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By R. I. Jaffee, C. M. Craighead, G. A. Lenning

Hydrogen forms a beta-stabilized system with titanium, with a beta eutectoid at about 300°C and 44 atomic pct H2. 'The solid solubility of hydrogen in alpha decreases from about 8 to about 0.1 atomic pct from 300°C to room temperature. Hydrogen has little effect on tensile properties, but decreases notch-bar toughness to a large degree. This latter effect appears to be the result of increased notch sensitivity. PRIOR to this investigation, only a small amount of information was available on the effect of hydrogen on the mechanical properties of titanium. The effects of the other interstitially soluble elements, carbon, oxygen, and nitrogen, had received detailed study. Jaffee and Campbell1 indicated that hydrogen up to 1 atomic pct did not affect tensile properties deleteriously. Pitler' indicated that 1 atomic pct H, in titanium reduced the impact strength appreciably, but his alloys contained appreciable amounts of oxygen, and it was difficult to attribute the embrittlement entirely to hydrogen. The high temperature portion of the equilibrium diagram for the Ti-H system was established by McQuillan," and his data generally corresponded with the results of Kirschfeld and Sieverts," Gibb and Kruschwitz," Bevington, Martin, and Mathews," and other investigators. The lower concentration limit of the hydride phase varied considerably among investigators, and Gibb and Kruschwitz9 ad shown that small amounts of contaminants in either titanium or hydrogen caused considerable variation in this lower limit. In view of this pronounced effect of contaminants, the extrapolated value of McQuillan's, about 48 atomic pct at the 325°C eutectoid, appeared the most reasonable. McQuillan's lowest experimental value was 54 atomic pct at a temperature of 450 °C. The density of titanium had been shown to decrease with increasing hydrogen content, but discrepancies were noted among the various investigations. The best values indicated that the density was decreased from 4.56 grams per cc at 0.27 atomic pctl to 3.84 grams per cc at 61.3 atomic pct? This investigation was conducted to determine the effects of hydrogen on a titanium, both in high purity and commercially pure metals, and on high purity a titanium alloys. Material and Fabrication The literature indicated that impurities in either the hydrogen or the titanium must be kept to a minimum. For this reason, the initial studies were made with high purity iodide-refined titanium. The vendor's analysis of the iodide titanium and the hydrogen content of the as-fabricated Y4 in. diameter rods are shown in Table I. Two 1 lb ingots were prepared by arc melting under argon in a water-cooled crucible, using a water,cooled tungsten electrode. This equipment has been described.' As-cast Brine11 hardness numbers of 88 and 58 for these ingots were low enough to insure that the high purity of the metal was maintained during arc melting. The ingots were hot forged to % in. diameter rods at 800°C, cleaned by grit blasting, and then cold swaged to Yz in. diameter rods. The rod was then air annealed at 725 "C, ground to remove scale, and cold swaged to Y4 in. diameter (75 pct reduction in area). The material was then annealed for 1 hr in argon at 800°C to develop an equiaxed a grain size of about 0.05 mm. Micro tensile specimens and microimpact specimens were machined from this rod prior to treatment in the Sieverts-type absorption apparatus. Two lots of commercially pure RC-55 titanium were also used in this investigation to determine the effects of hydrogen and the normal impurities on mechanical properties. The commercially pure RC-55 alloy was obtained in the form of % in. diameter rod. The analysis of this material is also given in Table I. The % in. diameter rods were hot swaged

Jan 1, 1955

By Richard H. Hopkins, R. W. Kraft

A new technique facilitating the rapid determination of the three-dimensional morphology of phases suspended in an opaque matrix is described. The vapidity of the technique is based upon continuous cinephotomicrographic recording of specimen microstructure as the specimen surface is removed under controlled conditions in an electrolytic cell. The advantages of the technique for determining spatial morphologies in opaque materials are illustrated by application of this method to the study of the configuration of faults in a specimen of directionally solidified CuAl2-Al eutectic alloy. A spatial model of the eutectic fault network deduced in this manner has substantiated the facts that faults in this alloy tend to lie parallel to one another in a direction close to that of the specimen growth axis and that the majority of faults tend to bridge lamellae rather than run parallel to them as growth proceeds. For the specimen studied fault density decreased as growth proceeded. ALTHOUGH metallographic observation is a powerful tool for investigating the correlation between structure and properties in metallic alloys, ordinary metallographic methods suffer the fundamental limitation that any conclusions concerning the three-dimensional structure of these opaque materials must rely upon inference from two-dimensional microsections. For this reason it is frequently impossible to make valid judgments regarding the true spatial distribution of the micro-constituents in specimens under investigation. Several techniques have been devised to circumvent the basic limitation of planar microsec-tioning and employed with varying success. These include construction of three-dimensional models of alloy microstructure from sequences of photomicrographs,1-3 quantitative deduction of spatial features based upon statistical studies of data from random and/or selected plane microsections,4-6 and selective dissolution of one phase in a two-phase alloy to reveal the topography of the phase remaining.' However these techniques also have certain obvious disadvantages. Construction of three-dimensional models is a very time-con- suming procedure due to the tedious polish-etch-photograph cycle needed to obtain the necessary photomicrographs to portray the spatial microstructure. Statistical methods by their very nature give only average values of the quantities being studied and cannot therefore give a detailed physical picture of the microstructure to be observed. Finally, the technique of selective dissolution is only applicable in systems where the phases are of vastly different chemical reactivity; it is of little use in the study of single-phase alloys. Since the determination of the three-dimensional structure of opaque materials is hindered by two facts—the materials are opaque to radiation in the visible spectrum and construction of spatial models of microstructure is quite laborious—two solutions to the problem suggest themselves: 1) use radiation of energy great enough to render the alloy transparent, i.e., some microradio-graphic method, or, 2) devise a rapid means to section and record alloy microstructure. Stereomicroradiography has indeed been used to study internal arrangements of phases in several materials8,9 but the method, in general, is limited to very thin specimens (due to X-ray absorption) and simple microstructures. It would seem then that development of a rapid, simple, and generally applicable technique for studying the details of alloy microstructures in three dimensions can best be undertaken by following the second approach above. Using this idea a new technique for rapid evaluation of spatial microstructures was developed based upon cinephotomicrographic recording of the micro-structure of a specimen undergoing controlled electrolytic dissolution. It was further felt that application of this technique to the careful study of the spatial configuration of faults in a CuAl2-Al eutectic alloy would yield information that could be correlated with the extensive data3,6,10-12 already compiled concerning the solidification and crystallography of this eutectic. The practicality and usefulness of similar methods for studying three-dimensional features in alloys has recently been illustrated by the study of dislocation loops in zinc13 and spheroidized structure in steel.14

Jan 1, 1965

By G. A. Vissac

O. R. LYONS *—I wish to thank Mr. Vissac for his compliment. I hope that his paper is not only well received, but that it will serve to bring forth more papers on the subject of thermal drying. One of the primary purposes of the work performed by Battelle for Bituminous Coal Research in investigating the thermal drying of coal was to stimulate other investigators and to get them to contribute their knowledge in the form of papers such as this one. We at Battelle and the personnel of Bituminous Coal Research are very gratified that Mr. Vissac and other persons have responded in this matter of the thermal drying of coal. I wish to state that I think that Mr. Vissac's paper is a very clear and easily understood description of a method of calculating the design requirements for a screen type drier, and I think that it would be exceedingly valuable to operators and to those who intend to purchase any type of thermal drier and use it in the future, if the manufacturers or operators who have such information for other types of driers would provide the same type of information for the other makes of driers now on the market. 1 also wish to point out—an idea that is new to me, and I know is new to most of the operators of driers in the United States-—the idea of recovering the heat that is normally lost in the coal and in the exhaust gases. This heat is not being recovered at most (of the thermal drying operations in the United States, and the possibility of recovering it should be called to the attention of every single one of those operators. I know many of them have never given any thought to the matter, but they will be interested once they realize the ease with which it could be done and the savings that could be realized. I also wish to compliment Mr. Vissac for presenting the method of analysis that he uses to determine the difficulty of drying any particular coal. It is a very simple method, and yet it seems to me that it should be a very effective, very efficient method for determining the difficulty of drying for his particular problems. C. Y. HEINER*—I do not know that I can add anything very illuminating to what Mr. Vissac has said. I think anything that Mr. Vissac said in regard to coal drying is a contribution because, to my personal knowledge, he has studied the matter carefully for many years and made many valuable contributions. I am not too familiar with coal drying problems in the east, but I know in the west we have not made enough coal drying studies. I think coal operators too often just take the coal as it is and make more or less the best of it. There are relatively few washing plants in the west now, and so the problem has not come to the front as much as it probably will in the future. In this connection, it seems to me that this matter of drying the raw coal, as Mr. Vissac brings up, is an extremely important one. We have not a continuous miner ourselves, yet, but we expect to get some this year, and we think the percentage of fine coal-—that is, minus 3/16 in.—will double. We have about 20 pct minus 3/16 in. in the 8 in. by 0 size now, and we think we will likely have 40 pct, which will have a surface moisture of the order of 8 pct. To wash it satisfactorily, we will have to dry the raw coal first in order to screen it, and after that, I suppose, there will have to be dry cleaning of some sort. We have not really used dry cleaning on fines in the west yet to my knowledge, but it is a matter that has to be faced by the industry, and I am very hopeful that Mr. Vissac's study will assist us in that connection. W. L. McMORRIS*-In my company we are preparing largely metallurgical coal for a great number of byproduct coke plants. The most outstanding thing to me about the requirements of moisture in the finished product is that there is a different requirement for almost every coke plant. Each operator has a different set of factors on which he establishes his coking costs where they involve moisture. For our corporation operations in Birmingham, my company does not produce the coal, but in Birmingham they are getting away with moistures very much higher than our plant at Clairton, Pa., would tolerate. The moisture that we have to produce for the plants along the lakefront where they are subject to much more severe weather is something else again. We have not tackled heat drying, primarily because our customers do not know what heat drying will do to the coking characteristics of the coal. If the temperature of drying can be held down

