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By L. E. Young

The purpose of this paper is to start a discussion on: (I) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, park walls, and filling, there will be no danger to men, equipment, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movemerit of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on conveyors on break lines, the rate of retreat should be increased substantially During 1935 and 1936, the United States Bureau of Mines, under a cooperative agreement with the Pittsburgh Coal Co., carried on studies of roof movement at Montour To. 10 mine. The work war done urider the direction of Mr. H. P. Greenwald, Supervising En neer, Experi-

Jan 1, 1938

By L. E. Young

The purpose of this paper is to start a discussion on: (I) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, park walls, and filling, there will be no danger to men, equipment, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movemerit of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on conveyors on break lines, the rate of retreat should be increased substantially During 1935 and 1936, the United States Bureau of Mines, under a cooperative agreement with the Pittsburgh Coal Co., carried on studies of roof movement at Montour To. 10 mine. The work war done urider the direction of Mr. H. P. Greenwald, Supervising En neer, Experi-

Jan 1, 1938

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

By Howard Smith

OF late considerable experimental and, theoretical interest has been shown in the rates of transformation from a single phase, usually a supercooled solid solution, into one or more phases. Such reactions may involve both diffusion and transformation of the major constituent, as in iron alloys, or it may simply involve diffusion, as in superstructure forma-tion and in age-hardening systems. Most of the work has been confined to ferrous alloys1-9t although two investigations have been made on copper alloys10,11. That such work may be of considerable, practical importance has been demonstrated by Bain12, by the workers at the Kaiser Wilhelm Institut fur Eisen-forschung13,14, and by the everyday use of precipitation and age-harden-inn principles15. Experiments in this country have generally followed Davenport and Bain's technique of rapid supercooling followed by isothermal treatment. In Germany16,17 the work has been extended to the study of the influence of accurately controlled and measured rates of cooling. The work on steel indicates that there are two subcritical temperature ranges where reaction starts sooner after quenching and proceeds at a more rapid rate than at other temperatures. At subcritical temperatures above Ar" where reaction is dependent upon atomic migration there is a period of time of which the length depends upon the alloy content and the temperature, before which no reaction has been detected. Daven-port and Bain1 find that different sorts of atoms in solid solution in gamma iron affect the length of this "prereaction" period differently, manganese

Jan 1, 1935

By William Carton, Cyril U. Cooledge

BecauSe the rich La Colorada orebody of the Cananea Consolidated Copper Co. does not outcrop at surface, after its discovery (by churn drill) and before mining was begun, a large amount of development work was done to learn the shape and extent of the ore and to provide for economic and effective mining. As these openings progressed, the actual shape of the orebody became known and with this knowledge came the realization that mining this rich and unusual deposit without loss of ore or danger to workmen presented several difficult problems. This paper will describe one of these problems; namely, the handling of an inverted cone-shaped core of barren rock, on the periphery of and below which the ore occurred. It mas clear that as the ore was mined out from around and under this inverted cone of rock, weighing about 3,000,000 tons, it would hang over the workings, held suspended only by its own tensile strength and threatening to crash into the stapes below with disastrous results to men and mine. The method of mining developed during the years 1928,1929 and 1930 anticipated and provided for the eventual collapse of this core of rock. In November 1936 the core settled down gradually on the edges of the stopes, descending a total of about 50 ft. vertically. The men in the stopes had ample warning and no lives were endangered. There were no air blasts in the mine. The core broke loose from its top support at the 500-ft. level along old fracture planes and evidently is crushed to the ninth level. Movement was of short duration; the following shift went to work in the stopes as usual. No ore was lost. Geological Structure The shape of the orebody is illustrated in Fig. 1. The geology of the Colorada orebody has been described by V. D. Perry1 and by W. G.

