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By Robert H. Richards

The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe. In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper. In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger's work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal. The laws that have been claimed as the laws of jigging by the several authorities are: 1. The law of equal-settling particles. 2. The lam of interstitial currents. 3. The law of acceleration. 4. The law of suction. The first of these has been considered by investigators, generally, to be the most important of all, and the larger part of the work of jigging is thought to be governed by it. But that it does not cover the whole of jigging is clear to all; and to account for the increased efficiency which we may call the extra jigging-catch, the other three laws have been advanced. The investigation described in this paper was undertaken to determine, as far as possible, to what extent each of the four laws con-

Jan 1, 1895

By H. Scott

IN a paper read before the Institute of Metals, Rosenhain 1 described a new type of furnace designed primarily for the thermal analysis of metals by the inverse-rate method and used by him in the metallurgical department of the National Physical Laboratory with considerable success. In his discussion of this furnace, Rosenhain pointed out some difficulties met with in its operation, such as uniformity of rate of heating or cooling being inadequate for the degree of accuracy aimed at. To overcome this difficulty, he suggested, in place of motor propulsion, a gravity drive controlled by a"hydraulic cylinder with a relief valve whose width of opening can he regulated to allow of any desired rate of motion." The authors, in constructing a thermal-analysis furnace of Rosenhain's type, have therefore followed this suggestion and also added certain features that increase somewhat the convenience and simplicity of its operation. Requests for information regarding this furnace and the highly satisfactory results obtained from its use, it is believed, justify describing its construction and operation in sufficient detail to make possible its duplication or improvement. Description of Furnace.-The details of the furnace construction are shown in Fig. 1, which is drawn to scale. The heating tube is of /4 in. (6.35 mm.) wall "alundum" heated at the upper end by seventeen turns of 0.52 mm. platinum wire, which is coated with "alundum" cement supplied for this purpose. The cement coating is essential when a high temperature (over 1000° C.) is required, as it prevents hot spots with the resulting burning out of the heater. This platinum-wire winding, unlike "nichrome," is entirely satisfactory for temperatures of at least 1000° C. It has been maintained at that temperature continuously for 2 months and shows no signs of deterioration. This temperature is maintained by a current of 5 amp. drawn from 30 volts potential, so its necessarily continuous operation is quite economical.

Jan 8, 1919

By R. W. Cahn, C. D. Graham

Two predictions of the oriented growth theory of recrystallization textures have been tested by measuring the orientation dependence of the rate of growth of a single grain into a strained single crystal of aluminum, and determining the orientations of artificially and spontaneously nucleated grains growing preferentially into strained aluminum single crystals. Growth rates are found to be insensitive to orientation, except that new grains with orientations similar to the matrix or to a twin of the matrix have very low mobilities. Similarly, new grains growing preferentially into a strained crystal have random orientations, except that orientations near that of the matrix or its twins are avoided. The predictions of oriented growth theory are thus not confirmed. BASICALLY, the oriented growth theory of re-crystallization textures1 rests on the assumption that the rate of growth of a recrystallizing grain depends strongly on the orientation of the growing grain relative to the strained matrix into which it grows. In particular, the theory holds that in face-centered-cubic metals the orientation which corresponds to maximum growth rate is one in which the growing grain and the matrix are related by a rotation about a common <111> direction. The amount of rotation, as derived from several kinds of experiments,2-1 has been assigned various values, generally in the range between 20" and 40". (A <111> rotation of 60" is a twin relationship.) The conclusion that boundary migration rates depend strongly on orientation is based almost entirely on indirect evidence; there have been very few direct measurements of boundary migration rates as a function of orientation.* " The present investigation was undertaken to provide such measurements, to help make possible a decision between the oriented growth and oriented nilcleation theories of recrystal-lization textures. The basic experimental program consisted of measuring the rate of growth of a single recrystal-lizing grain consuming a strained single crystal, with the orientations of both grains preselected so that the effect of orientation on growth rate could be determined. A prerequisite for such an experiment is a strained single crystal which will support the growth of a new grain but which will not spontaneously nucleate new grains on heating. That is, the crystal must support the growth of a grain nucleated artificially, but contain no recrystalliza-tion nuclei which will become active at the testing temperature. Beck was apparently the first to note that such a condition could exist," and to make use of the condition for am experiment of the type described here.&apos; The present work was actually suggested, however, by a report of Tiedema". " that an aluminum single crystal strip, oriented with a (111) plane in the plane of the strip and a < 112> direction parallel to the tensile axis, would not recrystallize after 20 pet extension even when heated almost to the melting point, provided that the strip was heavily etched before being heated. This result could not be duplicated in the present work. In fact, it was found that any crystal which deformed in multiple slip (<100>, <112> and <111> orientations) underwent spontaneous nucleation after 15 pet extension, even if etched. However, crystals which deformed in single slip, and which did not develop heavy deformation bands, could be extended 15 pet without showing spontaneous nucleation at temperatures up to 600°C. Crystals oriented within about 10o of <110> which developed heavy deformation bands could be extended 10 pet without showing spontaneous nucleation. In all cases a heavy etch was required to prevent nucleation. Etching was necessary because of the presence of an oxide layer on the crystal surface at the time of straining, which leads to preferential nucleation at the surface.&apos;&apos; Grain Growth Rates Experimental Procedure and Results—Aluminum strips of 99.6 pet purity (principal impurities 0.19 pet Fe and 0.12 pet Si), 1 mm by 1 cm in cross section, were grown into single crystals of controlled orientation by the strain-anneal method of Fuji-wara.&apos;"&apos; " A sharp temperature gradient was maintained in the strips during growth by lowering them into a salt bath controlled at 650°C. Crystal orientations were determined by the etch-pit method of Barrett and Levenson" to an accuracy of ±2O. The crystals were extended by 10 or 15 pet in a simple hand operated tensile machine. Crystal orientations were rechecked after extension, and were found to be in agreement with the orientations predicted by the formula of Schmid and Boas." After extension, the grip ends of the single crystal specimen were cut off with a jeweller&apos;s saw, and the crystal heavily etched (at least 20 pet wt loss) in hot 10 pet Na or KOH solution. A region of severe local deformation was then introduced at one corner of the strip, usually by cutting off the corner with shears. Heating this end of the strip caused a large number of new grains to nucleate at the sheared edge. One of these grains grew to occupy the full width of the strip. The appearance of the strip at

