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By H. L. Eiselstein, F. P. Huston, B. B. Betty

An extensive program for the establishment of creep data on high-nickel alloys has been in progress during the past seven years. This paper presents the accumulated data on two solid solution alloys, cold-drawn, annealed Monel and cold-drawn, annealed Inconel. Data on these two alloys in other conditions will be published at a later date. Monel, a nickel-copper alloy, is normally considered a corrosion-resistant material, but it will be shown that it also has considerable creep strength, validating its use at temperatures up to and including 900°F. Inconel, a nickel-chromium-iron alloy, is definitely a heat-resisting alloy possessing good creep strength and oxidation resistance up to iiooOF., and because of its oxidization resistance has been used successfully at much higher temperatures for lightly stressed parts. The literature contains but meager data on the creep properties of high-nickel alloys. Howevcr, Bennett and McAdam have presented a substantial quantity of creep data for cold-drawn Monel.1 The material as tested was not representative of mill production for it was cold-drawn to a reduction of area of 40 per cent as against 13 per cent, which is the mill standard for Monel. Twenty-two individual tests were run on each alloy in the investigation described in the following pages. The data and curves presented herein represent an integration of all the tests to obtain the most accurate picture of the creep properties of these alloys. Neither of the two alloys was found to be embrittled by the combination of temperature and stress, as evaluated by room-temperature tensile and impact tests that were made following creep testing. These data indicate that no tendency toward embrittlement exists. It is recommended that 6300 lb. per sq. in. be used as a working stress for cold-drawn, annealed Monel at 900°F. and 13,200 lb. per sq. in. for cold-drawn, annealed Inconel at the same temperature. Table 8 lists recommended working stresses, based on 80 per cent of the stress to produce a minimum creep rate of 0.01 per cent per 1000 hr., for Monel and some steels. Equipment The equipment used for these tests consists of Colville creep-testing machines manufactured by the Tinius Olsen Testing Machine Co. The load is adjusted, depending on the stress level, to give an error in the stress of not more than ± 0.1 per cent. This is based on considerations of lever sensitivity and the stress used for the standard (A.S.T.M. Tentative Standard E22-38T) 0.505-in. diameter creep specimen having a 2-in. gauge length. The single-specimen furnaces are provided with primary and secondary windings, from

Jan 1, 1945

By K. K. Clark

Excessive injection pressures in water injection wells may create deeply penetrating fractures, or may open up existing reservoir fractures. If these fractures are oriented toward offset producing wells, oil recovery at injected water breakthrough and ultimate recovery will be impaired. A method of calculating fracture lengths from pressure fall-off test data is presented. The method is based on a linear flow model that simulates conditions present during the early-time period after shutting in an injection well. Fracture lengths can be calculated directly if formation permeability is known. A graphical technique is presented that provides fracture lengths based on permeabilities calculated from normal fall-off tests, where those permeabilities are adjusted for flow geometry. Test data from four injection wells and results obtained from applying the method to these wells are discussed. Introduction Rates of water injection into nonstimulated wells in low permeability reservoirs frequently fall below economically desirable levels. Therefore, some form of stimulation such as hydraulic fracturing often is performed on these wells. Usually these fractures penetrate a short distance from the well — short as compared with interwell spacing — and therefore should not create problems of water channeling to offset producing wells. In the past, some operators have been tempted to increase injection pressures continually to maintain a specified injection rate. But pressures cannot be increased indefinitely. Field data indicate that continued injection above fracture opening pressure can cause excessively long fractures to approach between well distances. If these long fractures intersect or closely approach offset producing wells, premature water breakthrough can result. It is difficult to seal effectively these fractures by various workover procedures after premature water breakthrough has occurred. This paper describes testing procedures that are potentially capable of detecting premature water breakthrough before it occurs. Knowledge of fracture lengths and fracture opening pressures can assist field engineers in selecting optimum operating conditions for water injection wells. Fracture lengths should be calculated from pressure fall-off tests on injection wells, and maximum permissible iniection pressures should be determined from step-rate injectivity tests. Equipped with this information, the field engineer is in a better position to recommend for a particular injection well the optimum operating conditions that will lessen the chances of channeling to offset producers. Historically, pressure transient tests have been conducted primarily on producing wells and analysis procedures have been based on radial flow concepts. Several authors have suggested that these same procedures be applied to tests conducted on water injection wells. This application is justified for wells that are not connected to extensive fracture systems. However, if the formation is severely fractured, the interpretation methods must be modified. Several authors have presented the pressure response of various systems that are intended to simulate reservoir conditions. A paper by Russell and Truitt* on vertically fractured svstems is probablv the most useful from the standpoint bf the fieid engineer. Russell and Truitt presented the pressure-vs-time behavior of a well connected to vertical fractures with various fixed lengths. Their permeability adjustment technique is used in this paper to refine methods of calculating fracture length and interwell permeability. Theory and Definitions Three flow-system geometries are considered in analyzing injection well test data. These various geometries are applicable during specific time intervals of transient pressure tests. Schematic drawings of the flow models, and the time intervals over which they are applicable, are shown in Fig. 1 in the chronological order that they are applied to the pressure response of water injection wells in fractured formations. The very early response is simulated by an infinite linear system as shown in Fig. 1A. This representation permits the calculation of matrix surface area exposed to the fracture. The model shown in Fig. 1B is identical with the one studied by Russell and Truitt. They evaluated the transient pressure response of this vertically fractured system by finite difference techniques. The results were presented as tabulations of dimensionless pressure drop functions for a range of fracture lengths. A semilog plot of these data shows that the apparent matrix permeability can be related to the true matrix permeability by a simple exponential function. Their adjustment factor is used in this paper to improve the accuracy of matrix-permeability and fracture-length calculations.

