in wildcat drilling, more new fields and extensions to old fields were discovered this year. Although none of these discoveries was of such magnitude as to be important to the oil industry, the new developments in Montague and Cooke Counties portend greater and probably more important operations in these areas.

Jan 1, 1940

By Samuel Storchheim

IT was noted that variations existed in the magnetic properties, namely, coercive force, He, and rema-nence, Br, of 18/8 stainless steel wires of the same analysis when these wires were given the same percentage of reductiori of area at different rates of reduction. In order to determine the extent of these variations, a program was initiated whereby commercial 302 and 304 stainless steels were drawn with a wide variation of speeds. Ultimate tensile strengths and specific resistances, as well as the Hc-BT measurements, were determined. If variations of considerable magnitude were found, it was thought that the knowledge accrued from the investigation could probably aid in determining the particular drawing speed required to obtain desired properties for a given specification for a particular analysis of wire. Drawing Procedure Two specimens (set I, No. 302 and No. 304), the chemical analyses of which are given in Table I, were drawn at different speeds, namely, 45 to 3900 ft per min, directly from 0.016 in. diam wire to 0.004 in. diam wire, a 93.7 pct reduction of area. To obtain this high percentage of reduction, the wire at 0.016 in. was softened by annealing at 1150°C. It was then strung in a No. 16CF variable speed Vaughn drawing unit and passed through 13 B.&S. gage dies of successively smaller diameter, as shown in the accompanying table. Following this step, several hundred feet of the wire was drawn, at a particular speed, through the dies and wound upon a spool. Once the sample of wire was drawn at the desired speed, the spool with the finished sample was removed, tagged for later identification, and an empty spool was placed in the machine. Another wire sample was drawn at a different speed, after making the necessary adjustments upon the Vaughn unit. At the greater speeds, several thousand feet of sample were drawn to insure that the wire to be used for testing would be uniform. This was done because the desired speed was not reached instantly; the wire taking a short while to attain the required drawing rate. All speed measurements were made by placing a tachometer against one of the machine&apos;s pulleys during the actual drawing of the specimens. 84.4 pct reduction of area. The 0.072 in. diameter wire was also annealed at 1150°C. The process of obtaining samples was the same as described above. The only difference between the two was that the rates involved were not as extensive, set II covering a range of 625 to 1150 ft per min. Tensile tests were carried out for the 0.004 in. diam wires on a horizontal Scott Tensile Tester, while tensile tests for the 0.028 in. diam wires were made on a vertical Scott Tensile Tester. Each value listed in the tables represented the average of five samples with a maximum deviation of approximately 3 pct among the samples. Resistance per foot of the wires was determined by use of standard bridges accurate to the nearest hundreth of an ohm for the 0.004 in. wire, and to the nearest thousandth of an ohm for the 0.028 in. wire. The resistances per foot were then converted to resistivities by use of the following equation: P = RxCM where R is the resistance per ft in ohms per ft; CM, the area in circular mils; and P, the resistivity in ohms—CM. The values listed in the tables likewise

Jan 1, 1952

By F. F. Aplan

Mineral processing engineers have recorded an- other year of active research and development work. Most gratifying was the broadly based attendance at the Mineral Processing Fundamental (formerly Basic Science) Committee sessions at the 1968 Annual Meeting of the AIME. Because of the availability of good papers, the active discussion and the growing attendance, sessions have grown from one to three at the annual meeting. Prof. M. C. Fuerstenau of the University of Utah will chair the Mineral Processing Fundamentals Committee for the next two years and we may thus be assured of continued active leadership. The name change from "Basic Science Committee" to the more descriptive "Mineral Processing Fundamentals Committee" approved by the MBD executive council is a welcome improvement. Our profession continues to attract the interest and cooperation of those in other professional groups. The 1968 Engineering Foundation Particulate Matter Conference, under the chairmanship of John Karpinski of Bethlehem Steel, was devoted exclusively to comminution this year. It attracted conferees from five continents and served as a particularly stimulating source of interchange of knowledge from many technical fields. Next year&apos;s conference will be under the chairmanship of Professor L,. G. Austin of The Pennsylvania State University. This conference plus the Symposium on Wettability and Flotation to be held at the annual American Chemical Society meeting in Minneapolis in April indicates the success achieved in the inter-disciplinary approach to problems. Other evidence of this spirit of professional cooperation is the forth- coming book on Size Reduction edited by D. W. Fuerstenau. This is the outgrowth of an AIChE symposium on size reduction held in 1965.