Jan 1, 1950

By H. E. Stauss, J. Hino

INTEREST in silicon has arisen again in the past decade as a result of improvements in crystal rectifiers.' Although the preparation of silicon was first reported by Berzelius in 1880, the early product was of relatively low purity, and only the need for rectifiers in World War II led to the production of a 99.9+ pct pure powder. This material in crystalline form was consolidated into massive silicon for use, and the method developed was to melt it with selected added constituents as "doping" agents. Melting techniques, therefore, are of great importance. There are two basic problems in producing silicon ingots free of doping additions; one is the prevention of spitting and the other is prevention of cracking of the ingot during freezing. The most satisfactory arrangement yet developed for producing massive silicon is to melt and freeze in a cylindrical quartz crucible surrounded by a concentric heating element and concentric radiation shields or insulation. For example, use can be made of a tubular heater with a high frequency generator as the source of power and reflecting shields of alundum cylinders. The spitting of silicon is related to gas evolution, and the gas comes from two primary causes—adsorbed gas and the reaction products of silicon and the crucible. Gas is also released from bubbles contained in the quartz crucible walls. Improved removal of adsorbed gas can be achieved by means of controlled melting and freezing. The seriousness of the problem in vacuo is reduced with an electrically operated mechanical movement of the high frequency power coil. The upper portion of the powder charge is melted first and the high frequency coil lowered until the powder is completely molten. During cooling the high frequency coil is raised slowly. These means also reduce the final nonviolent extrusion of large beads of metal through the ingot top during freezing. Better control of spitting and bead extrusion is obtained when melting is done under helium at. atmospheric pressure instead of in vacuo. The problem of reaction between silicon charge and crucible in practice is confined to the reaction between silicon and quartz. This2 apparently is: Si + SiO2 + 2SiO The part that this reaction plays in spitting has not been isolated for separate study. SiO is a volatile vapor at the melting point; of silicon and is released freely during melting in vacuo, but hardly at all in helium at atmospheric pressure. The cracking of ingots is a major difficulty in melting silicon, and its prevention requires special melting techniques or the addition of "toughening" agents such as aluminum or beryllium.' The cracking of the ingots has been explained as being the result of the expansion that occurs upon freezing; although direct observation of freezing ingots reveals visible cracks on the surface only after a red heat has been reached, suggesting that cracking is the result of differential contraction of silicon and quartz. Silicon wets quartz, and the ingot adheres tightly to the crucible. Therefore as ingot and crucible cool, the two either have to pull apart, or at least one must crack. Surprisingly, in spite of the relative thinness of the quartz and the thickness of the ingot, the ingot and the crucible both crack. Microscopic and X-ray4 studies fail to show any plastic flow other than twinning in the ingots. Slow cooling fails to prevent cracking. Another possible solution to cracking is to weaken the crucible. Use of thin-walled crucibles finally led to success with fused quartz crucibles with a wall thickness of 0.25 to 0.50 mm. With such thin-walled fused quartz crucibles consistently uniform success is secured in producing sound ingots 30 mm in diam from the purest available grade of silicon (99.9+) without the use of any type of addition. Melts are made in the size range of 50 to 100 g. Omission of a deliberately added doping agent is not sufficient to insure pure ingots. The reaction of silicon with crucibles and the resultant solution of impurities in the silicon is well-established." In this laboratory, the presence of Al, Be, and Zr has been found spectroscopically in ingots melted in contact with alumina, beryllia, and zircon. The best crucible materials reported in the literature are MgO and SiO2. Use of MgO in this laboratory has resulted in a heavy deposit of magnesium on the furnace walls, showing that a reduction of the magnesia occurred and the resulting magnesium removed from the melt by volatilization. In the case of quartz, the silica is reduced and SiO liberated to deposit on the equipment walls. There probably is real danger that oxygen is dissolved in the ingot when either magnesia or silica is used as the crucible material. Preliminary analyses by Dean Walter in his vacuum unit in this laboratory6 indicate the presence of oxygen in undoped silicon melted in quartz.

Jan 1, 1953

By J. C. Swartz

New measurements of graphite and cementite solubilities in ferrite have been obtained to resolve disagreements among previous data. To measure graphite solubility, specimens of iron were equilibrated with rarious carburizing atmospheres at temperatures be-twee~z 480" and 1435°C. The carbon activity of each atmosphere relative to graphite was taken from published data. After quenching from each equilibration treatment the concentration of carbon (typically 10 pprn by wt) was determined from the height of the Snoek peak in the internal friction spectrum. A few inclividual analyses by combustion support the reszdts of Smith on the solubility of graphite near the eutectoid temperature. Combination of these combustion and internal friction analyses determines In a, (at 0.01 wt pct) = 24,000/RT - 12.72, where a, is the activtity relative to graphite in ferrite at fixed cornposition. The same specimens were used to determine the solubility of self-stressed cementite precipitates. The results indicate solubilities of 6.3, 23.2, and 68 pprn carbon by wt at respectively 400°, 500". and 600°C. The once large discrepancy between the cementite solubility determined by internal frictiori and that calculated from flee energy data has been almost completely resolved. A recent study1 (hereafter designated I) on the solubility of cementite in a iron did not fully resolve the disagreement among previous data. The remaining disagreement is illustrated by the phase diagram in Fig. L The data of I are represented by the line labeled "stress-free" cementite. They determine a heat of solution of cementite of (14.8 * 0.2) kcal per mole which contrasts with the (20 * 1) kcal per mole derived from Smith's graphite solubility2 and the formation energy of cementite.3 Toward resolving this disagreement we have obtained new data on the solubilities of graphite and cementite. METHODS As in I the Snoek peak in the internal friction spectrum was used to measure the concentration of carbon dissolved in ferrite. This method relies on the relation C=kQ-1 [1] in which C is the concentration of dissolved carbon, Q-I is the Snoek peak height, and k is a proportionality factor which is a function of the peak temperature, polycrystalline texture, and other parameters characteristic of the ferrite lattice. To determine true heats of solution via Eq. [1], it is necessary to establish that k is independent of the temperature from which the specimen is quenched. Some evidence on this point is contained in a separate report.* Additional evidence is shown by the data points in Fig. 1. These represent the Snoek peaks of two specimens carburized to about 10 ppm C, copper plated, and quenched first from 888º then from 588°C. The copper plate was removed before each Snoek peak measurement. These data show that there is no detectable dependence of k on quenching temperature. The solubility of graphite was determined by repeatedly carburizing various specimens of iron wire with gas mixtures of known carbon activity relative to graphite. To cover a wide temperature range within the a phase boundaries it is desirable to use as low a carbon concentration as is compatible with reasonable precision. With the present internal friction apparatus the best compromise of these desires is a concentration near 10 wt ppm. The dashed line in Fig. 1 was used to approximate the activity of carbon* for