Jan 1, 1940

By Cyril U. Cooledge, William Carton

BecauSe the rich La Colorada orebody of the Cananea Consolidated Copper Co. does not outcrop at surface, after its discovery (by churn drill) and before mining was begun, a large amount of development work was done to learn the shape and extent of the ore and to provide for economic and effective mining. As these openings progressed, the actual shape of the orebody became known and with this knowledge came the realization that mining this rich and unusual deposit without loss of ore or danger to workmen presented several difficult problems. This paper will describe one of these problems; namely, the handling of an inverted cone-shaped core of barren rock, on the periphery of and below which the ore occurred. It mas clear that as the ore was mined out from around and under this inverted cone of rock, weighing about 3,000,000 tons, it would hang over the workings, held suspended only by its own tensile strength and threatening to crash into the stapes below with disastrous results to men and mine. The method of mining developed during the years 1928,1929 and 1930 anticipated and provided for the eventual collapse of this core of rock. In November 1936 the core settled down gradually on the edges of the stopes, descending a total of about 50 ft. vertically. The men in the stopes had ample warning and no lives were endangered. There were no air blasts in the mine. The core broke loose from its top support at the 500-ft. level along old fracture planes and evidently is crushed to the ninth level. Movement was of short duration; the following shift went to work in the stopes as usual. No ore was lost. Geological Structure The shape of the orebody is illustrated in Fig. 1. The geology of the Colorada orebody has been described by V. D. Perry1 and by W. G.

Jan 1, 1940

By David K. Mitchell

The mineral pyrite (or marcasite) occurs in coal beds as balls, lenses, veinlets and bands. Several million tons are w-asted annually on the refuse dumps from coal mining and coal-preparation activities. Sporadic attempts have been made in the United States to recover this pyrite for manufacture of sulphuric acid but only a few plants have succeeded in recovering it on a commercial scale. Shipments of pyrite from coal mines during 1941 were reported as follows: Illinois -The Midland Electric Coal Corp., Henry County, shipped 12,026 long tons containing 46 pct sulphur, at its Atkinson preparation plant. Indiana—The Snow Hill Coal Corp. produced pyrite from its Talleydalc preparation plant in Vigo County. Kansas—The Mineral Products Co. produced 3902 long tons of pyrite containing 44 pct of sulphur from picking table and washery refuse. Specifications for coal pyrite for acid manufacture rangc from 5 to 8 pct maximum carhon limit, and 42 to 45 pct minimum sulphur limit. Where flash roasting is practiced, the pyrite must be minus 100-mesh. Most companies give no size specifications. One company specifies 20- mesh or finer. Impurities in pyrite other than carbon may limit its use—for instance, arsenic, probably as arseno pyrite-—even though a concentrate can be made complying with specifications otherwise. Pyrite-recovery Plants Bradford breakers and picking tables may be used to make a marketable product where the pyrite occurs largely in sizes coarser than about I in. To make a grade of concentrate acceptable to sulphuric-acid plants the pyrite must break freely from the accompanying coal and slate, which is a rare condition to find. Most pyrite occurring in coal beds requires crushing and an abrasive type of grinding to free it of entwined coal and slate, followed by mechanical concentration by jigs, tables or other concentrating devices suitable for heavy ores, to make a satisfactory concentrate. At the Snow Hill Coal Corporation's plant in Indiana and at the Midland Electric Corporation's plant at Xtkinson, Ill., the final concentrate is made by a mechanical jig. The most recent and complete mill for concentrating pyritc from coal-mine refuse is that of the Mineral Products Co. at West Mineral, Kans., in which jigs and tables are used. Many regrinds and recirculations of products are necessary to get a concentrate of uniform grade. Trends On the whole, the economics of recovering pyritc from coal is not favorable. Cer-

