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By J. B. Austin

It is now well established, chiefly through the work of Davenport and Bain,' that the influence of temperature upon the rate of transformation of austenite to ferrite at constant temperature is represented by a curve of the type shown in Fig. 5 on page 295 and the reasons for this general shape have been discussed by them in a qualitative way. Thus, the upper part, or nose, of the curve is the resultant of two factors of which the rate of change with temperature is not the same, and by analogy with other like cases it is almost certain that these factors are: (1) the chemical potential, or driving force, of the transformation, which is zero at the equilibrium temperature and increases rapidly as the temperature falls below this point; and (2) a factor analogous to viscosity, or resistance of the crystal lattice to a change in structure, which also increases as the temperature is lowered. Just below the equilibrium temperature this virtual "viscosity" of the metal is relatively low—that is, the metal offers little resistance to a change in lattice—but the driving force is also small, and the net result is that the reaction proceeds slowly. As the temperature is lowered the magnitude of both factors increases; but at first the driving force increases more rapidly than the resistance and the reaction is observed to proceed more rapidly. At lower temperatures, however, the resistance begins to increase faster than the driving force, and eventually, at the nose of the curve, overbalances it, causing the reaction to proceed more and more slowly thereafter. This concept is somewhat, though not completely, analogous to that employed in certain electrical cases where the precise factors are known and are separately measurable. The current I (in amperes or coulombs per second) flowing through a given wire is proportional to the impressed potential, or driving force E, and is inversely proportional to the resistance R of the wire; that is, I = E/R. Stated in a slightly different way, the time required for one coulomb to pass a given point (1/I) is equal to R/E. If the temperature of the whole circuit is changed, the resultant change in 1/I will depend on the relative rates of change of R and of E,

Jan 1, 1935

By J. B. Austin

It is now well established, chiefly through the work of Davenport and Bain,' that the influence of temperature upon the rate of transformation of austenite to ferrite at constant temperature is represented by a curve of the type shown in Fig. 5 on page 295 and the reasons for this general shape have been discussed by them in a qualitative way. Thus, the upper part, or nose, of the curve is the resultant of two factors of which the rate of change with temperature is not the same, and by analogy with other like cases it is almost certain that these factors are: (1) the chemical potential, or driving force, of the transformation, which is zero at the equilibrium temperature and increases rapidly as the temperature falls below this point; and (2) a factor analogous to viscosity, or resistance of the crystal lattice to a change in structure, which also increases as the temperature is lowered. Just below the equilibrium temperature this virtual "viscosity" of the metal is relatively low—that is, the metal offers little resistance to a change in lattice—but the driving force is also small, and the net result is that the reaction proceeds slowly. As the temperature is lowered the magnitude of both factors increases; but at first the driving force increases more rapidly than the resistance and the reaction is observed to proceed more rapidly. At lower temperatures, however, the resistance begins to increase faster than the driving force, and eventually, at the nose of the curve, overbalances it, causing the reaction to proceed more and more slowly thereafter. This concept is somewhat, though not completely, analogous to that employed in certain electrical cases where the precise factors are known and are separately measurable. The current I (in amperes or coulombs per second) flowing through a given wire is proportional to the impressed potential, or driving force E, and is inversely proportional to the resistance R of the wire; that is, I = E/R. Stated in a slightly different way, the time required for one coulomb to pass a given point (1/I) is equal to R/E. If the temperature of the whole circuit is changed, the resultant change in 1/I will depend on the relative rates of change of R and of E,

