Search Documents

By C. A. Hope, H. B. Wishart

THE number and severity of surface imperfections on rolled slabs, assuming the reception of uniformly good quality heats from the open hearths, depend upon a number of conditions associated with heating and rolling of steel in the primary mills. While there are other elements that have an effect on surface quality, rather than make this paper too lengthy the discussion of mill processing variables will be limited to three factors in order to illustrate their effect on slab surface quality: 1—amount of reduction between ingot and slab, 2—slab finishing temperatures, and 3—influence of roll changes. Measurement of the percentage of surface removed by scarfing on the flat surfaces of the slabs was used for evaluating quality in this study. A study of this nature must be made on slabs that are inspected and conditioned under uniform conditions and standards. In order to be certain that steel of the best possible steelmaking quality was received at the rolling mills, a low carbon deep drawing grade of rimmed steel, made for sheet mill application and manufactured under carefully controlled open hearth practices, was selected. Use of this particular steel thereby reduced the steel quality factor as a possible source of variation. The measure of slab surface quality is the amount of surface removed by scarfing during yard conditioning and is expressed as percentage of surface removal. This percentage was estimated by experienced personnel to uniform standards and it should be noted that these percentage figures are representative only for the grade selected and under the rigid inspection standards to which the slabs were subjected. Surface removal is a matter of concern because the imperfections, if undetected, often are the cause of poor surface quality in the finished product and their removal, by conditioning, add to the total plant costs. The data was collected at various times over a period of six months and, with normal weekly fluctuation in the level of quality, it is to be expected that for any period of sampling there will be some variation in the plotted results. The type of defect that is responsible for most slab conditioning at Gary Steel Works is a light angular surface break. This defect is usually interconnected to form large defective areas and occurs mainly on the bottom half of the slab on both sides. This type of defect is illustrated in Fig. 1, showing a bottom portion of a slab; while a close-up of an area of the same slab where the surface breaks were found is given in Fig. 2. The large dark areas are heat patterns, results of hot stacking and cooling. Independent of these light breaks, but sometimes associated with them, are larger and deeper isolated breaks. However, most of the surface removal occurs from conditioning the large areas of small breaks. There are also occasional scabs of varying degrees of severity but these are relatively infrequent. The slabs are generally free of rolled-in scale. Ingot to Slab Reduction vs Quality Some ten years ago at Gary Steel Works, the minimum slab ingot thickness was 30 in. Subsequent operating and other quality features indicated the desirability of using an ingot of reduced thickness with the result that a series of molds that would produce a 22 in. thick ingot with various widths was adopted as standard. A minimum number of the thicker mold sets are still used. From the standpoint of quality difficulties from pipe and segregation, the smaller ingots are an improvement. From a quality surface viewpoint, the slab product from the thin molds requires approximately twice the surface removal as the slab product from the thick molds. This is shown in Fig. 3 where the percentage of surface removal is plotted against slab product rolled from

