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By H. W. Gillett

Many of the parts of motor cars, aircraft, etc., that require strong light construction, hence must be made of high-quality steel, are stressed to the maximum limit only in a very small volume. In parts subject to bending stress a line or even a point may take the maximum stress. A series of endurance tests under repeated bending in progress in the U. S. Bureau of Mines laboratories, like similar tests by other investigators, has shown the great difference in life of sister bars of the same stecl, handled in the same way and tested at the same nominal stress. It is known that a surface notch or scratch greatly increases the local stress over the nominal calculated stress; internal notches, such as those formed by inclusions or sonims, probably have a similar effect. From the tetss made by the Bureau of Mines, the cleanliness of the steel at the dangerous section, or point of maximum stress, seems to be one of the most important factors in determining the life of the piece. The more localized the stress, the more does chance, rather than the average properties, dctermine the life of the steel. The usual test, a tension test of a bar taken longitudinally, is not sensitive to the local drop in strength (or tendency to increase the true local stress over the nominal) because of inclusions, which probably have a more injurious effect in hard heat-treated steels, such as must be used when great strength is sought, than in softer steels. Users of steel who make transverse tests find surprisingly low ductility on transverse bars of dirty steel, though the longitudinal tests may be good. Bending tests, reverse bending tests, and notch-bar impact tests,

Jan 1, 1923

By H. W. Gillett

Many of the parts of motor cars, aircraft, etc., that require strong light construction, hence must be made of high-quality steel, are stressed to the maximum limit only in a very small volume. In parts subject to bending stress a line or even a point may take the maximum stress. A series of endurance tests under repeated bending in progress in the U. S. Bureau of Mines laboratories, like similar tests by other investigators, has shown the great difference in life of sister bars of the same stecl, handled in the same way and tested at the same nominal stress. It is known that a surface notch or scratch greatly increases the local stress over the nominal calculated stress; internal notches, such as those formed by inclusions or sonims, probably have a similar effect. From the tetss made by the Bureau of Mines, the cleanliness of the steel at the dangerous section, or point of maximum stress, seems to be one of the most important factors in determining the life of the piece. The more localized the stress, the more does chance, rather than the average properties, dctermine the life of the steel. The usual test, a tension test of a bar taken longitudinally, is not sensitive to the local drop in strength (or tendency to increase the true local stress over the nominal) because of inclusions, which probably have a more injurious effect in hard heat-treated steels, such as must be used when great strength is sought, than in softer steels. Users of steel who make transverse tests find surprisingly low ductility on transverse bars of dirty steel, though the longitudinal tests may be good. Bending tests, reverse bending tests, and notch-bar impact tests,

Jan 1, 1923

By C. C. Harris

This article presents a general equation describing the xYt surface in batch grinding. This equation contains as special cases most of the relationships which have been deduced from kinetic studies. In an earlier paper an analytical solution of the integro-differential equation of batch grinding was proposed1 as a first approximation of the xYt surface.' A more general equation will be presented here, which appears to combine in a single statement many conclusions reached by experiment. A possible underlying mechanism is that the changing product fineness leads to changes in the particle crushing strength and in the probability of encounter with the crushing media.

Jan 1, 1969

By Linn Bradley, W. W. Strong, H. D. Egbert

A hot-dry method of cleaning the gas from blast furnaces has been shown1 to conserve the sensible heat energy of the gas, and in general it thus permits of a higher flame temperature. The electrical method of cleaning gases removes from 98 to 99 per cent. of the suspended matter in one operation when operating properly, thus making possible the use of a very clean gas for burning in the stoves. The use of such clean gas thus makes feasible a different type of hot-blast stove construction from that being used at present. It therefore seems advisable to construct the stoves from the viewpoint of getting the maximum amount of heat energy into the products of combustion. By preheating the air added to the top gas and obtaining a better mixture of the air and top gas, less excess air will be required and a higher flame temperature obtained from the combustion of the top gas. The interior of the stove should be provided with a kind of brick that will withstand a high flame temperature, will conduct the heat energy along certain directions, insulate the flow of heat along other directions and at the same time store heat energy so as to make the flow of such energy more uniform. It is quite likely that these results can be best obtained by using several kinds of bricks: one type which is a good insulator of heat energy to be used for lining the stove and for making partitions through the stove to restrain the flow of heat; another type of brick or material with high refractory qualities; and a third type which will be a good conductor of heat energy. The surface of the stove exposed to the atmosphere should be a minimum in comparison to the mass of checkerwork which it is possible to obtain, due regard being paid to other conditions. With clean and hot furnace top gas it will be advisable to consider a rearrangement of the checker work in the stoves. One season for the present size and shape of checker openings is to provide facility for

Jan 1, 1917

MAY 17-The last bit of verbal sod had hardly come to rest on the grave of the coal industry-which grave was being eagerly dug with typewriters and microphones by administration hangers-on and even an operator or two-when its leaders gathered for the 1950 Coal Convention of the AMC in Cincinnati on April 24. Surprisingly, mourning clothes were not being worn but the boys had on their diggers preparatory to digging their way out from under the muck. High costs created by wage and welfare demands, together with work stoppages, have caused markets to shrink, but even so, an optimistic air still prevailed as new techniques were disclosed at technical sessions. The administration, however, came in for its share of knocks.

