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By R. Fawley, M. A. Quader, R. A. Dodd

Stacking fault energies and annealing twin frequencies have been measured for austenitic stainless steels having a) constant 20 wt pct Cr and varying nickel contents, and b) constant 20 wt pct Ni and varying chromium contents. The effect of nitrogen has also been studied and, to a lesser extent, so has the effect of carbon. All measured stacking fault energies plot linearly against the corresponding annealing twin frequencies, suggesting that, for constant prior deformation and grain size, twinning frequency can be used to estimate stacking fault energy. Compositions low in nickel possess the lowest fault energy, while the maximum fault energy within the investigated composition range occurs mound 20 pct Cr-20 pct Ni. Nitrogen has practically no effect on stacking fault energy when increased from 0.005 to 0.05 wt pct, although Planar dislocation glide is associated with higher nitrogen contents; this may be a short-range order effect. Carbon may raise the stacking fault energy a little, and causes pronounced dislocation tangling in deformed alloys. The basically different dislocation structures promoted by nitrogen and carbon, respectively, are not associated with large variations in stacking fault energy, and the reason for the difference remains unknown. INTEREST in the dislocation configurations developed in plastically deformed alloys arises principally from a desire for an understanding of mechanisms of plastic deformation and fracture. Comparatively little basic work has been concerned with austenitic stainless steels, although considerable interest has developed in the fundamental aspects of deformation of these alloys since the suggestion that those compositions deforming essentially by planar glide are particularly prone to transgranular stress corrosion cracking.' Certain facts are well-established. An 18 Cr-8 Ni steel (type 304) has a low stacking fault energy which is increased by higher nickel contents, and the structure of these steels when moderately plastically deformed changes concomitantly from planar to less planar to distinctly tangled dislocation configurations. These changes are thought to relate to changes in stacking fault energy, and considerable effort has been expended in measuring stacking fault energies of austenitic stainless steels through the determination of node curvatures2"4 even though the method has limitations due to formula approximations,5 an upper limit of measurement of 50 erg cm-2 at the most,5 and the necessity of an extremely meticulous experimental technique. Therefore, it is not surprising that only qualitative agreement between different investigators is generally to be found.'-' At high energies where node radius measurements are inappropriate, some use has been made of annealing twin frequencies to estimate relative stacking fault energies, although a recent critical evaluation of the method suggests that it should be used cautionsly with due regard to effects of grain size and prior deformation.6 Finally, there is a question as to whether the structures of some deformed steels are due to ordering effects. In particular, the role of nitrogen in promoting planar dislocation motion has been suggested to be due to ordering,' but similar suggestions have been made for steels having low interstitial contents.4 EXPERIMENTAL Small ingots of austenitic stainless steels (-50 g) were prepared from components exceeding 99.99 pct purity, the nickel and chromium being Johnson Matthey "Specpure" metals. Carbon was added as pure graphite, and nitrogen as CrN. The components were accurately weighed, and it was assumed that the final composition was the same as the nominal composition

