Search Documents

By N. A. Gokcen, J. Chipman

A revised treatment of the authors' published data eliminates the complex relation previously proposed between concentration of silicon and activity coefficient of oxygen in liquid iron. Revised values of the thermodynamic properties of the liquid solution are presented. IN a recent experimental study of the reaction SiO2 (s) = Si+ 2O; Kf, = [% Si] [% O]² [1] the authors' found a substantially constant equilibrium product in liquid iron at 1600°C of 2.8x10-5 They also reported extensive data on the reactions: SiO2 (s) + 2H2 (8) = Si- + 2H2O (g); K'2= [% Si] (H2O/H2 [2] and H, (g) + 0 = H2O (g); K'3 =( H2 O [31 (H2) [%O] From the results on reaction 3 and earlier data of Dastur² on this same reaction in the absence of silicon, they determined the activity coefficient of oxygen, f0, on the basis of the definition K3 = (H2O)/ (H2)f0 [% 0] where K, is the equilibrium constant and f0, is taken as unity in the pure Fe-0 system. Similarly values of fsi were deduced from results on reaction 2. In a more recent study" of analogous reactions in the system Fe-A1-0, it was found impossible to reconcile the results on reaction 3 with Dastur's data; accordingly the latter were ignored and the equilibrium results were extrapolated to find a value of K, at zero concentration of aluminum. This procedure failed to locate the cause of the discrepancy but it did yield reasonable values of activity coefficients. It also avoided introduction of the complex empirical relation between the oxygen activity coefficient and the concentration of the added element. The same type of discrepancy exists for system Fe-Si-0.' In the earlier paper an attempt was made to fit both sets of data by a single curved line (Fig. 6 of ref. l), the form of which is contrary to the theoretical requirement of a finite slope at infinite dilution. In the light of experience on the Fe-A1-0 system the discrepancy must be recognized as one which can be resolved only by more refined measurements. Accordingly Figs. 6 and 10 are retracted. It is pointed out also that until the discrepancy is resolved Figs. 7, 8, and 11 are subject to some uncertainty. Qualitatively the following conclusions still appear valid: 1—The activity coefficient of oxygen is reduced by addition of silicon. 2—In dilute solutions the activity coefficient of silicon increases with its concentration. 3—With respect to equilibrium in reaction 1, the above effects are approximately compensating. The discussion of K'1 in the previous paper requires no revision. It was pointed out that the constancy of the product [% Si] [% 0]² ndicated a compensating effect of the activity coefficients of silicon and oxygen. Therefore, as a very good approximation, K1 = K'1 and the following average values are suggested both for K, and K', at the temperatures 1550°, 1600°, and 1650", respectively, 1.0x10-", 2.8~10-" and 5.5 ~lo-'. Revision of the thermodynamic treatment is necessitated by the recent appearance of new data, based on a combination of combustion and solution calorimetry,' which yields for the heat of formation of low-cristobalite from the elements, the value —209,330 ±250 cal per mol at 25°C. This is about 4000 cal larger than the value previously accepted. The new value for cristobalite is used, together with Kelley's tables of high-temperature heat contents" and entropies and with Korber and Oelsen's' heat of fusion of silicon to obtain the following equation for the standard free energy of cristobalite in the temperature range 1700" to 2000°K: Si (1) + 02 (g) = Si02 (crist.); ?F° = -217,700 + 47.OT [4] The free energy of solution of 0, in liquid iron is:8 O2 (g) = 20 (in Fe); AF° = -55,860 - 1.14T [5] and these two equations are combined to give: Si (1) + 20 = SiO, (crist.); AF° = -161,840 + 48.14T [6] ?F°1873 = -71,700 cal. From the experimental value of K, = 2.8x10-5, Si + 20 = SiO2 (crist.); ?F°1873 = -39,000 cal. [7] The combination of Eqs. 6 and 7 yields the free energy change when liquid silicon dissolves in iron to form the dilute solution of unit activity (1 pct). Si (1) = Si; ?F°1873 = -32,700 cal. [8] The heat effect in this process according to Korber and Oelsen' is an evolution of 28,500 cal per gram