Jan 1, 1956

By P. D. Southgate

VIBRATION, both ultrasonic and sonic, can affect the course of a variety of metallurgical processes. Reports of work on this subject have appeared at intervals over the last twenty years and a thorough review has been made by Hiedemann,' who gives a full list of references. It has been established that both refinement of structure and outgassing of the melt can be produced in most metals with sufficiently intense vibration. Many of the experiments in this field have been carried out using alloys of direct commercial interest in production- type casting equipment. Here a different approach is adopted, and simple binary alloys which exhibit different types of structure are used to facilitate examination of the effects produced under well-controlled conditions. Results from this kind of experiment should enable the basis of larger scale experiments with similar types of materials to be better substantiated. The alloys selected for this work are: 1) aluminum of 99.2 pct purity, the principal impurity being iron, near 0.4 pct; 2) A1-1.8 pct Fe, which is near eutectic composition; 3) A1-4 pct Fe—the second phase, of composition FeAl3, forms distinct acicular crystals; and 4) A1-12 pct Si—although this is of eutectic composition, the silicon normally appears in the form of large plates. Experimental Method There are three practicable methods by which acoustic vibration can be transferred to liquid metals: a) vibration of the whole of the container; b) electromagnetic induction; and c) insertion of a vibrating probe into the liquid. Method c is chosen here, and a frequency of 8 kc per sec is used. The end of the probe is electrically heated so that the metal near it will be the last to solidify. This ensures that vibration is transmitted directly to the liquid metal without passing through any solidifying and pasty intermediate region, which would attenuate acoustic waves severely. In addition, the heating prevents solid metal adhering to the probe, with consequent detuning. The transducer assembly is shown in Fig. 1. A stack of Permendur laminations 30 cm long acts as a half-wave vibrator and a winding along its length carries polarizing and energizing currents. It is joined by a half-wave coupling bar to a mild steel exponential horn, which tapers from 3.8 to 1.1 cm diam. A stainless steel stub 3 cm in length is welded on the free end. The assembly is supported by a plate located at the node of the coupling bar. Acoustic radiation losses are minimized by allowing the free end of the transducer to protrude above the surface of the cooling water. The exponential horn serves the function of matching the acoustic output impedance of the transducer to the radiation resistance of the probe into the melt. Electrical drive is provided by a 1 kw generator. Measurements of probe vibration amplitude during melt treatment are obtained from a gramophone pick-up with the needle attached to the wide end of the horn. This device is calibrated with a microscope before use. Liquid aluminum is very actively erosive and solution of materials with which the molten metal comes into contactcauses difficulties. Erosion of the probes in particular can be severe since it is greatly accelerated by the vibration. Tests of various acous-

Jan 1, 1958

By Robert A. Jankowski, Charles D. Taylor

The objective of this program was to conduct dust surveys at six longwall sections having double-drum shearers, that were regularly in compliance, and to identify the dust control techniques that were the most effective. As each of the mines selected had a record of regular compliance with the Federal Dust Standard, all sampling was "short-term" (often less than 30 minutes) and no attempt was made to relate the survey results to dust-sampling results obtained by the companies for compliance purposes. The sampling procedures (1) used during this survey were developed jointly by the Bureau of Mines and Foster-Miller Associates, Inc. In addition to monitoring dust levels, measurements were also taken throughout the shift to monitor airflow along the face and water usage on the shearer. This program was a cooperative effort of the Bureau of Mines and the Mine Safety and Health Administration (MSHA). The following MSHA health specialists contributed to its successful completion: Paul Lenyo, CMS&H, Dist. 2; Ellis Mitchell, CMS&H, Dist. 3; Carl Jenkins, CMS&H, Dist. 4; David Stritzel, CMS&H, Dist. 8; and John Prelc, CMS&H, Dist. 9. RESULTS CUTTING SEQUENCE - WORK LOCATION At all mines surveyed, an important factor in controlling dust exposure at the shearer is the design of the cutting sequence so as to allow the shearer operator to work most of the time on the intake-air side of the lead drum. It is generally accepted that most of the dust generated by a double-drum shearer comes from the lead drum, which in the raised position normally takes a full sump. Because the position of the drum that is in the raised position determines the horizon control, the operator must be close enough to carefully monitor its operation. Therefore, his position relative to the lead drum has a significant effect on his dust exposure. Dust profiles, such as those constructed from data collected at Mines A and B (Figure 1), show the large gradient in dust concentrations that can exist between the intake and return air side of the lead drum. When the primary cut is taken head to tail, the lead drum is downwind and dust levels can be maintained at a low level until air has passed the shearer (Mine A). Thus, shearer operators can stay in relatively uncontaminated air. When the primary cut is taken tail to head, the lead drum is upwind of the shearer controls, resulting in higher dust concentrations at the shearer operator's work location (Mine B). At the mines where this cutting sequence was used, it was company policy for the shearer operators to walk on the intake side of the lead drum, returning to the controls only to adjust the height of the lead drum. DIRECTED WATER SPRAYS AND PASSIVE BARRIERS It is not always possible to keep the shearer operator on the intake air side of the lead drum. Various techniques have been tried to keep the dust generated by the shearer away from the machine operators when they work adjacent to the shearer. At all mines visited, the external water spray nozzles were directed so that dust from the shearer was directed downwind and toward the face, and away from the shearer operators. The effectiveness of using external water sprays to keep dusty air close to the face was noted during Bureau of Mines efforts to develop improved water spray systems (2). Laboratory and underground tests showed that water sprays located properly and directed downwind can create aiflow patterns that move dust generated by the shearer toward the face and away from the shearer operators. Sprays directed upwind, into the airflow, can actually move dust away from the face