Jan 1, 1969

By Winston A. Wong, John J. Jonas

Commercial purity aluminum was deformed by extrusion over the temperature range 320° to 616°C and the strain rate range 0.1 to 10 per sec. Flow stresses and strain rates were calculated from the experimenLa1 ram pressures and speeds. The stress-strain rate-lemperature relationship in extrusion was found to be similar to that in creep. Extrusion, torsion, compression, and creep data extending over ten orders of magnitude of strain rate and over two orders of magnitude of stress were correlated by a single creep equation. It was concluded that hot-working is a thermally activated process, in which the rate-controlling mechanism is either the climb of edge dislocations or [he motion of jogged screw dislocations. The microstructural changes observed during extrusion were consistent with the proposed deformation mechanisms. ALTHOUGH great progress has been made in understanding the technology of extrusion, very little is known about the actual deformation mechanisms operating during flow. Previous accounts describing extrusion have indicated that the relationship between ram speed (V), pressure (P), and temperature (T) can be given as follows:1 V = apb and P = A' exp(-AT). In these equations, a and b are constants which depend on temperature, A' is a constant which depends on ram speed, and A is a "coefficient" with a different value for each metal. Although these equations have fairly wide application, they do not contribute much to a fundamental understanding of the deformation. Furthermore, extrusion has not hitherto been considered as a thermally activated rate process. This lacuna is surprising because hot-working is similar to high-temperature creep in several respects. There is, in fact, a fair body of experimental evidence suggesting that the material response under hot-working conditions is similar to that occurring under creep conditions, in spite of the many orders of magnitude difference in strain rate.2"4 Since creep has been extensively analyzed in terms of dislocation mechanisms, the comparison of hot-working to creep is useful, for it can suggest the possible deformation mechanisms operating during hot-working. In this paper, the hot extrusion of aluminum will be examined from the point of view of thermally activated deformation mechanisms, such as operate during creep. EXPERIMENTAL PROCEDURE The experimental procedure consisted of extruding commercial purity aluminum* over a range of ram velocities and temperatures at constant die reduction by the direct method. Details of the experimental equipment have been published elsewhere.5 Extrusion was carried out at each of the following billet temperatures: 320°, 376°, 445°, 490°, 555°, and 616°C at the following constant ram speeds: 0.002, 0.008, 0.02, 0.1, and 0.2 in. per sec.* All results were obtained using a square-shouldered die with an extrusion ratio of 40:1, giving a reduction in area of 97.5 pct. The ram force was the dependent variable, and was measured by means of strain gages on the ram and was plotted as a function of ram travel. The sequence of events before making an extrusion was duplicated before each run so as to minimize as much as possible variations in experimental conditions. For example, after the equipment had been assembled, the billet was allowed to heat up to temperature inside the insulated container. Once the container attained the desired temperature, a period of 1/2 hr was allowed to elapse before the extrusion was made. This time was found to be required to allow the billet to reach a steady-state temperature, as determined from previous tests. When all was ready, extrusion was carried out without interruption; that is, the billet was upset and extruded in one operation. EXPERIMENTAL RESULTS AND DISCUSSION The two usual experimental approaches for investigating high-temperature deformation exhibit an important common feature. In the first approach, which corresponds to creep, a constant stress (or load) is applied to the material at constant temperature and the resultant strain is recorded against time. After an initial transient stage, a state of constant strain rate exists (secondary creep), in which a steady-state condition is established which is sensitive to variation in either applied stress or temperature. In the second approach, a constant strain rate is applied and the resultant flow stress is recorded. This corresponds to the situation in hot torsion or hot compression, where it is observed that, for a constant test temperature, there is an initial rise in stress to a steady value which is maintained up to very high strains. In tests of this type, a steady-state region is also established in which the stress is sensitive to variation in either the strain rate or the temperature.3,4,6-16 In both types of tests, therefore, a steady-state region is established after an initial transient. In the case of hot-working this region may be called steady-state hot-working, and it is analogous to steady-state creep with which it has many common features. Stress Dependence of the strain Rate in Extrusion. In order to assess the stress dependence of the strain rate under extrusion conditions, and to compare it to that of creep, as well as of hot torsion and hot compression, the extrusion data were analyzed according to power, exponential and hyperbolic sine creep equations.