Jan 1, 1970

By S. J. Sindeband

Prior to discussing the metallurgy of sintered chromium borides, it is pertinent to outline some of the reasoning behind this investigation and the purposes underlying the work. This study was initiated as an aproach to the ubiquitous problem of a material for service at high temperatures under oxidizing atmospheres, and it was undertaken with a view to raising the 1500°F (816°C) ceiling to 2000°F (1093°C) or better. For the reason that no small, but rather a major, lifting of the high temperature working limit was being attempted, it was felt appropriate that a completely new approach be taken to this problem. A summary of the thinking behind this approach was published recently by Schwarzkopf.' In briefest terms, it was postulated that the following requirements could be set up for a material which would have high strength at high temperatures. 1. The individual crystals of the material must exhibit high strength interatomic bonds. This automatically leads to consideration of highly refractory materials, since their high energy requirements for melting are related to the strength of their atom-to-atom bonds. 2. On the polycrystalline basis, high boundary strength, superimposed on the above consideration, would also be a necessity. Since this implies control of boundary conditions, the powder metallurgy approach would hold considerable promise. Such materials actually had been fabricated for a number of years, and the cemented carbide is the best example of these. Here a highly refractory crystal was carefully bonded and resulted in a material of extremely high strength. That this strength was maintained at high temperature is exhibited by the ability of the cemented carbide tool to hold an edge for extended periods of heavy service. Nowick and Machlin2,3 have analytically approached the problem of creep and stress-rupture properties at high temperature and developed procedures whereby these properties can be approximately predicted from the room temperature physical constants of a material. The most important single constant in the provision of high temperature strength and creep resistance is shown to be the Modulus of Rigidity. On this basis, they proposed that a fertile field for investigation would be that of materials similar to cemented carbides, which have Moduli of Rigidity that are among the highest recorded. The cemented carbide, however, does not have good corrosion resistance in oxidizing atmospheres and without protection could not be used in gas turbines and similar pieces of equipment. It would be necessary then to attempt the fabrication of an allied material based upon a hard crystal which had good corrosion resistance as well. It was upon these premises that the subject study was undertaken and at an early stage it was sponsored by the U.S. Navy, Office of Naval Research. Since then, it has been carried on under contract with this agency. Chromium boride provided a logical starting point for such research, since it was relatively hard, exhibited good corrosion resistance, and, in addition, was commercially available, since it had found application in hard-surfacing alloys with iron and nickel. That chromium boride did not provide a material that met the ultimate aim of the study results from factors which are subsequently discussed. This, however, does not detract from the basis on which the study was conceived, nor from the value of reporting the results which follow. Chromium Boride While work on chromium boride proper dates back to Moissan,4 there has been a dearth of literature on borides since 1906. Subsequent to Moissan, principal investigators of chromium boride were Tucker and Moody,5 Wede-kind and Fetzer,6 du Jassoneix,7,8,9 and Andrieux." These investigators were generally limited to studies of methods of producing chromium boride and detennining its properties. Some study, however, was devoted to the chromium-boron system by du Jassoneix,7 who did this chemically and metal-lographically. This system is not amenable to normal methods of analysis by virtue of the refractory nature of the alloys involved, and the difficulties of measurement and control of temperature conditions in their range. Dilatometric apparatus is nonexistent for operation at these temperatures. Du Jassoneix made use of apparent chemical differences between two phases observed under the microscope and reported the existence of two definite compounds, namely: Cr3B2 and CrB. These two compounds, he reported, had quite similar chemical characteristics, but were sufficiently different to enable him to separate them. The easiest method for producing chromium boride is apparently the thermite process, first applied by Wede-

Jan 1, 1950

By Colin Baker, G. C. Smith

Investigation of the initiation and propagation of ductile failure in OFHC copper was undertaken to determine the role of nonmetallic inclusions. The effect of inclusion initiated voids on the formation of the internal cavity and the final shear separation was studied by metallographic eranzination of strained test pieces. A strain anneal technique was used to enlarge the voids under uniaxial stress conditions to elinzinate triaxial stress effects. Measurements of void size us stress and strain were made to show the point at which void im'tiation begins and becomes an important factor in the deformation process. The work of separation of copper-cuprous oxide was determined to attempt to correlate the breakdown of the matrix inclusion interface with void initiation and propagation. The zloid shape and position relative to the tensile axis suggested an interface breakdown mechanisnz of initiation. Evidence is presented that shows a basic similarity between the central cavity propagation and the 45-deg shear portions of the failure. DUCTILE fracture has been studied by a number of workers1-lo and attention drawn to the importance of hard second phase particles in the initiation of the failure. Holes formed at the matrix-particle interface can elongate by plastic deformation and then subsequently expand sideways to link up and produce a major crack. This is usually observed first in the center of the macroscopically necked region of a test-piece where the hydrostatic stresses are at a maximum. As the crack spreads sideways towards the free surface of the specimen, well defined shear zones develop from the crack tip and the final separation is along a direction at approximately 45 deg to the stress axis. This shear failure may also be associated with voids formed adjacent to second phase particles. In this way a cup and cone type fracture is produced. The stage at which separation takes place between particles and the surrounding matrix has not been clearly identified. In addition, although researchers have dealt with anisotropy of tensile behavior" as a result of material fabrication variables, not much is known about the microstructural features of aniso-tropic behavior. In the present work evidence on these points is presented in relation to the behavior of copper containing second phase particles of cuprous oxide. I. MATERIALS AND PROCEDURES EMPLOYED The material used was +-in. diam or 2-in. sq cold-drawn OFHC copper bar which contained 0.6 pct by volume of cuprous oxide inclusions. These ranged in COLIN BAKER, Junior Member AIME, formerly at -mnF of Metallurgy, University of Cambridge, Cambridge, England, is presently Research Scientist Reynolds Metals Co., Richrnand, Va. G. C. SMITH, Member AIME, is Senior Lecturer, Department of Metallurgy, University of Cambridge. Manuscript submitted June 20, 1967. IMD size from approximately 1 to 6 p in length and 1 to 4 p in width. The shape was generally slightly ovoid. Tensile tests were made on specimens having a gage length of 2.5 cm and diameter of 0.643 cm. Metallographic examination was carried out by sectioning deformed and fractured specimens; in addition fracture surfaces were examined optically and with a scanning electron microscope. Some measurements of the work of separation between copper and cuprous oxide were made, using a sessile drop technique which was a modification of that used by Kingery and umenick." The best metallographic results were obtained by using a vibratory polisher, which minimized smearing of the surface. 11. RESULTS A) Initial Experiments. Specimens from the +-in. diam rod were annealed for 2 hr at 650°C in uacuo, at which temperature complete recrystallization occurred without any change in the form of the inclusion. They were then fractured at temperatures from -190" to 600°C. Cup and cone fractures were obtained at all temperatures from -196" to 400°C. With increase in temperature there was, however, a continuous increase in the extent of the central transverse area and a corresponding decrease in the shear portion of the fracture. Above 400°C, the fractures became intergranular. Sections of specimens tested below 400°C revealed extensive small voids which were always associated with inclusions. However, the voids only reached dimensions greater than the inclusion size in the region of the macroscopic neck, where they were many times longer. Lateral expansion was found only near the fracture surface of the test pieces. As observed by Puttick, the voids were either (a) triangular holes initiated in the direction of the tensile axis and elon-