Jan 1, 1954

By E. M. Cox, A. S. Skapski, N. H. Nachtrieb, M. C. Bachelder

As a result of using copper-containing scrap in the steelmaking process, the copper content of steels has been steadily increasing for years. Consequently the possible role copper may play in the steelmaking process and in the finished product begins to attract the metallurgists' attention. Some time ago one of the present authors forwarded the idea—based on the results of the analysis of nonmetallic inclusions extracted electrolytically from steels—that sulphur in plain carbon steels is distributed mainly between copper and manganese, the amount of iron sulphide being very small; and that, consequently, the problem of copper and that of sulphur in steel cannot be treated separately.' At the time of the publication of the quoted paper little was known about the relative affinities of copper and manganese for sulphur at high temperatures except that at moderate temperatures (below 1000°C) the affinity of manganese for sulphur is much greater. To gather more experimental data on this subject, the present authors undertook the investigation of the equilibrium constants of the reactions: 2Mn(8 or 1) + S2(g) = 2MnS(s) 4Cu(s or 1) + S2(g) = 2Cu2S (S or I)* 2Fe(s) + S2(g) = 2FeS (s or 1) over a range of temperatures wide enough to establish the dependence of these equilibrium constants on temperature. From the equilibrium constants (K = l/Ps2) the free energy of formation (affinity) can be calculated from F° = -RTln 1/PSt (1) where the standard conditions chosen are: 1 atm of sulphur pressure and the activities of condensed components equal one. The decomposition pressure, Ps2, of sulphur over the respective sulphides is too small to be measured directly, but there is a way of eliminating this difficulty by measuring the equilibrium constant of the reaction between the sulphide and hydrogen. From the latter and from the equilibrium constant of the thermal dissociation of H2S we then calculate Ps2 for the respective sulphide. 2Mn + 2H2S = 2MnS + 2H, 2H2 + S2 = 2H2S_________ 2Mn + S2 = 2MnS The numerical values of the equilibrium constant of the thermal dissociation of H2S at different temperatures were taken from Kelley's paper, "The Thermodynamic Properties of Sulfur and its Inorganic Compounds."² In previous experimental work published by Jellinek and Zakowski3 and by Britzke and Kapustinsky4 the equilibrium constants of the reactions Metal sulphide + H2 = H2S + metal were determined by passing hydrogen, at different rates of flow, over the sulphide, analyzing the resulting H2S + H2 mixture and then extrapolating the H2S/H2 ratio (which is a function of the rate of flow) to the zero speed of flow, a method necessarily involving considerable uncertainty. In the present work the equilibrium ratio was actually measured instead of being extrapolated. The apparatus is shown in Fig 1. Experimental Procedure The sulphides were prepared by the following methods: FeS Powdered iron which had been reduced with hydrogen (ferrum reduc-tum) was mixed in stoichiometric ratio with sublimed sulphur and carefully ground. The mixture was put into an alundum crucible, covered with pure sulphur, and the reaction started by touching the mixture with a glowing iron rod. After the reaction was completed the product (still containing some metallic iron) was again ground with sulphur, put into a Rose crucible, covered with sulphur, and heated in a strong current of pure hydrogen. Analysis of the final product showed 62.46 pct Fe and 36.59 pct S. Theoretical for FeS: 63.53 pct Fe and 36.47 pct S. MnS Manganese sulphide (precipitated and carefully washed with distilled water containing H2S) was dried in a Rose crucible in an atmosphere of H2S and heated in a current of hydrogen for 2 hr at red heat. The product was then ground and ignited for several hours at 1000°C in a current of hydrogen sulphide. Analysis showed 64.53 pct Mn and 36.63 pct S. Theoretical: 63.15 pct Mn and 36.85 pct S. Some MnS samples were prepared from metallic manganese and sublimed sulphur by mixing and grinding them and then heating in a current of hydrogen sulphide in an alundum tube.