Jan 1, 1969

By K. W. Smith, E. A. Thomas

Various grades of synthetic mullite have been developed in recent years to replace or supplement natural sources of mullite deriued from the mullite group of minerals consisting of sillimanite, kyanite, and andalusite. Raw materials and heat treating processes used in making synthetic mullite are described. Chemical and physical data are given for typical grades and crystalline structure is illustrated with micrographs. Use of synthetic mullite as a refractory material in the glass and metallurgical industries is discussed. Mullite (3A12O3.2siO2), the only stable compound formed in the alumina-silica system, is usually present to some degree in all aluminum silicate ceramic products. The formation of mullite is considered beneficial to give rigidity to the structure and is dependent upon the ratio of Al2O3 to SiO2 in the original composition, particle size, degree of mixing, firing temperature, cooling rate, and the presence of auxiliary glass-forming fluxes. Mullite may also be formed at the reaction interface of fire clay or alumina-type refractories in contact with glass or slag melts. The term synthetic mullite is commonly used today to identify a class of sintered and fused aggregates or grains in the alumina-silica system having a highly developed mullite structure but derived mainly from raw materials other than the sillimanite group of minerals. Within the past 15 years extensive research has been done to develop economical processes to form sintered synthetic mullite aggregate to replace calcined Indian kyanite in super-refractories. Severa1 brands of such mullite are now being produced in commerical quantity and finding extensive use in refractories. Based on the service results of such refractories in many applications throughout the metallurgical, ceramic, and glass industry these developments have been considered successful and suitable substitutes for Indian kyanite now appear assured. EARLY DEVELOPMENT The conversion of kyanite, sillimanite and anda-lusite minerals of the sillimanite group to mullite and their use in refractories and porcelain have been discussed quite extensively in the literature by peck,' Grieg,' Riddle and Foster,3 Bowen and Grieg,4 and others and will only be mentioned here for reference to compare properties with synthetic mullite. In 1928, curtis5 reported on the development of a high temperature gas-converter process for forming synthetic mullite. The raw materials were derived mainly from lumps of high alumina clay of the correct natural composition or blends of clays and alumina that was interground and briquetted to form a suitable charge to maintain a surface combustion firing within the converter. Curtis was, no doubt, the first to illustrate by micrographs in natural color the crystalline structure of mullite derived from kyanite and mullite derived by sintering clay and alumina mixtures at temperatures above cone 32 (3123°F) and by electric fusion. In 1937, sei16 was issued a patent covering the use of a mixture of alumina-silica minerals and alumina in the proportion to form a mullite-yielding material at temperatures in excess of 3100' F. During the period from 1930 to 1940, economic conditions were not favorable for the production of synthetic mullite mainly due to an adequate supply of good grades of Indian kyanite ore suitable for conversion to mullite. Uncertain conditions on availability of the Indian kyanite during the early stages of World War II fostered further study on the development of synthetic substitutes. In 1943, McVay and wilson7 reported on an extensive investigation of domestic substitute materials. Their work covered essentially the use of mixtures of electric furnace mullite, calcined topaz, and calcined domestic kyanite. Compositions were found that gave equivalent or better hot load strength than Indian kyanite in mullite-type brick compositions; however, the calcining of the topaz presented certain physical and chemical problems on the disposition of silicofluoride and hydrofluoric acid while the high cost of electric furnace mullite was a limiting factor. In this work it was pointed out that water-quenched fused mullite was found to be unstable on reheat and gave poor hot load strength due to excessive glass present whereas the slow cooled or annealed mullite contained large crystals of mullite and corundum with little glass and gave superior results.

Jan 1, 1961

By J. C. Bradbury

The year of the Centennial is upon us. Not only is AIME marking its 100th birthday, but the cement industry is also celebrating 100 years of activity (see article by Roy Grancher, page 48). Fort Dodge, Iowa, and gypsum also tried to get into the act but missed by one year. Frank Apple-yard's gypsum article (page 53) informs us that the Fort Dodge area has been producing gypsum continuously for 99 years. That would seem to make AIME and the industrial minerals doddering oldsters. Not so-our Institute shows more energy than ever, and the word for industrial minerals is growth. These are the mineral resources of the future, the raw materials for the abundant life to come

Jan 1, 1971

By Harry M. Mikami

Chromite is the only ore mineral of metallic chromium and chromium compounds and chemicals. Because of this fact, chromite and chrome ore are used synonymously in trade literature. In commercial market quotations, chrome ore is the term commonly used. Chromite per se, because of properties imparted by its chromium content, is used in refractories and in special purpose molding sands for metal casting. There are many other minerals containing some, generally minor, amounts of chromium, but none are commercial sources of the element (Thayer, 1956). Chromium and chromite have many diverse uses that, directly and indirectly, critically affect vast segments of our modern industrial system. Most important are probably the metallurgical applications wherein chromium is a component of heat-, abrasion-, corrosion-and oxidation-resistant and high-strength alloys of many types. Stainless steels are the largest volume category of chrome-bearing alloys. Chromium chemicals are used in leather tanning, in pigments, dyes and mordants, printing, chemical process industries, photography, pharmaceuticals, metal plating, pure chromium metal production, and for many other purposes. Chromite is a necessary constituent in basic refractories indispensable for the production of steel, copper, cement, and glass. Under present conditions, the US and North America, with the possible exception of Cuba, have no commercial ore reserves. There are chromite deposits, as will be described, but they would be used only under highly abnormal conditions if all outside sources were cut off for an extended period. All chromite used in the US is imported from the eastern hemisphere in which are contained the principal world reserves. The main suppliers in 1980 were the Republic of South Africa (43%), the USSR (21% ), the Philippines (12%), Albania (11 %), Turkey (8%), and others (5%). The strategic nature of chromite is obvious. End Uses-Grades and Specifications As noted before, the three principal uses for chromite are metallurgical, refractories, and chemical with a fourth minor use as foundry molding sand. For metallurgical applications chrome ore is first reduced in electric carbon arc furnaces to various types of ferrochromium alloys. There are high, medium, and low carbon ferrochromiums with carbon ranging from 0.01 up to 10%. Chromium itself ranges from 50 to 73 %. Ferrosilicon chromium and ferrochromium-silicon grades have chromium from 33 to 67% and silicon from 3 to about 48%. Since iron is reduced with chromium, the Cr:Fe ratio of the ore will determine the ultimate grade of the ferrochromium whereas carbon and silicon can be controlled during processing. MgO, A12O3, CaO, and excess SiO2, are removed in slag. A small amount of pure chromium metal is prepared by alumino-thermic and electrolytic processes from essentially iron-free chrome components that have been made via the chemical route. The higher grades of ferrochromium with chromium in the 66 to 73% range can only be made from ores with not only high chromium content, but low iron, i.e., high Cr:Fe ratio. These ores, conventionally termed metallurgical grade, have Cr2O3 contents of 45 to 56% with Cr: Fe ratios of 2.5 to 4.3. A standard composition is generally 48% Cr2O3 and 3:1 Cr:Fe ratio. Very high grade ores are often blended with lower grades even with the high iron chemical grade. For some ferrochromiums, additions of high alumina refractory grade are used as slag conditioners to facilitate smelting while still contributing chromium values. A lower grade ferrochromium, the high carbon charge chrome, has become the predominant grade in use today for making chromium-bearing steel alloys. This