Jan 6, 1950

The Honor Roll includes the names of all members of the Institute whom we know to be on active military duty at the date of its compilation, February 7, 1918. We are aware that there are many others of whose activities we have not been informed, and we shall be grateful for information as to any such omissions from the Roll. 1. MEMBERS ON ACTIVE MILITARY SERVICE Mail addressed to members on the first division of the Roll and sent to the office of the Institute Will be forwarded according to the best of our knowledge at the time. AARONS, J. BOYD, Capt., 4th Reinforcements, 11th Infantry, Australian Imperial Force. '05 ADAMS, HENRY, Capt Asst. to Dept. Engr., Northeastern Department. '02 AGNEW, FRANK VANS '04 ARBE, FREDERICK R., Capt 33d Engineers. '97 ALDER, ALFRED Engineers' Reserve Corps. '17 ALFORD, NEWELL G., Sgt., Bureau of War Risk Insurance, Headquarters 84th Division. '14 ALLEN, HEMAN H., Private Co. D., 8th Reserve Engineers. '17 AMBLER, HARRY A., Lieut 30th Infantry. '16 ANDERSON, ALEXANDER, Lieut Royal Garrison Artillery. '07 ANDERSON, GEORGE K., JR., See. C, 1st Co., 3d Officers' Training Camp. '17 ANDREWS, CLARENCE W., 1st Infantry Co., Officers' Training Camp, 83d Division. '13

Jan 1, 1923

By AIME AIME

TRAINED as a mining engineer and with no little experience in the field of mining, his interests and activities later transferred to the alloying, fabrication, and physical metallurgy of nonferrous metals, principally silver, Robert H. Leach represents in his professional life both of the major phases of the fraternity of mining and metallurgical engineers. In his personal characteristics, his wide circle of true friendships, his kindly, sympathetic interest in the problems of his fellow engineers, be they the junior men of the mineral industries or the mature and experienced men, he typifies the characteristics and attitude so desirable in the professional man.

Jan 1, 1939

By H. H. Rachford, and J. D. Rice

The effectiveness of digital computing machines in making technical calculations depends on how well the work is arranged to utilize the capability of the machines. This note presents a particularly useful way of calculating hydrocarbon vapor-li.quid equilibrium in the flash vaporization (or condensation) system. The method is well suited to sequence-controlled computing equipment. It is not limited to equilibrium calculations and may be used for solution of most implicit equations in one variable. INTRODUCTION There is increasing interest in the use of electronic digital computers in research and engineering calculations. This is a fortunate and inevitable trend in view of both the increasingly extensive numerical work which is becoming a routine part of many daily production operations and growing demand for the overwhelming amounts of calculations required by newly developed numerical methods for solving heretofore unsolved problems. Machines are in many ways ideally suited to the task but of necessity present certain difficulties. for a particular poblem to be solved must often be formulated quite differently from the way it would be arranged for manual solution. This is done in order to take advantage of the inherent speed and precision of electronic computers and at the same time to limit the need for number storage to the capacity of the machine. Therefore, this note is submitted to present a general and quite powerful method of finding solutions of the frequently encountered implicit equation: F(x,y1,y2,...ya)=0.......(1) where the root, x, is to be found for a given set of y1, ... yn.. The procedure is well suited for use with computing machines, for it usually requires but little storage or programming beyond that necessary to evaluate F. HYDROCARBON EQUILIBRIUM The method is described in terms of the problem it was designed to solve, i.e., the calculation of hydrocarbon vapor-liquid equilibrium in flash vaporization. Given the composition of a hydrocarbon mixture and appropriate values of the equilibrium ratios K, to find the phase ratio and compositions in a closed system: let z, be the mol fraction of the i-th component in the mixture. If K, is the ratio yl/xl, where y, and x,

