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POSITIONS VACANT Position as superintendent of all-sliming cyanide plant in Montana will he open in spring. Thoroughly experienced man wanted. No. 6. Position as engineer for iron-mining company in Virginia is open. Single man with experience in underground surveying preferred. No. 7. ENGINEERS AVAILABLE (Under this heading will be published notes sent to the Secretary of the Institute. by members or other persons.) Member, 34 years old, married, nine years responsible position in South America, excellent knowledge of Spanish, Latin-American people and customs, with present employer seven years, six years as manager and legal representative of a mining company, desires to make a change April, 1914. Prefers position requiring energy, executive ability, business tact and practical knowledge dealing with political and legal authorities, rather than strictly technical position. No. 35. Technical graduate, married, with four years' experience in assaying, surveying, sampling,. and mine supervision in Utah and Mexico, open for engagement. No. 37. Member, aged 28, desires opening on engineering or sales force of machinery house, or manufacturing concern. Twelve years' experience, in smelters, cyanide plants, concentrators and gold dredges, steam, gas and electric machinery and mechanical drafting. At present foreman for a silver-lead company. No. 40.

Jan 1, 1914

By Ulick Evans

I SHOULD like to commence by saying how much I appreciate the honor which the American Institute of Mining and Metallurgical Engineers has done me in inviting me to visit your country, and to deliver this lecture before you. In choosing a subject, and in deciding what to include and what to omit, I have endeavored to discuss as far as possible work carried out recently in Europe with which you may not be unduly familiar. It would be poor return for your hospitality, and a mistaken sort of compliment indeed, if I were to load the lecture with accounts of researches 'carried out in your own country-researches with which you are probably better acquainted than I. Not that I have in any way excluded work done on, this side of the Atlantic from my survey; one would indeed find it difficult to write on this, or on any other branch of science, without mentioning American work. But I have endeavored as far as possible to concentrate on aspects of the case which will, I hope, be comparatively fresh to you, and I feel fairly certain that this will be in accordance with your own wishes. If a strip of iron is heated strongly at one end, the other end remaining cold, there is produced over the heated portion a layer of oxide scale, the thickness of which diminishes steadily with the distance from the hot end. Somewhere in the middle of the strip, the thickness of the oxidized layer will become comparable .to the wave length of light, and over this region the thin films give rise to a series of beautiful interference tints, commonly known as "temper colors." The colors are caused by the fact that two trains of light waves are reflected respectively from the outer and inner surfaces of the oxide film, .and the possibility arises that the "crests" of one series of waves may coincide with the "troughs" of the other, thus diminishing the intensity of the light of some particular wave length. The state of affairs in this part of the strip is shown diagrammatically in Fig. 1, in which the film thickness is enormously exaggerated, of course, in comparison with the length of the strip; the

Jan 1, 1929

By W. T. Lankford, Low J. R., Gensamer M.

The problem of sheet metal formability is one which has received a vast amount of attention during recent years. In spite of the great amount of study and experimental work which has been devoted to this problem, many of its fundamental aspects are still not well understood. No generally satisfactory test has been developed which is capable of providing a reasonably adequate evaluation of sheet metal formability, particularly in borderline cases. Anomalies persistently arise in which a lot of supposedly satisfactory material exhibits excessive breakage when formed. This lack of suitable technological tests greatly hinders the design of new parts and the substitution of new materials in parts of existing design, frequently necessitating considerable costly trial and error experimentation on an actual production basis. When, at the beginning of World War 11, it became apparent that mass production methods of forming would bc required in the aircraft industry if the large numbers of military aircraft needed were to be supplied, renewed attention was focussed on the problem of sheet metal formability. It was widely recognized that the formability requirements placed on sheet metals had been steadily increasing in severity through the years, especially as greater and greater emphasis was placed on streamlined designs with the resultant freer application of doubly curved surfaces. The recent advent of several new high strength aluminum alloys of more limited formability than some of the older alloys also served to emphasize the need for new approaches to the problem. It seemed evident that progress in the technology of sheet metal forming would depend to a great extent on the development of more reliable criteria for the evaluation of formability. Although the problem is admittedly very complex, the most logical approach appeared to be through studies of the fundamental material properties of sheet metals, especially under complex stress conditions simulating those prevailing in actual forming operations. Most previous investigations have failed to make full use of existing knowledge of fundamental material properties, and in many instances have attempted correlations with properties which are now recognized as being ambiguous in nature. This investigation was undertaken, therefore, with the aim of developing methods for the study of the flow and fracture of sheet meta1s under combined stresses, and of making use of such methods as might be developed in