Jan 1, 1983

By G. Sachs, E. P. Klier, W. Beck

HYDROGEN embrittlement of steels has recently attracted much attention because it is asso- ciated with a variety of failures, especially those of aircraft structural components.' For instance, one of the undesirable properties of the ultra-high strength steels used for landing gears is their pronounced susceptibility to hydrogen embrittlement during plating. The presence of hydrogen in these steels becomes particularly apparent through delayed or sustained load failures of parts which have been subjected to low loads for an extended time. A number of variables are involved in causing a reduction of strength and ductility through hydrogen

Jan 1, 1957

By T. J. Koppenaal, M. E. Fine

A yield point effect attributed to short-range ordevi?g (SRO) occurs in Cu base Al. At at 296°K varies with heat treatment, decreasing as the annealing ternperature is raised .from 433Oto 598°K. Davies aid Cahn' observed a corresponding decrease in SRO. (523 °K anneal, measured at 77°K) is approximateZy proportional to the variations of A7 with strain rate and testing temperature are also Consistent with the idea that is associated with SRO. A preliminary investigation of the tensile properties of a Cu-Al single crystals showed the presence of a rather strong yield-point effect (drop in flow stress after initial yielding). The object of this research was to investigate its origin and behavior. a Cu-Al alloys are particularly interesting because diffuse X-ray scattering measurements by Davies and Cahn,' Houska and Averbach,' and Borie established the presence of short-range order. The degree of local order may be changed with heat treatment.' cottrel14 suggested that the presence of local order might result in a yield-point effect, and thus the possibility exists here for experimentally ascertaining the importance of short-range order with respect to yield points in these alloys. Since a 12 pct difference exists between the atomic sizes, elastic or Cottrell locking5 must also be considered. Further, Howie and swanne have shown that the stacking fault energy of copper is reduced by aluminum additions. The width of extended dislocations should thereby increase. hus the conditions appear attractive for Suzuki locking.' Finally, the possibility of stress-induced order at dislocations, schoeck locking,' must also be examined, EXPERIMENTAL PROCEDURE Alloys up to 14 at. pct Al were prepared by induction melting high-purity (99.999 pct) Cu and (99.996 pct) Al in a graphite boat under a dynamic vacuum of 5 X 10o mm of Hg. After homogenizing the ingots at 900°C for at least 24 hr under vacuum, they were rolled with intermediate anneals to strips 1.55 mm thick. Single crystals 10 in. long were grown by lowering strips, contained in a split graphite mold sealed in fused quartz at 5 X lo-' mm of Hg, through a single coil induction heater at a constant rate of 1/2 in. per hr. Tensile specimens 1.25 in. long were cut from the single crystal strips and reduced cross sections about 0.7 in. long and 3.0 to 3.5 mm2 in area were introduced by filing and abrading.8 To remove the worked portion about 10 pct of the cross-sectional area was removed by etching. Back-reflection Laue photographs of a filed and etched specimen were taken before and after annealing at 900°c for 24 hr. Small, well defined Laue spots were obtained with no visual difference in the two photographs. Further, specimens with and without the reduced sections began yielding at about the same stress. Hence, for our purposes, filing and abrading did not affect the structure of the specimens. Each single crystal specimen was annealed at 900° c in vacuum for at least 24 hr and furnace cooled; while cooling through the range of 250o to 200°c, the rate was about 55°C per hr. Orientations were determined by the usual back-reflection Laue