Jan 1, 1952

By C. D. King

THE key to maximum production of ingots for the war effort is maximum production of pig iron. For any given furnace and ore, the most important single influence on blast-furnace production is the quality of the furnace coke. It is generally recognized that undoubtedly deterioration of Pittsburgh coking coals will be accelerated by the depletion of some of the better grades of coal; the extension of mine mechanization, with attendant degradation of coal quality; and the opening of new coal fields, some of which are known to be fairly high in sulphur. All of these factors, contributing as they do to higher ash and sulphur, and not infrequently to inferior quality of coke, made it desirable that an extensive study be undertaken to determine the effect of washing some coals that closely approximate the average chemical composition of coking coals to be expected in the future by the subsidiaries of the United States Steel Corporation in the Pittsburgh district. It was deemed advisable to study the improvement obtained by washing such coals and to determine the need for supplementing the existing coal washery at Clairton to assure continued maximum production of pig iron from presently available furnace stacks. The existence of the coal washer at Clairton made it possible to conduct tests on coals used in raw form and on similar coals after washing. This study covers an investigation of the quality of furnace coke as affected by washing coking coals, and is confined to the use of IOO per cent high-volatile Pittsburgh seam coals from Fayette and Greene Counties in the manufacture of furnace coke. It covers the improvement in chemical and physical properties as well as the degree of uniformity in coke obtained by washing these coals, and includes the effect on blast-furnace production and practice. The test period involved is four months; the plants, Clairton by-product coke plant, and the Carrie No. I and No. 2 blast furnaces at Rankin, Pa., Carnegie- Illinois Steel Corporation. Clairton By-Product Coke Plant And Coal Washer The Clairton by-product coke plant carbonizes 30,800 net tons of coal daily in 22 batteries containing 1482 ovens. Three oven sizes are used, commonly known as wide, medium, and narrow types, recognizing the difference in oven width. These ovens also differ in height and length. The present coal washer has a daily capacity of approximately 14,000 tons, leaving 16,800 tons to be carbonized in raw form. Washed coal is used on all the narrow ovens and on three of the six batteries with ovens of medium width, raw coals being used on all the remaining ovens. The customary arrangement is

Jan 1, 1944

By H. W. Hitzrot

THE new 4800-ton fine-grinding plant at the Hollinger Consolidated Gold Mines property at Timmins, in the Porcupine district of northern Ontario, went into operation in November 1937, and represents the culmination of an experimental program. The plant is a moderately low rectangular building of hollow tile on a steel frame, large enough to house four 7 by 15-ft. ball mills, with a 12 by 27-ft. classifier beside each mill. At one end is space for the addi-tion of another mill and classifier or a mill and classifier for the regrinding of table concentrates. This regrinding is now done in the old grinding department of the main mill building. Also within the new building are the four 6-in. sand pumps for lifting the product from the low-dis-charge ball mills up to the classifier feed launders and the containers and appurtenances of a complete dust-collecting system. Together with the usual overhead crane, these constitute the major units of equipment within the new plant. The location is at the lower end of the main mill buildings toward the old tailings pond, now so neatly leveled off and sodded to rival the very best of our own W.P.A. projects. Close by the new grinding plant is a large dome-shaped structure-the new fine-ore bin designed and built by Mr. Longmore and the Hollinger milling and engineering staffs. There are four separate automatically loaded inclined belt conveyors leading up from the bottom of the bin to the grinding plant. Each belt is equipped with a recording weightometer, in the grinding building. The whole structure and the machinery within it give the impression of permanence and a carefully integrated design with close attention to details, giving the operators every advantage for consistently good work.

Jan 1, 1939

By Wilford S. Wright

FOR the past four years the management of the Black Hawk Consolidated Mines plant at Mogollon has conscientiously kept accurate records pertaining to cost of operation and the performance of certain equipment. These records have been valuable in coordinating the work in the mine, mill and power plant. Also, as to quantity and kind of equipment and supplies most suitable from the standpoint of economy and dependable operation, they have served as a guide. Through comparison with records at other mines, where the same things are being done in a different way, they have pointed out mistakes to be avoided. No outstanding accomplishments, either in costs or performances, are revealed; in fact, some of the results are perhaps quite inferior to those obtained at similar plants, but it is with the thought that more records should be published for the benefit of the mining profession that the author presents these data. To other operators and to mining engineers who are called upon to make estimates for prospective operations, the information herein should be helpful. GENERAL CONDITIONS Mogollon is in the southern part of Catron County, southwestern New Mexico. It lies near the western border of the Mogollon Range, 14 miles east of the Arizona line. Silver City, 80 miles to the southeast, is the nearest railroad point. The connecting road, over which supplies are hauled into camp by trucks, is an improved highway for about 50 miles; the remainder consists of graveled roads and unimproved steep mountain grades. One general supply truck and one tank truck make daily round trips. Hauling of supplies to the mine has cost at the rate of $0.08 per ton-mile; or, on the basis of ore production, $0.30 per ton mined. Lumber, hauled in from local mills, has cost an average of $30.00 per 1000 board feet, $8.50 of which has been for hauling. The annual consumption averages 108,000 board feet. Lime, hauled from a plant in Arizona, is about the only other item not brought out from Silver City. Fuel oil for the generation of power is the item of greatest hauling expense, the f.o.b. Mogollon cost of approximately $0.06 per gal. being nearly twice the f.o.b. refinery price. Water for power plant, mill and camp use flows to camp storage tanks through a 4-in. pipe line from a spring and intake 3 miles up Silver Creek Canyon. A few times, particularly in the month of June, mill operations have been suspended for two or three days because of water shortage. MINING CONDITIONS During the years 1938, 1939, 1940 and 1941, the mine produced 230,059 dry tons