Jan 1, 1947

By Low J. R., Gensamer M., W. T. Lankford

The problem of sheet metal formability is one which has received a vast amount of attention during recent years. In spite of the great amount of study and experimental work which has been devoted to this problem, many of its fundamental aspects are still not well understood. No generally satisfactory test has been developed which is capable of providing a reasonably adequate evaluation of sheet metal formability, particularly in borderline cases. Anomalies persistently arise in which a lot of supposedly satisfactory material exhibits excessive breakage when formed. This lack of suitable technological tests greatly hinders the design of new parts and the substitution of new materials in parts of existing design, frequently necessitating considerable costly trial and error experimentation on an actual production basis. When, at the beginning of World War 11, it became apparent that mass production methods of forming would bc required in the aircraft industry if the large numbers of military aircraft needed were to be supplied, renewed attention was focussed on the problem of sheet metal formability. It was widely recognized that the formability requirements placed on sheet metals had been steadily increasing in severity through the years, especially as greater and greater emphasis was placed on streamlined designs with the resultant freer application of doubly curved surfaces. The recent advent of several new high strength aluminum alloys of more limited formability than some of the older alloys also served to emphasize the need for new approaches to the problem. It seemed evident that progress in the technology of sheet metal forming would depend to a great extent on the development of more reliable criteria for the evaluation of formability. Although the problem is admittedly very complex, the most logical approach appeared to be through studies of the fundamental material properties of sheet metals, especially under complex stress conditions simulating those prevailing in actual forming operations. Most previous investigations have failed to make full use of existing knowledge of fundamental material properties, and in many instances have attempted correlations with properties which are now recognized as being ambiguous in nature. This investigation was undertaken, therefore, with the aim of developing methods for the study of the flow and fracture of sheet meta1s under combined stresses, and of making use of such methods as might be developed in

Jan 1, 1947

While coal was undoubtedly seen by the Spanish explorers in Texas, no mention can be found of it in any of their available published records; it was likely noticed by the first Americans, and coal along the Rio Grande River was reported in 1834.1 The next record is that of brown coal in Bastrop County in 1837 by James Nicholson and Judge Pinckney Hill? Dr. Riddell saw brown coal along the Trinity River in 1839 and described it as follows: "In the banks of the Trinity, associated with the iron ore, and overlying the brown coal, whole trees and fragments of trees, piled sometimes one upon another, present themselves completely transformed into stone. In some logs a diversified metamorphosis is observable; one portion of the vegetable structure having been replaced with silex, another with brown oxide of iron, and a third is bitumenized or converted into coal. "In concern with Dr. F. B. Page, I took considerable pains in the exploration of the Trinity brown coal formation., As no excavations for working have yet been made, the best places for inspecting the formation are where the Trinity cuts its way through the highlands, or where its banks present themselves in bold high bluffs, as at New Cincinnati, and near the site of the projected town of Osceola. The coal lies in horizontal strata, dipping one foot in thirty to the northwest. The main stratum at the latter place, just above Bedias creek; is represented by the concurrent statement of W. C. Brookfield, surveyor, Mr. James S. Hunter, of Huntsville, Texas, Dr. Page, and some other persons whom I consulted, as between six and seven feet in thickness, the lower portion being between three and four feet above low water mark. Unfortunately, during my sojourn there, the river was unusually high and turbid for the season of year; I could not consequently verify the same by personal observation and measurements. The most considerable coal beds which I had opportunity fully to inspect, were in the Trinity bluffs, southwest side, at New Cincinnati, six miles lower down, and just below the mouth of Salt creek, near six miles above. The workable stratum of brown coal in each of these localities is about five feet thick, and situated some fifteen feet or so above low water mark. In quality it is said to be precisely similar to the coal in the seven feet bed."2 . Moore in 1840 mentioned coal in the vicinity of Great Salt Lake, through which the Brazos flows; lignite in Bastrop County; lignite in the banks of the Colorado River a few miles above Lagrange in Fayette County; a deposit of excellent coal in the bed of the Sabine River, 30 miles above the