Jan 1, 1962

By A. S. Yue, A. G. Guy

A study was made of the effects of a prolonged flux of zinc atoms through the a solid solution of zinc in copper. The experimental arrangement consisted essentially of a copper disk about 0.01 in. thick, at one of whose surfaces a gaseous atmosphere containing zinc atoms was maintained, and at the other surface a gaseous atmosphere with a minimum of zinc atoms was maintained. During prolonged theothersurfaceexposure at high temperatures the zinc content of the copper disk gradually built up to the steady-state concentration distribution and then remained at this value. The concentration-distribution curves for various conditions were determined by chemical analyses. The results showed that the condition of steady-state diffusion was achieved. The diffusion coefficients calculated from the experimental data, although not of high precision, agreed with the values obtained by other workers using unsteady-state methods. Relatively slight porosity developed in the specimens in the course of diffusion. A LTHOUGH most diffusion studies have been made under unsteady-state conditions, it is known' that the steady-state method is often superior with respect to the directness and accuracy of interpretation of the data. Steady-state diffusion of gases through metal diaphragms is well known. Also, Harris' and Smith" have used the steady-state method in studying the diffusion of carbon in aus-tenite. The accepted mechanism in this system involves the motion of the interstitial carbon atoms in the rigid framework of the lattice of iron atoms. Thus, there is little difficulty in visualizing the steady flow of the small carbon atoms through the austenite. The situation in substitutional diffusion is quite different. Here the atoms are comparable in size, and it is not evident how a steady flow of one of the atoms through the solid solution might be achieved. At the time the present research was started, it was known that a previous exploratory attempt to produce steady-state diffusion in a substitutional alloy, the Au-Ag system,' had been unsuccessful and had indicated that perhaps there were basic difficulties that could not be ovei-come. Therefore, the present research began as a study of the effect of a prolonged flux of metal atoms through a substitutional solid solution. Eventua.lly, it was possible to produce actual steady-state diffusion in the system chosen for study, the a Cu-Zn alloys. Experimental Procedure The aim in the experiments was to maintain a high zinc content, about 30 pet, at one surface of a copper sheet, and to maintain a low zinc content, near 0 pet, at the opposite surface. The zinc would then diffuse into and through the copper, first building up to the steady-state concentration distribution and then maintaining this distribution. The three types of specimens that were used are shown in Fig. 1. In type A specimens the copper disk through which diffusion occurred was welded to the top of a cylindrical molybdenum tube, the bottom of which also was sealed by welding. At the diffusion temperature the brass chips in the molybdenum container were the source of the zinc vapor which maintained the lower surface of the copper disk at 30 pet Zn. The upper surface was maintained at 0 pet Zn by the vacuum in which type A, and also type B, specimens were diffused. Since the molybdenum container was impervious to zinc vapor, it was intended that the only path of escape for the vapor from the brass chips would be through the thin copper diffusion disk. However, it was found that small leaks often developed at the welded joints during the diffusion treatment, and in most specimens some of the zinc was lost in this manner. Although even small losses of this kind were a serious handicap in attempting to determine the flux through the disk, they did not prevent the maintenance of satisfactory boundary conditions for the attainment of the steady-state condition. Type B specimens differed from type A in having a weight of about 300 g supported on the copper disk by 15 to 20 short quartz rods. This change was made when it was observed that the copper disk was being bowed upward by the difference in the pressures acting on its two surfaces. Since the grain-boundary cracking which occurred in the bowed specimens could be attributed largely to the accompanying creep,3 it was desirable to minimize this effect. The counterweight was effective in significantly decreasing both bowing of the disk and cracking at grain boundaries. Type C specimens differed considerably from the others in that the low-zinc atmosphere at one sur-

Jan 1, 1959

By H. F. Yancey, O. L. Furse

For several years the Bureau of Mines at its Northwest Experiment Station, in cooperation with the Mines Department. of the University of Washington, has been studying the breakage and degradation of coal. The first phase of the study was devoted to the determination of the friability of many coals of various ranks and comparison of various methods for estimating friability.' A study of the relative ease or difficulty with which various coals are reduced to the fine size required for use as pulverized fuel followed the completion of this work. Baltzer and Hudson2 list twelve research organizations in the United States, two in England, one in Germany and one in Canada that are reported to be engaged on this problem; showing the general appreciation of the need for a simple method of estimating the grindability of different coals. Hardgrove,3 ho has advanced a method for estimating grindability, points out that pulverizer tests of different coals are incomplete and unsatisfactory. He compares such tests to that of a boiler test made without knowledge of the calorific value of the coal. Frisch arid Holder4 also stress the same point. They state that,

Jan 1, 1934

By John H. Schemel

Large Zircaloy-2 hammer or press forged bars did not exhibit the uniform excellent corrosion resistance to steam normally expected of the alloy in wrought form. Weight gains of coupons cut from forged bars were 40 to 60 mg per sq dm compared to the 28 mg per sq dm obtained on hot rolled sheet and strip. The mechanism of this corrosion and its relation to microstructure is discussed. After these observations, a solution heat treatment followed by rapid cooling was tried on coupons from eight heats of forged bars. The basket-weave structure resulting from the quench did not show agglomeration of intermetallic compounds. These coupons showed uniformly good corrosion resistance with weight gains very close to the 28 mg per sq dm expected of Zircaloy-2 after the 14-day steam test. A large forging was solution heat-treated and tested for structure, mechanical properties, and corrosion resistance. Corrosion resistance was excellent and uniform throughout the section. The normally anisotropic mechanical properties were changed to completely iso-tropic. Strength levels were raised while there was a small loss in ductility at the service temperature. Tempering of the quenched structure below the ß transus did not improve the ductility at the test temperature of 600°F. ZIRCALOY-2 end caps for nuclear fuel elements Zircaloy-2 is an alloy of 1.5 pct Sn, 0.1 pct Fe, 0.1 pct Cr, and 0.05 pct Ni, balance hafnium-free zirconium patented by Westing-house Electric Co. used in pressurized water reactors are machined from large hammer-finished forged bars. The bars forged for this application range from 3 1/2 in. to 7 1/2 in. squares. One of the tests used to evaluate Zircaloy-2 for this service is a 14-day exposure to very high-purity steam at 75oF and 1500 psi pressure. Normally wrought products will exhibit a black lustrous film of zirconium oxide after the test and show a weight gain of approximately 28 mg per sq dm. Coupons representing the forged bars exhibited a wide variety of corrosion results ranging from acceptable black coupons to some covered with white crystals of zirconium oxide that had weight gains of nearly 100 mg per sq dm. One of the most common effects was a white corrosion product that looked like a stain to some observers and the outline of massive metal grains to others. Very careful specimen preparation prior to the corrosion test did not affect the result and metallographic examination did not reveal a structural feature of a size and shape that would correlate with the corrosion product. In addition to the relatively poor corrosion resistance, the forged product was not as ductile as desired. The problem of obtaining uniform and more acceptable properties in these heavy-forged sections seemed to be a function of the microstructure of the metal and, in particular, the distribution of the intermetallic compounds. None of the four alloying elements however are appreciably soluble in a zirconium and are present as compounds which usually appear scattered randomly throughout the structure. Moudryl showed that the distribution of these intermetallic compounds in Zircaloy could be related to a ostringero corrosion failure. Grozier et al. discussed another structural defect that causes a similar corrosion effect. In this case, an elongated gas-void was determined to be the cause. M. L. Picklesimer held in his discussion of the Grozier paper that at least a part of the observed =stringersn were caused by the distribution of the intermetallic compounds. He proposed a