Jan 1, 1950

By R. I. Jaffee, F. C. Holden, H. R. Ogden

ECENT papers dealing with the properties of unalloyed iodide titanium have been directed primarily at the determination of base-line properties for alloy investigations. Early work was limited to a few tests because of the limited availability of iodide titanium at the time. In the results of papers by Campbell et al.,1 Gonser and Litton,2 Jaffee and Campbell,3 inlay and Snyder,4 and Jaffee, Ogden, and Maykuth, data on mechanical properties are presented for unalloyed iodide titanium in the annealed and cold-worked conditions. Data are presented in this paper which show the effects of heat treatment on the structure and mechanical properties of commercially produced iodide titanium. Correlation is made between microstruc-tural variables and the mechanical properties. Experimental Procedures Melting Stock: The melting stock used was as-deposited iodide titanium, produced by New Jersey Zinc Co. The furnished analysis showed the following range of impurities: N, 0.004 to 0.008 pct; Mn, 0.005 to 0.013; Fe, 0.0035 to 0.025; Al, 0.013 to 0.015; Mo, 0.0015; Pb, 0.0045 to 0.0065; Cu, 0.0015 to 0.002; Sn, 0.001 to 0.01; Mg, 0.0015 to 0.002; and Ni, 0.003. Hydrogen content as determined by vacuum-fusion analysis was 0.0091 wt pct (0.44 atomic pct) after arc melting and fabrication. Nitrogen analysis on the arc-melted and fabricated titanium showed a content of less than 0.002 pct N. The average hardness of the furnished stock was Rf 70, or approximately 85 VHN. Melting Procedure: The as-deposited rods were rolled, sheared, and degreased in preparation for arc melting. The charge was arc-melted with a tungsten electrode in a water-cooled copper crucible under a positive pressure of high purity (99.96 pct) argon. The final ingot was approximately 2 in. in diameter and showed no increase in hardness over that of the initial stock. Fabrication: Heating for fabrication was done in air. It was begun by forging the ingot into a 3/4 in. diam rod, at an initial temperature of 1600°F. Scale was removed by sandblasting. The rod was then swaged to 1/4 in. diam at room temperature through a series of 20 dies, with approximately 10 pct reduction in area between each die. An anneal of 1 hr at 850 °C in air was given after the 1/2 in. die, such that the final cold reduction was 75 pct. Sections cut from this rod were used for test and microstructure specimens. Heat Treatment: Heat treatments were carried out in resistance tube furnaces with stainless-steel linings, under an atmosphere of gettered argon. As further protection against contamination, the specimens were packed in titanium turnings in a titanium sleeve. Control experiments have shown negligible hardness increases with this method, indicating that contamination from oxygen and nitrogen is slight. Three cooling rates were employed in this work; these have been designated as water quenching, argon cooling (to simulate air cooling under a controlled atmosphere), and furnace cooling. The cooling rate for an argon cool is 100°C per min for the first minute, with an average cooling rate of 35°C per min over a 15-min period. A furnace cool requires about 10 hr, with an average cooling rate of 3.6oC per min during the first hour, and an average cooling rate of 1.2°C per min over the 10-hr period. Microimpact Test: The specimen adopted was based on the cylindrical Izod Type Y specimen (ASTM, E23-41T). All dimensions were reduced to half scale, including the notch radius. Specifications are shown in Fig. 1. The specimen is held vertically in an adapter and broken as a cantilever beam. Impact tests were run on a constant-velocity (11.34 ft per sec) Tinius Olsen impact testing machine with a total available energy of 100 in.-lb. Tests were made to determine the correlation between this microimpact and the standard V-notch Charpy impact test. Curves showing impact energy as a function of temperature for both impact tests are plotted in Fig. 2. Transition temperatures, when they occur, are about the same for both impact tests. All three titanium-rich materials have the same conversion factor, 10. Tensile Testing: Tensile tests were conducted on Baldwin-Southwark testing machines using the 600, 2400, or 3000 1b range. Specifications for the test specimen were taken from the 1948 edition of the ASM Metals Handbook, and are shown in Fig. 1. Strain measurements were made using an SR-4 resistance gage (Type A-7) cemented to the reduced section in conjunction with a lever-type extenso-meter. Readings on the SR-4 strain indicator were

Jan 1, 1954

The properties required for a com-pound to form useful thermoelectric materials are described. Uranium compounds which might have these properties are reviewed. Several of these compounds have been prepared and fabricated into compacts. The apparatus used for hot pressing, and for the measurement of thermoelectric power, electrical conductivity and thermal conductivity, is described. Detailed attention has been given to the properties of the nitrides. Preliminary studies on a number of other uranium compounds are reported. The figures of merit of the best materials so far examined are one-tenth of those necessary for a useful thermo-electric material. THE efficiency of thermoelectric materials for power generation and cooling is determined by their figure of merit, Z = a2 a/K, where a, a and K are thermoelectric power, electrical conductivity and thermal conductivity, respectively. It is well known that the largest values of Z are achieved with semiconductors (1). High mobility of charge carriers is necessary for simultaneously high thermoelectric power and electrical conductivity.The properties required for a com-pound to form useful thermoelectric materials are described. Uranium compounds which might have these properties are reviewed. Several of these compounds have been prepared and fabricated into compacts. The apparatus used for hot pressing, and for the measurement of thermoelectric power, electrical conductivity and thermal conductivity, is described. Detailed attention has been given to the properties of the nitrides. Preliminary studies on a number of other uranium compounds are reported. The figures of merit of the best materials so far examined are one-tenth of those necessary for a useful thermo-electric material. THE efficiency of thermoelectric materials for power generation and cooling is determined by their figure of merit, Z = a2 a/K, where a, a and K are thermoelectric power, electrical conductivity and thermal conductivity, respectively. It is well known that the largest values of Z are achieved with semiconductors (1). High mobility of charge carriers is necessary for simultaneously high thermoelectric power and electrical conductivity.

Jan 1, 1963

By D. E. Walsh

Over a period of seven years (1989-1996) the Mineral Industry Research Laboratory (MIRL) University of Alaska Fairbanks, has investigated the effects of temperature, residence time, and particle size on the degree of low-rank coal (LRC) upgrading for a non-evaporative, hydrothermal drying process, also known as hot water drying (HWD). Three Alaskan LRCs were used in this study: Usibelli coal (Seam No.4) from the Nenana Coal Field, Little Tonzona coal from near McGrath, and Beluga coal from the Beluga-Yentna field on the west side of Cook Inlet. Replicated, factorial tests were conducted. Experimental results indicate that most of the low-rank coal upgrading via HWD occurs rapidly within the first 10-20 minutes of residence time. Thereafter, the upgrading process slows down and over 100 minutes of additional residence time are required to produce similar percentage increases in coal properties to those achieved in the first 10-20 minutes. The properties of the hot water dried products were very sensitive to process temperature. Calorific value, carbon and oxygen contents, equilibrium moisture levels and Hardgrove grindabilities all appear to change linearly with temperature within the 275" C to 325" C range.