Jan 1, 1943

By Paul A. Beck, John Towers, W. D. Manly

Recent work on grain growth in high purity aluminum and in a solid solution type alloy of aluminum and magnesium1 showed that the isothermal increase of the average grain diameter D with time follows the equation D = K(tg + A)2 Eq 1 Here tg is that portion of the total annealing time 1, which is available for grain growth, that is the annealing time less the time necessary for complete recrystallization. The parameters A and n depend only on the temperature. A has the dimension of time, and is usually of the same order of magnitude as the time for recrystallization: R. In some instances R may be substituted for A in Eq I. This is the case for example at long periods of annealing or at high temperatures, where both A and R become small in comparison with t. In such instances Eq I is simplified to D = K, tn Eq 2 For high purity aluminum the exponent n increases in the ratio of about I to 5 in. the temperature range of 350' to 6w°C. 70-30 brass has been long known to exhibit grain growth of the continuous type, such as occurs in pure metals. For this reason, it was of interest to determine whether grain growth in brass also follows Eq I and 2 as it does in aluminum. Isotherma1 grain growth data for 70-30 brass were published in recent years by R. S. French2 and by H. L. Walker.' Fig I shows a log D vs. log t plot of French's data, together with the 500, 600 and 700°C data by Walker for 42.8 pct reduction by rolling. In such a log D vs. log t plot Eq 2 corresponds to a straight line with a slope of n. As seen in Fig I, the data of French and the 600°C data of Walker can be represented by straight lines. However, the 500 and 7c0°C data of Walker give curved lines and the average slope of his 500°C line is very different from the slope of the line representing French's data for the same temperature. Furthermore the curvature of the 700°C line suggests a tendency for grain growth to stop after 8 hr. If confirmed, this would constitute a definite deviation from Eq 2, not explainable on the basis of the specimen thickness effect found in high purity aluminum.' Walker's specimens were 0.125 in., or 3.18 mm thick, while the deviation occurs at a grain size of approximately 0.4 mm. A further point of divergence arose recently, when J. E. Burke suggested4 on the basis of Walker's data, that, instead of Eq 2, grain growth in 70-30 brass follows the equation D - D, = K . tgn Eq 3 Here D, is the grain size as recrystallized at the temperature in question. Although it was possible to show5 that, for pure aluminum, for which isothermal grain growth has been carefully investigated, Eq 3 is incompatible with the experimental facts, the situation remained somewhat obscure with respect to 70-30 brass. In view of the discrepancies between the published data on brass from different

Jan 1, 1949

By John Towers, Paul A. Beck, W. D. Manly

Recent work on grain growth in high purity aluminum and in a solid solution type alloy of aluminum and magnesium1 showed that the isothermal increase of the average grain diameter D with time follows the equation D = K(tg + A)2 Eq 1 Here tg is that portion of the total annealing time 1, which is available for grain growth, that is the annealing time less the time necessary for complete recrystallization. The parameters A and n depend only on the temperature. A has the dimension of time, and is usually of the same order of magnitude as the time for recrystallization: R. In some instances R may be substituted for A in Eq I. This is the case for example at long periods of annealing or at high temperatures, where both A and R become small in comparison with t. In such instances Eq I is simplified to D = K, tn Eq 2 For high purity aluminum the exponent n increases in the ratio of about I to 5 in. the temperature range of 350' to 6w°C. 70-30 brass has been long known to exhibit grain growth of the continuous type, such as occurs in pure metals. For this reason, it was of interest to determine whether grain growth in brass also follows Eq I and 2 as it does in aluminum. Isotherma1 grain growth data for 70-30 brass were published in recent years by R. S. French2 and by H. L. Walker.' Fig I shows a log D vs. log t plot of French's data, together with the 500, 600 and 700°C data by Walker for 42.8 pct reduction by rolling. In such a log D vs. log t plot Eq 2 corresponds to a straight line with a slope of n. As seen in Fig I, the data of French and the 600°C data of Walker can be represented by straight lines. However, the 500 and 7c0°C data of Walker give curved lines and the average slope of his 500°C line is very different from the slope of the line representing French's data for the same temperature. Furthermore the curvature of the 700°C line suggests a tendency for grain growth to stop after 8 hr. If confirmed, this would constitute a definite deviation from Eq 2, not explainable on the basis of the specimen thickness effect found in high purity aluminum.' Walker's specimens were 0.125 in., or 3.18 mm thick, while the deviation occurs at a grain size of approximately 0.4 mm. A further point of divergence arose recently, when J. E. Burke suggested4 on the basis of Walker's data, that, instead of Eq 2, grain growth in 70-30 brass follows the equation D - D, = K . tgn Eq 3 Here D, is the grain size as recrystallized at the temperature in question. Although it was possible to show5 that, for pure aluminum, for which isothermal grain growth has been carefully investigated, Eq 3 is incompatible with the experimental facts, the situation remained somewhat obscure with respect to 70-30 brass. In view of the discrepancies between the published data on brass from different