Jan 1, 1948

By David K. Mitchell

The mineral pyrite (or marcasite) occurs in coal beds as balls, lenses, veinlets and bands. Several million tons are w-asted annually on the refuse dumps from coal mining and coal-preparation activities. Sporadic attempts have been made in the United States to recover this pyrite for manufacture of sulphuric acid but only a few plants have succeeded in recovering it on a commercial scale. Shipments of pyrite from coal mines during 1941 were reported as follows: Illinois -The Midland Electric Coal Corp., Henry County, shipped 12,026 long tons containing 46 pct sulphur, at its Atkinson preparation plant. Indiana—The Snow Hill Coal Corp. produced pyrite from its Talleydalc preparation plant in Vigo County. Kansas—The Mineral Products Co. produced 3902 long tons of pyrite containing 44 pct of sulphur from picking table and washery refuse. Specifications for coal pyrite for acid manufacture rangc from 5 to 8 pct maximum carhon limit, and 42 to 45 pct minimum sulphur limit. Where flash roasting is practiced, the pyrite must be minus 100-mesh. Most companies give no size specifications. One company specifies 20- mesh or finer. Impurities in pyrite other than carbon may limit its use—for instance, arsenic, probably as arseno pyrite-—even though a concentrate can be made complying with specifications otherwise. Pyrite-recovery Plants Bradford breakers and picking tables may be used to make a marketable product where the pyrite occurs largely in sizes coarser than about I in. To make a grade of concentrate acceptable to sulphuric-acid plants the pyrite must break freely from the accompanying coal and slate, which is a rare condition to find. Most pyrite occurring in coal beds requires crushing and an abrasive type of grinding to free it of entwined coal and slate, followed by mechanical concentration by jigs, tables or other concentrating devices suitable for heavy ores, to make a satisfactory concentrate. At the Snow Hill Coal Corporation's plant in Indiana and at the Midland Electric Corporation's plant at Xtkinson, Ill., the final concentrate is made by a mechanical jig. The most recent and complete mill for concentrating pyritc from coal-mine refuse is that of the Mineral Products Co. at West Mineral, Kans., in which jigs and tables are used. Many regrinds and recirculations of products are necessary to get a concentrate of uniform grade. Trends On the whole, the economics of recovering pyritc from coal is not favorable. Cer-

Jan 1, 1948

By Gilbert H. Cady

Those coal mining and preparation engineers and operators who read this article will probably be most concerned with those parts which deal with the applied aspects of coal petrology in the fields of mining and technology. Actually the two categories overlap to such a degree that they are essentially one. The article appears to suggest that there are two points of veiw in the field of applied coal petrology. From one viewpoint the interest is in the attributes of the various macerals (Fig. 4)-vitrinite, exinite, and inertinite-in terms of utilization (when the coal is burned, coked, gasified, hydrogenated, etc.). From the other point of view, assuming that the macerals do possess individuality in behavior, interest attaches to the possibility that coal of a particular type (maceral composition) can be prepared by discriminating methods of preparation and blending. Most of the 29 items listed for mining and technology can be assigned to one or the other of these two categories.

Jan 5, 1958

By D. H. Baldwin, R. E. Reed-Hill

WITH the polarized-light microscope, the basal-plane trace may be located on hcp crystal surfaces to an accuracy of approximately 1 deg. This determination can also be made on very small crystalline areas, approaching a micron in width. Measured basal-plane trace distributions on selected specimen surfaces can yield1,2 valuable texture information. However, the polarized-light microscope is probably best suited to orienting