Jan 1, 1997

By B. Currie

Maintenance of quality electrowon copper requires an electrolyte which has suitable chemical and physical characteristics. The proper design and operation of the solvent extraction plant is essential to the quality of the electrolyte sent to electrowinning. An aspect that is not well appreciated is that the return electrolyte can have negative effects on the operation of the solvent extraction plant. Poor SX plant operation creates below optimum electrolyte conditions. High Eh in the return spent electrolyte can degrade the SX reagent with large decreases in copper transfer capacity and increases in internal entrainment. The synergistic interaction of the SX and EW plants needs a single-source design approach to address the interactions. The design elements in the SX and EW plants required to manage the electrolyte conditions are discussed.

Jan 1, 2014

By Y Pan

The recycling of steel is a crucial aspect of the shift toward a sustainable metals industry. The emphasis on steel recycling through the introduction of the scrap based mini-mill concept is also matched with a desire for greater product quality and reduced environmental impact, which, in turn, has generated important innovations. There have been significant advances in the technology for recycling steel over the last 20 years and this paper will provide an overview of these developments and discuss future directions in steel recycling including scrap management, control of tramp elements, electric arc furnace technology and ladle metallurgy.

Jan 1, 2004

By S Jayakumari, E Ringdalen, V Canaguier

Silicomanganese (SiMn), containing approximately 16–30 per cent Si, is produced in submerged arc furnaces using various Mn sources and quartz as the primary raw materials, along with fluxes and reductants. In the high-temperature zone known as the coke bed, a silica-rich slag is formed. SiMn is produced through the reduction of SiO2 from the slag. Dissolution of quartz into slags with different compositions, the primary slag formed from the Mn sources and flux before any MnO reduction occurred, representing conditions at the top of the coke bed, and dissolution of quartz into a partially reduced slag to simulate conditions inside the coke bed has been investigated. Experimental investigations were carried out to study the dissolution of quartz particles of varying sizes, 5 mm and 25 mm in synthetic slags with different compositions at temperatures between 1400°C and 1600°C, with varying holding times. Observed results are compared with liquidus compositions and equilibrium phases for original and formed slags. Particle size has been shown to be of little importance for the dissolution. Quartz dissolved more easily in slag at top of the coke bed than slag in the coke bed. Complete dissolution was observed after 30 mins at 1600°C in all cases, but not after 0 mins.

Jun 19, 2024

By Tell Ertl

THE Piceance Creek Basin in northwestern Colorado is believed to contain the richest large deposit of oil shale in North America. The major portion, about 1650 sq miles, is bounded by the White River on the north, the Grand Hogback, which runs from Meeker to Rifle, on the east, the Colorado River to the south, and the drainage basin of Salt and Douglas Creeks on the west. The Basin is a plateau 7000 to 9000 ft high, composed of 3000 ft of the Green River series of Eocene age and surrounded by a steep escarpment of 1000 to 3000 ft. From the escarpment the beds dip gently toward the center. Although oil shale is found in all members of the Green River series, the rich thick beds are found chiefly in the Parachute Creek member. This is normally capped by 100 to 200 ft of the Evacuation Creek, the youngest member of the Green River series. Actually the Piceance Creek Basin oil shale is not a shale, nor does it contain oil. It is magnesium marlstone holding solid organic matter capable of being broken down by heat into gases, some of which can be condensed into oil. The marlstone is resilient nonporous rock, difficult to sample by pick or hammer and moil. Many companies and individuals prospected the Colorado oil shale shortly after the first World War,1 see Fig. 1, but because of the discovery of large quantities of petroleum in the late 1920's in California, Oklahoma, and East Texas, interest in oil shale development waned and did not revive until World War II. In 1944 the writer, employed by the Bureau of Mines, prospected the high grade oil shale in numerous places along the southern outcrop of the Piceance Creek Basin. Several channel samples about 100 ft in length were cut, see Fig. 2. An eightman crew needed a week to cut a satisfactory channel 80 ft long in the cliff face. The Phillips Petroleum Co., the Union Oil Co. of California and others also prospected the oil shale outcrop. In 1945 the Bureau of Mines initiated a core drilling program for the purpose of obtaining accurate samples from the Piceance Creek Basin. The U. S. Geological Survey set up a program for the geological study of the Basin that is still going on.2 Until the end of 1951 a total of 31 holes was drilled for core with diamond drills, and, in addition, cuttings through the oil shale have been obtained from 4 gas wells drilled by standard rotary oil well rigs. The Bureau of Mines drilled 12 of the holes, the Union Oil Company of California 8, the Standard Oil Company of California 6, the Sun Oil Company 3,

Jan 1, 1952

By E G. Prado

We have confirmed on bench scale the removal of chlorides and alkalies (+95%) and over 2/3 of the zinc, lead and cadmium from EAF dusts. This has been achieved with arrononium acetate solutions alone, or with combinations of water wash, amonia-ammonium carbonate and ammonium acetate solutions. Also confirmed are the process routes for the recovery of the aforementioned elements into marketable products. The technology involves the complete recycling of the reagents. The FAF residue is returned to the electric furnace without risk of impurities buildup. Commercial scale testing with the recycled dust was satisfactory, including quality of the slag and its behavior during the melting stage. A cursory feasibility evaluation is presented.