Jan 1, 1957

By G. Sachs, E. J. Ripling, J. J. Lynch

It is general practice to evaluate the strength properties of a particular metal from its stress-strain (s1 — el) curve obtained by means of a conventional tension test. Such a stress-strain curve, Fig I, illustrates two important properties of a metal, its ability to strain harden, and its ability to withstand a certain limiting stress, the "fracture stress," (s), and a certain limiting strain, the "ductility" (es), before it fails by separation. These two fracturing characteristics are the coordinates of the point of fracture in Fig I. In the case of a metal which necks in a tension test, both the fracture stress and the ductility (measured in a tension test) are dependent upon (I) the shape of the neck and (2) average values of the stresses and strains over the cross-section at the moment of fracture. However, for the pur. pose of this investigation, these average quantities, rather than the actual values, may be considered for reasons of simplicity. It appears that the conclusiom also hold true if the analysis were carried out for actual values of fracture stress and ductility at the locos of failure. In this paper, the effects of straining (at room temperature) by various methods on the above metal characteristics, which were determined by subsequent tension tests will be discussed. According to Our present knowledge, any such prestrainitlg results in a stress-strain curve (in subsequent testing by tension), Fig 2, the general shape, or flow characteristics, of which can be derived from the original stress-strain curve of the unstrained metal minus a certain portion exhausted by the initial straining. This phenomenon is called strain hardening, and may be measured by the magnitude of the cut-off, or the "effective strain,&apos;&apos; from which the new curve must start in order to coincide in its plastic branch with the original stress-strain curve.

Jan 1, 1949

By M. R. Pickus, I. W. Pickus

Ordinarily age-hardening is thought of as being associated with a limited solubility of one metal in another. Much less has been written about the type of age-hardening that attends the formation of superstructures. Solid solutions generally have a disordered or random arrangement of atoms; that is to say, in a unit cell, such as that of the face-centered cubic lattice, there is no distinction between atomic sites. Atoms of a given metal may occupy cube corners or face centers. Under certain conditions, however, some alloys develop what is known as an ordered structure. In this case, cube corners would be occupied by only one type of atom and face centers by another type. Associated with this ordering process are many interesting changes in physical and electrical properties. Moreover, in many instances the alloys become susceptible to age-hardening. From the evidence now to be described, it appears that age-hardening in 14-carat gold alloys is due to the formation of both a superstructure and a precipitate. Alloys of the metals gold, silver and copper were known in antiquity. The available knowledge regarding their constitution has been ably summarized and extended by Sterner-Rainer,&apos; Jänecke,2 Carter,3 Wise,4 and Coleman.5 Despite the long familiarity with these alloys and the numerous investigations of their properties that have been made, there is still much that remains unexplained. It has been known for a long time that the hardness of these alloys is closely related to the rate of cooling. Similar changes have been observed in the binary gold-copper systemI6 one alloy of which corresponding to the formula CU³AU, has been the subject of a careful and competent report by the English investigators, Sykes and Evans.7 They have established the fact that the shift of atoms from the ordered to the disordered condition takes place in some critical temperature range. At temperatures above the critical range the structure is random, and at temperatures below it the structure is ordered. No difference between these two structures is revealed by the microscope. Both have a face-centered cubic lattice and complete solubility, so that there is no evidence to suggest that the changes in properties are associated with a phase change. The more slowly the alloy is cooled, the higher is the degree to which the ordering process proceeds and the more marked is the increase in hardness. As experimental data were accumulated on I4-carat gold alloys, several contradictions arose. Certain observations tended to confirm the existence of a superstructure, while other observations seemed to be inconsistent with such a transformation. Present Investigation As a focal point about which to develop this subject, it is expedient to consider first