Jan 1, 1969

By A. E. Chute

The shortage of sulfur is not only continuing but appears to be worsening, attended by steadily rising prices. At the same time emphasis on air-pollution abatement is also increasing. These two factors, a rising market and the growth of environmental attention, have encouraged producers to carefully review all possible sulfur sources. As a result, production of sulfur from hydrogen sulfide occurring in petroleum is receiving greater attention than ever before. Until about a decade ago, the practice of recovering sulfur from hydrogen sulfide separated from gases (either found naturally or generated in desulfurization of liquid petroleum) was wide1y recognized but contributed little to total free-world sulfur production. However, during the past ten years, the production of sulfur from this source has increased so rapidly that it now accounts for a substantial portion of total production. This trend shows no signs of slackening, and current forecasts predict that recovered sulfur may become the dominant source of supply within ten years, exceeding mined sulfur production. This paper is intended to list sulfur sources and relationships, and to discuss the potential of producing sulfur from petroleum. The processing involved, in addition to product storage and transportation will also be discussed along with important economic aspects of sulfur recovered from hydrogen sulfide. For many years, most of the world's elemental sulfur has been produced from salt domes, predominantly by the Frasch process. During the past decade, however, another production source has developed so quickly that it is expected to surpass the Frasch production sources within a short time. This new source lies in the petroleum gases and liquids from which dramatically increasing quantities of elemental sulfur are being recovered. In the phraseology of the trade, the sulfur so obtained is know as "recovered sulfur," a term which does not, as one might expect, include sulfur recovered from other sources such as smelter gases. The growth rate of recovered sulfur compared to that of Frasch sulfur, total elemental sulfur, and total Free World sulfur in all forms is shown in Fig. 1 Since 1963, sulfur consumption has exceeded production,with the natural result that the price of sulfurhas continually increased. The posted price reported for f.o.b. Port Sulphur, La., has risen from as low as $18 per ton in 1962 to $32.50 per ton in mid-1967. With freight and other charges, delivered prices have of course run much higher, amounting to $45 or $46 per ton on the east and west coasts. In some cases, spot sales for as much as $60 have been reported. Although it is playing an ever-increasing role in the sulfur market, recovered sulfur was originally a by-product of the removal of hydrogen sulfide from natural and petroleum refinery gases. Today, however, it is often the most valuable product of a multi-product processing facility. Since there are two major sources of recovered sulfur—production and refining processes —natural gas is included with liquid petroleum for purposes of this discussion. Sulfur from these sources is produced in the form of gaseous hydrogen sulfide which is removed from a gas stream and converted to elemental sulfur. Gases in which hydrogen sulfide occurs naturally are natural gas and the gas produced from a high=pres-sure crude=oil or condensate field.

Jan 1, 1969

By E. J. Nielsen, P. R. Strutt

A study has been made of the progressive changes in the distribution of etch-pit structures occurring during high-temperature creep in copper + 7 wt pct Al single crystals oriented with a [113] tensile axis. The two equally stressed glide systems with the highest Schmid factor would be expected to form subboundaries of the type predicted by Kear.2 The alignments of etch-pits on sections parallel to different (111} planes consistent with these types of boundaries were not observed. However, they were consistent with planar subboundaries (on a macroscopic scale). From an analysis of Amelinckx1 it may be shown that stable cross-grid dislocation boundaries may form in the primary slip planes. These boundaries form when dislocations with a Burgers vector not in the slip plane move into the plane by combination of climb and glide. THE geometry of subboundaries formed by the interaction of dislocations of two glide systems has been analyzed by Amelinckx,1 and the particular types produced by deforming fee crystals are predicted by ear.' In this paper types of boundaries which may be formed when climb as well as glide occur are discussed as this is relevant in high-temperature creep. It is assumed in the present investigation that the etch-pits observed in Cu + 7 wt pct A1 on surfaces parallel to {111} planes delineate the sites of dislocations. Although there is no direct evidence for this previous work on a-Cu/Al single crystals by Mitchell, Chevrier, Hockey, and Mon-aghan,3 would show this assumption to be reasonable. The alignments of etch-pits which form during creep are studied on sections parallel to each {111) plane. It is then deduced that these alignments are consistent with a specific type of planar subboundary. The Cu + 7 wt pct A1 single crystals had a [113] tensile axis and Fig. 1(a) shows schematically the relation of the slip planes and slip directions (as represented by tetrahedron ABCD) with reference to the tensile axis. The two equally stressed glide systems with the maximum Schmid factor namely ß-AD and (a-BD, from the analysis of Kear,2 would be expected to form the boundaries shown in Fig. l(a) and (b), also Fig. 5(a) and (b). EXPERIMENTAL PROCEDURE The a-Cu/Al single crystals were grown and annealed in a "gettered" argon atmosphere. Chemical analysis showed the aluminum content to be uniform in each crystal and the difference between crystals was maintained to an accuracy of ± 0.25 wt pct. The initial dislocation density and mean subgrain diameter after annealing was -106 cm-2 and 250 µ, respectively. Surfaces parallel to (111) planes were produced by specially developed electrolytic machining processes. The {111} faces were next electropolished for 5 min in a solution consisting of 25 g chromium trioxide, 113 ml glacial acetic acid and 40 ml water; the applied potential was 8 v. Dislocation etch-pits were revealed using l an etchant described by 1 ml bromine, 45 ml HCl, and - 250 ml water. RESULTS In crystals strained into secondary creep at higher stresses (443 and 750 g - mm-2 at 650° C aligned rows of etch-pits parallel to slip plane traces were evident in sections parallel to the (1111, (ill), and (111) planes, see Fig. 3. As well as the longitudinal alignments in Fig. 3, well formed randomly oriented arrays indicative of an equiaxed subgrain structure are evident. At the lower stresses (100 to 230 g . mm-2) only an equiaxed structure formed during creep. The sections in Fig. 3 are from a crystal crept for 70 hr at 650°C with a CRSS of 443 g.mm-2. Two identically oriented crystals were also deformed at the same temperature and stress for 5 min and 4 hr. In the crystal crept for 5 min, the etch-pits were randomly distributed with no tendency for directional alignment, see Fig. 2(a). As shown in Fig. 2(b) aligned arrays were evident after 4 hr creep but they were not nearly so well defined as in Fig. 3. The alignments (parallel to the arrows) in Fig. 3 are consistent with the existence of boundaries in the two main slip planes a and ß. The way in which this is deduced is seen by reference to Fig. l(c), where the existence of boundaries in the a and ß planes is verified by sectioning parallel to a,ß, and d. The (111) and ß(111) planes intersect the d(111) plane along BC [101 ] and AT [011] and alignments parallel to [101] and [011] are clearly evident in Fig. 3(c) in a section parallel to the d(111) plane. Similarly the a, and ß planes in Fig. l(a) intersect each other along DC [110] and hence there will be an alignment parallel to [110 ] in sections parallel to the a-plane and the ß-plane; this is evident in Fig. 3(a) and Fig. 3(b). It is interesting to note that alignments of etch-pits consistent with the boundaries predicted by Kear2 were not observed; see Figs. l(a) and l(b). The geometry of boundaries in {111} planes as shown in Fig. l(c) is discussed later. In Fig. 4(a) the individual etch-pits are resolved and the alignments are exactly parallel to the slip trace direction [101]. However, in some areas alignments deviate away from the slip trace direction by as much as 10 to 15 deg, this is evident in Fig. 4(b), and in Fig.