Jan 1, 1942

By Pradeep K. Rohatgi, Clyde M. Adams

Structures produced upon solidification of the eu-tectic composition (33 wt pct Cu) aluminum copper alloy have been examined as a function of freezing rate dfs /d? , the rate of change of fraction solid (fs) with time (8). Slow (dfs/d? = 0.0016 sec-1), intermediate (dfs/d? = 0.02 sec-1) and rapid (dfs/d? = 0.4 to 7.30 sec-1) freezing rates were used. The lamellar Al-Cual2 eutectic is arranged in the form of rod-shaped colonies at rapid freezing rates. The colonies are aligned parallel to the direction of heat flow, whereas the lamellae within the colonies are aligned at various angles, as high as 90 deg, to the direction of heat flow. The colony spacing (C) is proportional to the square root of inverse freezihg rate. The relationship is C = 15.5(dfs/d?)-1/2 where C is in µ and 8 is in sec. The ratio of colony spacing to lamellar spacing is greater than 20.0 and increases with a decrease in the freezing rate. A duplex dendritic structure is produced at intermediate freezing rates. A fine lamellar eutectic is arranged within the dendrites (exhibiting side branches at an angle close to 60 deg from the main stem) and a coarse irregular eutectic appears in the interdendritic regions. The duplex eutectic structure is also produced at slow freezing rates. However, at slow freezing rates there is a Platelat of CuAl2, along the center of the main stem of each dendrite and the other lamellae are arranged perpendicular to the central platelet. THE eutectic between CuA12 and a! aluminum has been reported to freeze in a lamellar form by several workers.'-3 chadwick4 has measured the interlamel-lar spacing as a function of growth rate. Kraft and Albright2 have reported on irregularities in the lamellar structures, and have proposed growth models which account for the formation of faults during solidification. In certain instances the lamellar eutectic has been found to exist in colonies. The colony formation315 has been attributed to the breakdown of a planar liquid-solid interface due to rejection of impurities. The aim of the present work is to study the structures produced from the eutectic aluminum-copper alloy under relatively fast solidification rates, such as encountered in casting and welding operations. The solid-liquid interface presumably remains planar under conditions of slow unidirectional freezing which produce lamellae aligned parallel to the direction of heat flow. The local growth velocities are the same over the entire interface and are equal to the rate of growth of the all-solid region. The spacing between the eutectic lamellae is inversely proportional to the square root of the growth rate of the all-solid region. Under the freezing conditions used in the present study, the solid-liquid interface is cellular or dendritic and the local growth velocities are different in the different regions of the interface. The relationship between the growth rate of the all solid region and the local growth velocities varies with the location and the shape of the interface. The growth rate of the all-solid region is, therefore, an inadequate parameter to describe the eutectic micro-structures which depend upon the local growth velocities. For this reason the structures have been examined as a function of freezing rate, dfs/d?, where fs is the fraction solidified at time 0. The freezing rate was varied by a factor of 4000. The relationship between the freezing rate, dfs/d?, and the growth velocit of the all solid region depends upon the specimen geometry and the shape of the interface. EXPERIMENTAL PROCEDURES The A1-33 pct Cu alloy used throughout this study was made in an induction furnace, using electrolytic copper and aluminum of commercial purity (99.7 pct), the primary impurities being silicon (0.12 pct), iron (0.14 pct), and zinc (0.02 pct). Three ranges of freezing rates were investigated: 1) A spectrum of rapid freezing rates (ranging from 0.40 to 7.30 sec-1) was obtained in arc deposits made on 2-in. thick cast plates of the eutectic alloy. The arc was operated at constant power and was made to travel at constant velocity on the surface of the plate that was in contact with the chill surface during solidification. The pool of liquid metal formed under the moving tungsten arc solidified rapidly by heat extraction through the unmelted plate. Conditions of unidirectional heat flow were achieved near the fusion zone interface, especially in the center of the arc deposits. The great advantage of the arc technique is that rapid cooling and freezing rates can be varied in a qualitative way. The correlation between the arc parameters and the solidification rate is given by the following relationship:6-8