Jan 1, 1965

By Herbert H. Uhlig

Although the mechanical properties of high-carbon manganese-iron alloys, particularly the Hadfield manganese steels, have been established, the literature discloses discrepancies in the reported properties for the low-carbon alloys. Hadfieldla summarized the existing data up to 1927, including the investigations of Guillet, Arnold, Strauss, Burgess and Aston, and reported his own values for alloys containing for the most part from 0.06 to 0.I5 per cent carbon. He noted: From these comparisons it wil! be seen that while there is a broad and general agreement as to the character of the alloys at the different manganese percentages, there are disparities in individual cases, especially as regards the degree of toughness or brittleness displayed by an alloy with certain percentages and with particular types of treatment. These differences are not always readily explainable.lb His data showed that alloys containing 4 to 10 per cent manganese water-quenched from Iooo°C. were brittle and hard with maximum brittleness at about 7 per cent. Slight improvement in ductility was obtained with compositions from 10 to 17 per cent manganese. Alloys containing up to 17 per cent manganese slowly cooled rather than quenched from 87o°C., he found, were slightly improved in ductility with significant improvement in alloys analyzing 4.1 and 4.8 per cent manganese. Recently Walters, Kramer and Loring2 reported mechanical properties for alloys made up from electrolytic manganese and ingot iron and containing from 0.02 to 0.04 per cent carbon. They showed that a tempering treatment at 54o°C. (Iooo°F.) for one hour significantly improved the ductility of compositions ranging from 6.7 to &apos; 20.7 per cent manganese. The differences of these compared with Hadfield&apos;s results they considered to originate in this tempering treatment plus the fact that Hadfield&apos;s alloys contained higher carbon and phosphorus (0.06 to 0.I5 per cent C; 0.06 to 0.07 per cent P compared with 0.02 to 0.04 per cent C, <o.ooI per cent P). In this paper it is shown that of the low-carbon alloys (0.02 to 0.03 per cent) containing from 3.3 to 21.5 per cent manganese moderately or rapidly quenched from IOOO°C. some are brittle or ductile, depending on presence or absence of hydrogen. Hydrogen is readily absorbed at high temperatures, and much of it is retained when the alloys are cooled to room temperature. The presence of hydrogen in the range of composition from 10 to 18 per cent manganese is a major factor in determining relative ductility. At 22 per cent manganese, and also at compositions below 10 per cent manganese, factors other than or in addition to hydrogen play a role. These are discussed. Also data are presented to show that hydrogen absorbed by the high-carbon alloys of Hadfield composition is without effect on their mechanical properties.

Jan 1, 1944

By Herbert H. Uhlig

Although the mechanical properties of high-carbon manganese-iron alloys, particularly the Hadfield manganese steels, have been established, the literature discloses discrepancies in the reported properties for the low-carbon alloys. Hadfieldla summarized the existing data up to 1927, including the investigations of Guillet, Arnold, Strauss, Burgess and Aston, and reported his own values for alloys containing for the most part from 0.06 to 0.I5 per cent carbon. He noted: From these comparisons it wil! be seen that while there is a broad and general agreement as to the character of the alloys at the different manganese percentages, there are disparities in individual cases, especially as regards the degree of toughness or brittleness displayed by an alloy with certain percentages and with particular types of treatment. These differences are not always readily explainable.lb His data showed that alloys containing 4 to 10 per cent manganese water-quenched from Iooo°C. were brittle and hard with maximum brittleness at about 7 per cent. Slight improvement in ductility was obtained with compositions from 10 to 17 per cent manganese. Alloys containing up to 17 per cent manganese slowly cooled rather than quenched from 87o°C., he found, were slightly improved in ductility with significant improvement in alloys analyzing 4.1 and 4.8 per cent manganese. Recently Walters, Kramer and Loring2 reported mechanical properties for alloys made up from electrolytic manganese and ingot iron and containing from 0.02 to 0.04 per cent carbon. They showed that a tempering treatment at 54o°C. (Iooo°F.) for one hour significantly improved the ductility of compositions ranging from 6.7 to &apos; 20.7 per cent manganese. The differences of these compared with Hadfield&apos;s results they considered to originate in this tempering treatment plus the fact that Hadfield&apos;s alloys contained higher carbon and phosphorus (0.06 to 0.I5 per cent C; 0.06 to 0.07 per cent P compared with 0.02 to 0.04 per cent C, <o.ooI per cent P). In this paper it is shown that of the low-carbon alloys (0.02 to 0.03 per cent) containing from 3.3 to 21.5 per cent manganese moderately or rapidly quenched from IOOO°C. some are brittle or ductile, depending on presence or absence of hydrogen. Hydrogen is readily absorbed at high temperatures, and much of it is retained when the alloys are cooled to room temperature. The presence of hydrogen in the range of composition from 10 to 18 per cent manganese is a major factor in determining relative ductility. At 22 per cent manganese, and also at compositions below 10 per cent manganese, factors other than or in addition to hydrogen play a role. These are discussed. Also data are presented to show that hydrogen absorbed by the high-carbon alloys of Hadfield composition is without effect on their mechanical properties.