Jan 1, 1943

By M. R. Pickus, I. W. Pickus

Ordinarily age-hardening is thought of as being associated with a limited solubility of one metal in another. Much less has been written about the type of age-hardening that attends the formation of superstructures. Solid solutions generally have a disordered or random arrangement of atoms; that is to say, in a unit cell, such as that of the face-centered cubic lattice, there is no distinction between atomic sites. Atoms of a given metal may occupy cube corners or face centers. Under certain conditions, however, some alloys develop what is known as an ordered structure. In this case, cube corners would be occupied by only one type of atom and face centers by another type. Associated with this ordering process are many interesting changes in physical and electrical properties. Moreover, in many instances the alloys become susceptible to age-hardening. From the evidence now to be described, it appears that age-hardening in 14-carat gold alloys is due to the formation of both a superstructure and a precipitate. Alloys of the metals gold, silver and copper were known in antiquity. The available knowledge regarding their constitution has been ably summarized and extended by Sterner-Rainer,&apos; Jänecke,2 Carter,3 Wise,4 and Coleman.5 Despite the long familiarity with these alloys and the numerous investigations of their properties that have been made, there is still much that remains unexplained. It has been known for a long time that the hardness of these alloys is closely related to the rate of cooling. Similar changes have been observed in the binary gold-copper systemI6 one alloy of which corresponding to the formula CU³AU, has been the subject of a careful and competent report by the English investigators, Sykes and Evans.7 They have established the fact that the shift of atoms from the ordered to the disordered condition takes place in some critical temperature range. At temperatures above the critical range the structure is random, and at temperatures below it the structure is ordered. No difference between these two structures is revealed by the microscope. Both have a face-centered cubic lattice and complete solubility, so that there is no evidence to suggest that the changes in properties are associated with a phase change. The more slowly the alloy is cooled, the higher is the degree to which the ordering process proceeds and the more marked is the increase in hardness. As experimental data were accumulated on I4-carat gold alloys, several contradictions arose. Certain observations tended to confirm the existence of a superstructure, while other observations seemed to be inconsistent with such a transformation. Present Investigation As a focal point about which to develop this subject, it is expedient to consider first

Jan 1, 1943

By D. W. White

The kinetics of isothermal transformation of ß-to-u uranium have been studied over a broad temperature range in alloys containing from 0.3 to 4.0 atomic pct Cr. Two modes of transformation are indicated by the existence of two C-curves in the TTT diagram. The upper temperature mode is regarded as a nucleation and growth mechanism, whose rate is controlled by diffusion of chromium in the ß phase matrix. The lower temperature mode is martensitic in nature. The M, temperature increases with decreasing chromium content, suggesting that the two transformation processes become synonymous in unalloyed uranium. URANIUM metal undergoes two allotropic transformations in the solid state. The a phase, orthorhombic in crystal structure,&apos; is stable from room temperature up to about 665°C. The ß phase, characterized by a complex tetragonal structure,&apos; prevails from 665" to about 770°C. The y phase is body-centered-cubic3 and is the stable modification from 770°C up to the melting point (about 1130"). In uranium of reasonable purity, neither of the two high temperature phases can be retained by quenching. However, the addition of certain alloying elements to uranium makes it possible to retain either the y-uranium phase or the ß-uranium phase at room temperature. Chromium alloyed in small amounts with uranium will permit retention of the ß-uranium phase in a metastable state at room temperature upon quenching from a ß-phase temperature.&apos; From available information&apos; on the equilibrium phase diagram for the U-Cr alloy system (Fig. I), it is to be expected that, however sluggish in its rate, the ß phase in such alloys should decompose eutectoidally to a phase and elemental chromium. It was the aim of this investigation to measure the rate and study the nature of this decomposition as a function of temperature and of chromium content. The investigation was reported in classified literature about five years ago and has recently been declassified for publication. In the meantime, there have appeared the papers of Holden,5 Mott and Haines,".&apos; and Butcher and Rowe8 ealing with the metallography and the crystallography of the ß-to-a transformation in U-Cr alloys. These investigators have confirmed several of the phenomenological observations that will be described in the present paper and have examined in considerable detail certain aspects of the transformation and its mechanism. Although all of these investigations have concerned themselves experimentally with U-Cr alloys for the most part, an important consequence has been a clearer understanding of the nature of the ß-to-a transformation in uranium metal itself. Experimental Procedure This investigation dealt with a series of uranium alloys varying in chromium content from 0.3 to 4.0 atomic pct (0.066 to 0.90 weight pct). On five of the alloys, rates of isothermal transformation from the ß to the a phase were measured over a wide temperature range, leading to the development of TTT (time-temperature-transformation) diagrams. Transformation rates were measured over certain narrow temperature ranges on additional alloys. The alloys were prepared by vacuum melting and casting, using zircon or magnesia crucibles and graphite molds. Electrolytic chromium was used as the alloying addition, and the uranium was Mallin-ckrodt biscuit metal that had been vacuum remelted and cropped to remove many of the nonmetallic impurities that had floated to the top of the ingot. The ingots, 3/4 or 1 in. diam, were reduced in size by swaging. Alloys containing less than about 2 atomic pct Cr were swaged at 250° to 275°C, with initial and intermediate anneals at 550°C after every 75 pct reduction in area. Alloys with higher amounts of chromium were swaged at 550" to 600°C, although at the smaller sizes some of them were reduced by the procedure used on the more dilute alloys. Before use as test specimens, the swaged rods were annealed at 700" to 720°C for several hours, followed by slow furnace-cooling. The purpose of the anneal was to achieve the maximum amount of solution of the available chromium into the ß phase, as well as to remove extensive preferred orientation. The isothermal transformation rates were measured dilatometrically, using a quenching dilatometer and an experimental technique similar to those employed by Davenport and Bain in their original work on the transformation kinetics of austenite in