Jan 1, 1969

By Harry C. Swanson

TRANSPORTING concrete from mixer to forms has always been a problem. Twenty-five years ago this task was generally accomplished by means of wheelbarrow or concrete buggy. On large dam jobs, as the number of these projects increased, the gantry crane or highline came into use. Today several methods of handling concrete are employed on smaller surface construction jobs, for example, transit-mix trucks or dumpcrete trucks, which have crawler cranes with buckets for placing concrete into forms. In 1944, during early stages of developing Mather mine A shaft, several large underground concrete jobs were necessary. At this time the Cleveland-Cliffs Iron Co, purchased the first pump-crete machine, introduced by the Chain Belt Co. of Milwaukee. The machine was used to pour approximately 200 cu yd of concrete for a dam, or bulkhead, located 400 ft from the shaft. Concrete was mixed on surface, lowered down the shaft 1000 ft in a 2-cu yd bucket hung under one skip, spouted into the bowl of the pumpcrete machine from the bucket, and pumped directly into the forms. Since the day of the first pipeline concrete in 1944 to the present time, other equipment and other methods have been developed to permit transportation of concrete by pipeline through vertical and horizontal distances totaling 1 mile from mixer to forms. Much of the efficiency in present handling of underground concrete can be credited to the Bethlehem Cornwall mines, where concrete was transported through 6-in. pipe for great distances down an inclined shaft and along levels into forms.' During initial development of Mather mine B shaft, with concrete work under way on two or more levels at one time, the pneumatic concrete placer, Fig. 1, was selected as best adapted for underground concrete transportation. The 3/4-cu yd pneumatic placer is a small machine readily moved from one location in the mine to another. It can be equipped with two sets of mine car wheels, which will permit moving on regular mine tracks. It is therefore possible to send concrete through the pipe at great velocity; the pipeline is clean after each shot except for the film of cement adhering to the inside. With the proper slump in the concrete, it is possible to shoot concrete 2000 ft with this machine, using the mine supply of compressed air at 95 psi. This equipment was first used at Mather mine B shaft to concrete slusher drifts, Figs. 2 and 3, and finger raises located about 2000 ft from the shaft. In several instances there were bends into crosscuts and up vertical distances into the forms. For the first pours two placers were used. The first was located near the shaft where the concrete could be spouted into it from a 2-cu yd concrete bucket on the cage. The second was set on the side of the drift at a point approximately 1500 ft from the shaft. The concrete was shot directly into the second placer from the first unit and from the second machine directly into the forms. After completion of several pours with the two machines, a trial pour with only one placer located at the shaft proved that the second placer could be eliminated. Since then all pours have been successfully completed with only one placer underground. As production of iron ore from the mine increased and the development program expanded, use of the cage for handling mine supplies and concrete became a major problem. This brought about the first attempt at shooting concrete vertically down the shaft for 2600 ft. A 6-in. pipeline with victaulic couplings installed during shaft sinking was used for the trial. One placer was set on surface 250 ft from the collar of the shaft so concrete could be spouted directly into it from the mixer. This machine shot the concrete 250 ft horizontally on surface to the shaft, 2600 ft vertically down the shaft, and 100 ft horizontally into the second placer located near the rib of the shaft station or plat. The second machine shot the batch into the forms, about 2000 ft. Total distance horizontally and vertically was 4800 ft. The entire time cycle for a ¾-cu yd batch of concrete from the mixer on surface to the forms underground totaled about 5 min. During the past two years the two-placer method from the mixer on surface to the forms underground has proved a very efficient means of transporting underground concrete. Advantages of using pipeline concrete are as follows: 1—Interference with normal mining operation is eliminated. When the cage, skips, mine cars, or mine openings are used for transporting concrete and materials used for making concrete, mine operation suffers in one way or another.

Jan 1, 1955

By Charles M. Packer, Oleg D. Sherby, Roy H. Johnson

Originally round tensile specimens of a eutectic Zn-A1 alloy develop elliptical cross sections during superplastic deformation. This observation, coupled with a detailed study of the microstructure and preferred orieniation, suggests that crystallographic slip and continuous grain boundary migration or re-crystallization are important processes during super-plastic deformation. In spite of the extensive activity in superplasticity1-15 and the numerous explanations proposed, no single model has had universal acceptance. It has been established, however, that the general requirements for superplastic extension of two-phase alloys include an extremely fine, stabilized grain size of the order of a few microns, a temperature about equal to or greater than one-half the melting point, a critical range of strain rate, and a similarity in the mechanical strength of the major phases. The proposed models can perhaps best be characterized in terms of the important phenomena associated with them. These phenomena include: phase instability,1 diffusional creep by volume diffusion3 or grain boundary diffusion4,5 slip and continuous grain boundary migration or recrystalliza-tion,= grain boundary Sliding,7-9,13,14 and dislocation glide.'5 In this paper, experimental observations will be reported which support a model involving slip and continuous grain boundary migration or recrystalliza-tion. Specifically, a correlation will be made between this model and the development of elliptical cross sections as originally round specimens are superplas-tically deformed. For the most part, superplasticity studies have been conducted with eutectic or eutectoid alloys. Probably the most thoroughly studied material has been the monotectoid Zn-A1 alloy.1,2,6,12,13,15 No attention to the eutectic Zn-A1 alloy has previously been reported, and the results discussed in this paper represent part of a general study of the superplastic properties of this alloy. MATERIALS The alloys used in this investigation were prepared by melting appropriate quantities of 99.99+ pct A1 and 99.999 pct Zn in air, mixing, and pouring into a water- cooled stainless-steel mold. Wet-chemical analysis was conducted with each heat of alloy prepared, using the procedure of Fish and smith.16 The composition of the eutectic alloy was 95.1 wt pct Zn. Ingots about 2 in. thick were rolled to 0.4-in. plate at about 300°C with a reduction of 5 to 10 pct per pass. Specimens were machined from the plate with the tensile axis parallel to the rolling direction. The specimens were round, with 0.150-in.-diam, 1.25-in.-long gage length, and 0.25-in.-diam threaded grip sections. EXPERIMENTAL PROCEDURE Specimens were mounted inside a uniform-temperature quartz tube which was surrounded by a double elliptical radiant furnace with a 12-in.-long uniform-temperature hot zone and a low thermal capacity. The tube extended through the top and bottom of the furnace and permitted rapid quenching of the loaded specimens when quickly filled with cold water at the conclusion of the test. The quench precluded any effects on specimen microstructure from a normal, slow cool. Constant stress was applied to test specimens by suspending a load on a constant stress cam of the type described by Hopkin.17 The design of this cam permitted application of a constant stress for elongations up to 200 pct. For greater elongation, approximately constant stress conditions were maintained by systematically reducing the load manually. RESULTS As part of an investigation of the superplastic properties of the eutectic Zn-A1 alloy, evidence was obtained for the development of elliptically shaped cross sections as originally round specimens were extended. For example, after an elongation of about 100 pct, a round specimen with an initial diameter of 0.150 in. became elliptical with major and minor axis of 0.128 and 0.88 in., respectively. Photographs are presented to illustrate the ellipticity developed during superplastic deformation, Fig. 1. The specimen shown was deformed at a stress of 500 psi, at a temperature of 285°C, and a strain rate of 2.28 x 10-2 min-1. The strain-rate sensitivity exponent* was measured at *The strain-rate sensitivity exponent, m, is defined as d In o/d In c where o is the steady-state flow stress and E is the strain rate. this temperature and in the strain rate range 10"3 to 10-1 min-1 was found to be about 0.5. This value is typical of those observed with superplastic materials. The material studied exhibited negligible strain hardening during superplastic deformation, the creep rate remaining constant under constant stress and temper-

Jan 1, 1969

By J. E. Powell, F. H. Spedding

WHILE rare earths are reported to be widely distributed in nature and are not really rare," in practice, there are only a few minerals which are sufficiently rich in rare earths to serve as practical sources. Perhaps the best known of these is monazite which is a phosphate mineral containing rare earths and thorium. This mineral occurs as a dense brown sand in gravel beds and is particularly rich in the light rare earths of the cerium subgroup. This mineral is processed commercially for its thorium, cerium, and lanthanum content, and, consequently, furnishes rich concentrates from which neodymium, praseodymium, samarium, europium, and gadolinium may be obtained. Unfortunately, monazite is rather lean in rare earths heavier than gadolinium. A second mineral which is rich in the light rare earths is bastnasite, a fluoro-carbonate. Extensive deposits of this ore have been discovered in the western United States and have received considerable newspaper publicity in recent years. While bastnasite is very rich with respect to cerium, lanthanum, and neodymium, it contains even less heavy rare earths than does monazite. One of the better sources of heavy rare earths of the yttrium subgroup is gadolinite, a black silicate rock from which the rare-earth content can be extracted readily by acid leaching. It is obtained chiefly from Norway at the present time, although there are known deposits in the United States. Other sources of heavy rare earths include fergu-sonite, euxenite, and samarskite which are refractory tantalo-columbate ores. These minerals require caustic fusion or reduction to carbides with carbon before the rare-earth content can be extracted. All of the minerals which are rich in the heavy rare earths contain yttrium as a major constituent. After the rare earths have been extracted as a group from an ore by chemical means, it is generally convenient to precipitate them from acid media with oxalic acid in order to eliminate certain non-rare-earth impurities such as iron, beryllium, etc., which are usually present. The oxalate can then be readily ignited to R2O3. The oxide can be dissolved in acid and is the starting point for subsequent separation into the pure components. Perhaps the principal reason why the rare earths have not been studied as extensively as other elements of the periodic table, whose natural abundances are comparable, is that they are extremely difficult to separate from each other by the usual chemical means. Prior to 1945, the separation of one trivalent rare earth from another was a laborious process. All separations were based on repeated fractionation processes, i.e., fractional precipitation, fractional decomposition, fractional crystallization, etc. These processes were repeated from a few hundred to many thousands of times in order to obtain individual rare-earth salts of reasonable purity. Of course, mention should be made that, in the few cases where a rare earth could be oxidized or reduced to a valence state other than three, more conventional chemical means could be utilized to separate the oxidized or reduced ion from the other normally trivalent rare earths. The ionic states which deserve special mention are CeIV, SmII, Eu11, and Yb11. When it is possible to remove an element of the series efficiently, due to an optional valence state, its immediate neighbors also become easier to isolate. For example, binary mixtures of lanthanum and cerium, and praseodymium and cerium can be obtained by a relatively small number of fractional operations. The tetravalent state of cerium then allows the complete resolution of the binary mixtures by ordinary chemical means. Although the tetravalent state of cerium has been known for a long time, the divalent states of samarium, europium, and ytterbium were not used extensively in separations prior to 1930 because they are relatively unstable in aqueous media.'-" No attempt will be made to give a comprehensive review of the extensive literature dealing with the separation of rare earths. Rather, this paper will be confined to a review of those methods which have been developed at Iowa State College during recent years, and which have proved extraordinarily successful for the isolation of highly pure rare earths in quantity. It was obvious that, if pure rare earths were to become generally available, methods would have to be developed wherein the thousands of fractional operations made necessary by the similarity of rare-earth properties could be performed automatically. The development of chromatographic techniques and ion-exchange resins appeared to offer a mechanism by which this objective could be accomplished. A number of early attempts were made to separate rare earths by these means; for example, Russell and Pearce12 passed a mixture of rare earths through a cation-exchange column and reported