Jan 1, 1982

By Frank G. Miller

The lower cost of producing oil from naturally flowing wells compared with pro-luction costs accruing from artificial lifting methods has stimulated much research, rith the joint purpose of extending the natural flowing life of wells and of increas-ng the productivity of small wells. The iboratory investigation described herein was made to determine the effect of a lotted liner on the pressure gradient in the icinity of the wall of a flowing well. Flow estrictions caused by the liner induce nergy losses between the oil-bearing for-lation and the inside of the liner, which lay be reduced by improved liner design, nd thereby the flow capacity of wells may e increased. These losses have been evalu-ted for rectangular slots of different sizes, nd means are suggested for reducing them. The dearth of information concerning the ature of the flow of fluids from uncon-slidated sands through small openings in he walls of. pipes—as represented by the ow of oil from an oil sand into a slotted ner—is acknowledged. Although the bene-ts to be realized by operators through the se of optimum liners is just beginning to e recognized generally, Coberlyl in 1937 ointed out that the functioning of screen is is an important factor in the pro-uction of oil. From his study on the :lection of size of oil strings for wells in California, Parks2 concluded, in part, that the perforated section of the oil string deserves continued study, especially with respect to the selection of perforations. The growing use of gravel packing resulting from certain research findings lends even more significance to the problem of selecting optimum liners, as the application of these methods usually requires slotted liners or other kinds of perforated liners. The present study was made to obtain further information for the guidance of engineers and operators in selecting slotted liners and to develop a laboratory method that may be used in analyzing possible pressure conditions surrounding most types of perforated casings used in producing oil wells, so that the present inadequate fund of knowledge on this important subject may be expanded. Discussion of ProbleM At the beginning of the investigation the following assumptions were made regarding bottom-hole conditions of a producing oil well and the oil-sand reservoir it penetrates: (I) Conditions of steady-state flow exist, (') a a homogeneous liquid is being produced) (3) no contaminating material (such as drilling fluid) is present between the liner and the face of the oil-bearing sand, (4) the well is vertical and completely penetrates a horizontal sand stratum of uniform thickness occurring between two impermeable strata, and (5) the flow is wholly viscous. If the foregoing assumptions are made, with the added requirements that the sand

Jan 1, 1941

By J. J. Bean

Concentrating mixed sulfide-oxide copper ores by the leach-precipitation-flotation method is an old operation at the Miami Copper Co. The idea was conceived and the method developed at Miami by F. W. Maclennan and Harmon Keyes during the years 1929 to 1934, and it was these men who gave the term LPF to this process. Miami at that time had considerable reserves of mixed sulfide-oxide ore.* In the development of a suitable treatment method, it was natural that leaching of the oxides with acid and the precipita¬tion of copper from the resulting copper sulfate solution by iron was investigated. The separation… • The term oxide as used in this article includes the copper oxides, carbonates, and silicates.

Jan 12, 1960

By W. H. Adams

Among the persistent experimenters of the present century no one man is more widely and favorably known in the metallurgical world than the late Peter Spence of Manchester, England, to whom we are indebted for many of the successful processes in the manufac ture of acids and alkalies, and for much of that perfection in me chanical detail which goes so far towards insuring success. For the past twenty-five years—a period covering the greatest changes in soda-processes and a revolution in acid-manufactures ef fected by the substitution of pyrites for brimstone—Mr. Spence was constantly engaged in perfecting the plant for the economical treat ment of pyritous ores; and no text-book has been complete without reference to his many inventions, patented or otherwise. The results of his labors for the past six years were not given to the public, by reason of the active competition existing among man ufacturers on the continent of Europe and in Great Britain ; but it was well known and conceded that the crowning triumph of his .life had been achieved in the successful working of his automatic desulphurizing furnace, which mechanically calcined "smalls" or finely crushed pyrites—the bugbear of all chemical manufacturers. That he was met by many delays and disappointments, and that