Jan 1, 1970

By E. A. Elevatorski

Wollastonite, named after William H. Wollaston, an English chemist, is a calcium metasilicate, CaSiO3. It has a short history as an industrial mineral. The earliest production of wollastonite is reported to be from a deposit near Code Siding, located north of Randsburg, Calif. At this locality small tonnages of wollastonite were quarried during 1933-34 and 1938-41, and processed into mineral wool. This operation was largely experimental and virtually no United States production was again reported until the 1950s when a large deposit near Willsboro, N.Y., was developed by the Cabot Corp. A processing plant was placed on-stream in 1953, with nearly continuous production to date, and it is currently operated by Interpace Corp. Since 1958, wollastonite deposits in the Little and Big Maria Mountains of Riverside County, and in the Panamint Range of Inyo County, both in California, have operated intermittently for production of both ornamental and commercial wollastonite. During 1973, the United States was the major producing country, furnishing about 75% of the world's output. Recent production also has come from Finland, Mexico, and Kenya. Small amounts have been shipped intermittently from India, USSR, New Zealand, Republic of the Sudan, Republic of South Africa, and South-West Africa. The principal use of wollastonite is in the manufacture of ceramics, especially wall and floor tiles. Other uses are for paints, fillers, adhesives, reinforcing agents, plastics, fluxes, and glazes. Mineralogy Pure wollastonite, CaSiO3, has the composi¬tion of 48.3 % CaO and 51.7 % SiO,. However, it is seldom found in the pure state due to the ease with which it takes into solution the metasilicates of manganese, magnesium, iron, and strontium. Predominantly, wollastonite occurs as a contact metamorphic deposit forming between limestones and igneous rocks. Commonly associated minerals are garnet, diopside, epidote, calcite, and quartz. It has a specific gravity of 2.8 to 3.0, and hardness of 4.5 to 5 on Mobs' scale. When pure, it has a brilliant white color, but with impurities it may be grayish or brownish. Luster is vitreous to pearly. Melting point of wollastonite is about 1540° C. Wollastonite occurs in coarse-bladed masses, rarely showing good crystal form. It is usually acicular or fibrous, even in the smallest of particles. The most unique property of crushed and ground wollastonite is its cleavage. Fragments of crushed wollastonite tend to be needle-shaped, imparting a high strength, and this property is the basis for many of its uses. The fiber lengths are commonly in the ratio of 7 or 8 to 1, length to diameter. Some crystals of wollastonite fluoresce under short-wave or longwave ultraviolet light, or both; colors ranging from yellow-orange to pink-orange. Specimens may also show phosphorescence. The brightness of wollastonite is a property of considerable importance to the paint industry. Material, 99% pure, with a size of -325 mesh, has a General Electric reflectance rating of 92 to 96%. Chemically, wollastonite is inert and this property makes it useful as a filler and reinforcing agent. There are two polymorphs of calcium silicates: wollastonite, a low temperature form, and pseudowollastonite, a high temperature form. Inversion of wollastonite to pseudowollastonite occurs at about 1120° C, resulting in an increase in the coefficient of expansion and a color change. Pure white wollastonite, on inversion, may change to a cream tint, or various shades of red or brown. The color change is thought to be due to the presence of iron and strontium.

Jan 1, 1975

By Fred Bond

THERE is acute need for a method that will measure the size distribution of finely di-vided materials, particularly when the par-ticle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the sam-ples produced are adequate for a consider-able amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essen-tially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the set-tling rate. The balance appears to be in-herently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have re-stricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investiga-tion might lead to modifications that would make it a valuable tool for the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribu-tion determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used, in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared, early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could he accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the dis-tribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1939