Jan 1, 1955

By Wilson T. Lundy

The history of the production of sulfur from salt domes in Louisiana and Texas originated with the operations of the Union Sulphur CO. at Sulphur, La., followed by the Freeport Sulphur Co. at Bryanmound, Tex. Including the present development of Grande Ecaille by the Free-port Sulphur Co., which constitutes the tenth dome to be equipped for the production of sulfur in the Gulf Coast, less than 10 per cent of all the known domes have proved to contain sulfur in commercial quantities. The Grande Ecaille salt dome is in the tidal marsh of the Mississippi River delta in Plaquemines Parish, Louisiana. It is 10 miles southwest of the right descending bank of the river approximately 45 miles below the city of New Orleans and is within 4 miles of the shore line of the Gulf of Mexico. Terrain Characteristic of the delta region, the terrain consists of a low, flat, uninhabited area of marsh land intersected by many shallow lakes and bayous. With the exception of salt grasses, the region is devoid of vegetation and presents, in all directions, an unobstructed path to the vagaries of the winds. The general character of this area can be best visualized from the mechanism of its formation.' Offshore bars formed enclosing long narrow lagoons between the bar and the inner shore line, the lagoons communicating with the sea by means of tidal inlets. The water in the lagoons, being comparatively quiet, favored the deposition of fine debris composed of sand carried into the lagoons by action of the waves, tides and river-borne sediments from the land surface. As this material accumulated the bottoms of the lagoons were built up and eventually salt grasses obtained a foothold. The successions of growth and decay of these grasses formed a brown fibrous mat varying in depth from a few inches to several feet. This mat of vegetation virtually floats on an ooze that is several feet thick and is composed of alluvial sediments and very fine sand, and the whole is underlain by an unctuous clay. The decayed vegetation from the upper layer when dried has a peaty appearance.

Jan 1, 1934

By James K. Stanley

When a plastically deformed mctal is heated to a certain temperature, it undergoes a complete change in microstructure, the consequence of which is a marked alteration of mechanical properties such as hardness, strength and ductility. This change in microstructure occurs by re-crystallization and is a process involving the formation and growth of strain-free nuclei in the deformed matrix. These nuclei continue to form with time and grow until a new grain structure replaces the cold-worked structure. The formation of the nuclei in the deformed sheet of I per cent silicon ferrite is illustrated in Fig. I. If a recrystallization is conducted iso-thermally, a nleasurement of the fraction of the matrix recrystallized plotted against time leads to an isothermal recrystallization curve, first established in 1942.1 Such recrystallization curves are shown in Fig. 4. These curves show that the recrystallization of a cold-worked metal is best considered as a rate process rather than a time independent process such as is suggcsted by the improperly named and misleading recrystallization diagrams involving deformation, temperature, and grain size.2-5 Any study of the rate of recrystallization resolves itself into a study of the component rates of nucleation and growth. The previous paper1 provided an account of the determination of the rates of nucleation; N, the number of nuclei formed per unit time per unit of unre-crystallized area, and growth, G, the radial growth in unit time, in the recrystallization of silicon ferrite (I per cent Si). A method was developed to furnish experimental data for evaluating the effect of the recrystallization variables on N and G. The mathematical analysis for the derivation of the isothermal recrystallization curve was developed for a two-dimensional case (in thin sheets where the diameter of the recrystallized grain is greater than the sheet thickness). The present paper is a continuation of the study of recrystallization of I per cent silicon ferrite begun in 1942.1 In this work the effect of the factors deformation, temperature, grain size, composition, and recovery is studied with respect to the rates of liucleation and grouth. At the same time it is shown how the cooperation of N and G affects the isothermal recrystallization curve. The study of these variables on N and G has a definite bearing on the mechanism of recrystallization and should lay a foundation for a rational theory on the subject. Procedure The procedure used in these experiments was essentially the same as that described previously but in certain details some changes were made in the interests of speed. With few exceptions, the procedure is the same for the study of all the variables. Where the procedure is different from standard manipulations attention is called to this fact.

Jan 1, 1945

By F. C. Pittman, D. W. Harriman, J. C. St. John

This paper mentions briefly the history of hydraulic jetting as applied to perforating and fracture initiation. It points out the advantages of hydraulic perforation and undercutting as an aid for creating a fracture at the point desired rather than depending upon the weakest point in the formation for breakdown. It describes early experimental work with jet nozzles in search of better nozzle materials. The effect of splash-back damage and its subsequent influence on jet body and tool design during this work is discussed. A series of cutting-rate curves for jets cutting steel and steel-cement-formation combinations is presented to show the effect of hydrostatic head and the point of diminishing returns with respect to cutting time. There is a series of photographs showing various types of rock formation in which perforation and undercutting tests were made. These stones were drilled and the casing cemented in place as in an actual well. The casing was perforated and circularly cut as if preparing for a fracturing job. The conclusion reached in the paper is that hydraulic jetting with sand-laden fluid can be used for perforating and undercutting casing, cement and formation rock for the intended purpose of inducing the formation to fracture at a desired point. INTRODUCTION Hydraulic jetting as a means of cleaning a formation during acidizing has been used for many years. The acid-jet gun was used to clean formation and for drilling cement from casing with acid. This tool was dropped to a seating ring installed on the tubing and could be retrieved by reverse circulation or wire line. In this process, the fluids were directed against the formation to clean and penetrate beyond the mud-damaged area. After the development of the hydraulic fracturing process, interest in jetting the formation with abrasive-laden fluid was renewed. The cutting action of abrasive fluid on pumping equipment, which is a well known problem, has been utilized to perforate and undercut casing, tubing and formation. In this process, surface areas are provided in the formation on which the frac- turing pressures may work to produce a fracture at the location desired. EQUIPMENT The tools used consist of bodies containing two, three or four jets in a single horizontal plane equally spaced around the circumference. The body is threaded to the end of a string of tubing and run into the well. In addition, an expendable tool is available that may be left in the hole after perforating and produced through until necessary to remove the tubing. The bottom of each tool is equipped with a ball-type back-pressure valve. The ball can be reversed to the surface and recovered. This allows reverse circulation so that loose sand which accumulated below the tool while jetting may be removed before the fracturing job. The present jetting tools are of such length that, when screwed together, the jets fall on 12-in. spacing. ANALYSIS OF THE PROBLEM Early work with nozzles indicated that hardened steel was not a suitable material for jets and that more durable material would be required. Ceramics were tried and found to be superior to steel but still too shortlived for most applications. Tungsten carbide, which was tried and found to be the best material available, is now being used for jet nozzles. Analysis of the problems presented by this process indicated that the following information was needed. 1. The effect of submergence on a jet stream and the effect of submergence on the cutting rate of a jet stream. 2. The cutting rate and depth of a jet stream in steel. 3. The cutting rate in various formations and point of diminishing returns. 4. Size of hole or slot cut in a pipe by a given jet. 5. Fluids and sands used. 6. The flow of various weight fluids through the jet nozzle and the discharge coefficients. 7. The type cut formed in the formation by the jet stream. 8. The stretch and contraction of tubing due to temperature and pressure. The cutting effect of a jet stream on a target in the atmosphere is rapid and spectacular as most of the