Jan 1, 1949

By A. H. Geisler

INTRODUCTION THE correlation of property changes during precipitation with structure has progressed, sometimes rapidly but other times more slowly, since the fundamental discovery of Merica, Waltenberg and Scott.1 The predominent factor that hampered the progress has been limitations imposed by the various detection methods. Refinements in X ray diffraction techniques and in metallographic methods, which have been extended by the electron microscope, have contributed new information within the last few years. These permit an extension of the theory as proposed by Mehl and fetter in 1940.2 Now that a suffcient number of alloys has been investigated to establish a general mechanism of the precipitation process, a correlation of the facts into a generally applicable theory of age-hardening is both warranted and desirable. 'I he purpose of the paper is to provide an orderly correlation of the phenomenological facts of precipitation hardening. Speculation on mechanism of hardening will be confined to that consistent with existing theories of hardening. Age-hardening accompanies the formation of a new structure, the precipitate, as provided by an alloy system in which solid solubility decreases with decreasing temperature. Upon this premise alone all such systems would be expected to include age-hardenable alloys. Alas, this is not always the case. Few attempts have been made to explain the variable degree of age-hardening among different alloys or to explain the influence of small alloying additions upon the hardening. Dispersion hardening as originally postulated3 is not adequate.* Coherency hardening-the term that will be used to distinguish the properties of a two-phase mixture in the unique and unstable transition state at which the phases are strained into precise atomic registry (continuity or coherency) in planes

Jan 1, 1948

By A. R. Gregory, A. L. Podio, K. E. Gray

Dynamic elastic properties of dry and water-saturated Green River shale samples were computed from compressional- and shear-wave velocity measurements. P- and 5-wave velocity measurements were made in three mutually perpendicular directions with respect to the bedding planes. Measurements were also made in several different directions by varying the angle between the bedding planes and the direction of propagation of the wave for angles of 0, 30, 45, 60 and 909 The oriented samples were subjected to both confining pressure and axial loads, in excess of the confining stress, in the direction of propagation. In general, P- and S-wave velocities increased with increasing stress levels, with a corresponding increase in Young's modulus. Water saturation caused the P-wave velocity to increase and the S-wave velocity to decrease. Elastic moduli decreased upon saturation, except for Pois son's ratio, which increased, indicating some degree of weakening of the material. The samples showed a moderate degree of anisotropy; this was to be expected from the laminated nature and shallow occurrence of Green River shale. INTRODUCTION This paper presents some results of an experimental determination of the elastic coefficients of anisotropic materials (in particular, finely layered rocks and minerals such as Green River shale) from measurements of dilatational and shear-ultrasonic-wave velocities. Ultrasonic techniques have been used extensively in nondestructive testing. Several methods have been proposed by Mcskimmin, 1 and some of these have been used successfully to measure ultrasonic velocities in rocks. Hughes and Cross, 2 Wyllie et al., 3 and Birch 4,5 developed pulse first-arrival techniques for the measurement of dilatational and shear velocities. Williams and Lamb 6 used the method of cancellation of a traveling wave, which was later modified by Myers et al.' and perfected by McSkimmin. 8 Although this method is highly accurate, it has not been used as widely as the pulse-transmission methods recently reported by Jamieson and Hoskins 9 King,10 and Mattaboni and Schreiber. 11 It has been common practice to use some form of crystal transducers, either quartz or ceramic, that has been cut or polarized in different directions in order to generate either compressional or shear waves. However, accurate determination of shear wave velocities has been difficult due to problems that arise in obtaining a pure shear wave from cross-polarized crystals, which usually also generate a small amount of compressional energy. As reported by Gregory, 12 this energy can be seen as a long precursor preceding the sharp break of the shear first arrival. The need for generating pure shear waves led to interest in mode-conversion techniques, which are based upon conversion of the mode of vibration through wave reflection or refraction at a discontinuity. Arenberg13 showed that for certain materials and for certain angles of incidence it is possible to generate pure shear modes by reflection at a boundary. Jamieson and Hoskins 9 used a pyrex glass-air interface for generating pure shear waves, and King 10 used this method successfully for measuring shear-wave velocities in rocks. Gregory l4 arrived at a similar result by refraction of a wave at an aluminum-oil interface. A plane compressional wave, traveling in the oil phase, is incident on the aluminum at an angle larger than the critical angle for compressional waves, and thereby generates a purely transverse, plane-polarized wave in the aluminum. During the last few years methods have been developed that allow the simultaneous determination of shear and compressional velocities in solids.