Jan 1, 1994

By A. Patti, S. Reutzel, D. M. Herlach, L. Ratke, I. Egry

Cu-Co shows a metastable miscibility gap in the region of the undercooled melt. Undercooling of the melt below the binodal leads to separation of the melt into a Co-rich LI-phase and a Curich L2-phase. Experimentally, undercooling into the metastable miscibility gap is realised by means of electromagnetic levitation (EML), processing in drop tube (DT) and by melt flux embedding. As undercooling is large in these experiments, the velocity of the solidification front is high and the microstructure is frozen in instantaneously. Samples have been undercooled and solidified in the TEMPUS-facility (container less electromagnetic processing under weightlessness) during parabolic flight under reduced gravity conditions. Microstructures of solidified samples have been analysed and compared to those processed under gravitational conditions. The influence of convection on phase growth is much lower in reduced gravity. The microstructure shows spherical droplets of the minority phase, statistically dispersed in the majority phase.

Jan 1, 2004

By Harold P. Rue

The problem of removing hydrogen sulphide from natural gas has become within the last few years one of major importance to the natural gas and petroleum industry. Several gas fields in the United States produce natural gas containing hydrogen sulphide, and a number of oil fields produce gas which contains hydrogen sulphide. 3 The percentage of hydrogen sulphide in natural gas produced in these fields varies from a fraction of 1 per cent to as high as 20.5 per cent by volume. Hydrogen sulphide is probably the most toxic gas associated with natural gas, and from the standpoint of health and safety it is important that the hydrogen sulphide be removed if the gas is to be used for domestic purposes. Hydrogen sulphide, besides being toxic and therefore a hazard to animal life, is under certain conditions an active corrosive agent and very destructive to equipment. The annual loss caused by the corrosive action of hydrogen sulphide on equipment amounts to hundreds of thousands, perhaps millions, of dollars. The largest percentage of natural gas produced in the United States comes from wells which also produce oil. This associated gas invariably carries with it light fractions of petroleum, which when separated from the gas, condense to the liquid form at ordinary temperatures and pressure. Commercial application is made of this natural condition, and "wet gas" is processed to obtain so-called natural gasoline by employing the principles of absorption, adsorption, or compression and subsequent expansion accompanied by cooling. In the manufacture of natural gasoline from wet gas which contains hydrogen sulphj.de, if this contaminating gas is not first removed, some of the hydrogen sulphide may oxidize to form free sulphur and water. The free sulphur will dissolve in the gasoline produced by any of the aforementioned methods and cause the product to be positive to the corrosion test and there-fore unsuitable for commercial use in that condition. The objectionable sulphur compounds can be removed by washing the gasoline with a solution of caustic soda or other chemicals, but this treatment is expensive. It is advantageous therefore to remove the hydrogen sulphide from the gas before it is processed in a natural-gasoline plant.

Jan 1, 1932

By Herbert J. French

ALLOY steels have become essential to industry in meeting the rigid requirements on materials imposed by our, advanced technology. In comparison with the total ingot capacity of the steel industry, the volume of alloy steels is relatively small although for many years annual alloy-ingot tonnage has, been in seven figures. However, the monetary value of the alloy-steel production is exceedingly high and the benefits derived from the products are relatively great. The trend in total ingot production since 1932 has been generally upward with only two major interruptions. That of the year 1938 was due to a decrease in general business activity whereas that of 1946 resulted largely from work stoppages. Traditionally, the tonnage of alloy-steel ingots produced was in the neighborhood of 5 to

Jan 1, 1948

By Shuqiang Guo, Xionggang Lu, Yuyang Bian, Weizhong Ding, Lan Jiang, Kai Tang, Changyuan Lu

For recovery of rare earth elements from the NdFeB based permanent magnet scraps, a high temperature process was used. Permanent magnets scraps were firstly oxidized in air. The optimal oxidation conditions under air are at temperature of 700oC holding for 30min. After the oxidation process, the oxides were reduced by graphite crucible at 1500oC under Ar atmosphere. By this way, the rare earth elements were recovered in the form of oxides, and Fe was separated to the metal phase. Boron distributed in both the rare earth oxides (REO) containing slag and the metal phase. In order to reduce the boron contents in the rare earth oxides, the carbon saturated iron bath and NdFeB added carbon saturated iron bath were used to refine the slag. By this process, the rare earth oxides with a comparatively high purity of 98.2% were gotten.

Jan 1, 2015

By Aarne Visnapuu

Unmodified pneumatic rock drills may have noise levels of 115 to 130 dB at the operator's position. Experimental modifications have been made to a standard drill to suppress the noise from the three main sources: the air exhaust noise, the noise radiated from the drill, and the resonance noise of the steel drill rods. A prototype model developed at the Bureau of Mines, Rolla Metallurgy Research Center, operates at a noise level below 100 dB. A close-fitting case and muffler unit, consisting of a metallic skeleton filled with viscoelastic absorber and having a durable cover, provided both muffling and noise absorption. Damping alloys were used at strategic points in the drill. Drill steel resonance noise was reduced by a constrained-layer treatment on the outside of the drill rod. The singular and combined effects of the treatments are presented in detail.