Jan 1, 1969

By Albert H. Fay

The gypsum industry makes significant contribution to the wealth of our nation. This non-metallic mineral ranks in the highest order with America's most precious resources. Evidence of this is borne out by the fact that gypsum is a vitally necessary element in the building, industrial and agricultural industries. In 1967, the United States consumed 14 million tons of this valuable ore. Of .this amount 69% was required by the building industry for the manufacture of building materials. An additional 21% was directed to the industrial market, for the manufacture of Portland Cement and for other industrial uses. The remaining 10% was used for agricultural purposes.

Jan 1, 1969

By Joseph P. Nugent

The new combination gypsum plaster and gypsum wallboard plant of Compania Industrial Kaiser S.A., the first of its kind in Mexico went into production in April of 1969. This was approximately fourteen months from the signing of the formal order for the plant and equipment. Compania Industrial Kaiser S.A. is an affiliate of the Kaiser Gypsum Company in the United States and will market practically the same line of products and to the same standards as those produced in American plants. Located in the City of Puebla, the plant will readily service the major Mexican sales areas. It is approximately 85 miles away from Mexico City on a modern, four-lane, divided highway and distribution to other major consumer areas can be readily effected by the use of a good highway system, as well as, by rail. This, plant is the, sixteenth Gypsum Wallboard Mill supplied abroad by my company, United States Wallboard Machinery Company. Other installations are in Australia, New Zealand, Chile, England, Scotland, Ireland, Finland, South Africa, Latvia and Germany. Two new mills are on order; a small unit for Brazil and a comparatively large unit for New Zealand. All these mills have one thing in common with plants in the United States and Canada; they are equipped with standard, time-proven and tested equipment and they are designed in accor¬dance with the latest engineering thinking in order to produce efficiently, the highest quality product at lowest cost. They differ generally in the size of plant, the factors that brought them into being and in the market that they supply. I believe that these differences will be of interest to you.