Jan 1, 1962

By B. E. Grant

There are several exceptions from the practical operating viewpoint that might be taken with the paper. The author recommends using a "curve" in plotting safety factors of ropes and suggests that the U. S. Bureau of Mines change its present "step curve" method to the "curve" method. From an engineering theoretical point of view that is possible, but from a practical standpoint it is not possible. Rope manufacturers fabricate their ropes in diameter gradients of 1/16 in. to 1/4 in. which automatically sets up a step pattern gradient. If ropes were manufactured in the diameter gradients of 1/1000 of an inch or thereabouts, the curve method could be used. Also, from a practical standpoint, if an operator is to hoist from a depth of 4000 ft, for example, he will determine the size of the rope necessary for that depth, and it is only natural that he will have safety factor to spare at lesser depths, and in plotting this excess capacity the natural end result is a curve. The U. S. Bureau of Mines tables are set up so that the operator will know what size rope at the required safety factor he will need at his maximum depth. He is not concerned with lesser depths. W. A. Boyer (author's reply)-Mr. Grant states, "Rope manufacturers fabricate their ropes in diameter gradients of 1/16" to 1/4" which automatically sets up a step pattern gradient." There is no connection or relationship between the "size" pattern gradient and the present "factor of safety" step pattern gradient. The inherent factor of safety values for any particular size of rope with a given connected load when plotted for various depths is a curve, and with modern rope material and construction the inherent factor of safety curve is quite far removed from the present recommended factor of safety step curve. This is shown quite clearly in Figs. 3 and 4 of my paper.

Jan 11, 1954

By L. C. Weiner

For zinc single crystals, xo = 3o, a surface coating raises both the cleavage and yield strengths over a large temperature range. The "brittle temperature," associated with slip after completion of twinning, does not coincide with the point of intersection of the flow and cleavage curves, which is associated with twinning. A surface film has no effect on the brittle temperature, while it lowers the intersection temperature some 20°. For crystals, yn = 83o, a coating decreases the cleavage strength, making it temperature independent, as well as increases the brittle temperature or its equivalent, the intersection temperature, 20°. These observations are described on the basis of a dislocation-pile-up-at-a-barrier model for brittle fracture; in crystals x,, = 3o the number and distribution of twins play a vital role. IN a recent investigation on the effects of solid environments on the brittle fracture of zinc single crystals,' it was demonstrated that the presence of a surface film changes the cleavage strength of these crystals, either increasing or decreasing it, depending on the crystal orientation. An increase in cleavage strength of some 43 per cent was found for coated crystals oriented x, — 3o K = 28",* while a decrease of 48 per cent was observed with crystals X" = y» — 83". Moreover, these effects were found

Jan 1, 1959

By R. F. Hehemann, Darrell W. Smith

The kinetics of alloying- in W-5 rot pct Re powder compacts were investigated at temperature about the upper limit for the formation of the x phase, such that a single intermediate phase was involved in the process. The rates and directions of motion of the a-o and o-b interface were assessed as functions of tinze at the sintering teri7peraticve by quantitative izetallog-ralhic techtziques. The iiotion 01 these interjuces could be specified approxitnate1.y by u Parabolic )-ate law and deviations from this ,rate law were attribuled to a complex interaction between surface dif'fusion and volume diffusion during the initial stages of sintering. WHEN binary or more complex alloys are produced by sintering compacted blends of elemental powders, a complication is encountered which does not arise in the sintering of pure metals. In addition to concern for grain size and densification, the rate of inter diffusion of the component elements must be considered. The general problem of alloying during sintering has been treated by numerous investigators.'-7 These investigations have been concerned only with systems that form continuous series of solid solutions and a concentric-sphere diffusion model4 provides a useful description of homogenization in these stems.' Some controversy remains, however, over the contribution of surface and grain boundary diffusion to the homogenization process. Heckel% ePorts that homogenization can be described by volume diffusion at all temperatures, whereas other invetiators'' recognize the importance of surface and grain boundary diffusion, particularly at lower temperatures. Analysis of the homogenization process in partially miscible systems is complicated by the motion of the interfaces separating the individual phases. A simple analytical solution does not exist for such finite systems with spherical symmetry. It was the purpose of this work to examine the kinetics of the formation and dissolution of an intermediate phase in a binary system through an assessment of the motion of the interfaces separating this phase from the terminal solid solutions. PROCEDURE The W-Re system is an example of a partially miscible binary system and was selected for study because of its current importance in refractory-metal technology. The equilibrium phase diagram, Fig. 1, shows that the o phase will be formed by interdiffu-sion between tungsten and rhenium. At temperatures between approximately 2125" and 282O°C, the o phase will appear as the only intermediate phase in the diffusion system. In this work, a mixture of elemental powders containing 5 pct Re was employed. In such a mixture, the rhenium particles will be distributed randomly in a tungsten matrix. During sintering, a o-phase layer will form at the W-Re interface. The development and subsequent disappearance of the o phase are controlled by the relative rates and directions of motion of the 0-0 and a-p interfaces. The motion of these interfaces can be inferred from quantitative metallographic measurements of the average radii of the o shells surrounding rhenium particles. Elemental tungsten and rhenium powders of commercial purity were employed in these investigations. The rhenium powder was spheroidized from +200 mesh agglomerates by plasma-arc spraying and was then classified to yield a powder composed of essentially