By C. E. McManus

MANY mechanical advances have been made on mining equipment during the year 1951. There have been a number of trends established and many modifications made on open-pit equipment to increase the efficiency and availability of all the machines necessary in the moving of overburden and iron ore. Some years ago, the trend toward larger shovels for the loading of off-highway trucks began, but in the last year, it has become general practice to use the 5 to 7 ¼ -yd quarry-type shovels in the loading of haulage units. For years these larger shovels were used in the locomotive haulage pits. As the truck capacities increased from 15 to 20 to 30 tons, the need for larger loading units became apparent. Today in most mines, large shovels are in evidence and a few 8-yd shovels will be delivered this year for loading off-highway trucks. Torque Converter-Shovel The Diesel-driven shovel with its friction bands has been modernized with the torque converter. There have been about ten shovels remodeled to take a torque converter in the drive system. The large high-torque, low-speed Diesel engine was removed and replaced by a high-horsepower, high-speed, automotive-type engine. This engine was connected directly to the torque converter. The torque converter was connected to the shovel through the standard original sprocket and chain. Dual governors controlled engine performance. One governor controlled the high idle of the engine; the other governor, which is connected through a flexible shaft to the output shaft of the converter, controlled the loading of the engine. With this dual governor hook-up, the engine anticipates load conditions and is operating at high idle and full throttle before the shovel load is transmitted back through the converter to the flywheel. It has been found that with this automotive-type engine and converter, the shovel capacity has been increased about 20 pct. Also, the wear on the friction bands, breakage of hoist cables, and other mechanical breakages has been reduced materially. Alloy-Steel in Shovels The shovel equipment manufacturers have been experimenting with low-temperature-strength, high-alloy steels to combat the excessive breakage that occurs in extremely cold weather. High-nickel alloy steel has been used in critical areas that are affected by low temperatures, the most notable being dipper sticks. Most shovels ordered today are equipped with some of this special, alloy steel. More and more manganese alloy is being used for replacement parts such as shovel pads, idlers, drive sprockets, etc. Although the initial cost of these parts is considerably higher than the standard replacement items, the life of these manganese parts is considerably longer and well worth the added expenditure. Dipper-teeth repair is still a problem. Most companies use the small replaceable inserted tooth. It has become common practice among some of the companies to "job out" their dipper-tooth repairs to outside welding companies. This necessitates an additional inventory of teeth, but it does guarantee an adequate supply of replacement teeth at all times. These contractors have set up their shops on a production basis and can do an acceptable job at a high rate of speed. Thermite welding has been used in retipping teeth. To date, the process cannot be called successful but with improvements the time required to repoint the dipper teeth will be decreased considerably. The submerged arc process has been tried in the replacement of these dipper points, but like thermite welding has not proven successful. Here again, if a method can be developed to use submerged arc, the job of teeth repair will be made much easier. New model shovels in 6 ½ and 8 cu yd sizes fea-

Jan 1, 1952

Oil-well driller with extensive experience in this line of work. Location, Bolivia, South America. Salary depends on experience. R.-789. Mining Engineer, with geological knowledge, who can locate suitable spots for drilling oil wells. Location, Bolivia, South America. Salary depends on man. R-788. Construction Engineer, mechanical or civil engineer with experience in installing oil plants for foreign field. Must be able to install entire equipment including tanks, piping, buildings, etc. Salary depends on experience. R-782. Geologist, competent petrographer for micropetrographic work and training of two assistant students under the direction of the Director of a Geological Institute. Engagement is for six months with option on the part of the Director for an equal period: Location, Mexico. Salary, 450 pesos Mexican gold ($225 per month). R-765. Operating Mechanical Electrical Engineer, with extensive experience in charge of the maintenance, repair, and betterment of all mechanical and electrical equipment on mining operations. Desirable that the man have had this experience in connection with phosphate mining. Applicant must be competent to direct shop repairs on motors and generators, including rewinding, the building and maintenance of transmission lines, etc. Must also have ample machine-shop experience to enable him to direct repairs of light locomotives, steam shovels, brown hoists, caterpillar tractors, and auto trucks. Duties will include the betterment and maintenance of phosphate-rock washers and rotary-work dryers. The applicant must also be competent to conduct efficiency tests on all such equipment and be enabled to interpret data collected. Splendid opportunity for the right type of man. Climate and living conditions excellent. The company will furnish house rent free, including light .and water. Location, Florida. Salary depends on experience. R-854.

Jan 7, 1919

By Koichi Kashida, Mayumi Someno, Kazuhiro Goto

The present work has two objectives: first to develop an experimental method which would give some new information on the micromechanism of the reduction of oxides by gases at elevated temperature; second to clari,fy the intermediate phases of the W-0 system, formed during the reduction. A Galvanic cell with the solid electrolyte , ZrO2 . CaO, was imbedded in powders of W03, CuO, or Fe20s with two measuring electvodes and with a reference electrode. The change of the intraparticle gas composition was measured at An oxygen concentration cell consists of two electrodes separated by an electrolyte through which the transference of electrical charge is accomplished predominantly by the migration of oxygen ions. Many works have been reported on the oxygen con- 600" to loo@ C during the reduction by the gas mixture of hydrogen and argon. The intraparticle gas composition changes stepwise with time. The electromotive force of such temporary interruption corresponds to the equilibrium electromotive force of two solid phases formed during the reduction. The intermediate phases of W-0 system, which are formed in a large quantity during the reduction by hydrogen, are W0 2 W02.72 and WOz. The micromechanism of the reduction of oxides by gases is discussed. centration cells with the solid electrolyte of solid solution of zirconia and lime, since Kuikkola and wagnerl demonstrated the possibility of determination of standard free energy of formation of oxides by an electromotive-force method with the Galvanic cell. One of the present authors (K.G.) and his coworkers have applied the cells with the solid electrolyte of zirconia and lime to the following measurements:

Jan 1, 1969

New Device Eliminates Blasting in Coal A non-explosive device developed by duPont utilizes the high pressure of a gas generated inside a steel tube which is inserted in a hole drilled in a coal seam to break down the face of coal. Chemical reaction is started by an electric current which produces heat to initiate the action. The same heat destroys the starter wire as soon as electric current is no longer needed. The tube containing the chemical is closed at the outer end by a plug with electrical connections, and at the other with a disk that is ruptured by the compressed gases formed. When the gas has been liberated in sufficient quantities to create a desired pressure the disk breaks and the released gas breaks down the coal face. The new device is called a Chemechol.

Jan 10, 1951

By Don Rose

In the USA the cost of steel ribs for tunnels approximates $100 million each year. European practice has long since abandoned heavy steel ribs for tunnel support, and tunnel coats in Europe (normalized for wages) are about half the costs incurred in the USA. A feeling has existed for some time that the USA practices of supporting tunnels with heavy steel ribs have been overly conservative. The USA practice is based on rock load coefficients by Karl Terzaghi. In 1946, Karl Terzaghi published a tunnel rock classification system (Terzaghi, 1946), with the rock loads on tunnels predicted for each class of rock. No data on real rock loads were presented by Terzaghi and his rock load coefficients may have been largely intuitive. His classification system and associated predicted rock loads have been widely used in the USA. Each rock class, taken from Terzaghi's classification system, is assumed to generate loads of loosened rock resting as dead load. The dimensions of the loosened rock are described by rock load coefficients multiplied by the tunnel diameter. The resulting rock loads are used by design engineers, contractors and agencies to size supporting steel ribs. Terzaghi clearly stated that he had conservatively assumed high rock loads for his classes 4, 5 and 6 to take a presumed effect of groundwater into account. If the tunnel was not affected by ground- water, Terzaghi stated those rock loads should be reduced by 50 percent. Twenty two years later Tor Brekke (1968) wrote a paper clearly showing that based on observation of more than 250 tunnels groundwater does not affect tunnel rock loads. In 1969, Deere, et al., published measurements made on a number of tunnels, and a well-known curve was drawn by Deere to illustrate Terzaghios coefficients graphically. Deere's text stated that Terzaghi's predicted rock loads were too high and should be reduced. Cording and Deere (1972) more recently published data indicating that very large real rock caverns and chambers were being successfully built using rock bolts, which can take only a very limited rock load, thus indicating that real rock load is much smaller than Terzaghi or even Deere predicted.