Jan 1, 1885

Experimentation which measures differences in pressure across the interfaces of immiscible fluids in the interstitial spaces of porous media may be termed "capillary pressure experimentation". In the literature of petroleum technology since 1941 there have appeared twelve papers popularizing capillary pressure concepts and developing applications of these concepts for the solution of problems of practical reservoir engineering importance, such as the determination of connate water, fluid distribution. in transition zones, reservoir rock textural properties, and oil recovery from petroleum reservoirs.' Although a review of the literature would be justified at this time in order to reconcile the conflicting viewpoints which are contained in the cited papers, the object of this note will be of more limited scope. It is believed that the recent paper of Muskat alls sufficient attention to many of the uncertainties which arise upon examination of the published literature. such that until satisfactory counter-proposals can be made it will serve our purpose only to mention some other like uncertainties. This will emphasize further the need confronting petroleum technologists to re. consider and reformulate the application possibilities of capillary pressure experimentation. In particular, I sug- gest that we examine the thesis that capillary pressure experimentation as above defined can lead to measurements reflecting the recovery of oil from petroleum reservoirs, as was proposed first" by Amyx and Yuster" and was first reduced to practice by the experimentation of Welge. In fact. I shall deal exclusively with the Welge papers since it is the principle one on this subject which has appeared to date. I shall attempt to show that the possibility of describing oil recovery features in terms of capillary pressure phenomena has not been established entirely. The Welge paper was a pioneering effort to evaluate this recovery application possibility. P. P. Reichertz' comments on the Welge paper state that non-wetting phase discontinuities are developed occasionally in the Welge experiment, and restate Muskat's argument that discontinuous fluid elements (partially saturating the interstices of porous media which are elsewhere saturated with some other immiscible phase or phases) are not subject to the requirements of hydrostatic equilibrium. It is the purpose of my comment to show that it is unnecessary to make Reichertz' postulation regarding non-wetting phase discontinuities (however valid) when it is desired to criticize welge's theoretical treatment of his problem. It can be shown that Welge's method of measuring values for ''capillary pressure" is invalid in many instances of application, such that his reported curves of capillary pressure Versus fluid saturation often have no physical meaning, even throughout the interval of fluid saturation where it might be otherwise suspected that no phase discontinuities occur. By considering established principles of capillary pressure experimentation it can be shown that the pressure difference experimentally observed between wetting and non-wetting fluid Phases which are contained in external reservoirs will reflect on the capillary pressure difference at the interfaces of contact between these phases only when the following conditions are satisfied: (a) There shall be a balance between the opposing forces of gravity and capillarity, as obtains under conditions of hydrostatic equilibrium when the positions of the interfaces of contact become fixed in pore spaces of certain geometry (b) The wetting and non-wetting fluids within the interstitial spaces shall everywhere be continuous with the external wetting phase reservoir and the external non-wetting phase reservoir, respectively. It will become apparent immediately that in any instance when a greater pressure is recorded in the external wetting phase reservoir than in the external non-wetting phase reservoir, one may establish either that static equilibrium has not been attained or that discontinuities in one or more of the fluids have been developed. This is because the pressure otherwiee is always ereatest in the non-wetting phase at each static interstitial interface of contact with the wetting phase. such that the externally measured pressure in the non-wetting phase likewise must be greatest if the above conditions are to be satisfied.