Jan 1, 1956

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth&apos;s crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth&apos;s crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth&apos;s crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth&apos;s crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By C. R. Fast, George C. Howard

Laboratory and field testing of various squeeze cementing techniques and materials revealed that many improvements could be made in squeeze cementing operations. The use of a slow-pumping squeeze cementing procedure permitted the control of the quantity of cement displaced into a formation and aided in obtaining a high final squeeze pressure. Field testing indicated the desirability of obtaining high final squeeze pressures, the need for improved formation breakdown fluids, and the necessity of controlling the pressure differential during testing after a squeeze job. INTRODUCTION During the past few years, squeeze cementing operations have been investigated, both from the theoretical as well as the practical point of view, in an effort to arrive at some solution to the many and varied problems that arise with this type of operation. A review of well files indicated that in many instances, wells were being squeeze cemented four and five times before a satisfactory pressure buildup was obtained. There seemed to be considerable variation in opinion as to the proper method of squeeze cementing, as well as disagreement as to the proper breakdown agent, the quantity of cement that should be used, type retainer and length of WOC* time that was necessary. Consequently, it was deemed advisable to approach this problem theoretically, field testing each idea developed in hopes of eventually arriving at a squeeze cementing procedure that would give reasonable assurance of a successful job after one squeeze cementing operation. This investigation was. therefore, divided into two broad headings: (1) Preliminary studies, which include both theoretical and laboratory studies, and (2) Field investigations to determine the proper squeeze cementing methods. PRELIMINARY STUDIES Overburden Pressure Studies Squeeze cementing problems are so intimately related to the earth&apos;s overburden pressure that solutions to them are very difficult, if not impossible, without an understanding of the nature and magnitude of the overburden pressures encountered at the depths of producing wells. It was thus felt that the first approach to research on squeeze cementing should be made through a study of these pressures. Since there has been rather loose usage of a number of the terms related to overburden preasure by different writers, the terms to be subsequently used are defined here. Theoretical overburden pressure is the calculated pressure at any given depth exerted by the theoretical weight of overlying formations as calculated from the average rock density. Fluid displacement pressure is that pressure at which fluid can be injected into a formation after it has been broken down. It may be more or less than the theoretical overburden pressure. Formation breakdown pressure is that pressure at which a formation parts or breaks and is usually thought of as fluid displacement pressure plus rock strength. Breakdown agent is that fluid with which the formation is fractured. The first step in the study of the earth&apos;s overburden pressures involved a review of pertinent technical literature. The general opinion expressed was that the overburden pressure gradient of the earth&apos;s formations is roughly 1.0 psi per foot of depth, and that application of sufficient pressure to stratified formations. will cause them to part at or parallel to the bedding planes. The second step in the study of overburden pressures involved a study of available well data in an effort to obtain some definite information as to the actual values experienced in the field for the above mentioned terms. Data from 115 cement squeeze jobs in the Gulf Coast area and 46 cement squeeze jobs and acid jobs in the West Texas-New Mexico area were closely analyzed. The analysis of these data showed that the average formation breakdown

Jan 1, 1950

By Charles A. Colton

The results of a series of analyses extending over a period of three weeks at the Cedar Point Iron Company&apos;s furnace, Port Henry, New York, are given in Tables I and 11. This furnace uses a very pure magnetite and Lehigh and Lackawanna anthracite. The flue leading the gas from the "down-comer" to the boilers was tapped by a 2 inch gas pipe, which carried the gas to the Orsat apparatus. The pressure of the gas not always being sufficient, owing to the small amount made, to force it into the apparatus, I omitted taking samples several days, and with the exception of the last three days of the campaign, made the analyses whenever opportunity offered. I find the Orsat apparatus, as described by Prof. Egleston," to work very well, with one exception. The CO is not absorbed as readily in the ammonia-copper solutiou as he states in his description of the apparatus, as many as 50, and sometimes GO, passes being necessary to absorb all the CO. The power of absorbing rapidly increases as the solution is used, and this would indicate that the more oxygen it contains the quicker will it do the work. Probably the addition of a small amount of some oxidizing agent would remedy this. When the furnace was working in its normal condition, I had no occasion for using the filter, the amount of fume being so small as not to canse any inconvenience. The gas burned with the flame peculiar to CO, and contained just enough solid particles to give it a slight reddish tinge.