Jan 1, 1967

By T. K. Perkins, L. R. Kern

A study of fluid mechanics, rupture of brittle materials and the theory of elastic deformation of rocks shows that, for a given formation, crack width is essentially controlled by fluid pressure drop in the fracture. Operating conditions which cause high pressure drop along the crack (such as high injection rate and viscous fluids) will result in relatively wide cracks. Conversely, operating conditions which cause low pressure drop (low injection rates and thin fluids) will result in relatively narrow cracks. Charts and equations have been derived which permit the estimation of fracture widths for a variety of flow conditions and for both horizontal and vertical fractures. INTRODUCTION There has been considerable speculation concerning the geometry of hydraulically created fractures in the earth's crust. One of the questions of practical importance is the width of fractures under dynamic conditions, i.e., while the fracture is being created and extended. Such width information could be used, for instance, to help estimate the area of a fracture generated under various conditions. Also, there has been a recent trend toward the use of large propping partiles.13, 15 Therefore is is desirable to know what factors can be varied in order to assure entry of the large particles into the fracture. There has been some work on fracture widths reported in the literature. In particular, there have been several Russian publications dealing with this sub-jeCt.1.31,3 These papers have dealt principally with the elastic theory and the application of this theory to hydraulic fractures. These studies have not led to an engineering method for estimating fracture widths under dynamic conditions. A recent paper3 has reviewed and summarized the Russian concepts. An earlier paper- from our laboratories also discussed the application of the elastic theory to hydraulic fractures. This first approach, based largely on photoelastic studies, has proved to be too simplified to accurately describe the fracturing process. However, these early thoughts have served as a guide during the development of more exact concepts. We would like to present in this paper our current concepts regarding fracture widths and some estimates of hydraulic fracture widths for several conditions. We believe that it is now possible to predict with fair accuracy the factors influencing fracture widths. Furthermore, the method of prediction has been reduced to a simple and convenient graphical or numerical calculation. CRACKS IN A BRITTLE, ELASTIC MATERIAL Many investigators2, 4, 30 have shown that competent rocks behave elastically over some range of stresses. Of course, if the tensile stress imposed upon a rock exceeds some limiting value, then the rock will fail in tension. In similar manner, there are some limiting shear stresses that can be imposed upon rocks. Hubbert and Willis11 have discussed the shear conditions which will lead to failure. Under moderate stress conditions (such as those likely to be encountered when hydraulically fracturing) and when stresses are rapidly applied, relatively, most rocks will fail in a brittle manner. Hence, for this discussion of hydraulic fractures in the earth's crust, we assume the rocks behave as brittle, elastic materials. Let us develop the discussion in the following way. (The following thoughts are applicable only to brittle materials.) 1. First we consider a brittle, elastic system. An energy balance will show the minimum pressure necessary to fracture rock, and from this pressure we calculate the minimum crack width resulting from extension of a hydraulic fracture. 2. Then we will show that, under ordinary fracturing conditions, fracture widths are appreciably greater than the minimum widths of extending fractures. In fact, we will find that crack width is controlled by fluid pressure drop in the fracture. 3. We will discuss pressure drops in fractures and resulting crack widths for various operating conditions and both vertical and horizontal fractures. 4. Finally, we will discuss the significance of these concepts, their relationship to fracturing pressures, etc. First, consider minimum fracture extension pressures. We can shed some light on this question by considering the theory proposed by Griffith7, 8 Yo explain the rupture of brittle, elastic materials. Griffith recognized that solid materials exhibit a surface energy8 (similar to surface tension in a liquid). The fundamental concept of the Griffith theory is that, when cracks spread without the application of external work (in the interior of an elastic medium which is stressed

By A. W. Sommer, H. H. Kellogg

It is shown that SO3-O2 mixtures react with sphalerite at an appreciable rate ill the temperature range of 361° to 527°C to fornz ZnSO4. The rate of reaction follows a parabolle lax. Oxygen, or O2-SO2 mixtures, have a negligible effect on sphalcrite in the same temperatuee range. PRACTICAL roasting of sphalerite is usually performed at 800°C or higher. The calcine is composed of zinc oxide unless the roaster atmosphere contains relatively large amounts of SO2 and the temperature is held to 800oC or lower, in which case zinc sul-fate may also form. Ong, Wadsworth, and assell' have made a careful kinetic study of sphalerite oxidation under these "normal conditions" and have concluded that the rate of the reaction is controlled by the decomposition of an activated complex adsorbed on the sphalerite surface. They found the rate of oxidation to be small at 700°C. Extrapolation of their data to 400°C would indicate an almost negligible rate at this temperature. In our work sphalerite was reacted with air, mixtures of SO2, O2, and N2, and mixtures of SO3, O2, and N2 in the temperature range 361o to 527OC. Negligible rates of oxidation were found, except for the gas mixtures containing SOs. With this latter gas, the oxidation of finely divided sphalerite was fairly rapid and zinc sulfate was the product. Based on the limited evidence available, the rate of sphalerite oxidation by SO3 is postulated to be controlled by gaseous diffusion through pores or cracks in the zinc-sulfate coating. This evidence for the direct reaction of sphalerite and SO, at low temperature may prove of importance to the understanding of zinc-sulfate formation in the dust-collecting equipment usually associated with zinc roasters. The roaster gas carries off fine dust, much of which may be unreacted sphalerite. The temperature in dust-collecting equipment drops from the roaster temperature (about 800°C) through the range of temperature we studied, to ambient temperature. Such dusts are known to contain far larger amounts of zinc sulfate than the primary calcine. It has been assumed in the past that this sulfate is formed by reaction of ZnO dust with SO3 (or SO, plus 0,) in the partly cooled gases. Our work shows that an alternative possibility exists—the direct reaction of SO3 with ZnS dust. EXPERIMENTAL Reaction rates for sphalerite at 350° to 600°C are relatively small so that it was necessary to use finely divided material with a relatively large surface area in order to obtain measureable amounts of reaction. In the preliminary experiments, pure mineral sphalerite, ground to pass a 325-mesh sieve, and chemically precipitated ZnS (in the form of an impalpable powder) were used. In the quantitative rate experiments the ground mineral sphalerite was processed in an Infrasizer to obtain a product with particle size between 9 and 18 µ. The analysis of this material was 66.7 pct Zn, 0.09 pct Fe, and 32.7 pct S (theoretical sphalerite is 67.1 pct Zn, 32.9 pct S). The sized powder was carefully mixed and divided into l-g samples. The apparatus used for the quantitative rate measurements is shown in Fig. 1. For the preliminary experiments the following change was made: The external catalyst furnace (B, C)* was not used. *Letters refer to Fig._______1 .___- Rather, when catalysis of the SO2 + O2 reaction was desired, the glass beads in basket M were replaced by vanadium-oxide pellets. Procedure—A l-g sample of ZnS was placed on a shallow stainless-steel tray, I, and spread evenly to a depth of about 1mm. The tray was placed in the reaction assembly and the assembly inserted in the cold furnace. The furnace tube was flushed with dry argon and then heated to the desired reaction temperature. The temperature was controlled to ±0.5oC. Gas mixtures (O2 + N2 or O2 + SO2) were prepared from tank gases by means of a mixing device identical to that employed by Darken and Gurry.2 The total flow rate of gas was 205 ml per min to point A of Fig. 1. The accuracy of the individual and