Jan 1, 1949

Experimentation which measures differences in pressure across the interfaces of immiscible fluids in the interstitial spaces of porous media may be termed "capillary pressure experimentation". In the literature of petroleum technology since 1941 there have appeared twelve papers popularizing capillary pressure concepts and developing applications of these concepts for the solution of problems of practical reservoir engineering importance, such as the determination of connate water, fluid distribution. in transition zones, reservoir rock textural properties, and oil recovery from petroleum reservoirs.' Although a review of the literature would be justified at this time in order to reconcile the conflicting viewpoints which are contained in the cited papers, the object of this note will be of more limited scope. It is believed that the recent paper of Muskat alls sufficient attention to many of the uncertainties which arise upon examination of the published literature. such that until satisfactory counter-proposals can be made it will serve our purpose only to mention some other like uncertainties. This will emphasize further the need confronting petroleum technologists to re. consider and reformulate the application possibilities of capillary pressure experimentation. In particular, I sug- gest that we examine the thesis that capillary pressure experimentation as above defined can lead to measurements reflecting the recovery of oil from petroleum reservoirs, as was proposed first" by Amyx and Yuster" and was first reduced to practice by the experimentation of Welge. In fact. I shall deal exclusively with the Welge papers since it is the principle one on this subject which has appeared to date. I shall attempt to show that the possibility of describing oil recovery features in terms of capillary pressure phenomena has not been established entirely. The Welge paper was a pioneering effort to evaluate this recovery application possibility. P. P. Reichertz' comments on the Welge paper state that non-wetting phase discontinuities are developed occasionally in the Welge experiment, and restate Muskat's argument that discontinuous fluid elements (partially saturating the interstices of porous media which are elsewhere saturated with some other immiscible phase or phases) are not subject to the requirements of hydrostatic equilibrium. It is the purpose of my comment to show that it is unnecessary to make Reichertz' postulation regarding non-wetting phase discontinuities (however valid) when it is desired to criticize welge's theoretical treatment of his problem. It can be shown that Welge's method of measuring values for ''capillary pressure" is invalid in many instances of application, such that his reported curves of capillary pressure Versus fluid saturation often have no physical meaning, even throughout the interval of fluid saturation where it might be otherwise suspected that no phase discontinuities occur. By considering established principles of capillary pressure experimentation it can be shown that the pressure difference experimentally observed between wetting and non-wetting fluid Phases which are contained in external reservoirs will reflect on the capillary pressure difference at the interfaces of contact between these phases only when the following conditions are satisfied: (a) There shall be a balance between the opposing forces of gravity and capillarity, as obtains under conditions of hydrostatic equilibrium when the positions of the interfaces of contact become fixed in pore spaces of certain geometry (b) The wetting and non-wetting fluids within the interstitial spaces shall everywhere be continuous with the external wetting phase reservoir and the external non-wetting phase reservoir, respectively. It will become apparent immediately that in any instance when a greater pressure is recorded in the external wetting phase reservoir than in the external non-wetting phase reservoir, one may establish either that static equilibrium has not been attained or that discontinuities in one or more of the fluids have been developed. This is because the pressure otherwiee is always ereatest in the non-wetting phase at each static interstitial interface of contact with the wetting phase. such that the externally measured pressure in the non-wetting phase likewise must be greatest if the above conditions are to be satisfied.