By H. W. Schadler

The superplastic behavior of low carbon and manganese bearing steels has been evaluated. The results of elevated-temperature stress-strain rate and elongation tests are reported which indicate that high strain rate sensitivity (>0.5) and adequate elongations are achievable in ultrafine-grained steels 1 to 2 p, but at strain rates which are not commercially attractive. It has been demonstrated that the fine grain size is retained after long times and high strains if the temperature is kept within the range of the two-phase (a + ?) field. INTEREST in superplasticity has been stimulated by the desire to: 1) understand the origin of, and mechanisms responsible for, the large uniform elongations observed, and 2) exploit this property for commercial advantage in metal forming operations. Although the Zn-22 wt pct Al alloy presently being studied as a model material1-5 may find application in sheet forming and extrusion, the potential of super-plasticity should best be realized in large tonnage materials, such as steel and aluminum alloys. The degree of superplasticity in low-carbon and manganese-bearing steels has been evaluated. The results of elevated-temperature stress-strain rate and elongation tests on ultrafine grain size material are reported. Avery and Backofen6 and Hart7 have shown that geometrically stable flow leading to extensive uniform elongation in the tension test is associated with high values of the strain rate sensitivity, m, defined: Lozinsky had reported that titanium and zirconium experience permanent deformation if subjected to a constant load and cyclic heating through the temperature range of the phase transformation. Although strain rate sensitivities in excess of about 0.2 had not been reported previously for steel, permanent deformation had been observed11-13 in a wide variety of steels subjected to a constant load and cyclic heating through the temperature range of the a-? phase transformation. Thus by analogy, steel could be expected to exhibit high strain rate sensitivity but only in the a + ? condition. High strain rate sensitivity has been observed at 650°C (a + Fe3C), but not reported as such, by Bailey, Dickenson, and pearson14 in 1931 at a strain rate of about 10-9 per min. It then remained to determine whether high tensile elongations would be observed in a rate-controlled test at constant temperature and at what strain rate strain rate sensitivity values greater than 0.5 would be observed. Since previous experience8 had indicated the importance of fine grain size to realizing high m at reasonable strain rates, it was first necessary to produce an ultrafine grain size and then keep the grains from growing during the test. The results of this investigation show that fine grain size can be readily produced16 and maintained by restricting the temperature of testing to below the ? transus. Further, superplasticity (high m and large uniform elongation) is observed. However, the strain rate range is only marginally useful for commercial forming operations with the finest grain size produced. MATERIAL The material investigated initially was a 1.9 wt pct Mn, 0.42 wt pct C, hot-rolled bar previously used by Low and Turka1015 and available in the laboratory. The 0.500-in. round was cold-rolled to a 0.090-in. flat, annealed for 4 hr at 850°C in argon, air-cooled, and cold-finished to 0.050 in. Subsequently, four additional steels of the compositions given in Table I were investigated to explore the effects of manganese, carbon, and test temperature on the observed stress-strain rate behavior. These steels were melted under argon, cast to 0.75 by 2 by 5 in. slabs, hot-rolled at 850°C, surface-finished to 0.13 in., and cold-finished to 0.050 in. Sheet tensile specimens 0.200 in. x thickness with 1- or 2-in. gage length were cut parallel to the rolling direction. Table I also includes the nominal transformation temperatures for the AISI 1340 and the four experimental steels. EXPERIMENTAL PROCEDURE Production of Fine Grain Size. Ultrafine grain size (1 to 5 p) was considered essential for this studv. Grange16 has described two techniques for producing

Jan 1, 1969

By Frank Doxey

AT Dominion Steel & Coal Corp. it has long been recognized that continued mechanization of mine operations is necessary in the Pictou, Cumberland, and Sidney coal fields of Nova Scotia. The varied physical conditions in these fields call for special consideration of individual cases before planning is finalized. Because standard equipment cannot be procured which would operate successfully, many experiments have been necessary over the years to keep pace with the progress made in other countries. There are two mines, producing 2000 tpd, located in the Pictou coal field. The field is badly distorted and crossed by many faults. Seams are highly inclined and irregular and vary in thickness from 5 to 40 ft. Entries are difficult to maintain because of squeezing of the coal. ribs and movement of the roof and pavement. Output from the three operating mines in the Cumberland field is 3000 tpd. The field is highly inclined, inclination varying from 12° to 32°. Overlying beds consist of shales and massive sandstone lenses of extreme toughness and are responsible for bumps when the stresses are relieved by extraction. At greatest depth these are among the deepest coal workings in the world. Depth of cover ranges from 2300 to 4000 ft. This prohibits room-and-pillar working and necessitates longwall operation. Working of contiguous seams concurrently to maintain output increases the already difficult conditions. The Sydney field, with a frontage of about 30 miles, is the most important of the Nova Scotia coal fields. With the exception of one small area it is now wholly submarine. Output is approximately 21,000 tpd. Seams are 21/2 to 8 ft thick, and cover in the areas varies from 600 to 2300 ft, with an average of 1500 ft from sea bottom to the top of the seam. The seams dip in a seaward direction, pitches ranging from 6" to 4.0". The shoreline is the last place of entry to the seams and distance from the bank to the working faces is generally over 3½ miles, in some cases as much as 6½ miles. Ventilation is a problem and requires the construction of large permanent airways. Getting and Loading Coal: In 1925, in view of heavy pressures exerted by thickness of cover overlying the seams, roadways and pillars of the room-and-pillar system being worked began to break up and coal was lost. It was decided that a change in the method of extraction in areas with heavy cover was necessary, and experiments were made with many short walls and longwalls varying between 90 and 250 ft. Trial and error proved that the best operating length was between 400 and 500 ft, delivering all coal to the dip, with roadways to the face following a level course. The change-over was gradual, and the technique of roof control developed with the system, so that falls to the face are now very infrequent. An advantage of longwall mining is that it yields 95 pct extraction, especially important in coal seams of high quality or in seams where faults or disturbances restrict the workable areas. This percentage of extraction is based on the fact that the longwall advancing system takes development faces where pitch permits instead of driving headings and leaving roadway pillars. This system yields high tonnage during development and limits loss in extraction to duff left during operations. Accompanying disadvantages, on the other hand, are the heavy construction cost of main roadways and the necessity of driving all new flank face roadways through the gob. If the main roadways are driven through the solid, and large enough pillars are left on each side for protection against flank face weights, then the width of solid coal is approximately 1700 ft. This represents 10.6 pct of the coal available, or 89.4 pct extraction of the whole. These pillars, however, are of such size that they provide a useful pillar drawing area as a final operation of the mine. It may be that although the seam cannot be generally mined by the room-and-pillar method, it can be adapted to

Jan 1, 1955

By Donald B. Evans, Robert D. Pehlke

The solubility of nilrogen in liquid binary alloys of iron with Litanium. zivconium, columbium, vanndiurn, and tantalum was measured for alloy composiLions up to the solalbility limils of lhe alloy nitrides. All five alloying agents were found to decrease markedly the activity coefficient of nitrogen in liquid ivon. The metal/nitvogen mole ralios in the alloy nitrides formed were generally .found to be slighlly greater than 1.0, but in no case greater than 1.5. From the experimental data, the standard free energies of fortmation of titanium and zir-conium nitrides have been calculated for the Lemperaluve range 1550° to 1750 C. The solublily Products for columbium, tantalum, and vanadium nitrides are also reported. A number of research investigations have examined the effect of refractory metals on the solubility of nitrogen in liquid iron. Although data on zirconium are not available, investigators are in agreement that titanium, vanadium, columbium, and tantalum markedly increase the solubility of nitrogen in liquid iron. This fact alone makes desirable the acquisition of thermodynamic data for these elements in liquid iron. Since refractory metals are known to be stable nitride formers, they have been suggested as steel denitrifying agents, and some of their nitrides have recently been considered as containment materials for liquid iron and iron alloys. Most available thermodynamic data for these metals relate to their dilute concentrations, but effective thermodynamic treatment of these applications requires data at concentrations near the solubility limit of the alloy nitride. Although some work has been done at relatively high alloy concentrations in liquid iron (particularly for vanadium 2,3 and titanium 2,4), the results have been somewhat contradictory. Disagreement may be partly attributed to the fact that the compositions of most refractory metal nitrides have been shown to be nonstoichiometric, and to vary 2,5-8 depending on the temperature and nitrogen gas pressure with which the solid nitride phase is in equilibrium. One purpose of this study consequently has been to determine the compositions of the refractory metal nitrides precipitated from a liquid iron solution. EXPERIMENTAL PROCEDURE Rao and Parlee2 and Evans and Pehlke 9 have discussed the technique for measuring the solubility product of an alloy nitride phase in liquid iron by finding the point of departure of the nitrogen solubility from Sieverts' law. The method consists of measuring the solubility of nitrogen in a melt of iron containing a known concentration of a second metal as a function of the nitrogen gas pressure over the melt. In this study the second metal was one of the refractory metals titanium, zirconium, columbium, vanadium, or tantalum. When the nitrogen pressure at which the refractory nitride forms is reached, a deviation of the measured solubility of nitrogen in the melt from Sieverts' law is observed in the form of a "pressure halt." The concentration of nitrogen in the melt associated with this breakpoint in the nitrogen-absorption curve is then used to calculate the nitride solubility. The Sieverts method was used to measure nitrogen solubility as a function of nitrogen pressure and temperature. The experimental equipment for this technique has been previously described in detail. 1,9 Charge materials used were vacuum-melted high-purity iron (Ferrovac-E) and the best commercial grades of the refractory metals obtainable (in all cases at least 99.8+ pct pure). Recrystallized alumina crucibles were used to hold all melts except those containing zirconium, for which zirconia crucibles were necessary. Temperatures were measured by a disappearing-filament type optical pyrometer sighted vertically downward on the melt surface through a 1/4-in.-diameter sight hole in the crucible lid. By means of a technique previously described, 9 in which the refractory-metal nitride was precipitated at one temperature then redis-solved by raising the temperature 50°C and precipitated again at a higher temperature, it was possible to obtain data over a temperature range of up to 200°C on a single melt. It was found that this technique could not be used with melts containing zir-