Jan 1, 1973

By J. W. Spretnak, G. W. Powell, J. H. Bucher

Tlze room-temperature tensile fracture oj smooth, round specitnens of three ultrnhigh- strength steels tempered to a wide range of strength levels was studied by means by light and electron-microscopic examination of the fracture surfaces. The fracture of AISI 4340 and 300 M at all the strength levels studied, and H-11, except after tempering at 1200° and 1300°F, occurs in three stages. The initiation of fracture is internal (except in some lightly tcmpeved specimers in which fracture is initiated at surface flaws), and is nucleated largely by separation at metal-second phase intevjaces. TIze voids grow and, coalesce to form a crack. When the crack has reached a sufficienl size, rapid propngutio~z ensues. Failure in this stage of fracture usually occurs by dimpled rupture of inicroshear stefis. In the case of H-11 tempered in the 1125° to 1300°F range, fracture in the shear steps is predominantly by concentrated deformation without void formation. The termination of fracture is usually occomplished by the formation of a shear lib in which fracture occurs by shear dimpled rupture. In the case of H-11 tempered at 1200° and 1300°F, no shear lip was obserued, and the radial elelments extend to the surface—a true termination slage does not exist. ThE tensile fracture of several metals and alloys has been investigated.2-4 In the case of polycrystal-line materials, cup-cone fracture usually results. The mechanism of cup-cone fracture may be summarized as follows.5 Cavities are formed in the necked region of the specimen. They usually are initiated by inclusions or second-phase particles. The cavities extend outwards by means of internal necking, and a crack lying about perpendicular to the length of the specimen is formed in the necked region. Subsequent crack growth occurs by the spread of bands of concentrated plastic deformation inclined at an angle of 30 to 40 deg to the tensile axis. Cavities are formed in the bands of concentrated deformation. The deformation bands zigzag across the bar with the net result that mac-roscopically the crack extends about perpendicular to the specimen axis. The final separation, or cone formation, appears to occur by continued crack propagation along one of the deformation bands out to the surface of the specimen. The micromechanics of the tensile fracture of ultrahigh-strength steels have not been thoroughly investigated. Larson and carr6,7 studied the tensile-fracture surfaces of AISI 4340 with a low-power microscope and reported that three stages of fracture could be observed in general. A centrally located region characterized by circumferential ridges, an annular region characterized by radial surface striations, and a peripheral shear lip were found. It was first pointed out by 1rwin8 that the central region is very probably one of fracture initiation and slow growth, and that the annular, radially striated region is one of rapid crack growth. Presumably the crack grows slowly, assuming roughly a lenticular shape, until it is large enough for the initiation of rapid propagation. In this investigation, it was attempted to determine the fine-scale aspects of the room-temperature tensile fracture of some ultrahigh-strength steels, and to relate the variation in fracture mode with microstructure. The steels studied were AISI 4340, 300M, and H-11 tempered to a wide range of strength levels. I) EXPERIMENTAL PROCEDURE The compositions of the steels studied are given in Table I. The steel was received in the form of hot-rolled bar stock 5/8 to 1 in. in diameter from which oversized specimens were machined and heat-treated. The heat treatments employed are given in Table 11. Subsequent to heat treatment, the specimens were ground to the final dimensions and stress-relieved by heating for 1 hr at 350°F (with the exception of the as-quenched steel). Standard smooth round specimens of 0.252-in. diameter and 1-in. gage length were tested in a Tinius Olsen Universal Testing Machine using a cross-head speed of 0.025 in. per min. The relatively coarse aspects of the fracture topography were determined by light-microscopic examination of sections through the fracture surface of nickel-plated specimens. A direct carbon-replication technique9 was used in the electron-microscopic study of the fracture surfaces. The replicas were examined in the electron microscope, and stereo pairs of electron micrographs were taken. The stereo pairs were then examined using a Wild ST4 Mirror Stereoscope. Carbide and inclusion particles extracted in the replicas were analyzed by selected-area electron diffraction. II) EXPERIMENTAL RESULTS The mechanical testing data are summarized in Table 111. The values reported are the average of