Jan 1, 1935

By R. C. Ferguson, Harlowe Hardinge

Oscar Johnson—In my opinion, the effect of mill speeds on grinding costs must be studied along with capital investment and dollars gathered together as profits. Comparing the entire groups of operators with those who have had the opportunity to make slow-speed mill studies, I think you will find the latter small in numbers. Most managers want the equipment worked to its maximum output. There are, however, some installations where plant and mill sizes are such that they can do the job with reduction of mill barrel speeds. The past and the present installations of the industry are laid out to get the most capacity for the least capital outlay. This is the case even with the plants of Chile Exploration, International Nickel, Morocco, and Anaconda, now under construction or being changed. The industry recognizes that most all equipment it buys today is good and can be depended upon for efficient performance. Under this scheme of things, I am doubtful that slow-speed ball mill operation will be generally applicable. With reference to the U. S. Bureau of Mines laboratory tests, I think table II could have been omitted. It is inconclusive as to maximum efficiency for the low-pulp level mill on hard ore. There should be no question about this point. However, data on mill speeds can be found to substantiate various theories as well as refute them. Gow, Guggenheim, Campbell and Coghill, in their paper on Ball Milling,' believe their 2 x 2 ft laboratory mill reflects results that can be expected from large mills. If so, then referring to their table 11, they state, "The conclusion to be drawn from this second series is that high speed, not exceeding 72 pct of the critical, favors capacity, as before, but that with proper conditions of operation high speeds may give as good efficiency values as low speeds. In this case the efficiency values are nearly constant. A horizontal curve would indicate that the amount of grinding was directly proportional to the power expended, and these tests suggest that such a coildition can be made to exist in commercial operations." Table II (From Paper by Gow et a1)2 Speed. Pot Critical 32 42 52 62 72 82 Capacity: Surface tons per hr (65- mesh) 266 42.1 54.4 65.9 74.3 74.1 Surface tons per hr (200- mesh) 56.1 87.4 112.7 137.1 154.2 153.0 Efficiency: Surface tons per net hp hr (65-mesh) 35.7 36.3 36.3 35.4 34.3 32.3 Surface tons per net hp hr (200-mesh) 75.3 75.3 75.1 73.7 71.0 66.0 Ore in mill, 1.b. 98 100 100 113 122 165 The field performance data, table 111, represents much effort in its collection and preparation. But, one must realize that there are many variables that effect the efficiency of grinding mill operation, and too much must not be assumed as to the effect of some specific change. Possibly with changes in mill speed, the results might be more consistent by also a change in ball rationing, type of ball, volume of ball charge,. p.ulp level and amount of pulp in the mill, pulp consisting, design of liner, circulating load, etc. Also, changes in ore character must be reckoned with when evaluating grinding performance. At present the Climax Molybdenum Corp. is running at much reduced capacity. Mr. James Duggan informs me that at mill speeds of 17 rpm, they save a $0.025 per ton on liners and $0.025 per ton in power, but, if the demand for molybdenum increased, he would go back to higher speed to obtain maximum tonnage, as the values from the increased tonnage would far more than offset the one half saving at the slower speed. The Jnspiration ran a six months' test between mills running 21 rpm and 23.5 rpm. The slower mills ground 10 pct less ore with a slight saving per ton, but when the reduced plant tonnage was checked back into the actual cost figures of concentration, the high-speed mills with their greater tonnage showed considerable advantage. To be convinced of possible practical results from the predictions in the conclusions, I think we would have to rely on the analysis of expert cost accountants to furnish the necessary proof figures. Hardinge and Ferguson are to be commended for the work in preparing this paper. I am convinced that our Massco engineers should go into higher speeds with our equipment. Harlowe Hardinge (authors' reply)—For one, I heartily agree with Mr. Johnson's opening statement that the effect of mill speeds on grinding costs must be studied along with capital investment and dollars gathered together as profits. It was on this basis and for this reason the paper was written. Mr. Johnson, on the other hand, takes the position that, on the whole, low speeds are not justified from the economic standpoint, basing his principal reason on the fact that lower mill speeds cut mill capacities and hence reduce the gross income from the product produced. There is no denying this point. It is almost axiomatic. It is for this very reason that the overall advantage of lower mill speeds has been discounted and even overlooked. It was for this reason mainly that the paper was written in the first place. It is one thing to plan an efficient operation at the outset, basing one's figures on the tonnage requirements at the time, and it is quite another to be confronted with the problem of increasing the output of an existing installation at a minimum of capital expenditure. Economic consideration of a new installation is greatly influenced by referring to an old one. Too often, the analyst assumes that if this practice is followed in the new installation, one would not go wrong. It is just here that he may be wrong. Past practice and low capital expenditure are all too frequently given priority over the engineer's analysis of operating costs. When we are able to start fresh, we should give proper weight to other economic factors which do not exist in an old installation. It is these economic factors that make it possible to spend at the outset just a little more money and get it back in a matter of months and effect big savings for years to come. F. C. Bond—This paper is of considerable importance in that it emphasizes a modern trend to operate ball mills at somewhat slower speeds than formerly. We have checked the data in the paper with that obtained