Jan 1, 1969

By Jack White

MUFULIRA Copper Mines, Limited, conducted tests on the concentrator in 1942 to determine which type of ball mill, that is, Conical Trunnion overflow or Cylindrical Grate discharge, produced the greater quantity of finished product at the lowest cost. All the data which follows applies to Mufulira ore and to the particular degree of grinding produced with the classifiers installed at Mufulira concentrator. JACK WHITE, Member AIME, is Concentrator Superzntendent, Mufulira Copper Mines, Ltd., Mufulira, Nortltern Rhodesia. Sun Francisco Meeting, February 1949. TP 2729 B. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Feb. 28, 1949. Test Procedure: The test was carried out using ball mills No. 1 to 9 (conical trunnion overflow) as the standard with which to compare No. 10 (cylindrical grate discharge mill). The conical trunnion overflow ball mills are 10 ft diam by 72 in., and the cylindrical grate discharge mill is a No. 99. Each mill runs in closed circuit with a Dorr type DSFX classifier 8 ft wide by 30 ft long. The feed is considered as being identical to all ten units. The figures for the test were derived as follows. Dry Tons Milled: For No. 10 unit (cylindrical grate discharge mill) this figure was taken from the ball mill weightometer, which was corrected for error, and then for moisture content. The weightorneter was checked twice a week during the test, and the error did not exceed 3 pct at any time. The moisture was obtained from a 24 hr moisture sample taken by the ball mill operator hourly, and placed in a closed bucket. The sample was cut where the conveyor drops the feed into the ball mill chute. The Mill Sampling Department made a daily moisture determination on this sample. To obtain the dry tons on units No. 1 to 9 the No. 10 figure was deducted from the month's dry tons milled figure, which, in turn, was taken from the crusher weightometer tons corrected for weightometer error and moisture. All tons reported in this test are short tons of 2000 lb. Ball Mill Hours: This was taken daily from the Shift Boss reports giving actual running hours for each unit. Screen Analyses: Coarse Heads (Ball Mill Feed): The monthly composite coarse heads screen analysis, done by the Mill Sampling Department, was used for the minus 200 mesh in the feed to the mills. F. X. Classifier Overflow: The ball mill operators took an hourly 24 hr sample of the overflows of units No. 1 to 9. This was a hand sample, but cut with a special cutter, and is believed to be very reliable. On No. 10 unit, an hourly 24 hr sample, and an hourly shift sample were cut in the same way. These five samples were split, filtered, and dried by the Research Department and were then wet screened on a 200 mesh screen. The average of the three shifts samples on No. 10 unit had to check the 24 hr sample within 1.5 pct to be acceptable. A weighted composite was cut each day from both 24 hr samples, and at the end of each month it was screened as follows: Wet screened through 325 mesh, the plus 325 then screened on a rotap for 15 min through 65, 100, 150, 200, and 325. This was done in duplicate. All splitting, drying, and screening of samples was done by one of the Mill Research staff, to insure accuracy. F. X. Classifier Overflow Densities: These were taken from the Shift Boss reports. Densities were taken by the ball mill operator every hour. Circulating Loads: These were taken a number of times during the test both by direct method (weighing a measured portion of classifier rake sand, and deducting moisture) and by calculation using the formula:

Jan 1, 1951

By Jack White

MUFULIRA Copper Mines, Limited, conducted tests on the concentrator in 1942 to determine which type of ball mill, that is, Conical Trunnion overflow or Cylindrical Grate discharge, produced the greater quantity of finished product at the lowest cost. All the data which follows applies to Mufulira ore and to the particular degree of grinding produced with the classifiers installed at Mufulira concentrator. JACK WHITE, Member AIME, is Concentrator Superzntendent, Mufulira Copper Mines, Ltd., Mufulira, Nortltern Rhodesia. Sun Francisco Meeting, February 1949. TP 2729 B. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Feb. 28, 1949. Test Procedure: The test was carried out using ball mills No. 1 to 9 (conical trunnion overflow) as the standard with which to compare No. 10 (cylindrical grate discharge mill). The conical trunnion overflow ball mills are 10 ft diam by 72 in., and the cylindrical grate discharge mill is a No. 99. Each mill runs in closed circuit with a Dorr type DSFX classifier 8 ft wide by 30 ft long. The feed is considered as being identical to all ten units. The figures for the test were derived as follows. Dry Tons Milled: For No. 10 unit (cylindrical grate discharge mill) this figure was taken from the ball mill weightometer, which was corrected for error, and then for moisture content. The weightorneter was checked twice a week during the test, and the error did not exceed 3 pct at any time. The moisture was obtained from a 24 hr moisture sample taken by the ball mill operator hourly, and placed in a closed bucket. The sample was cut where the conveyor drops the feed into the ball mill chute. The Mill Sampling Department made a daily moisture determination on this sample. To obtain the dry tons on units No. 1 to 9 the No. 10 figure was deducted from the month's dry tons milled figure, which, in turn, was taken from the crusher weightometer tons corrected for weightometer error and moisture. All tons reported in this test are short tons of 2000 lb. Ball Mill Hours: This was taken daily from the Shift Boss reports giving actual running hours for each unit. Screen Analyses: Coarse Heads (Ball Mill Feed): The monthly composite coarse heads screen analysis, done by the Mill Sampling Department, was used for the minus 200 mesh in the feed to the mills. F. X. Classifier Overflow: The ball mill operators took an hourly 24 hr sample of the overflows of units No. 1 to 9. This was a hand sample, but cut with a special cutter, and is believed to be very reliable. On No. 10 unit, an hourly 24 hr sample, and an hourly shift sample were cut in the same way. These five samples were split, filtered, and dried by the Research Department and were then wet screened on a 200 mesh screen. The average of the three shifts samples on No. 10 unit had to check the 24 hr sample within 1.5 pct to be acceptable. A weighted composite was cut each day from both 24 hr samples, and at the end of each month it was screened as follows: Wet screened through 325 mesh, the plus 325 then screened on a rotap for 15 min through 65, 100, 150, 200, and 325. This was done in duplicate. All splitting, drying, and screening of samples was done by one of the Mill Research staff, to insure accuracy. F. X. Classifier Overflow Densities: These were taken from the Shift Boss reports. Densities were taken by the ball mill operator every hour. Circulating Loads: These were taken a number of times during the test both by direct method (weighing a measured portion of classifier rake sand, and deducting moisture) and by calculation using the formula:

Jan 1, 1951

By O. Hoover, M. Herman, V. V. Damiano

The Jetter and borie' teclznique of determining textures using a spherical specimen has been applied to tlze study of compression-rolled beryllium sheet. Snzall spheres the order of 1 mm in diam cut from the beryllium sheet were autotnatically rotated about tz41o axes using the G.E. single-crystal goniometer. Quantitative pole figures were obtained without tke need to apply absorption corrections. Compression-rolled beryllium exhibited peak intensities ,for (0002) planes of positions tilted 10 deg to the rolling plane and a near random distribution of (1010) planes about the nornal to the rolling plane. TECHNIQUES for determining textures of rolled sheet material are amply described in the literature. The techniques are found to be variations of two basic methods. One due to Decker, Asp, and arker, referred to as the transmission method, utilizes a thin-sheet specimen in which the X-ray beam enters the specimen from one side and the intensity of the beam which emerges from the opposite side is measured. The second method due to chulz,3 referred to as the reflection method, utilizes a thick specimen and the intensity of the beam emerging from the same side is measured. The two rotations of the specimen in the beam are designated a and 8. In order to completely determine the texture of sheet material, it is generally necessary to use a combination of the two methods. The calculations involved in correcting the raw X-ray data for absorption effects and the combining of the data obtained by the two methods are very laborious and time consuming. To avoid the intensity corrections which arise as a result of the changing diffraction volume and path length within the sample other methods have been proposed. The Norton method utilizes a cylindrically shaped specimen cut from the sheet material. Since the rods have rotational symmetry, the absorption correction is constant for rotations about the sheet texture. Jetter and Borie' employed a spherical specimen to analyze the fiber texture of extruded aluminum rods. The spheres were rotated rapidly about the fiber axis to include a large number of grains in the X-ray beam and changes in intensity with respect to tilts of the fiber axis were measured. The absorption correction was constant for all angles and was neglected. The Jetter and Borie' technique finds excellent ap- plication to very fine-grained low-absorbing metals in which the entire sphere volume can contribute to the diffraction volume. In the case of low-absorbing metals, however, serious limitations on specimen thickness occur as demonstrated by Braggs due to de-focussing effects. Peak shifts may occur which negate the assumption that integrated intensities are proportional to peak intensities. These limitations in sphere size to the order of 0.5 to 1 mm for beryllium require that the grain size be sufficiently small to include a large enough statistical sample. The present paper describes the application of spherical specimens less than 1 mm in diam to the quantitative determination of pole figures for compression-rolled beryllium sheet having a grain size the order of 10 p. EXPERIMENTAL 1) Specimen Preparation. Two techniques for spark-machining beryllium spheres were tried. One involved the use of a hollow cylinder as a cutting tool. The tool was fed into the rotating cylindrical specimen as shown in Fig. l(a). The hollow cylinder was carefully aligned such that the axis of the cylinder and the axis of the specimen lay in the same plane and were 90 deg to each other. As the hollow cylinder was fed into the rotating cylindrical specimen, a spherical shape was formed as shown in Fig. 1. Alignment was very critical. Slight misalignment resulted in the formation of a barrel-shaped specimen instead of a sphere. A second technique involved the use of a cutting wheel shaped as shown in Fig. 2 with a groove of the desired radius. A section of the sheet specimen was first turned into a cylinder on the left part of the cutting wheel. It was then shifted to the right and a spherical specimen was turned as shown in Fig. 2. The axis of the cylinder lay in the plane of the sheet. Flats corresponding to the rolling plane of the sheet were used to grip the specimen during the machining operation and these served to identify the rolling plane of the sphere. 2) Rotation of Spec=. The spherical specimen is shown mounted on the G.E. single-crystal goniometer in Fig. 3. The knob A of the goniometer shown in Fig. 3 rotates the specimen about the pedestal axis. These angles have been designated as @ angles. The knob B rotates the specimen about an axis perpendicular to the pedestal axis. These angles have been designated as p angles. A device was made to automatically drive the single-crystal goniometer by means of two flexible shafts connected to the A and B knobs as shown in Fig. 3. The motor system was designed to rotate the knob A, thus rotating the specimen through angles of $I while the B knob remained stationary. After one complete