Jan 1, 1965

By W. Rostoker, R. F. Domagala, R. P. Elliott

The phase equilibria of the Hg-Th system over the composition range 0-100 pct Th and temperatures up to 1000°C have been studied for a small-volume, closed system. The solubility of Th in liquid Hg is about 5 pct at 300°C and decreases sharply with decreasing temperature. Two intermediate phases occur, Hg3 Th and HgTh. The structures of these are hexagonal (nonideally close-packed) and face-centered cubic, respectively. The HgTh phase decomposes eutectoidally at 400°-500°C. The solubility of Hg in solid thorium seems to be negligible. AFULL-phase diagram for this system would have to be defined on temperature-composition-pressure co-ordinates. This paper describes the pseudo phase diagram of a closed system, that is, where the alloy enclosed in a small volume equilibrates with a vapor pressure of mercury dictated by composition and temperature. Because of the experimental difficulties in studying a system of this nature, many of the phase relations can only be sketched. Alloy Preparation Alloys over the full range of composition were made from triple distilled mercury and one of two grades of thorium. For the bulk of the work, a calcium-reduced metal in sintered pellet form of reported 99+ pct total thorium content was used. Arc-melted specimens of this thorium gave a hardness of 135 VPN. The microstructure showed small primary dendrites of ThO2. A number of alloy compositions were made with a high-purity, iodide-decomposition thorium metal. The are-melted hardness of a button of this material was 35 VPN. Although the microstructure of the arc-melted specimens showed no dendrites of ThO2, there was definite evidence of an unidentified phase enveloping the grain bound-aries. There were no distinguishable differences between the constitution of alloys made with the two grades of thorium metal. Under normal conditions thorium is not wetted by liquid mercury. The film of ThO2 on all thorium metal cannot be penetrated by either liquid or vaporous mercury. It was therefore necessary to comminute thorium in the presence of mercury under such conditions that oxide films could not reform on the newly exposed metal surfaces. This was accomplished by the use of a high-speed, carbide-tipped rotary cutter incorporated in a chamber purged with argon and connected at the bottom to a demountable Vycor bulb containing a weighed amount of mercury. This experimental device is fully described in a separate paper.1 Alloy compositions were calculated by weighing the empty bulb, the bulb containing the mercury, and the bulb containing the mercury and the thorium chips. Many alloys were analyzed chemically for thorium and/or mercury after subsequent homogenization; the agreement between analyzed and calculated compositions was invariably very close. Bulbs containing the requisite amounts of mercury and fine thorium chips were clamped off, removed to a sealing unit, evacuated and sealed. Amalgamation under these conditions proceeded rapidly even at room temperature. To insure homogeneity, the specimens were annealed to 300-400°C. Alloys containing less than 30 pct Th remained pasty after all treatments, indicating an equilibrium condition of liquid plus solid. Alloys with more than 30 pct Th were transformed into a dark powdery product. These latter specimens were annealed for times of up to 1 week to complete interdiffusion. Many of the alloy compositions are pyrophoric. On exposure to air they oxidize with considerable evolution of heat to a mixture of ThO2 and free mercury. It was mandatory that alloy specimens be handled in a "dry box" purged thoroughly with argon. All X-ray diffraction specimens were powdered, screened, and sealed in capillary tubes within the dry box. Experimental Procedures Thermal analysis experiments, useful only in the mercury-rich region of the system, were conducted with the alloys in their original containers. A reentrant thermocouple well formed an integral part of the bulb. These bulbs were heated in a silicone oil bath and cooled in a dry ice-acetone mixture. The rates of heating and cooling were slowed by immersing the specimen bulb in a larger tube containing silicone oil. This provided a suitable thermal lag. In all tests, pure mercury was run as a basic standard. While the invariant reaction at about the melting point of mercury was detected by thermal analysis, the heat effect at the liquidus was not sufficient to produce an inflection in the cooling curve. It was necessary to determine the liquidus temperatures at the mercury-rich end of the system by "breaks" in electrical reslstivity versus temperature curves for individual alloys. The apparatus for this purpose consisted of a pyrex tube about 2 in. diam and 12 in