Jan 1, 1951

By Harlowe Hardinge, R. C. Ferguson

Oscar Johnson—In my opinion, the effect of mill speeds on grinding costs must be studied along with capital investment and dollars gathered together as profits. Comparing the entire groups of operators with those who have had the opportunity to make slow-speed mill studies, I think you will find the latter small in numbers. Most managers want the equipment worked to its maximum output. There are, however, some installations where plant and mill sizes are such that they can do the job with reduction of mill barrel speeds. The past and the present installations of the industry are laid out to get the most capacity for the least capital outlay. This is the case even with the plants of Chile Exploration, International Nickel, Morocco, and Anaconda, now under construction or being changed. The industry recognizes that most all equipment it buys today is good and can be depended upon for efficient performance. Under this scheme of things, I am doubtful that slow-speed ball mill operation will be generally applicable. With reference to the U. S. Bureau of Mines laboratory tests, I think table II could have been omitted. It is inconclusive as to maximum efficiency for the low-pulp level mill on hard ore. There should be no question about this point. However, data on mill speeds can be found to substantiate various theories as well as refute them. Gow, Guggenheim, Campbell and Coghill, in their paper on Ball Milling,' believe their 2 x 2 ft laboratory mill reflects results that can be expected from large mills. If so, then referring to their table 11, they state, "The conclusion to be drawn from this second series is that high speed, not exceeding 72 pct of the critical, favors capacity, as before, but that with proper conditions of operation high speeds may give as good efficiency values as low speeds. In this case the efficiency values are nearly constant. A horizontal curve would indicate that the amount of grinding was directly proportional to the power expended, and these tests suggest that such a coildition can be made to exist in commercial operations." Table II (From Paper by Gow et a1)2 Speed. Pot Critical 32 42 52 62 72 82 Capacity: Surface tons per hr (65- mesh) 266 42.1 54.4 65.9 74.3 74.1 Surface tons per hr (200- mesh) 56.1 87.4 112.7 137.1 154.2 153.0 Efficiency: Surface tons per net hp hr (65-mesh) 35.7 36.3 36.3 35.4 34.3 32.3 Surface tons per net hp hr (200-mesh) 75.3 75.3 75.1 73.7 71.0 66.0 Ore in mill, 1.b. 98 100 100 113 122 165 The field performance data, table 111, represents much effort in its collection and preparation. But, one must realize that there are many variables that effect the efficiency of grinding mill operation, and too much must not be assumed as to the effect of some specific change. Possibly with changes in mill speed, the results might be more consistent by also a change in ball rationing, type of ball, volume of ball charge,. p.ulp level and amount of pulp in the mill, pulp consisting, design of liner, circulating load, etc. Also, changes in ore character must be reckoned with when evaluating grinding performance. At present the Climax Molybdenum Corp. is running at much reduced capacity. Mr. James Duggan informs me that at mill speeds of 17 rpm, they save a $0.025 per ton on liners and $0.025 per ton in power, but, if the demand for molybdenum increased, he would go back to higher speed to obtain maximum tonnage, as the values from the increased tonnage would far more than offset the one half saving at the slower speed. The Jnspiration ran a six months' test between mills running 21 rpm and 23.5 rpm. The slower mills ground 10 pct less ore with a slight saving per ton, but when the reduced plant tonnage was checked back into the actual cost figures of concentration, the high-speed mills with their greater tonnage showed considerable advantage. To be convinced of possible practical results from the predictions in the conclusions, I think we would have to rely on the analysis of expert cost accountants to furnish the necessary proof figures. Hardinge and Ferguson are to be commended for the work in preparing this paper. I am convinced that our Massco engineers should go into higher speeds with our equipment. Harlowe Hardinge (authors' reply)—For one, I heartily agree with Mr. Johnson's opening statement that the effect of mill speeds on grinding costs must be studied along with capital investment and dollars gathered together as profits. It was on this basis and for this reason the paper was written. Mr. Johnson, on the other hand, takes the position that, on the whole, low speeds are not justified from the economic standpoint, basing his principal reason on the fact that lower mill speeds cut mill capacities and hence reduce the gross income from the product produced. There is no denying this point. It is almost axiomatic. It is for this very reason that the overall advantage of lower mill speeds has been discounted and even overlooked. It was for this reason mainly that the paper was written in the first place. It is one thing to plan an efficient operation at the outset, basing one's figures on the tonnage requirements at the time, and it is quite another to be confronted with the problem of increasing the output of an existing installation at a minimum of capital expenditure. Economic consideration of a new installation is greatly influenced by referring to an old one. Too often, the analyst assumes that if this practice is followed in the new installation, one would not go wrong. It is just here that he may be wrong. Past practice and low capital expenditure are all too frequently given priority over the engineer's analysis of operating costs. When we are able to start fresh, we should give proper weight to other economic factors which do not exist in an old installation. It is these economic factors that make it possible to spend at the outset just a little more money and get it back in a matter of months and effect big savings for years to come. F. C. Bond—This paper is of considerable importance in that it emphasizes a modern trend to operate ball mills at somewhat slower speeds than formerly. We have checked the data in the paper with that obtained