Jan 1, 1960

By James T. Gow, Oscar E. Harder, Anton de S. Brasunas

This paper deals with the results obtained and the techniques employed in determining: 1. Liquidus and solidus temperatures of the HH and HT type heat-resistant alloys. 2. The relation of true temperatures (thermocouple) to apparent temperatures (optical pyrometer) for the molten HH and HT type alloys. This work was the outgrowth of needing to know something definite about these temperatures in order to study the effect of pouring temperatures, shake-out times, and heat-treatments on the properties of some heat-resistant alloys. The information developed is thought to be of interest to industry for guidance in foundry practices and the industrial heat applications of the alloys. This paper is based upon work that has been done for the Alloy Casting Institute at Battellc Memorial Institute. Liquidus and Solidus Temperatures of HH and HT Type Alloys Experimenta1 Procedures Temperature-time curves were obtained during the cooling and solidification of several HH and HT type alloys. The metal was melted in an Ajax high-frequency, induction furnace and poured into a core-sand mold for cooling. The temperature measurements were obtained by means of a platinum, platinum-rhodium thermocouple contained within a fused silica sheath, which was extended through the side wall of the dry core-sand mold to a point at about the center of the mold cavity, which was 3 in. in diameter by 5 in. deep. The cold junction of the thermocouple was kept in an ice bottle, and the temperature was recorded automatically on a direct-reading potentiometer recorder. Through a switching arrangement, the temperature recorded was checked occasionally with a portable Leeds and North-rup potentiometer indicator. Less than a 5°F. variation in the two instruments was always found. This is within the limit of accuracy of readings. The thermocouple used was checked for accuracy against a standard couple, both before use on this work and after completion of the work, by the instrument laboratory. Temperature-time Cooling Curves Fig. I is an enlarged reproduction of a part of one of the cooling curves over the temperature range of 2600' to 2200°F. for an alloy of the HT type with 0.45 per cent carbon, 16 per cent chromium, and 36 per cent nickel. This is a typically shaped cooling curve as obtained for the alloys. It will be noted that two temperatures "re shown on Fig. I for the liquidus temperature. It is thought likely that the higher temperature, A, at the point at

Jan 1, 1945

By T. Seldenrath

In the development of a fluid -operated hammer drill' for accelerated penetration of hard rock formations in oil wells, a research investigation was conducted to evaluate the percussion effects obtained with different design characteristics and to determine the possibilities of percussion in the low frequency range. Tests were conducted on granite blocks and comparable impact forces were measured with a load cell under selected test conditions. These full-scale laboratory tests provided an evaluation of the effectiveness of percussion which was further supported by actual downhole field performance. While much pertinent data have been presented by other investigators the method of evaluation described in this article resulted in good correlation between laboratory and field performance and may be applicable in other low frequency percussion developments. EXPERIMENTAL METHOD For these tests the bit was held stationary and the test block was rotated and forced upward against the bit by a hydraulically-lifted rotary table. "Weight on bit" was calculated from pressure readings on the fluid system of the lifting cylinders—corrected for tare and friction. Percussion was obtained with several tubular hammers of different weights up to 320 lb. These were lifted mechanically and allowed to drop by gravity from various heights onto a slidably-mounted bit sub or "floating anvil" for calibration of the load cell response with known kinetic energy of the hammers. During evaluation of percussion effects, the hammers were hydraulically operated to provide a range of percussion frequencies up to 1,020 blows per minute delivered to the anvil. To obtain comparable test readings, the load cell of the strain gauge type, was attached to the bottom of the anvil or bit sub in place of the bit. The load cell rested on a typical granite test block mounted on the drilling table. The latter was hydraulically supported as in the actual drilling operation. The effect of support resistance was the same for all tools when calibrating. Impact forces so determined werethusdirectly comparable with one another for the purposes of this investigation. When a roller bit was substituted for the load cell for actual drilling, the impact force would probably be reduced due to the resiliency of the bit body, legs. cones and teeth and the penetration of the teeth into the rock. However, since the bits and rock specimens were uniform in these tests, an evaluation of actual tool performance, in terms of parameters previously determined with the load cell at the selected standard conditions of calibration, proved satisfactory. Throughout these tests, 8¾-in. standard tricone, hard rock toothed roller bits and carbide-insert roller bits were used. Rotary speeds were 50 and 100 rpm; static weight on bit was applied up to 40,000 Ib, and percussion frequencies up to 1,020 blows per minute were available. During this investigation it was found that toothed bits on which the teeth had developed flat ends about 3/16 in. wide did not change appreciably for the duration of a test. Hence, all toothed bits used in this study were in this condition. Conventional reference curves obtained in these tests show that increasing weight on hit by 2:1 yielded an increased penetration rate of approximately 2.7:1, while an increase in rotary speed of 2:1 netted an increased penetration rate of roughly 1.7:l. Results are thus of the same order as those reported for hard rock drilling by other investigators." CALIBRATION Under the selected standard test conditions previously described, with the lifting table hydraulically supported, and the anvil interposed between hammer and load cell, the hammers were dropped from known heights. Thus, with the kinetic energy of the hammer known, the corresponding maximum impact force shown by the cell was determined. (It may be of passing interest to note here that special drop tests with the hammers showed that no appreciable reduction in impact force resulted from introduction of the anvil or hit sub.) From these calibrations, it was possible to determine the theoretical kinetic energy available in the hammer from the maximum impact force shown by the load cell while operat-