Jan 1, 1969

By Robert J. De Angelis, James H. Barker

An improved method for solving dynawzical dislocation problems using a digital computer is described in this paper. Interactions between two distinct types of dislocations were studied: attractive screw dislocations; and Lomer lock forming dislocations. One dislocation is positioned in the lattice and is initially at rest, while the other dislocation is moved through the lattice on an intersecting slip plane at a constant velocity in the range 0.5 to 0.999C. (C is the transverse velocity of sound.) The results obtained from these computations indicate that screw dislocations account for a small fraction of the total strain over a wide portion of the range of velocities studied. They further indicate that mixed dislocations mainly repel other dislocations in the neighborhood of the active glide plane. From this a possible explanation for cell formation is put forth. The density of Lomer locks expected to exist after a strain of 0.2 was found to be 1.4 x 106 cm-2 which is in good agreement with indirect experimental estimates. IN the past, predictions of favorable or nonfavorable dislocation reactions were based on the associated changes in elastic strain energy. Such considerations take no account of the probability of the two dislocations coming into contact to react. Venables1 was the first to approach these probabilities by considering the interactions between two moving screw dislocations on perpendicular glide planes. Because of the restrictive types of dislocations and glide plane geometry employed, his results have limited application to metallic crystals. The work to be presented here develops a general approach to solving dynamical dislocation problems; either dislocation-dislocation interactions, presented here in detail, or dislocation interactions with any other suitably defined stress field. Two types of dislocation-dislocation interactions common to face centered cubic (fee) materials are considered: those between pure screw dislocations of opposite sign on intersecting slip planes and those between mixed dislocations on intersecting slip planes, that can react to form a perfect dislocation. This latter reaction, referred to as the Lomer reaction, produces a locked product dislocation that finds it energitical favorable to disassociate into two Shockley partials and a stair-rod dislocation. This partial configuration known as a Lomer-Cottrell (L-C) lock plays a major role in work hardening of fee crystals. seeger2 names the L-C lock as the prime contributor to Stage II hardening while Kuhlmann-wilsdorf3 and Meakin and Wils- dorf4 also state that it is a significant contributor to work hardening. However, with a few notable exceptions,5-7 direct observations of the Lomer lock and the L-C lock by electron transmission microscopy are scanty, and even these are subject to other interpretations.5,6 In a study of partial dislocations present in austenitic stainless steel, whelan8 did not observe any L-C locks at the head of pile-up groups. This result contradicted existing work hardening theories and led him to postulate an alternate theory based on the stress required to break away dislocations intersecting a pile-up group, from their stacking fault nodes. Due to the importance of the Lomer reaction in producing L-C locks which are an essential feature in current work hardening theories and because there exist no data giving direct quantitative values for the density of locks, and because there has even been some doubt expressed as to whether this important reaction occurs at all, a study of the dynamic behavior of the mixed dislocations which form the Lomer lock was undertaken. Due to their ability to cross-slip with relative ease, screw dislocations play an important role in the deformation of fee crystals. For this reason, the second type of reaction considered here is between screw dislocations of opposite sign. In addition, computations in volving screw dislocation interactions are relatively simple, thus providing a convenient check on the cornputational scheme employed. DEFINITION OF PROBLEM The force exerted on a dislocation due to a generalized stress field is given by the Peach and Koehler9 equation: Here t2 and b2 are respectively the tangent and Burgers vectors of the dislocation, and T1 is the stress dyadic defining the local stress field. The stress field may be externally applied or generated internally by the presence of a lattice defect, such as a second dislocation, as is the case in this work. Frank10 has shown that an equivalent momentum, P, of a screw dislocation can be defined by: Here, EST is the total energy of a screw dislocation and ESo is its rest energy. The left side of Eq. [2] is the time derivative of momentum and the right side is the position derivative of the energy due to the dynamical nature of the dislocation. The total energy of a dislocation is the sum of the potential and kinetic energies. Weertman11 has developed the expressions which were used here; these give the potential and kinetic energies of uniformly moving edge and screw dislocations in an isotropic medium.

Jan 1, 1969

By Charles C. Boley

The Bureau of Mines dried and carbonized two wood wastes, one softwood (redwood) and one hardwood (oak), using continuous, vertical entrainment techniques previously developed for use with coal. It was demonstrated that these techniques are readily applicable to wood waste and that appreciable changes in the yields of carbonization products can be obtained by varying operating conditions. A limited amount of experimental work was done on briquetting the charcoals. Firm briquets were formed with oak charcoal, although greater quantities of starch binder than used commercially for kiln-produced charcoal were required. Redwood charcoal did not briquet successfully under the test conditions employed.