Jan 1, 1965

By J. W. Spretnak, D. A. Chatfield, G. W. Powell, J. R. Eifert

In nzost cases, the driving force for a lattice transformation is produced by supercooling below the equilibriunz transformation temperature. The interfnce reaction in isothermally annealed, multiphase diffusion couples may involve a luttice transformation which also requires a driving force. Direct experinzental evidence has been obtained for the existence of the driring force in the form of a supersaturated phase at the aocc)-0@cc) interface in Cu:Cu-12.5 ult pct A1 couples; the super saturation is equivalent to an excess free energy of approximately 3 cal per mol at 905. A tentatiue interpretation of the dynanzic situation a1 the interface based on the free energy-composition diagram is proposed. THE presently accepted theory of diffusion in multiphase couples1 states that there will be a phase layer in the diffusion zone for every region which has three degrees of freedom and which is crossed by the diffusion path in the equilibrium phase diagram. For binary systems, this restriction excludes all but single-phase fields and, for ternary systems, only one- and two-phase fields are included. In addition, Rhines"~ as well as other investigators3 6 have reported that the compositions of the various phases adjacent to the interfaces are, for all practical purposes, the compositions given by the intersections of the diffusion path with the solubility limits of the single-phase fields of the equilibrium phase diagram. Some studies of the rate of thickening of these intermediate diffusion layers indicate that the thickness of the layer changes para-bolically with time, or: where x is the position of the interface relative to an origin xo, t is the diffusion time, and k is a temperature-dependent factor. crank7 shows mathematically that, if the compositions at an interface are independent of time and the motion of the interface is controlled by the diffusion of the elements to and from the interface, then the segments of the concentration penetration curve for a semi-infinite step-function couple will be described by an equation of the form: hence, Eq. [l] follows from Eq. (21 if the interface compositions are fixed and if the motion of the interface is diffusion-controlled. Although the concept of local equilibrium being attained at interfaces has assumed a prominent role in the theory of diffusion in multiphase couples, experimental evidence and theoretical discussions which challenge the general validity of this concept have been reported in the literature. arkeen' has stated that strict obedience to the conditions set by the equilibrium phase diagram cannot be expected in any system in which diffusion is occurring because diffusion takes place only in the presence of an activity gradient. Darken also noted that it is usually assumed that equilibrium is attained locally at the interface although the system as a whole is not at equilibrium, the implication being that the transformation at the interface is rapid in comparison with the rate of supply of the elements by diffusion. ISirkaldy3 indicates agreement with Darken in that he believes the concept of local equilibrium is at best an approximation because the motion of the phase boundary requires that there be a free-energy difference and, hence, a departure from the equilibrium composition at the interface. Seebold and Birks9 have stated that diffusion couples cannot be in true equilibrium, but the results obtained are often in good agreement with the phase diagram. The initial deviation from equilibrium in a diffusion couple will be quite large because alloys of significantly different compositions are usually joined together. Kirkaldy feels that the transition time for the attainment of constant interface compositions (essentially the equilibrium values) will be small, although in some cases finite. Castleman and sieglelo observed such transition times in multiphase A1-Ni couples, but at low annealing temperatures these times were quite long. Similarly, ~asing" found departures, which persisted for more than 20 hr, at phase interfaces in Au-Ni and Fe-Mo diffusion couples. Braun and Powell's12 measurements of the solubility limits of the intermediate phases in the Au-In system as determined by microprobe analysis of diffusion couples do not agree with the limits reported by Hiscocks and Hume-Rothery13 who used equilibrated samples. Finally, Borovskii and ~archukova'~ have stated that the determination of the solubility limits of phase diagrams using high-resolution micro-analyzer measurements at the interfaces of multiphase couples is not an accurate technique because of deviations from the equilibrium compositions at a moving interface; diffusion couples may be used to map out the phase boundaries in the equilibrium diagram, but the final determination of the solubility iimits should be made with equilibrated samples. The purpose of this work was to investigate the conditions prevailing at an interface in a multiphase diffusion couple and to compare the interface compositions with those associated with true thermodynamic equilibrium between the two phases. Microanalyzer techniques were used to measure interface compositions in two-phase Cu-A1 diffusion couples annealed at 80@, 905", and 1000°C for various times.

Jan 1, 1969

By Rollyn P. Jacobson

THE town of Pacific, in Jefferson County, Mo., is 127 miles west of St. Louis. Since the area lies entirely on the flood plain of a cutoff meander of the Meramac River, it was considered a likely environment for accumulation of commercial quantities of sand and gravel. Excellent transportation facilities are afforded by two major railways to St. Louis, and ample water supply for washing and separation is assured by the proximity of the river. As a large washing and separation plant was planned, the property was evaluated in detail to justify the high initial expenditure. An intensive testing program using both geophysical and drilling methods was designed and carried out. The prospect was surveyed topographically and a 200-ft grid staked on which electrical resistivity depth profiles were observed at 130 points. The Wenner 4-electrode configuration and earth resistivity apparatus" were used. In all but a few cases, the electrode spacing, A, was increased in increments of 11/2 ft to a spread of 30 ft and in increments of 3 ft thereafter. Initial drilling was done with a rig designated as the California Earth Boring Machine, which uses a bucket-shaped bit and produces a hole 3 ft in diam. Because of excessive water conditions and lack of consolidation in the gravel there was considerable loss of hole with this type of equipment. A standard churn drill was employed, therefore, to penetrate to bedrock. Eighteen bucket-drill holes and eight churn-drill holes were drilled at widely scattered locations on the grill. The depth to bedrock and the configuration will not be discussed, as this parameter is not the primary concern. Thickness of overburden overlying the gravel beds or lenses became the important economic criterion of the prospect.** The wide variety and gradational character of the geologic conditions prevailing in this area are illustrated by sample sections on Fig. 2. Depth profiles at stations E-3 and J-7 are very similar in shape and numerical range, but as shown by drilling, they are measures of very different geologic sequences. At 5-7 the gravel is overlain by 15 ft of overburden, but at E-3 bedrock is overlain by about 5 ft of soil and mantle. Stations L-8 and H-18 are representative of areas where gravel lies within 10 ft of surface. In most profiles of this type it was very difficult to locate the resistivity breaks denoting the overburden-gravel interface. In a number of cases, as shown by stations M-4 and H-18, the anomaly produced by the water table or the moisture line often obscured the anomaly due to gravel or was mistaken for it. In any case, the precise determination of depth to gravel was prevented by the gradual transition from sand to sandy gravel to gravel. In spite of these difficulties, errors involved in the interpretation were not greatly out of order. However, results indicated that the prospect was very nearly marginal from an economic point of view, and to justify expenditures for plant facilities a more precise evaluation was undertaken. The most favorable sections of the property were tested with hand augers. The original grid was followed. In all, 46 hand auger holes were drilled to gravel or refusal and the results made available to the writer for further analysis and interpretation. When data for this survey was studied, it immediately became apparent that a very definite correlation existed between the numerical value of the apparent resistivity at some constant depth and the thickness of the overburden. Such a correlation is seldom regarded in interpretation in more than a very qualitative way, except in the various theoretical methods developed by Hummel, Tagg (Ref. 1, pp. 136-139), Roman (Ref. 2, pp. 6-12), Rosenzweig (Ref. 3, pp. 408-417), and Wilcox (Ref. 4, pp. 36-46). Various statistical procedures were used to place this relationship on a quantitative basis. The large amount of drilling information available made such an approach feasible. The thickness of overburden was plotted against the apparent resistivity at a constant depth less than the depth of bedrock for the 65 stations where drilling information was available. A curve of best fit was drawn through these points and the equation of the curve determined. For this relationship the curve was found to be of the form p = b D where p is the apparent resistivity, D the thickness of overburden, and b a constant. The equation is of the power type and plots as a straight line on log-log paper. The statistical validity of this equation was analyzed by computation of a parameter called Pearson's correlation coefficient for several different depths of measurements, see Ref. 5, pp. 196-241. In all but those measurements taken at relatively shallow depths, the correlation as given by this general equation was found to have a high order of validity on the basis of statistical theory.