By Charles Austin

IN a recent paper the authors1 discussed the reactions to tempering of hypereutectoid steels quenched from 1000° C., as revealed by studies on changes in hardness, electrical resistivity, coercive force and metallo-graphic characteristics. The data, which related specifically to temper-ing temperatures of 550°, 650° and 710° C., for varying periods up to 125 hr., permitted the following important conclusions: 1. The rate of softening of the steels at the temperatures examined differed markedly although the steels were of "similar" general chemi-cal composition. 2. The temperature of maximum softening spread over a range from about 650° C. to the eutectoid inversion. 3. The divergence in behavior was ascribed, at least in part, to a profound difference in tendency to graphitization on annealing at sub-eutectoid temperatures. 4. The mode of spheroidization of the cementite, as revealed by metallographic studies, also varied considerably in the different steels. The purpose of the present investigation is to pursue further the study of the difference in behavior of the steels on tempering over a wider range of temperature. To this end the following features have received particular attention: 1. Comparison of temperatures of maximum softening of the various steels when the quenched samples were tempered for 5 hr. and for 75 hr. followed by furnace cooling and by quenching in water. 2. Determination of the effect of quenching temperature, prior to tempering, on the rate of softening. Quenching temperatures of 1000° and 850° C. were used in the investigations. 3. Examination of the microstructures obtained with the various heat-treatments employed.

Jan 1, 1938

By Edward A. Loria

Vanadium is one of the materials being considered for use in fast-breeder nuclear reactors. It is a good heat conductor and nearly transparent to radiation, properties regarded as ideal for nuclear fuel containers. The problem has been the metal lacks ductility needed for forming. In our program at Reno Laboratory the effects of the U.S. Bureau of Mines (previous affiliation) the effects of oxygen, nitrogen, and carbon have been reported21,22 nd most recently the effects of boron and boron with carbon.23 The continuing study by the Ames Laboratory of the effects of hydrogen, the most subtle and fugitive element in its relationship to structure and properties, is commendable. The solubility of oxygen, nitrogen, and hydrogen in vanadium (and other bcc metals as well) is related to material purity. With the available limit on metal purity and the interaction (clustering) of hydrogen with the other interstitial and substitutional elements present in their base metal, would the authors comment on the tolerance of hydrogen in relation to oxy- gen that will avoid intergranular fracture and above what content or how seriously harmful in oxygen at various carbon levels? Understanding the true effects of hydrogen (and other interstitial impurities) in vanadium depends on knowledge of the amount present under various conditions and its distribution between various possible positions. Significant amounts of hydrogen may be in "thermo-dynamic" solution, but not as individual atoms in interstitial positions. It may be in grain boundaries, in subgrain boundaries, in vacancies, or in dislocations. Some of the hydrogen may be paired or in complexes with impurities in substitutional solid solution in vanadium. This makes the analysis of the effect of hydrogen vastly more difficult. It should not be expected that hydrogen in grain boundaries will affect slip in the same manner as hydrogen in interstitial positions, nor will the complexes react to heat treatment the same way as hydrogen in dislocations. It is gratifying that the authors have quoted results from two of our inestiations,' but neglected one2' which applied the Petch theory to electrorefined vanadium of high purity and analyzed the effects of oxygen, nitrogen, and carbon on the ai and ky values obtained by the extrapolation and grain size methods. Details can be found in the paper. Briefly, we obtained a ui value of 10,300 psi (t = 5150 psi) at 273°K. The metal also exhibited profuse twinning with high ductility at 123" and 77°K. Nitrogen was more effective than oxygen in increasing ui, the increase being about twice as much for the same impurity level. Carbon additions resulted in only minimal changes in Ui. The corresponding ky increased as oxygen and nitrogen increased, with nitrogen being more effective. Carbon additions resulted in little change. Although the difference in yield strength of vanadium was explained on the basis of the Cottrell-Bilby model of the tearing away of dislocations from the impurity atoms,

Jan 1, 1970

By William Rawles

THIS report is the first of a series planned by The Mineral Inquiry, organized by the American Institute of Mining and Metallurgical Engineers to make factual studies of the world's mineral resources in their political and international relations. The efforts of The Inquiry are directed toward filling certain notable gaps in available information, without duplication of many other investigations touching this field which are being conducted by other organizations, public and private. Much of its work is indirect-suggesting topics for study by other individuals and organizations and aiding in their planning and correlation. The present report is designed to show the nationality of the commercial control of mineral resources, in addition to the geographic distribution of production by nation-in other words, the overlapping of political and commercial control. Detailed accuracy cannot be claimed for the figures presented. For some companies division of ownership by nationality has been very difficult to ascertain, as many companies are reluctant to dis-close the extent of their holdings in other corporations, and the impossi-bility of tracing all stock ownership is obvious. Also there are frequent changes in the distribution of. stock control. The percentages given rep-resent only the participation that has been identified definitely, even though it is known in some cases with fair certainty that larger interests exist, as, for instance, American participation in foreign chromite companies. In bringing together these figures we have had the cordial co-operation of the United States Bureau of Mines, the United States Geologi-cal Survey, the Mineral Division of the Bureau of Foreign and Domestic Commerce, the Brookings Institution, and of many specialists connected with the mineral industries covered. The report does not cover the entire list of minerals. Coal, although it is one of the most important minerals, was omitted because , not more than one or two per cent of the world's production comes from mines that are owned by companies foreign to the countries where the coal is produced. Others, such as gold, are omitted because sufficient data have not yet been accumulated. It is hoped that some of these may be covered in subsequent reports. It is not our purpose here to discuss the significance of the figures sub-mitted, but only to point out the general nature of the problems on which they have a bearing.

Jan 1, 1933