Jan 1, 1951

By Byron B. Morton

NICKEL-BEARING alloys are associated with petroleum in the fields of exploration, production, and refining. In the first- named field the geologist of today makes use of such instruments as the seismograph, torsion balance, and magnetometer, the selection of proper alloys and metals for the manufacture of which is an important matter. Nickel-bearing alloys are useful for parts that require resistance to corrosion or that must have non-magnetic properties. Where special co- efficient of thermal expansion are de- sired, they are obtained by using alloys high in nickel (20 to 60 per cent), since, by varying the nickel contents, alloys can be obtained ranging fro111 "Invar", with a low expansion between -40 and 175 cleg. F., to those with coefficients of expansion exceeding that of steels. The latter are obtained by additions of chromiurn to the alloys. Alloys containing 50 to 80 per cent of nickel, which possess high magnetic permeability, find application in certain instruments where this property is important.

Jan 1, 1935

By James R. Walpole

This paper will discuss the federal laws and regulations that are related to water quality. Both surface and underground water quality issues will be covered as well as point and nonpoint source requirements. Some of the subjects to be covered include the Federal Water Pollution Control Act (e.g., effluent guidelines, nonpoint source requirements, etc.), the Safe Drinking Water Act (e.g., underground injection control requirements; pits, ponds, and lagoons study, etc.), the Resource Conservation and Recovery Act (e.g., mining wastes study, etc.). The importance of related court decisions will also be discussed

Jan 1, 1982

[Admissions: B. M. Gottlieb, Chairman Edmond F. Egan K. Marshall Fagin John S. Fuller Edward E. Monteith T. A. Pollard Howard J. Ritts, Jr. Kenneth W. Robbins Harold E. Wright Advertising and Exhibits: Bernard F. Klein, Chairman Bob Diggs Brown R. E. Howard H. M. Krause, Jr. R. G. Parker Mrs. Evelyn R. Robertson]

Jan 1, 1961

By E. J. Lintner

CLAY mining in the 'United States is by no means a small industry for approximately ten million tons of shale and clay are recovered yearly. The bulk of this tonnage enters into the manufacture of paving, building and refractory brick, draintile, pots, sewer pipe, stoneware, and wall and floor tile. This group of manufactures is commonly known as the heavy clay products industry. The winning of the raw materials for this industry constitutes merely a step in the manufacturing process because the manufacturer usually owns and operates his own source of supply. The mining of kaolin and the whiteware and chinaware claps, however, is usually a separate industry.