Jan 1, 1969

By Karl C. Dean

All components of 15 automobiles manufactured between 1954 and 1965 were analyzed, and it was determined that a representative junk automobile would have the following composition (all figures in pounds): steel, 2,532; cast iron, 511; copper, 32; zinc, 54; aluminum, 51; lead, 20; rubber, 145; glass, 87; miscellaneous, 142. Time and motion studies and a cost evaluation were made to determine if such a typical vehicle could be economically burned in a smokeless incinerator and hand-dismantled, and if the resultant steel could be baled into a high-quality No. 2 bundle containing less than 0.10 percent copper. The cost evaluation showed that processing the composite car would cost about $51 to produce about $56 worth of marketable ferrous and nonferrous metal products and provide an annual rate of return on investment of 19 percent.

Jan 1, 1969

Jan 1, 1969

By M. N. Qureshy, D. D. Sarma, B. K. Verma

Kolar Gold Fields are one of the best known gold deposits in South India where gold occurs in quartz reefs in Archaean hornblende schists and shows large variation in grade. The history of mining goes back to 18th century. The workings at Nundydroog Mines, chosen for Operations Research studies, have entered a depth of 2150 meters. The gold values in these mines were thought to be erratically distributed. However, by using 10540 samples from 49 blocks of ore, it is established that the gold value properties in inch- pennyweight units follow a two parameter log-normal distribution. Emperical relationships between arithmetic means and estimates based on peripheral and internal block values have been worked out using the estimator suggested by Krige (1951) instead of 't' estimator suggested by Sichel (1952). These relations can be used in arriving at block estimates with respective standard errors. There is no significant emperical relationship between depth and the grade of ore.

Jan 1, 1969

By J. S. Kirkaldy, R. C. Dorward

The solubilities of copper and gold in silicon and germanium have been determined by equilibration of the solid semiconductors with coexisting liquidus phases. The experimental results were combined with estimated activity coefficients of the liquidus alloys to determine the following partial molar enthalpies and excess entropies of solution for the systems: Solubility measurements were also carried out below the eutectic temperature of the copper-silicon system. The partial molar enthalpy and excess entropy of copper in silicon with respect to Cu3Si were determined to be 40.2 ±0.5 kcal per mole and 9.7 i 0.5 cal per mole — OK, respectively. It has been dentonstrated that nu-cleation and growth of intermediate compounds are retarded in copper-silicon diffusion couples. This points out the dangers of determining equilibrium solubilities by dijjusion methods. THE thermodynamic requirement for equilibrium between contiguous phases at constant pressure and temperature is that the chemical potential of each component be constant throughout the system. Equating expressions for the chemical potential of solute, component 2 say, in two phases, alpha and beta, gives

Jan 1, 1969

Jan 1, 1969

Most types of nuclear power reactors use uranium dioxide fuel. Power reactors using natural uranium dioxide'fuel are of special interest to countries such as Australia that have their own uranium supplies. A wide range of uranium dioxide powders can be fabricated and the ideal one flows readily, presses without the need for binders or lubricants, sinters to the required density and gives low reject rates at all fabrication stages. Sinterable uranium dioxide is usually produced via the ammonium diuranate route. The A.A.E.C. is aiming to demonstrate production of nuclear grade uranium dioxide from Australian concentrates, improving technology where possible. Details are given of the dissolution, solvent extraction, precipitation, filtration, drying, and calcination-reduction steps. Solvent extraction from sulphate media is also under study with a view to developing a process to produce a nuclear grade product at the mine treatment plant site,

Jan 1, 1969

By P. Somasundaran Discussion by Knut L. Sandvik

Knut L. Sandvik (Mining Engineer, Mineral Dressing Laboratory, Technical University of Norway, Trond-heim, Norway) — The discovery that adsorption at solid-liquid interfaces is influenced by adsorption at other interfaces may prove very fruitful in the further development of flotation theory. Having reached the same conclusions as P. Somasundaran in some experiments with amine hydrochlorides, I would like to offer more direct evidence of the interfacial adsorption mechanism based on surface tension measurements and adsorption studies.' This evidence was derived from flotation tests carried out in a Hallimond tube at neutral pH and 60°C. The amount of amine solution and quartz surface were chosen to insure measurable concentration changes during flotation due to adsorption. Adsorption data for