Jan 1, 1944

By J. R. Hillebrand

From the abstract, "A realistic ore deposition model to serve as a conceptual framework." Further, on page 246, "The first area of study was the Josephine peridotite, now identified as an ophiolite terrane, located in northern California and southwestern Oregon (Fig. 3). Here, it was felt that we could test the models shown in Figs. 1 and 2 and, if successful, expand the model and test it in other chromite districts in the US and around the world." My comments refer only to chromite deposits in Europe and the Middle East. First, I question that may chromite deposits occur in the idealized ophiolite section shown in [Fig. 1]. Second, although some podiform deposits (referring to morphology) have been important (Gulernan, Turkey, for example), the stratiform deposits are of greater importance in tonnage and frequently grade. Examples include Nada, Yugoslavia; Bulqiza, Albania; Xerolivado, Greece; Saranovsk, Russia; and Abdasht, Iran.

Jan 1, 1984

By J. H. Scaff, J. E. Kunzler

The measurement of the electrical, thermal, and magnetic properties of metals at low temperatures, primarily in the range of liquid helium below 4.2°K, is a powerful tool for investigating many of the fundamental properties of the metallic state. Such measurements also have many practical applications, particularly as an analytical tool. One example of the practical utility of such measurements is illustrated by a short study we have made of the low-temperature resistance of copper used in preparing varistors. Copper-oxide varistors are prepared by the thermal oxidation of copper. This results in the

Jan 1, 1959

By I. M. LeBaron

The phosphate ore, or matrix, is a mixture of white pebbles of phosphate, of all sizes but mostly minus I to 1 1/4-in. diameter, in a matrix that varies from nearly all silica-sand gangue to a mixture of pebble, sand and clay. There is an occasional streak of hard pan of sand cemented with iron oxide, which can be drilled without much difficulty.

Jan 1, 1948

By I. M. LeBaron

The phosphate ore, or matrix, is a mixture of white pebbles of phosphate, of all sizes but mostly minus I to 1 1/4-in. diameter, in a matrix that varies from nearly all silica-sand gangue to a mixture of pebble, sand and clay. There is an occasional streak of hard pan of sand cemented with iron oxide, which can be drilled without much difficulty.

Jan 1, 1948

By M. J. McPherson, R. Venkataramani

R. Venkataramani (Assistant Professor of Mining Engineering, Dept. of Mining, The Pennsylvania State University, University Park, Pa.)-Y. J. Wang and L. W. Saperstein are to be congratulated for their paper on the computer solution of ventilation problems. The limitations on the problem size to be solved by the program (Appendix II) has been outlined in the paper. I would like to add the following additional limitations of this computer program: The dimensions of the variable J1and J2 should be changed to J, (550) and J2 (550) to handle problems containing more than 400 branches, and up to 550 branches. If there are a large number of branches common to the various meshes, another limitation on the problem size will be the dimension of the variable NA. While a higher-order polynomial fitting for the fan characteristic data points is more rigorous, a quadratic relation, if linear interpolation between the points is inadequate, will result in saving computing time without much loss of accuracy. Of course, this can be handled by minor modifications to the existing polynomial fitting routine in the program. M. J. McPherson (Dept. of Mining Engineering, University of Nottingham, Nottingham, England)-The

Jan 1, 1972

OF no less importance nor less terrifying to consider than the marvelous effects of guns are those produced with fire by powder in underground mines. These are truly not only similar to fearful natural earthquakes, but it can perhaps be said that these made by art surpass the wrath of the earth with greater effect. For if the latter shakes it happens that it causes the things on the surface to shake and sometimes to fall into ruins, but the former not only shakes but always functions and destroys-surely a marvelous effect which is almost incomprehensible, and if experience did not demonstrate it, it could scarcely be believed. Who would say that the mountains, things of such great hardness, would yield to men, easily opening their bowels? Likewise, one who had not seen it would say that it was impossible for men to have a way of administering at will fearful and destructive thunderbolts which are of such a kind that, although men make them, they cannot protect themselves against them; indeed they cannot call themselves safe from the evilness of gunpowder even in mountains composed of very hard stones or in budded structures. For, as is seen, there is no seemingly impregnable fortress that does not yield when guns are brought near it. If it happens, indeed, that guns can- not be brought near to some place because of the harshness of the site,