Jan 1, 1936

By T. M. Girdler

INDUSTRIAL progress and development in this country from the earliest daps to the present has proceeded at an ever-quickening pace. Yet during recent decades the nature of our industrial progress and development has undergone a change of great significance. The earlier days were a period of tremendous expansion. Population was increasing by leaps and bounds. Vast areas of new land were being .2 opened to settlement. And almost boundless new sources of timber, coal, oil, ores, and power were being opened to ever-expanding markets. Today, however, that picture has al- most completely changed. Today, with population increase tapered way off and the opportunity for free expansion into western frontiers gone, the great industrial development of our country continues on a vastly different front. Industrial progress and development today rest on a foundation of technology. The key- stone is research. Our frontiers to- day are frontiers of sciencec

Jan 1, 1939

By N. S. Keith

(Read at the Wilkes-Barre Meeting, May, 1877.) THIS question is suggested by a statement made by Dr. Siemens, widely printed in the journals of the day, that a continuous rod of copper, thirty miles in length and three inches in diameter, is capable of conveying that distance, electrically, energy equal to 1000 horse-power. It is not attempted to advance the statement that the source of power shall be zinc, nor even coal, but waterfalls, which from their situation are not practically available for manufacturing establishments in their immediate vicinity. In order to fully consider this subject., we must understand the doctrine, I may say the science, of the correlation of the forces, so called. We must understand that all matter is endowed with an amount of force, and that each atom and molecule, simple and compound, has its specific portion of the whole. This force, at rest, is called latent heat, intrinsic energy, or potential. In motion it is called heat, light, electricity, chemical affinity, attraction, magnetism, power, etc., according to its sensible manifestations. These are the effects of the one force active in different substances, or in different assemblages of matter. Force put in motion comes to rest by reason of the resistance to motion which it encounters; in overcoming

Jan 1, 1878

By Byron S. Gottfried

This paper describes a comprehensive computer program, developed under the joint sponsorship of the U.S. Environmental Protection Agency and the U.S. Bureau of Mines, that simulates the performance of coal preparation plants. A typical plant configuration may include several different washers, crushers, and screens as well as stream blenders and stream splitters, interconnected in whatever manner the user may specify. The program will predict the mass and energy yields of each unit and the properties of each flowstream (weight, ash, pyritic sulfur, total sulfur, and energy distributions), provided the feed properties and appropriate values for various control parameters are given. The program is used to assess washability characteristics of different coals, to determine the effectiveness of different plant operating conditions, and to compare the performance of various plant configurations. A brief description is given of the methods used to carry out the calculations for each type of unit. Results of some calculations are also presented. These results illustrate the versatility of the program for analyzing both simple and complex plant configurations. The paper concludes with a description of other accomplishments and future plans.