Jan 1, 1879

By O. N. Carlson, H. A. Wilhelm, H. E. Lunt, J. M. Dickinson

On the basis of data obtained from microscopic examination, melting observations, cooling curves, X-ray analyses, and resistance measurements, phase diagrams have been proposed for the Th-Cb and Th-Ti alloy systems. Both are simple eutectic systems and have no terminal solid solubility or intermediate phases. The eutectic between thorium and columbium occurs at a composition of about 8 wt pct Cb and a temperature of 1435°C. The Th-Ti eutectic occurs at 1190°C at the composition 12 wt pct Ti. No change was observed in the transformation temperature of thorium in either system or in the titanium transformation. RECENT study of thorium and its alloys has been promoted because of the possibility of employing this metal in nuclear reactors. Their corrosion resistant properties, nuclear characteristics, and high melting points put columbium and titanium among the many metals being employed in the study of thorium alloys. Since a knowledge of the phase relationships would be important in the application of such an alloy, investigations were undertaken to propose phase diagrams for the Th-Cb and Th-Ti systems. Experimental Procedures Thorium metal sponge was specially prepared for use in this investigation. Carbon in a quantity less than 0.04 wt pct was the principal impurity. There was also less than 0.01 pct each of iron, calcium, zinc, aluminum, and nitrogen in the thorium. Columbium, both as a powder and sheet metal, was obtained from the Fansteel Metallurgical Corp. The manufacturer&apos;s specifications indicated that the metal contains less than 1 wt pct total impurities. An analysis of the metal showed approximately 0.18 pct C in the powder and less than 0.05 pct C in the sheet. The titanium used was commercial sponge, reported to be 99.5 pct Ti. An analysis showed that this metal contained 0.2 pct Fe. Preparation of Alloys—Since the metals used in this investigation are reactive and might become contaminated on melting in a refractory crucible, the alloys were prepared by arc melting. The titanium sponge was employed in the form of small lumps while the columbium additions were made either as pressed pellets of powder or as clippings from sheet. The alloying material and the thorium sponge were melted together under argon in conventional arc melting equipment employing a tungsten electrode and a water cooled copper crucible.

Jan 1, 1957

By A. E. Bellis

There is a wide difference of opinion among rifle experts in the matter of barrel steel, and the relative importance to the life of the barrel of the steel&apos;s composition, heat treatment, structure, and physical properties. In order to promote discussion, which it is hoped may&apos; lead to the discovery of the source of some of the traditional beliefs on the subject, the results of some tests are presented here, with data on heat treating, physical tests, and erosion. The detailed metallographic study of this steel is given in another paper.l The conclusions from these tests should be capable of wider application than their direct bearing on the barrel-steel problem. The Government specifications for barrel steel for model 1903 rifle (Springfield) call for carbon 0.50 to 0.60 per cent., manganese 1.00 to 1.29 per cent., silicon under 0.25 per cent., sulfur under 0.06 per cent., phosphorus under 0.08 per cent. The minimum physical requirements are: Tensile strength, 110,000 lb. per sq. in. (7733 kg. per sq. cm.); yield point, 75,000 lb. per sq. in (5472 kg. per sq. cm.); elongation, 20 per cent.; reduction of area, 45 per cent. Material fulfilling these requirements gives practically no failures when proof-fired, with charge of 70,000 lb. per sq. in. pressure, which is 40 per cent. in excess of the service charge. The turning and drilling operations show up any seams or laps such as accidentally occur even in the best heats of open-hearth steel, so that faulty stock is practically all eliminated before proof-firing. These physical requirements are met either by rolling billets at a proper temperature down to the form of tapered barrel blanks or by heat treating bars that have been upset to cnlarge the breech section. The transformation temperature of this steel, on heating, is around 1350" F. (732&apos; C.), varying somewhat with the composition and the rate of heating. The actual treatment of the barrel blanks, as carried out by different manufacturers, gives four kinds of barrels, which will be called A, B, C, and D, for convenience. A barrels result from heat treating upset blanks by quenching at

Jan 1, 1920

By G. L. F. Powell

Bulk samples of silver have beat undercooled lo a large degree in contact with crystalline siliceous and ceramic oxide materials, indicating lhat stable oxides and oxide compounds are not the heterogeneous nucleants which normally catalyze cryslallization within a feu degrees of the equilibrium freezing point. Since 400-g samples were undercooled 250°C in contact with cristobalite, it is concluded that the undercooling required for homogeneous nucleation of sil11er is greater than 250°C. Undercooling was Jacilitated by precleaning the crucibles with a high-fires -sure blast of gas. IN numerous experiments on the undercooling of metal melts it has been assumed that a solid glassy surface, being non crystal line, will have no effect in catalyzing crystal nucleation from the melt. Conversely, it is usually accepted that any crystalline surface, in contact with a metal melt, will catalyze nucleation of metal crystals from the melt at degrees of undercooling less than that at which homogeneous nucleation will occur. Both these assumptions were implicit in the claim that homogeneous nucleation was observed in experiments1&apos;2 on the undercooling of small metal droplets (10 to 100 mp diam). The droplets were thought to be freed of suspended crystalline particles which would otherwise catalyze heterogeneous nucleation. They were supported on flakes of silica glass which were assumed to be amorphous, and therefore incapable of acting as substrates for heterogeneous nucleation. In later experiments, large samples of molten metal were undercooled to temperatures similar to those achieved by the droplet technique by melting in a fused-silica crucible3 or a boro-silicate glass slag.4 Since these samples were usually fully enclosed in glass at the moment of freezing, it seemed possible that nucleation was homogeneous when maximum degrees of undercooling were achieved, despite the large size of the samples (up to 500 g). In experiments on the undercooling of silver5 the metal was contained in vitreous silica crucibles, the