Jan 1, 1959

By J. A. Rowland, C. W. Funk

THIS investigation is a part of the United States Bureau of Mines work in conserving the Nation's resources. The isothermal sections presented were developed as a guide to a comprehensive investigation of the properties and fabricating characteristics of copper-base alloys containing manganese and tin. These alloys are being investigated as possible replacements for the commercial bronzes containing substantial quantities of tin. Development of the isothermal sections has, therefore, been limited to the area between 0 to 20 pct Mn and 0 to 25 pct Sn. Since Heusler1 reported the ferromagnetic properties of the Cu-Mn-Sn alloys in 1903, the system has been the subject of several investigations. These studies were largely concerned with correlation of magnetic properties and crystal structure.2-6 Vero,' however, established the solidus surface of the system, between 20 pct Mn and 40 pct Sn, by thermal and microscopic methods. The a, ß, and y solid solutions were also observed by Vero and reported to extend into the interior of the ternary system. For the present study, the annotated diagram of the Cu-Sn system prepared by Raynor' and the Cu-Mn diagram by Dean and coworkers9 were used as the binary borders of the ternary system. Procedure The metals used in this investigation were electrolytic manganese, washed cathode copper, and three-star tin. The manganese, produced at the Boulder City pilot plant of the Bureau of Mines, had a purity of 99.9 pct; the copper contained less than 0.004 pct Bi and 0.001 pct S; the tin contained 0.070 pct Pb, 0.070 pct Sb, 0.050 pct Fe, and 0.065 pct Si. Heats of 1 lb were melted in alundum crucibles with a 3-kw induction furnace. The heats were chill-cast in iron or copper molds to form 6-in. ingots 3/4 in. in diameter. Molds were washed with graphite or zirconia, depending on the manganese content, and preheated to 150°C. The maximum impurity content of any alloy was 0.03 pct Fe, 0.02 pct Si, and 0.02 pct Al; in most cases, they contained less than half this quantity of any of these impurities. Composition of the alloys and their treatment prior to homogenizing are shown in Fig. 1. Designations adjacent to each composition refer to the heat numbers. With a few exceptions, ingots containing 20 pct Sn or less were hot-swaged. These ingots were swaged, after a 24-hr preheat at 650°C, to obtain a total reduction of 70 pct in cross section. Intermittent reheating was necessary, and reductions were limited to either 0.025 or 0.050 in. in diameter per pass. Selection of a 200-hr homogenizing treatment was based on extensive experiments which indicated that virtual equilibrium was reached after 150 hr. Structures were retained by quenching in water. Grain sizes in the specimens homogenized at 350" and 450°C were generally small. These homogenizing treatments were preceded by a 50-hr anneal at 650°C to facilitate phase identification by increasing the grain size in these specimens. The specimens were furnace-cooled from this temperature to the homogenizing temperature, and the heat treatment was continued for the standard 200-hr period. The homogenized samples were bisected to provide an internal section for metallographic examination. Optimum definition of the microstructure was obtained by successive polishing and etching. Quarter-strength ASTM copper reagent No. 13 gave the most satisfactory results.10 Filings from interior sections of the samples were used for diffraction studies. These filings were annealed in evacuated glass tubes at homogenizing temperatures for periods exceeding 50 hr and quenched in water. During this treatment the manganese content was reduced by significant amounts, probably by vaporization. This change in composition was considered in applying the diffraction data, which were used only as a means of identifying phases where the data were consistent with the metallographic evidence. Phase Identification The a solid solution is readily distinguished by the copper-colored, twinned, polyhedral grains, as shown in Fig. 2, and a face-centered cubic X-ray pattern. Tukon indentations, using a 25-g load, indicate a Knoop hardness of 155 for a quenched from 650°C. Using white light developed by a Wratten 78 A filter, the ß grains in etched specimens have a dark brown tint in contrast to the lighter copper-colored grains of the a phase. Knoop hardness values of 284 were obtained for the ß structure in specimens quenched from 650°C. The ß structure was also distinguished from the a phase by its body-centered cubic lattice. The acicular structure appearing in Fig. 3 was evident in several alloys of higher tin content after quenching from either 750' or 650°C. Since a trans-

Jan 1, 1954

By W. D. Mcmillan

Kaolin, or china clay, is the term applied to a group of hydrous aluminum silicates. Because of its purity, light color, and refractory properties, kaolin is used extensively in the manufacture of high-grade ceramic wares and as a filler by the rubber and paper industries. Although there are numerous pottery and enamelware plants in Texas, and large rubber and paper industries; all of the kaolin used in these plants is from other States, There are two known occurrences of kaolin in Texas, namely, the Leakey deposit in Real County and the several deposits of the Medley district in southern Jeff Davis County. An investigation of the Mueller kaolin deposit in the Medley district was undertaken by the Bureau of Mines. Following an examination of this deposit by W. D. McMillan, engineer in charge of the Texas field office of the Bureau of Mines, a proposal was made to investigate the deposit by diamond core drilling.

Jan 1, 1949

By M. Feinendegen, Ph. Siebert, C. Clauser, K. Willbrand, M. Ziegler

"Three institutes of RWTH Aachen University collaborate on laboratory tests and numerical simulations of hydraulically driven fractures in igneous rocks. The project´s target is to enhance the understanding of hydraulic induced fractures for deep geothermal energy exploration. Based on the idea of creating new discrete fractures in hot dry rock (HDR) reservoirs, the current project stage deals with this process on a laboratory scale. Especially for this purpose, a new testing facility has been developed and laboratory tests are performed to verify a hydraulic fracture propagation code based on the extended finite element method (XFEM). The testing facility enables us to initiate and propagate fractures in large samples of dense rock under triaxial confining pressures and to monitor the fracture propagation by extensive measurements. This contribution gives a short introduction to the project‘s background and mainly focusses on the test facility, the experimental procedure and exemplary results.INTRODUCTIONThe most efficient technique to increase the permeability of subsurface rock is to initiate and open fractures by applying hydraulic pressure from a packed borehole-section and to inject fluid into these fractures to propagate them. Since its first use in petro industries to enhance the production of wells in natural gas and oil reservoirs, the interest in targeted creation of hydraulic fractures has increased exponentially. As the key technology to the extraction of unconventional gas from shale, hydraulic fracturing (HF) became a major topic in a heated public debate. Based on the fact that a fracture tends to propagate in a direction perpendicular to the minimal principal stress, hydraulic fracturing has become an established tool for estimating geological stress states in almost any depth. Enhanced geothermal systems (EGS) in HDR reservoirs use engineered fractures as a heat exchanging system for a cycling fluid driving a power plant."

Jan 1, 2015