Jan 1, 1977

By A. G. Metcalfe, A. Siede

The hardening of annealed copper during fatigue testing appears to be independent of the applied stress and to occur largely within the first 4000 cycles. Copper hardened by fatigue is more resistant to annealing than copper hardened by static means, and softens by a multistage process. Creep studies at 300°C show that copper hardened by fatigue also has greater resistance to creep than statically hardened copper. Some theoretical explanations are discussed. RECENT interest in the behavior of metals subjected to fatigue stems from observations of phenomena which could not be explained by current theories of the structure of metals. In 1953 Bullen et al.l showed that the hardening caused by fatigue at low stresses did not cause severe bending of the lattice as did hardening by static methods. This was later confirmed by Wood, 'and Broom and Ham.3 Clarebrough et al4 showed that as the stress level used in fatigue hardening was increased, bending of the lattice was introduced, eventually approaching that of metals deformed by conventional cold-working methods. The type of hardening introduced by fatigue has other interesting characteristics. Kemsley5 showed that copper fractured by fatigue at low stresses resisted annealing as compared to copper hardened an equal amount by static means. The work of Clarebrough etal, shows that the manner of energy release during annealing differs for fatigue-hardened and statically hardened metal in both magnitude and temperature range of release. In addition to hardening of the lattice, fatigue has been shown to cause softening in materials previously hardened by static methods,5 and also in age-hardened alloys.7 The superposition of a small fatigue stress on the static loading of high-temperature alloys has been shown to increase their resistance to creep.' The present work was an attempt to determine the relationship between fatigue hardening, resistance to annealing, and the creep properties of pure copper. EXPERIMENTAL PROGRAM The program described here was designed to answer three questions: 1) Can stress-cycle combinations well below the failure values give significant increases in hardness? 2) Does hardening, under different stress-cycle combinations, give increase resistance to annealing? And if so— 3) Does superior resistance to annealing confer superior creep properties over statically hardened material? Three-quarter hard OFHC copper was annealed in vacuo at 550°C for 1 hr to produce a strain-free material having a fine grain size and uniform hardness. (The standard deviation of the mean hardness of the annealed samples was less than + 1.9 Dpn). Annealing was performed after machining the fatigue specimens so as to avoid work-hardened surfaces. Jigs were used to avoid distortion. The fatigue properties of the annealed copper were determined using an accurately aligned Baldwin-Sonntag SF1-U machine operating at 1800 cycles per min. This limited the minimum number of cycles which could be examined to about 4000 stress reversals. Since failure resulted in specimen damage, hardness increase with number of cycles was measured by testing specimens fatigued to different fractions of the failure values. The results are shown in Fig. 1, and are superimposed on the S-N curve of the copper in Fig. 2. The resistance to annealing of fatigue-hardened material was compared to that of material hardened by uniaxial tensile straining. Specimens hardened to equal values by both methods were progressively annealed for 1 hr at temperature in vacuo. After each annealing treatment the hardness was measured using a Leitz Durimet hardness tester with a 500-g load. At least five tests were made for each hardness determination. The standard deviation for individual specimens varied from 0.26 to 1.48 hardness points. The results are shown in Figs. 3 to 5. The discontinuous nature of the annealing process has been brought out by drawing idealized curves through the data points. This can be justified by the consistency of the results as well as by general agreement with results of Kemsley.5 The creep resistance of fatigue-hardened and

Jan 1, 1960

By Mark Eisner

ONE'S JOB is the watershed down which the rest of one's life tends to flow write the Lynds in the first pages of their classic social study, "Middletown in Transition." Certainly engineers will confirm this statement after a check among those in their own profession with whose lives they are at all familiar. I have no hesitancy in acknowledging the truth of their observation for the men and women who are engaged in the profession of the law. It has been often remarked that American public life is overrun with members of the law profession. The highest public office in the land, that of President. has been occupied by lawyers almost to the exclusion of citizens of any of the other professions. Twenty-two Presidents of the United States out of the total of 31, were members of the bar. For the most part, members of Congress, the governors of the states, the state legislators and the mayors and other local leaders, men who occupy important positions of responsibility and public trust, have had legal training. Now this fact is no mere accident. Those who were fitted for the "job" of the practice of the law are favorably placed with respect to their participation in public life. Thus public service and public office is the watershed down which the "lawyer's" life tends to flow.

Jan 1, 1940

By N. S. Keith

This question is suggested by a statement made by Dr. Siemens, widely printed in the journals of the day, that a continuous rod of copper, thirty miles in length and three inches in diameter, is capable of conveying that distance, electrically, energy equal to 1000 horse-power. It is not attempted to advance the statement that the source of power shall be zinc, nor even coal, but waterfalls, which from their situation are not practically available for manufacturing establishments in their immediate vicinity. In order to fully consider this subject,, we must understand the doctrine, I may say the science, of the correlation of the forces, so called. We must understand that all matter is endowed with an amount of force, and that each atom and molecule, simple and compound, has its specific portion of the whole. This force, at rest, is called latent heat, intrinsic energy, or potential. In motion it is called heat, light, electricity, chemical affinity, attraction, magnetism, power, etc., according to its sensible manifestations. These are the effects of the one force active in different substances, or in different assemblages of matter. Force put in motion comes to rest by reason of the resistance to motion which it eucounters; in overcoming