Jan 1, 1968

By M. M. Singh, H. L. Hartman

This paper reports on the results of a fundamental investigation of the behavior of rock under impact of a chisel-shaped bit. Drop-tester studies were conducted with strain gauges attached to the rock and striking bit-edge. It was established that rock behaves viscoelastically. Little correlation was found to exist between the strain waveforms detected on the rock surface and in the bit; thus, strain-time curves obtained with transducers mounted on the bit cannot be used to explain the sequence of events in rock breakage. It is estimated that nearly 1 per cent of the total energy of the blow is expended in permanent deformation of the rock. The strain- energy distribution on a rock surface as a result of chisel impact, which follows a simple law, is presented graphically. Experiments also were conducted with gauges embedded in the rock vertically below the line of impact and at an angle of approximately 45&apos; to the vertical. No essential difference was observed in the type of wave obtained with embedded gauges and with gauges on the surface, as may have been anticipated from theory. INTRODUCTION Through the ages great strides have been taken towards improvement of the various techniques applied in the breakage of rock. Indeed, numerous applications of the rock-failure process are an integral part of present-day industry, including oil well drilling. Yet, astonishingly, little is known regarding the behavior of rock under dynamic loading or the mechanism of rock failure. The value of impact loading studies from the point of view of drilling is evident, however, and requires little elaboration because impact of a chisel edge on rock forms the basic action constituting most common methods of drilling. RELATED STUDIES Impact studies of communition and fragmentation conducted by Fahrenwald, et a1,8 Poncelet,l7 Axelson, et a1,2 Piret,16 Hartman and pfleider,ll Charles and deBruyn,5 and others have been of considerable help in understanding rock-breakage phenomena. Further insight into the basic action of drilling and penetration has been obtained by the work of Irving,13 Cherkasov and Shlyapin,6 BOrcherdt,3 Shepherd,19 Shreiner and Pavlova,20 Drilling Research Inc.7 Hartman,10 Appl and Gatley1 and several other investigators. However, knowledge concerning the stresses and strains induced in the rock and bit during impact remains scant. Recent photoelastic studies by Tandanand and Hartman (1961. 1962)22, 23 have shed light on stress distributions and Fracturing produced in plastics by chisel-shaped bits. In the field of transient strain Pulses and their role in rock drilling, the only extensive work has been performed by Drilling Research Inc. (DRI). They attached strain gauges to the shank of a bit and conducted drop-tester studies, using a die-shaped bit to obtain force-time diagrams. Their work led to the conclusion that, for a given rock type, the first peak of force occurs at a fixed level regardless of the total energy in the system, provided it exceeds a certain minimum threshold level. Further, on this basis an explanation was offered for the sequence of events in crater formation as the result of a single blow on rock. PURPOSE OF PRESENT STUDY The investigations reported in this paper were conducted in a manner similar to the DRI approach, but with the objective of determining the strain distribution in the rock around the area of bit impact and, to a limited extent, the strain in the chisel-shaped bit itself. It was expected that a knowledge of the disposition of these strains, along with the rate of attenuation of strain energy in the rock

By Edmund M. Warner

Any city dweller who has walked alone along a remote mine passageway has to be impressed by the eerie silence-the total absence of noise except for one&apos;s own breathing and scuffing of boots on the bottom. An underpound mine can have tremendous contrasts, from complete silence to the ear piercing clatter of percussion drills working in the mine roof. Noise in underground mining machines is both useful and detrimental. Without characteristic noises that are recognizable to miners, operators would have a more difficult job operating their machines. Noise serves as a warning of approaching machinery, and changes in noise give indication that breakdowns may occur. But excessive noise is a health hazard. In recognition of this fact, our congress included noise exposure as a part of the "Coal Mine Health and Safety Act of 1969." As [Fig. 1] indicates, allowable noise exposure is established by specifying a time duration permitted at different noise levels. This is the well known "Walsh-Healey" criteria which govern noise exposure in many industries. In most industries noise exposure is not a constant value. Noise emitted from coal mining machinery varies widely, and therefore interpretation of compliance is not a simple matter. Time, environment, instrumentation and machine productivity, as well as the designed machine characteristics affect the results. It is the purpose of this paper to present the underground coal face machinery noise problem from a manufacturer&apos;s point of view. Manufacturers are very much aware of their responsibility to alleviate the noise problem. Not infrequently, orders are received from coal operators that a given new machine must comply with "The Coal Mine Health & Safety Act" noise regulations. Such a request is indicative of the misunderstanding which exists with machine users, while indicating their desire to comply with the law. Obviously, if all machinery could be designed and used at some arbitrary low noise level, it would be possible to simplify the regulations. However, there still remains the pervasive problem of existing machines. Extensive investigation to create practical retrofit kits for existing machines, to substantially reduce noise have been only marginally successful. Certain machine mechanisms are inherent noise makers. The only really good solution is to substitute a quieter mechanism. Such overall new designs have been undertaken, and several examples are mentioned later in this paper. Before describing machine noise problems, it is necessary to define noise values. Noise levels are measured in decibels. The designation "DBA" is decibels measured on the "A" scale, or one in which the frequency sensitivity of the instrumentation is about the same as the human ear. The numbers are often misinterpreted because it is a logarithmic, rather than an arithmetic scale. In comprehending the numbers, it should be remembered that any increase of 3 dB doubles the sound power. In practical terms this means that two noises of equal power at the same distance away increases a dB reading by three. Consider [Fig. 2] showing a simplified case of a worker on a machine subject to