Jan 1, 1942

By J. W. Freeman, E. E. Reynolds, A. E. White

Fram a study of 63 systematic alloy modifications it was found that molybdenum, tungsten, and columbium, added individually or simultaneously, and increases in chromium cause major improvements in 1200°F rupture strengths of Cr-Ni-Co-Fe base alloys. Rupture strengths were a function of the effect of composition modifications on both the inherent creep resistance and the amount of deformation the alloy would tolerate before fracture. THIS paper describes the results of an investigation of a series of alloys with systematic variations of the chemical composition of the following basic alloy: C, 0.15: Mn, 1.7; Si, 0.5; Cr, 20.0; NI, 20.0: Co, 20.0: Mo, 3.0; W, 2.0; Cb, 1.0; N, 0.12; Fe, 32.0 pct. The 62 modifications of this alloy were produced under conditions which minimized all factors influencing properties at high temperatures except composition. Melting, fabrication, and heat treatment were carefully maintained constant. Stress-rupture properties at 1200°F were used as the primary criteria of evaluation of the alloy. The objective of the study was to obtain data for determining the fundamental role of the influence of alloying elements on properties of heat-resistant alloys at high temperatures. In addition the results should be useful in determining optimum chemical compositions, the sensitivity of properties to variations in composition, and the degree to which alloy content could be reduced while retaining worthwhile properties. It is difficult or impossible to develop correlations between properties at high temperatures and systematic variations in chemical composition from published data for wrought heat-resistant alloys developed for gas turbines.&apos; &apos; The main reason for this is the extreme dependence of the properties on conditions of treatment of the alloys." In most cases variation in final treatments between alloys so influences the properties that the influence of chemical composition is obscured. In addition it is recognized Table I. Basic Alloy and Some Modifications Used Basic AllOy, Variations in Element Pct Composition, Pct C 0.15 0.08. 0.40. 0.60 Mn 1.1 0.03,0.25.0.50,1.0,2.5 S1 0.50 1.2, 1.6 Cr 20.0 10, 30 Ni 20.0 0, 10,30 Co 20.0 0. 10, 30 MO 3.0 0. 1.2.3, 5, 7 W 2.0 0, 1, 5, 1 Cb 1.0 0.2,4,6 N 0.12 0.004, 0.08, 0.18 Fe 32.0 that variations exist between heats of the same alloy which are related to melting practice and that there is a strong possibility that conditions of hot working influence response to final treatments. The development of heat-resistant alloys has been based on the gradual accumulation of data roughly related to composition from extensive testing programs. There is every reason to believe that in most cases the optimum compositions have been achieved by this procedure in the alloys commercially available. There are, however, very little data showing the influence of systematic variations of composition free from the influence of other factors, particularly for alloys of the type investigated. Several investigators of cast alloys have demonstrated compositional effects, notably Grant,1-6 Epremian,t Guy,8 and Harder and Gow.9 Sykes10 eviewed the work on the wrought alloy Rex 78 and the systematic variations of carbon, copper, molybdenum, and cobalt leading to the development of the stronger Rex 337A alloy. From the papers by Wilson11 and Henry12 it is possible to deduce the beneficial effect of substituting cobalt for iron in 0.45 pct C-20 pct Cr-20 pct Ni-4 pct Mo-4 pct W- 4 pct Cb alloys. Wilson mentioned but did not present the extensive compositional studies involved in developing these alloys. Binder" showed optimum properties for 3, 2, and I pct, respectively, for molybdenum, tungsten, and columbium in 20 pct Cr-20 pct Ni-20 pct Co-30 pct Fe alloys for limited systematic variations of these

Jan 1, 1953