Jan 1, 1879

By J. C. Coughlin, M. C. Flemings, T. Z. Kattamis

Experiments on Al-4.5 pct Cu alloy shou the dendrite arnz spacing increases with time during isothermal holding in the liquid-solid region. This coarsening of the dendrite structure is then shown to occur at roughly the same rate during solidification as during isothermal holding. Final dendrite arm spacing in both types of experiments depends primarily on coarsening kinetics. It is concluded that driving force for the coarsening is reduction of liquid-solid sur/ace area. Calculations based on two simple models show qualitative apreement with experinzent. 1 HERE has been considerable interest in recent years in determining effects of solidification variables on dendrite arm spacing in cast alloys. The interest has resulted primarily from the clear evidence that 1) the degree of homogeneity which can be obtained in a cast alloy with commercially practical homogeni- zation treatments depends on dendrite arm spacing, and 2) mechanical properties of the heat-treated casting depend on the homogeneity obtained.'-' In wrought alloys, microsegregation from the original ingot is carried to some extent into the final wrought product, and affects mechanical properties in similar fashion Experimental evidence available indicates that dendrite arm spacing in cast aluminum alloys is influenced only by cooling rate (or "local solidification timev*) and alloy content.Fig. 1, for example,

Jan 1, 1968

By Donald H. McLauqhlin

ITEM expressed in billions of dollars have become so commonplace these day- that a mere statement of the latest figures for the country s gold reserve scarcely conveys m adequate sense of the immensity of the commitment the nation has made in building up its huge stock, two-thirds of which is now stored at Fort Knox. Kentucky. Only by measuring it against quantities that mean something tangible to a particular group can an adequate comprehension of its magnitude he rained; consequently, to mining engineers, a comparison with the value of output from well-known mining districts might best serve to give some degree of reality to the astronomical figure at which the country gold is now valued.

Jan 1, 1941

By J. V. W. REYNDERS

FIRST of all let me express my affectionate gratitude for the cordiality and good will of your reception. On the part of the men I venture to interpret the character of your greeting, not only as a recognition of the position to which you have been good enough to elect me, but also as an expression of your friendly attitude. However, I cannot pass over the tribute of the ladies so casually: Nor does it seem possible to do justice to my sentiments in addressing them collectively. I would feel more equal to the task if I could have the opportunity to talk to them singly, in doing which I know I may count upon their good sportsmanship not to compare notes. There has been some discussion between Mr. Kelly and myself as to our respective duties on this occasion: The precedents are not clear as to whether the retiring or the incoming president is expected to speak at length. Mr. Kelly's argument was that as the incoming president confines himself to promises for the future his field is a broad one and his opportunities for extending his remarks correspondingly unlimited.

Jan 1, 1925

[L. W. KEMPF, Chairman E. E. SCHUMACHER, Past-Chairman E. A. ANDERSON, Senior Vice-Chairman A. A. SMITH, JR., Vice-Chairman 11. A. MALONEY, Treasurer ERNEST KIRKENDALL, Secretary 29 West 39th Street, New York 18, N. Y. Executive Committee 1947 C. Y. CLAYTON A. B. GRENINGER CURTIS PIGOTT 1948 WALTER BONSACK W. A. DEAN LOUIS JORDAN 1949 J. D. HANAWALT W. A. JOHNSON E. W. PALMER]

Jan 1, 1946

By Edward L. Vickers

The Pacific rim countries, comprising more than half the globe, represent a complex mix of developed and developing nations. The area comprises a large segment of the industrialized world. Within its boundaries are also found many of the world's greatest mineral resources largely concentrated in the less developed countries. The conflicting objectives of these developed and developing nations are giving rise to changes in the traditional patterns of world resource development. Powerful political and socio-economic factors affecting the world today are having a great bearing on natural resource developments in the Pacific basin. New forms of partnerships have been emerging in developing nations which have had a great impact on the mining com- munity, lending institutions, as well as political relations. The United States and Japan have been substantially responsible in the past for the development of natural resources in this area of the world. Their role, however, is undergoing significant metamorphosis. The rapidly changing economic and social environment in the developing countries is producing new tensions which affect future collaboration between producers and users of natural resources. To understand current problems, I believe, it is worthwhile to examine historical trends in this area which may help defining alternatives facing us in the future. In modern times the United States was the first country in the Pacific basin to start development of resources on a massive scale. It began with the major exploration of the mineral-rich west of the United States and extended significantly later into Latin America and Australia. In the early 1950's, Japan became a significant