Jan 1, 1980

By D. S. Gleason, D. E. Severson, D. R. Skidmore

Pittsburg and Midway Coal Co. has modified the German Pott-Broche process, on which patents date back to 1927, to produce on a bench scale liquid products by solution hydrogenation of coal. A continuing program of lignite solution-hydro gena-tion experiments is directed toward investigating coal solution reactions, determining favorable conditions for the solution refining of lignite by the Pott-Broche process, and investigating some of the uses for the de-ashed product obtained from lignite The German Pott-Broche process1" on which patents date back to 1927, has been modified by the Pittsburg and Midway Coal Co., a Gulf Oil subsidiary, to produce on a bench scale liquid products by solution -hydrogena-tion of coal." The objectives of the present effort are to investigate coal solution reactions, to determine favorable conditions for the solution refining of lignite by the Pott-Broche process, and to investigate some of the uses for the de-ashed product obtained from lignite. This paper is a summary of results to date in a continuing program of lignite solution-hydrogenation experiments. The coal solution reaction program has several principal aims. The first of these is to determine whether lignite can be successfully dissolved in solvents that might be practical for commercial development. The second object is to determine whether the solvents function after successive cycles of use, recovery, and reuse. It seems necessary to the economics of a potential commercial process that the solvent be recycled. Third, it is desired to learn something about the distribution of the ash constituents between cake and filtrate. The extent of ash removal is important. The nature and quantity of mineral matter passing through the filter may determine end-use marketability. For certain use applications, trace quantities of certain minerals can be objectionable, e.g., titanium and vanadium must be very low in electrode carbon for aluminum production. The Solution Reaction The coal solution Process involves an extremely complex system of chemical reactions. An initial solvent such as anthracene oil is a mixture of hundreds of different compounds with a boiling range of roughly 500" to 750°F at atmospheric pressure. The coal macro-molecule is broken down by thermal decomposition and solvent action into myriads of different compounds, some the same as those comprising the solvent. This similarity in structures opens up the possibility of production and subsequent recovery of solvent. Some solvent is inevitably lost by reaction. Regeneration of solvent was not a problem in the early German Pott-Broche plant. The coal refinery was an integral part of a petroleum refinery complex and replacement solvent was readily available. A coal refinery using lignite, however, might be isolated from other hydrocarbon processing facilities and the regenerability of solvent could be vital to the economic success of the venture. Several structural features of the solvent molecules have been cited as important to the coal solution process.&apos;. The first of these is aromaticity of the material, the second, ability to transfer hydrogen to another molecule, as for example the ability of tetralin to transfer hydrogen and be converted to naphthalene. Finally, the presence of hydroxyl groups on aromatic rings within the molecule, i.e., phenolic character, seems beneficial. Mixtures of pure compounds have been tried by various investigators. Mixtures of o-cresol, a phenolic substance, and tetralin were found to dissolve bituminous coal better than either substance alone.3 This maximum solubility was not found with lignite." Hydrogen contributes to the reaction by hydro-genolysis and by combining with free radicals and molecular "loose ends" to stabilize the compounds formed in coal depolymerization. High boiling point, and correspondingly high molecular weight, seems to be a property which improves solution potential for coal with a given type of compound.&apos; The maceral components of the coal appear to have an important bearing on its ease of solution. The fusain portion is quite inert to solvent action, but the an-thraxylon material dissolves quite readily.3 The hydrogenation reaction can be improved by the use of a catalyst; commercial hydrogenation catalysts having been found effective. Although cost is involved in the use of catalyst and catalyst recovery, the resulting saving in time and perhaps lowered temperature or pressure might justify their use in the solution refining process and decrease the total process costs. Apparatus and Procedure The coal solution runs were made in a 1-gal stainless steel stirred autoclave. The autoclave was provided with thermocouple wells and a transducer to permit continuous recording of temperature and pressure. The autoclave stirrer was magnetically driven, eliminating the leakage inherent with a rotating pressure seal. For runs in which a catalyst was used, the catalyst in the form of beads was placed in a wire mesh container mounted on the stirrer shaft. A control system programmed the heatup and reaction cycle. The permissible heating rate was 5°F per min because of the need to minimize thermal stress in the autoclave body. The temperature was raised at that rate until the reaction temperature was attained and then the temperature was held constant for the desired length of time. The maximum temperature seldom exceeded the average run temperature by more than 15°F.