Jan 1, 1969

By K. R. Dorman

To further investigate the potential of precast concrete sets as a support medium for underground mines, the Bureau of Mines designed a five-piece precast concrete drift set for a small opening and tested it to destruction in a straining frame. Twenty-seven tests were made with three sizes of members using three loading conditions. In addition, six tests were made with sets in a distorted configuration, Test results and typical failure patterns are presented. A comparison of results with those previously reported for the three-piece set shows the five-piece set supports considerably larger total loads than does the three-piece set of equivalent cross section designed for the same size of opening. Recommendations are made for improvements in design.

Jan 1, 1969

By M. R. Geer

The Bureau of Mines surveyed the solid wastes that have accumulated from coal mining in Washington, Oregon, and Montana. Location, amount, character, and condition were determined, and both economic and environmental factors were considered. Areas covered by waste comprise 800 acres in Washington, 5 acres in Oregon, and 1,200 acres in Montana. In a few cases waste is being utilized, particularly cinder from burned refuse dumps, as fill in road construction and as a ceramic raw material. It is estimated that wastes deriving from coal mined for electric power generation by 1974 may amount to 3 million tons of washery refuse, 2.7 million tons of fly ash, and 1,000 acres of spoil banks.

Jan 1, 1969

By B. N. Das, H. E. LaBelle, G. A. Wolf

ZnxHg1-xTe and GUPxAS1-x crystals have been grown from solution by a traveling heater method (THM). In a floating zone type fashion a solution zone sandwich of liquidus composition is made to migrate through feed material of solidus composition by a slow-speed movement of <0.25 mm per hr of the total charge through a stationary radiation or rf heater. ZnxHg1-xTe of composition 0 < x < 0.3 and GUPxAS1-x of composition 0.5 < x < 0.7 have thus been grown from their solution in liquid tellurium and gallium, respectively. A simplified analysis of heat and material transport is given. In this method, Proper adjustment of the temperature distribution along the liquid solution zone axis eliminates instability of the crystal growth front and constitutional supercooling. 1) ZnxHg1—xTe: The solid-solution telluride was grown in sealed quartz tubes at a temperature of 500 to 650°C. For first Preparations mechanical mixtures SINGLE crystals of solid solutions of III-V and II-VI compounds have been grown by various techniques from the melt, from the gaseous phase, or from solutions in of ZnTe and HgTe were used. X-ray determinations showed the resulting crystals to be homogeneous throughout their entire length, except for the end sections. The homogeneity is greatly improved by reusing the ingots obtained from first Preparations as feed material in subsequent crystal growth runs. Ingots of up to 4.5 cm have thus been obtained. 2) GaPxAs1-x: Crystals were grown in a EN crucible at a temperature of 1050°C. For first Preparation a mechanical mixture of Gap and GaAs was cemented together by a minimum amount of liquid gallium through "wet" grinding of Gap and GaAs crystals in the liquid metal and subsequent exuding of excess gallium by compacting of the charge in the EN crucible. Electron microprobe measurements using P-Ka and As-Ka radiation showed uniformity over a length of 0.4 cm. Properties of the various Preparations are described. liquid metals.&apos;-&apos; Their growth from the melt by passing a liquid zone of pseudobinary liquidus composition through a solid rod of solidus composition is generally a convenient method of growth of single crystals of solid solutions of homogeneous composition. This method loses much of its usefulness, however, if the melting point or the vapor pressure of the solid solution is high. In the case of a compound having a high melting