Jan 1, 1982

By F. V. Lenel, G. S. Ansell, J. A. Dromsky

The growth of aluminum oxide particles in a nickel matrix was studied eve?. the temperature vange of 2140° to 2470°F. The instability of the dispersed alumina was shown to be independent of the crystal structure of the alumina. The activation energy for the growth of the dispersed alumina was found to be 84.7 1 2.0 kcal. The particle radius increased as a function of time. These results indicate that the growth is not diffusion controlled. It is believed that the rate controlling mechanism is the dissolution of the aluminum and oxygen atoms into the nickel lattice. THE strength properties of alloys which consist of a finely dispersed second phase in a metallic matrix depend upon the spacing between the second phase particles. It is therefore desirable to achieve very fine dispersions in these alloys. Furthermore, to retain the properties these very fine dispersions must be stable during fabrication and service of the alloys. The best known of the dispersion strengthened materials, the SAP type alloys, which consist of a dispersion of aluminurn oxide in aluminum, have exceptionally good stability up to the melting point of aluminum. There is evidence, however, that other dispersion strengthened alloys, even those consisting of refractory oxides in a metal matrix, may be less stable. This investigation is concerned with the stability of Ni-Al2O3 alloys in the temperature range in which these alloys are usually fabricated. The mechanical properties of Ni-Al2O3 alloys at elevated temperatures have been previously investigated by Crelnens and rant,' and Gregory and Goetzel.2 The behavior of these alloys in stress rupture tests appears to indicate that at temperatures below 1800°F they are highly stable. There is some doubt, however, as to their stability at the higher temperatures used during the conventional fabrication. Cremens and Grant, in preparing their test alloys, cousolidated, by powder metallurgical techniques, nickel powders as fine as 0.13 µ diam and alumina powders as fine as 0.018 µ. Metallo- graphic examination of the alloys following fabrication revealed that none had interparticle spacings of less than 2 µ. Considering the size of the original component powder particles, it is likely that the dispersions coarsened during fabrication. Gregory and Goetzel, in their studies of extruded alloys of 80 pct Ni—-20 pct Cr matrixes with nonmetallic dispersion, observed a definite coarsening of the alumina dispersions in alloys sintered at 2280°F as cantrasted to those sintered at 2000oF. Similar observations on the spheroidization and growth of thoria particles finely dispersed in a nickel matrix were made by D. K. Worn and S. F. Marton.3 As a result of such coarsening, much of the effort expended in the preparation of very fine powder mixtures would be lost. The mechanical properties of the alloys which had experienced coarsening would be expected to be poorer than if the original dispersions had been retained. EXPERIMENTAL PROCEDURE Ni-Al2O3 alloys were produced from powder prepared by a coprecipitation technique. Aluminum hydroxide and nickel hydroxide were coprecipitated from chloride solutions of the metals. The mixed hydroxides were calcined to form metal oxides and the nickel oxide in the mixture was selectively reduced to nickel by treating it in hydrogen. Specimens were compacted from the resultant powder which consisted of a fine, uniform mixture of aluminum oxide and nickel particles. The compacts were sintered by resistance hot pressing4, a densification technique which requires exposure times of the order of only a second or less at elevated temperatures. A conventional sintering process was not used, since the temperature required for densification would have to be in the region in which the stability of the dispersion was to be studied. A series of hot pressed specimens were treated in hydrogen at temperatures from 2140o to 2470°F (1171o to 1355oC, for times up to 120 hr. Changes in the microstructures were studied by electron microscopy using the two-stage preshadowed carbon replica method.5 In performing a lineal analysis on a series of micrographs from each specimen it was found more convenient to determine the mean free path between alumina particles rather than particle radii as the parameter of growth. Although these quantities are directly proportional for only spherical particles, the alumina particles in these alloys

Jan 1, 1962

By Lawrence Addicks

SOME three years ago the smelter connected with the Chrome, N. J., refinery of the United States Metals Refining Co. found itself embarrassed y constantly increasing piles of unsmelted blast-furnace flue dust. The charge was fine and 10 to 15 per cent. of it was blown over into the flue. Sulphur was at that time too scarce to make the sintering of the finer part of the charge attractive, and raw-ore smelting in a reverberatory with a partly oxidized charge. was not to be thought of. A great many schemes were considered, including leaching, blowing into the converters, and briquetting, the problem finally narrowing down to blast roasting and nodulizing. It was found by experiment that blast roasting would not yield a satisfactory sinter without the addition of coke dust or sulphide fines to augment the fuel value of the flue dust, and on this account, together with the low first cost of a kiln, the latter was decided upon. A couple of tons of flue dust Were tried out in the experimental kiln in the laboratory at Yorktown, Va., of J. H. Payne, who acted as consulting engineer in this connection. This kiln was approximately 2 ft. in diameter and 20 ft. long and Was fired with fuel oil. A run of several hours yielded excellent nodules. The kiln showed no tendency to build in and form "nose rings" and gave a fuel consumption of 50 gal. of oil per ton of flue dust. There was no indication of any stack loss. The roasting was strongly oxidizing. A study of what full-size kilns were doing on cement clinker and on nodulizing pyrites cinder indicated that a 60 by 6 ft. kiln would certainly not consume over half of the oil per. ton of flue dust shown on the test and as fuel oil at that time Was selling around 2 1/2 c. per gallon it was decided to let it go at that.

Jan 7, 1914

By Fred C. Bond

There is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool [or the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1943

By Fred C. Bond

THEM is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determinations of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool for the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1939

By Fred C. Bond

There is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool [or the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1943

By M. E. Volin, F. H. Erbisch, G. M. Wenberg

Bacterial leaching of copper and uranium is practiced under acidic conditions in environments furnishing sulfur and iron. However, many mineral deposits do not have these conditions; the chalcocite and native copper deposits in Michigan's Upper Peninsula are examples. Species of bacteria and fungi isolated previously from samples taken at the White Pine Copper Co. tailings pond and mine, were screened for solubilization of copper from chalcocite ore and flotation concentrate and from native copper jig concentrate. Certain Penicillium species solubilized significant amounts of copper under neutral to slightly acidic conditions in a carbon and nitrogen-enriched medium. Leaching apparently was accomplished by release of metabolites which chelated with the copper. The copper yield was highly dependent upon the medium composition and the concentration of copper in the source material. The standardized procedures which were developed in an attempt to maximize copper yield in leaching times of three to five days are described. This preliminary research indicates a biological leaching process for copper which is different from those in use, but whether it can be applied economically remains to be determined.