Jan 1, 1971

By Scott Howard

MANGANESE being perhaps the least expensive of the metallic alloying elements that can be advantageously added to iron in considerable quantities, the basic characteristics of its alloys with iron are properly receiving much attention at present. In the course of a dilatometric investigation of this system several years ago, the writer observed certain transformation phenomena not found in other iron-base alloys. The interpretation of those effects was not evident from the information then available, but recent X-ray studies clear up at least one anomaly and permit a more satisfactory description of the results than would have been possible otherwise. Aside from the new phenomena observed, the effect of manganese on the Ar3 transformation is of timely interest because of its bearing on the critical compositions of austenitic alloys, the applications of which are now being greatly extended. It is known that the properties of these alloys are unstable unless the Ar3 transformation occurs at a temperature considerably below atmospheric and that manganese is very effective in depressing the temperature of this transformation. The writer aims to establish a simple general relation which expresses the location of Ar3 quantitatively in terms of the content of the common alloying elements used in steel. A step in that direction is taken here. Early dilatometric investigations1 indicated that only one transformation other than the eutectoid A1 occurs in the high-iron alloys of the iron-manganese system. Dejean represents the Ar3 point as falling to 0° C. with a manganese content of 11 per cent and carbon content of between 0.30 and 0.40 per cent. Esser and Oberhoffer,2 using alloys low in carbon (under 0.03 per cent), arrived by extrapolation at 14 percent for the manganese content at which Ar3 is depressed to 0° C. Not until both low carbon contents and alloys having a manganese content

Jan 1, 1931

By Albert Sauveur

Some writers believe that when austenite transforms completely into pearlite on slow cooling through the thermal critical range, such transformation does not imply the formation of any of the so-called transition constituents: martensite, troostite and sorbite. Might it not be claimed with as much justification that when water freezes it does so suddenly, solid ice being obtained without passing through the intermediate stages of ice and water? Obviously, regardless of the speed of solidification, this would be erroneous. Before reaching the completed solid condition, this must of necessity pass through an unbroken series of stages when the system consists of mixtures of water and of ice, the former decreasing and the latter increasing in amount. Are not these "transitionV stages in the freezing of water similar to the transition stages occurring in the transformation of austenite into pearlite? To clarify, let us consider in Fig. 1 the mechanism of the transformation of eutectoid steel from its austenitic to its pearlitic condition as it cools slowly through its thermal critical range. It is generally admitted that this transformation is the result of two distinct phenomena: (1) the allotropic change of gamma iron into alpha iron and (2) the crystallizing out of solution of the carbide Fe3C. Whether this crystallizing of Fe3C implies also its formation is immaterial for our purpose. In other words, whether it is the carbon in atomic dispersion which is present in gamma iron or molecules of Fe3C has no bearing upon the matter to be discussed. The transformation of gamma iron into alpha iron cannot take place suddenly. It must of necessity be progressive, regardless of the speed with which it may take place. At A, for instance, there would be present AB gamma iron and BC alpha iron. The distance MN does not refer to falling temperature, but to the passage of time. It may be assumed that the transformation takes place at a constant temperature (the Ar321 point). In a similar way, the crystallization of Fe3C out of the austenite solid solution must be progressive as depicted between M and N. At A there would be present AB gamma iron, BC alpha iron, CD carbon dissolved in gamma and in alpha iron and DE Fe3C. This condition may be described according to individual preference as martensite or troostite. To sum up, can the metal pass from condition

Jan 1, 1931

By D. J. McAdam, G. W. Geil, D. H. Woodard, W. D. Jenkins

.In a series of papers, the authors and their associates have shown that the resistance of a metal to fracture is a function of all three principal stresses. Consequently since a technical cohesion limit is defined as the technically deter-minable resistance to fracture under a specific stress system, the technical cohesive strength comprises an infinite number of technical cohesion limits corresponding to the infinite number of possible combinations of the principal stresses. As shown in the previous papers, the technical cohesive strength increases with plastic deformation, with decrease in temperature, and with increase in the strain rate. The technical cohesion limit, therefore, is affected by the same factors that affect the flow stress,$ namely, the stress system, plastic deformation, temperature, and the strain rate. The effect of each of these factors on the fracture stress is qualitatively the same as its effect on the flow stress. The effect of any of the factors may be represented by a curve of cohesion limits, although only one point on the curve may represent actual fracture. Since the term "fracture stress" has come into general use with the same significance as technical cohesion limit, the authors are here using the shorter term with the understanding that it does not always refer to actual fracture. In the general investigation described in the previously-mentioned papers, 10-18,20,21,23 the influence of the stress system on the fracture stress was studied by means of tension tests of notched specimens. When a circumferentially notched cylindrical specimen is subjected to longitudinal tension, the minimum cross section is under transverse radial tension. The mean radial stress increases with the depth and sharpness of the notch, but is always less than the longitudinal stress. The greatest principal stress (S1), therefore, is longitudinal, and since the radial stress is effectively equal to the circumferential stress, the transverse principal stresses are equiaxial in that plane (Sz = S3). By the use of notched specimens in tension tests it was shown that the fracture stress increases with increase in the radial stress ratio (s3/s1) The evidence is based not only on the results of tests to fracture at various constant temperatures, but also On results of two-stage tests, in which each specimen was plastically deformed a predetermined

Jan 1, 1949