Jan 1, 1976

By O. D. Sherby, J. E. Dorn

SEVERAL years ago Zener and Hollomon1 suggested that the flow stress of metals might be related to the temperature and strain rate in accord with the functional equation: s=s(eeh/rt) [1] at the same state. The Zener-Hollomon relation also contains the significant tacit implication that the energy for activation, AH, is substantially independent of the state of the material. The utility of this method for correlating creep data with tensile data was illustrated in a preliminary reportL on the effect of alloying additions on the secondary creep rates of binary a solid solutions in aluminum as shown for Al-Mg alloys in Fig. 1. Not only do the secondary creep and ultimate tensile properties for each alloy correlate well on this plot but in addition the activation energy, AH = 17,900 R cal per mol. is identical for the various compositions. Similar types of curves correlating the secondary creep rates at 422°K (300°F) with ultimate tensile data were also obtained for a series of dilute a solid solutions of copper, germanium, zinc, and silver in aluminum. In all cases the activation energy for creep, AH, was found to be equal to about 17,900 R cal per mol independent of the type of alloying element or its concentration. The coincidence of the activation energies for these alloys is probably due to the fact that the activation energies for creep are rather insensitive to small composition changes. Alloying additions, as shown in Fig. 1, however, increased the stress necessary to obtain equivalent values of ee?H/RT. Thus the stress level in curves of the type represented by Fig. 1 gives the relative creep strengths of the various alloys. Inasmuch as these correlations between creep and tensile data were obtained for creep tests at 422°K, it appeared advisable to ascertain the range of secondary creep rates and temperatures over which correlations between creep and tensile data could be made on the basis of the Zener-Hollomon relationship. If, for example, the activation energy changes with different ranges of creep temperatures, the utility of the proposed analysis would be severely weakened. But if AH is constant not only for all dilute alloys, but also over wide ranges of temperature and secondary creep rates, confidence will be developed not only in the broad utility of the Zener- Table I. Chemical Analysis':' and Grain Size of Alloys Mean Grain Residual Impurities. Wt Pct Diam- Alloying Atomic-eter, Element Pct Si Fe Cu Mg Mn mm Aluminum 99.987 0.003 0.003 0.006 0.001 0.25 Magnesium 1.617 0.003 0.004 0.006 0.26 Copper 0.101 0.003 0.003 0.0006 0.001 0.29 Zinc 1.616 0.003 0.005 0.007 0.001 '0.26 * The authors express their appreciation to the Aluminum Company of America for the preparation and chemical analyses of these alloys. Hollomon relationship, but also in its theoretical justification. The following investigation was instituted in order to ascertain the range of validity of the Zener-Hollomon relationship when it is applied to creep and tension data. Materials, Equipment, Technique In view of rather extensive correlatable data now available on the plastic properties of a series of binary a solid solutions of magnesium, copper, germanium, zinc, and silver in aluminum, these alloys were again selected for the present investigation. Previous reports have already covered the tensile properties of these alloys at subatmospheric temperatures," and at elevated temperature," as well as their fatigue properties at atmospheric temperatures, nd their creep properties at 422°K.' Resistivity measurementsa as well as precision lattice constant determinations? evealed that these alloys are a solid solutions. After homogenization. 0.100 in. thick sheets were rolled to 0.070 in. in thickness and recrystallized to about the same grain size. Since the details of these treatments were reported previously," they will not be repeated here. In order to appropriately reduce the scope of creep tests in this investigation only the typical alloys shown in Table I were investigated. All creep specimens were machined such that their tensile axes were in the rolling direction of the 0.070 in. sheet stock. The gage section was 2 in. long and 0.500 in. wide with a reduced section of 3.50 in. Creep strains were measured by means of rack and pinion type extensometers with a sensitivity of 0.005 in. per division. Readings were estimated to 1/10 of

Jan 1, 1953