Jan 1, 1972

By Ronald K. Linde

Metastable Ag-Cu solid solutions at two compositions beyond the maximum limits of solubility obtainable by quenching from the solid state were obtained by rapid quenching from the liquid state. The process of transformation of the metastable solid solutions into the equilibrium phases was studied by means of X-ray diffraction intensity measurements and electrical-resistance measurements; metallographic examination was also performed. Results are compared with those for an alloy quenched from the solid state at a composition which exists as a solid solution at elevated temperatures. Activation energies for the trans-formation were computed to be 33,600 * 2500 and 33,100 * 2000 cal per g mole for the 60.1 and 75.0 at. pct Ag;Cu compositions, respectively THE kinetics of precipitation in supersaturated solid solutions obtained by quenching from high temperature has been thoroughly studied in many alloys, and detailed investigations of the early stages of nucleation and subsequent growth of the equilibrium phases have been carried out. All of these studies have been made on alloys quenched from the solid state, however, and it is the purpose of this paper to present some of the results on the kinetics of transformation of metastable solid solutions in Ag-Cu binary alloys whose compositions lie outside of the solid-state limits of solubility. Limits of solubility in the solid state can be increased by rapid quenching from the liquid state. This was first demonstrated by Falkenhagen and Hofmann, who obtained appreciable increases in solubility limits of the elements of the first transition series in aluminum by rapid cooling of liquid alloys through contact with a copper mold maintained at liquid nitrogen temperature.' The same basic idea of cooling a liquid alloy by conduction onto a substrate rather than by convection of a gas or liquid (conventional quenching) has been recently revived and extended to very high rates of cooling by Duwez and his collaborators. The new technique was first applied to Ag-Cu alloys because the existence of a eutectic in this system is not predicted by the Hume-Rothery rules of alloy phase formation. Rapid quenching from the liquid state resulted in metastable solid solutions at all concentrations. The kinetics of decomposition of these metastable solid solutions containing 60.1 at. pct Ag;Cu (eutectic composition) and 75.0 at. pct Ag;Cu is the subject of the present paper. EXPERIMENTAL TECHNIQUES Alloys were made in 10- to 20-g heats using silver of purity 99.99 pet and copper of purity >99.999 pct. Components were weighed accurately to 0.1 mg and melted by induction heating in an alumina crucible under an atmosphere of hydrogen. Weight losses amounted to less than 0.02 ~ct in all cases. Rapid cooling from the liquid state was achieved in an apparatus of the type described by Pietrokowsky. 3 In this technique a freely falling drop of molten alloy is caught between a stationary anvil and a fast moving piston, both anvil and piston being lined with copper. The resulting foils were approximately circular (about 2 cm in diam) and from about 50 to 150 u in thickness, depending on the pressure driving the piston. Metallographic samples were prepared for polishing by edge-mounting foils in Quickmount. The mostef-fective etching procedure was found to be: 10 parts NH4OH (concentrated), 1 part H2O2 (30 pct), 5 parts H2O, swab for 5 to 10 sec. The transformation of the metastable alloys to equilibrium was followed by X-ray diffraction and electrical-resistivity measurements. The peak intensity and the integrated intensity of suitable Bragg reflections of the metastable and stable solid solutions were studied with a Norelco dif-fractometer, using nickel-filtered copper KO radiation. The peaks were step-scanned at intervals of 0.05 deg. Using either a Kelvin bridge or a null circuit with a Leeds and Northrup K-2 potentiometer, the changes in electrical resistance due to phase transformation were measured for specimens cut into strips about 20 mm long and 4 mm wide. All resistivity measurements were carried out at liquid-nitrogen temperature. The isothermal heat treatment was accomplished by sealing the samples in argon-filled aluminum containers with stainless-steel O-rings. Containers were then suspended in wax baths with temperatures in the

Jan 1, 1967