Jan 2, 1969

PHILIP D. BLOCK, JR., vice president of Inland Steel Co., visualizes a fine future for the Menominee Range of the Upper Peninsula of Michigan. He sees a future unclouded by threat from foreign ore imports or the development of low grade ore processing in Minnesota. The statement was made during the opening of Inland&apos;s new Cayia mine near Crystal Falls. Inland, according to the vice president, is planning to use an increased amount of the high phosphorous ores found on the Menominee Range. He said that other steel companies will probably do the same, because the steel industry has learned how to use ores of high phosphorous content. He said: "I do not mean to imply that we can use an unlimited amount of high phosphorous ores or that we can burden our blast, furnaces with 100 pct high phosphorous ores, but we have reached the point where we can absorb a much larger percentage of these ores without any detrimental effects. Foreign ores and lowgrade Minnesota ores cost too much to offer real competition, Block said. Transportation costs from the Menominee range to steel producing centers in Chicago and on Lake Erie are less than for any other range in this country. In the meantime, the American operators of the Bomi Hills iron ore mine in Liberia, have reportedly signed a new agreement with the Government. Several months ago, President Tubman of Liberia expressed a definite dissatisfaction with the original contract. Informants state that the agreement only needs the approval of the Export-Import Bank, which loaned Liberian Mining Co. $4 million to develop the iron ore properties. Majority stockholder of the Liberian Mining is Republic steel, with 61.57 pct of the stock. Under the new contract, the Liberian Government will start to share in the profits when the indebtedness is liquidated and the return of invested capital accomplished, or April 1, 1957, whichever is earlier. Under the old agreement the Liberian Government received a 5 cent per ton royalty and an additional sum based on the price of pig iron. The royalty rate reached more than 17 cents per ton this year. After debt liquidation the Liberian Government will receive 25 pct of net profits for the first five years; 35 pct for the next ten years; and 50 pct thereafter. Until the Government starts to share in profits it will receive a royalty of $1.50 per ton in U. S. currency, in addition to royalties provided for in the old agreement.

Jan 1, 1952

By ROBERT. RICHARDS

I. INTRODUCTION The object of this paper is to enlarge the field of settling velocities treated by me in my former papers, Close Sizing Before Jigging, and Sorting Before Sizing.&apos; There seemed need of work both on coarser and on finer sizes. Messrs. A. Sidney Warren and M. L. Nagel undertook the investigation for the coarser sizes, from 12.85 mm. down to 2.05 mm. diameter. Their work, because of the closer spacing and because of the increased number of observations and consequent stronger averages, called for a revision of the former work. Messrs. G., A. Barnaby and Ralph Hayden undertook this part of the work, from 2.49 mm. down to 0.28 mm., which is near the limit of sifting. Their work covers the ground much more minutely and comprehensively than the former papers. There remained to be covered the portion of the field too fine for investigation with the sieves. This part, covering the range of grains from 0.48 to 0.03 mm., was undertaken by Mr. E. S. Bardwell. For it he used the elutriation method. II. THE FIRST, OR COARSEST, SECTION OF THE FIELD. The first desideratum in this investigation was a series of sieves for sizing the sands preparatory to making the tests. It became necessary, therefore, to decide on a sieve-scale for this purpose. A sieve-scale is a series of sieves in which the dimensions of the holes of the successive members form a series increasing by a. definite ratio. There are three natural sieve-scales : 1, progressing by doubling the width of the hole for each suc-

May 1, 1907