Jan 1, 1967

By Edwin B. Wilson, Joseph W. Leonard, Richard W. Borio

preparation of specification coals for the utility industry is approached from the standpoint of a cooperative effort with the power company to assure that the shipped product will be a noncorrosive coal. Selective mining, coal preparation, the use of additives, and coal blending are mine-site techniques proposed as means for upgrading corrosion-retarding constituents of utility coals (CaO and MgO) while, at the same time, reducing the concentration of those constituents of coal (Na20 and K,O) which cause corrosion. Data obtained from large-scale boiler testing in combination with bench-scale physical and chemical tests are used as a basis for the formulation of mine-site procedures to improve coal combustion utilization. Electric power generation remains the greatest market for coal in the United States. A major reason for this strong market has been the ability of the coal industry to supply a superior product for combustion while maintaining competitive prices. Now that the coal industry is engaged in intensive competition with nuclear power for future energy demand, it becomes ever more imperative that superior coal products are produced. One important problem when burning some coals is a liquid phase corrosive attack on boiler tube metal in the superheater and reheater areas of the furnace where steam temperatures may exceed 1050°F. In addition to causing power outages and high maintenance costs, corrosion is a continuing barrier to the future development of more efficient steam cycles which permit lower generation costs when using coal. Research methods of the past which have been directed at finding solutions which could be applied at the power plant site have been only partially successful and are generally costly. This paper contains a suggested --method of corrosion control through investigation of the problem at the source of the trouble—the coal supplier facility. It is proposed that mine-site pre-ventative procedures be considered as an effective means of cooperative corrosion control between the power company and the coal supplier. Economic justification must be applied to the individual situation. This paper is based on recent work by Combustion Engineering, Inc. and the Coal Research Bureau of West Virginia University under a contract from the Department of the Interior Office of Coal Research.',' Results which are of importance to this discussion may be summarized as follows: 1) The alkali minerals of coal (Na2O and K2O), as measured by an acid leaching process, can be related to corrosion rate in utility boilers. As these constituents increase in a coal product, its corrosiveness can be expected to worsen. 2) The alkaline-earth minerals contained in coal, reported as total CaO and MgO reduce corrosiveness 2s their concentration increases. 3) Naturally occuring, alkaline-earth-bearing materials, such as limestone and dolomite, may be added to a coal to reduce its corrosiveness. 4) Coals with very low iron contents tend to be less corrosive. These results provide the groundwork for examination of the system of operations which occur at the supplier facility from the seam face where mining is begun to the point of loading for shipment. The Mining System Fig. 1 is a cross section of one of the typical coal seams (designated coal A) that was boiler tested during this research program. This seam is overlain by material which consists primarily of a gray-black shale. In the lower third of this seam, there exists a thin rock parting of less than 4 in. in thickness which is consistent throughout the seam. The floor material is fireclay. In order to examine mineral distribution throughout this particular seam, the Coal Research Bureau collected a

Jan 1, 1971

By F. W. Davis

SOME idea may be gained of the tremendous consumption of refractories by the open-hearth steel manufacturers from a statement made by A. T. Green at a meeting reported by T11.e Industrial Chemist of London, as follows: "At a very progressive steel plant in the Midlands, with a battery of five open-hearth furnaces working. twelve months and making 3000 tons of steel per week, the cost of refractories per ton of steel produced averages about $0.50 for the actual open- hearth casting and $0.12 for those operations incidental to the rolling of the metal." .These figures, when translated into the annual tonnage of steel, represent a very considerable expenditure.

Jan 1, 1930