Jan 1, 1956

By E. Douglas Sethness

The uranium industry is booming. In Texas alone, there are about 22 different companies with active exploration programs. Twelve solution mines have been permitted; three surface mines have been authorized; and two mills are currently in operation. However, the industry also has a problem, and that is the disposal of radioactive wastes. Over the past several years, stories concerning nuclear wastes have appeared frequently in the news. One of the most frequently cited cases occurred in Grand Junction, Colorado. In 1966, after ten years of investigations, the U. S. Public Health Service (PHS) discovered that tailings from a uranium mill were being used as fill material and aggregate for local construction purposes. It was estimated that between 150,000 and 200,000 tons of material had been removed and used under streets, driveways, swimming pools, and sewer lines. In addition, tailings had been used under concrete slabs and around foundations of occupiable structures. Further studies prompted the Surgeon General to warn that the risk of leukemia and lung cancer could be doubled at the measured radiation levels. More recently, the L. B. Foster Company discovered that its building site in Washington, West Virginia, was radioactive. While digging a foundation, the ground erupted and a ball of fire 30 feet high shot out. Evidently, the dirt was laced with radioactive thorium and zirconium, a potentially explosive mixture contained in a Nigerian sand which had been used by the previous site owners in the manufacture of nuclear fuel rods. Just this month we have read about legal suits to stop exploration for a nuclear waste disposal site in Randall County, Texas. The U. S. Department of Energy is trying to locate a deep underground nuclear waste depository for final burial of over 76 million gallons of high-level wastes. The problem is acute, the wastes are accumulating at a rate of about 300,000 gallons per year. Nor do these numbers include the spent fuel elements from nuclear power plants that are in temporary storage facilities. Fortunately, public awareness of these and other related issues is high. Unfortunately, the differences in the waste products from the nuclear fuel cycle are not always apparent to the general public. There are two distinct types of radioactive wastes: "high-level", which consist of spent fuel or wastes from the reprocessing of spent fuel; and "low-level", which, in general, are by-product wastes. There are numerous non-technical definitions that can be applied to help the layman differentiate between high-level and low-level wastes. For this latter purpose, it is best to think of them in terms of what we can see and feel. In general, high-level wastes are physically hot and can cause acute radiation sickness in a short period of time. Low-level wastes are not hot, but may cause chronic health effects after long exposure. The wastes which we are concerned with in the uranium mining and milling industry are low-level wastes. As recently as ten years ago, there were very few controls or regulations governing tailings disposal methods. At the same time, mine reclamation was not enforced through either state or Federal laws and the long-term viability of abandoned tailings ponds was not assured. The regulatory climate has changed significantly in the last decade, however. The low-level radioactive wastes generated by uranium mining and milling are generally contained in a tailings pond. Approximately 85-97% of the total radioactivity contained in uranium ore is present in the mill waste that goes to such tailings ponds. The isotope Radium-226 is probably the most potentially harmful radioactive parameter in the ponds. Radium emits gamma radiation and is also an alpha particle emitter. Because gamma radiation is very penetrating, it presents a potential health problem when a source is located external to the body. Gamma radiation will go through the body, causing damage to each cell encountered on the way. Although alpha particles have very little penetration capability, they can cause extensive cell damage. For this reason, alpha particles are a problem after inhalation or ingestion. Radium creates a health hazard by both of these mechanisms. Radium decays to radon gas which can be inhaled and serve as an alpha particle emitter. Additionally, radium is very soluble and readily enters the natural hydrologic cycle if allowed to leach from a tailings pond. With a half-life of 1620 years, radium has plenty of time to be taken into the food chain and end up in our bodies, emitting alpha particles. Because the potential health problems are better understood today than ten years ago, and because the Nuclear Regulatory Commission (NRC) has developed increasingly stringent government regulations, the uranium mining industry applies a high level of technology to the disposal of nuclear wastes. In most cases, low-level radioactive wastes are disposed of at or near the site where they are produced. There are six commercial burial grounds for low-level wastes, but it would not be economical to ship all mine or milling wastes to these sites. The on-site disposal methods most often used are ponding

Jan 1, 1979

By K. E. Brown, A. R. Hagedorn

Continuous, two phase flow tests have been conducted during which four liquids of widely differing viscosities were produced by means of air-lift through 1%-in. tubing in a 1,500-ft. experimental well. The purpose of these tests was to determine the effect of liquid viscosity on two-phase flowing pressure gradients. The experimental test well was equipped with two gas-lift valves and four Maihak electronic pressure transmitters as well as instruments to accurately measure the liquid production, air injection rate, temperatures, and surface pressures. The tests were conducted for liquid flow rates ranging from 30 to 1,680 BID at gas-liquid ratios from 0 to 3,-270 scf/bbl. From these data, accurate pressure-depth traverses have been constructed for a wide range of test conditions. As a result of these tests, it is concluded that viscous effects are negligible for liquid viscosities less than 12 cp, but must be taken into account when the liquid viscosity is greater than this value. A correlation based on the method proposed by Poettmann and Carpenter and extended by Fan-cher and Brown has been developed for 1¼-in. tubing, which accounts for the effects of liquid viscosity where these effects are important. INTRODUCTION Numerous attempts have been made to determine the effect of viscosity in two-phase vertical flow. Previous attempts have all utilized laboratory experimeneal models of relatively short length. One of the initial investigators of viscous effects was Uren1 with later work being done by Moore et al.2,3 and more recently by Ros.4 However, the present investigation represents the fist attempt to study the influence of liquid viscosity on the pressure gradients occurring in two-phase vertical flow through a 1¼-in., 1,500 ft vertical tube. The approach of some authors has been to assume that all vertical two-phase flow occurs in a highly turbulent manner with the result that viscous effects are negligible. This has been a logical approach since most practical oil-well flow problems have liquid flow rates and gas-liquid ratios of such magnitudes that both phases will be in turbulent flow. It has also been noted, however, that in cases where this assumption has been made, serious discrepancies occur when the resulting correlation is applied to low production wells or wells producing very viscous crudes. Both conditions suggest that perhaps viscous effects may be the cause of these discrepancies. In the first case, the increased energy losses may be due to increased slippage between the gas and liquid phases as the liquid viscosity increases. This is contrary to what one might expect from Stokes law of friction,' but the same observations were made by ROS4 who attributed this behavior to the velocity distribution in the liquid as affected by the presence of the pipe wall. In the second case, the increased energy losses may be due to increased friction within the liquid itself as a result of the higher viscosities. The problem of determining the li- quid viscosity at which viscous effects becomes significant is a difficult one. Ros4 has indicated that liquid viscosity has no noticeable effect on the pressure gradient so long as it remains less than 6 cstk. Our tests have shown that viscous effects are practically negligible for liquid viscosities less than approximately 12 cp. Actually there is no single viscosity at which these effects become important. These effects are not only a function of the viscosities of the liquids and of the gas but are also a function of the velocities of the two phases. The velocities in turn are a function of the in situ gas-liquid ratio and liquid flow rate. Furthermore, the role of fluid viscosities in either slippage or friction losses will depend on the mechanism of flow of the gas and liquid, i.e., whether the flow is annular. as a mist, or as bubbles of gas through the liquid. These mechanisms are also a function of the in situ gas-liquid ratios and the flow rates. It would thus seem that the best one could hope for is to determine a transition region wherein the viscous effects may become significant for gas-liquid ratios and liquid production rates normally encountered in the field. The viscous effects might then be neglected for liquid viscosities less than those in the transition region but would have to be taken into account when higher viscosities are encountered. There are numerous instances where crude oils of high viscosity must be produced. The purpose of this study has been to evaluate the effects of liquid viscosities on twephase vertical flow by producing four liquids of widely differing viscosities through a 1 % -in. tube by means of air-lift. The approach used in this study was as follows:

Jan 1, 1965