Jan 1, 1969

By J. G. Benford, E. B. Stanley

THERE have been numerous papers in the literature1 on the subjects of secondary and tertiary recrystalli-zation in silicon steels. Secondary re crystallization is believed to occur in silicon steel by either a surface-energy phenomenon such as in the usual development of cube texture or by a second-phase phenomenon such as in the usual production of cube-on-edge texture, (110)[001]. Tertiary recrystallization in silicon steel is thought to be a surface-energy phenomenon in which, for example, grains having a (110) plane parallel to the sheet grow at the expense of other grains in the matrix including those having a (100) plane parallel to the plane of the sheet. In all these instances, the orientations involve either a preferred (100) or (110) plane in the plane of the sheet. Until very recently, there had been no experimental evidence reported of the occurrence of a texture by secondary or tertiary recrystallization that involves a (111) plane in the plane of the sheet, although Kohler reported that grains having the (111) plane parallel to the sheet surface can also grow by a surface energy mechanism. Stickels observed a secondary texture in iron described as "near {554}(225)" about 5 deg from {lll}(211).3 Mee reported that in a vacuum-remelted commercial 3 pct Si steel {lll}(hkl) secondary recrystallization took place in a high vacuum and in pure hydrogen.4 Recently in our Laboratory, large-grained structures such as shown in Fig. 1 having an orientation near (111)[211] or (111)[2ii] have been observed. The arrows point to areas of relatively small matrix grains of the kind that the much larger (111) grains consumed while growing. It is of interest that the matrix grains of samples annealed at 2000°F were essentially the same size as those in samples annealed at 2200°F, a matrix-grain-size stability that is characteristic of secondary recrystallization processes. A torque disc taken from Grain 4 of the sample shown in Fig. 1 revealed a very flat magnetic-torque curve, as expected, with a maximum torque of 7000 dyne-cm per cu cm compared to the typical 180,000 dyne-cm per cu cm observed for conventional (110)[001] textured material. A back-reflection Laue pattern for Grain 4 is shown in Fig. 2 and indicates a near-perfect (111)[211] orientation. The other six numbered grains in the sample of Fig. 1 had a similar orientation. The small circles next to each number were the target areas for the X-ray beam. The starting material was an 0.011-in.-thick oriented silicon steel, (110)[001] texture, containing 3 pct Si. It was lightly pickled, cold-rolled to 0.005 in., and annealed 4 hr at 2200°F within a nickel box (not gas-tight) inside a tube furnace through which dry hydrogen was flowing. The samples were heated to 1500°F in 1 hr and then at 60°F per hr to 2200°F. There were other

Jan 1, 1969

By H. H. Keller, E. J. Couch

Damage to production wells subjected to the high temperatures associated with in-situ combustion projects has been a problem since the advent of this thermal recovery technique. Injection of water down the annulus of hot wells has been successfully utilized for cooling and prolonging the life of such wells. A mathematical model that is suitable for predicting the effectiveness of cooling water in a particular application is developed. Typical results for practical ranges of the various parameters involved are presented. INTRODUCTION In the normal course of in-situ combustion operations, highly damaging conditions develop in the production wells as the combustion zone approaches, and these wells are subjected to high temperatures (up to 1500F). The resulting well damage is recognized as one of the more serious operating problems unique to the in-situ combustion process. Even in operations where well completions have been specifically designed to cope with this problem, the question arises as to how this destructively high temperature can be kept within tolerable limits. A simple and economical approach to this problem is to circulate cooling water down-hole. This method has been used with some success in shallow reservoirs. At greater depths, however, the heat exchange with the overburden surrounding the well and between the fluids in the tubing and the annulus tends to equalize the temperatures of the two fluid streams so that the cooling capacity delivered to the bottom of the hole decreases with well depth. This method would provide no appreciable control over the bottom-hole temperature at great depths. In order to delimit the condition under which cooling by water circulation is effective, the wellbore temperature must be related to the water inlet rate and temperature; to the reservoir depth, production rate, and initial temperature; and to the combustion at at bot tom-hole depth. A model that meets these requirements and that will offer an approach for developing engineering solutions to practical design and operating problems is described in this paper. MATHEMATICAL MODEL Previous studies of temperature distributions include those for flowing wells1p2 and those for hot fluid injection. Adams and Haddenhorst 6 presented solutions for the down-hole circulation of hot oil in the treatment of paraffin-deposition problems. In this paper the thermal model presented by Ramey 4 is adapted to the flow system shown schematically in Fig. 1. Water at temperature Ti is injected at a rate wi and flows down the annulus outside the tubing. It mixes at bottom-hole depth D with the fluids produced at race w from the hot reservoir at temperature T. This mlxtureJ. of injected water and reservoir fluids flows up the tubing and is produced at the surface at TI,. In order to describe the temperature response in this system, we make use of the usual conservation of

Jan 1, 1969