Jan 1, 1949

By M. J. Marcinkowski, K. S. Sree Harsha

A detailed numerical analysis has been made of the equilibrium configuration of partial dislocations in a blocked deformation twin under an externally applied stress. Twins made up of both pure screw and pure edge partials have been considered. The components of stress in the vicinity of the twin tip associated with each of these configurations have been plotted. It has been found that at some critical degree of oblateness the shear stress fields of the blocked screw or edge twin can both sPontaneously nucleate slip, whereas only the component of stress oxx about the edge twin can nucleate and propagate cracks. TWINNING becomes a predominant mode of plastic deformation at low temperatures and/or high strain rates. Fig. l(a) shows what must be the first step in the formation of a deformation twin, namely the formation of a loop of imperfect dislocation bounding a stacking fault. In an fcc crystal the partial dislocations have Burgers vectors of the type 1/6 a,(112) and the fault is of the intrinsic type while in the bcc crystal the partials have Burgers vectors of the type ao(lll). The stacking sequence of (111) planes in a perfect fcc crystal is given by ABC ABC, and so forth, and in one which contains a twin by ABCABACBA, and so forth. It is apparent that the stacking fault and twin give rise to no mistakes associated with adjacent close-packed planes; however, with respect to second-neighbor close-packed planes the faulted crystal has twice as many mistakes as the twin. The energy of the twin boundary may thus be taken to be one-half that of the intrinsic fault boundary. In the case of the bcc crystal the stacking sequence of (112) planes is given by ABCDEFABCD, and so forth, in a perfect crystal, by ABCDCDEFA, and so forth, in a crystal which contains a fault, and by ABCDCBAF, and so forth, in one which contains a twin. An analysis similar to that applied in the fcc crystal shows that both the fault as well as the twin involve no neighbor violations across adjacent planes. However, there are twice as many violations across second-neighbor (112) planes associated with the fault as compared to that of the twin. Thus once again the energy of the twin boundary may be taken as one-half that of the fault. It is important to note that, unlike the fcc, the faults in the bcc crystal involve first nearest-neighbor violations and are thus expected to be of much higher energy than those in fcc crystals. A more detailed analysis of the material discussed above can be found in Ref. 1. To a good approximation then, the lenticular twin shown in Fig. l(b) can be generated by adding partial dislocation loops on successive (111) planes for fcc crystals or (112) planes for bcc crystals in the manner shown, with no additional expenditure of chemical energy other than that required for the fault shown in Fig. l(a). In practice, deformation twins are much more extended than that shown in Fig. l(b) and more closely resemble one shown schematically in Fig. l(c). It is readily apparent that the free energy of the twin and matrix are identical. In those cases where the partials lead to a structural change, the free energy of the material contained within the dislocation array is lower than that of the matrix and we have the so-called martensite transformation. The present investigation is the first in a series of five major theoretical-experimental efforts which will deal with the static and dynamic behavior of twin nucleation and growth. There has been a recent surge in activity pertaining to the equilibrium shapes of twin lamellae2'3 and

Jan 1, 1969

By P. M. Blair, D. W. Peaceman

The shape and position of the gas-oil transition zone during downdip displacement of oil by gas has been calculated using flow equations which include the effects of gravity, relative permeability, capillary pressure and compressibility of the fluids. The calculations treat the problem in two space dimensions, and results are compared with data from a laboratory model tilted at 30° and 60° from the horizontal on displacements near and above the maximum rate at which gravity segregation prevents channeling of the gas along the top of the stratum. The good agreement between calculated and experimental results demonstrates the validity of the tecbnique as well as that of the flow equations. INTRODUCTION Knowledge of the fluid distribution and movement in an oil reservoir is important in producing operations and estimation of reserves. The history of the oil industry has included steady progress in improving the accuracy of calculations which provide the required knowledge. The earliest method of calculating reservoir performance consisted of material-balance equations based on the assumption that all properties were uniform throughout a reservoir.l For many reservoirs such a simple formulation is still the most useful. However, when large pressure and saturation gradients exist in a reservoir, the assumption of uniform values throughout may lead to significant error. To reduce these errors, Buckley and Leverett2 introduced a displacement eqation which considers pressure and saturation gradients. Methods available at that time permitted solutions to the Buckley-Leverett equation in one space dimension; these solutions have been very useful in solving many problems related to the production of oil. However, the one-dimensional methods are not adequate for systems in which saturations vary in directions other than the direction of flow. An example of such a system is the case of gas displacing oil down a dipping stratum in which the gas-oil contact becomes significantly tilted. Of course, the Buckley-Leverett displacement method cannot predict the tilt of the gas-oil contact. Recent improvements3,4 of the one-dimensional Buckley-Leverett method achieve some success in predicting the tilt of the gas-oil contact at sufficiently low flow rates. However, at rates high enough that the viscous pressye gradient nearly equals or exceeds the gravity gradient, even these improved one-dimen,sional methods incorrectly predict the shape and velocity of the contact. Further progress in estimating such fluid movements in a reservoir appears to require consideration of the problem in more than one space dimension. The recent two-dimensional method of Douglas, Peaceman and Rachford5 appears adaptable to calculate changes with time of the saturation distribution in a vertical cross-section of a reservoir. The movement of saturation contours should represent the moving fluid contacts and include the effects of crossflow due to gravity, as well as variations in the rock and fluid properties. The nonlinear nature of the equations used in the method has prevented proof of the validity of the solutions. Douglas, Peaceman and Rachford made some comparisons with experiment but did not include cases in which gravity was important nor cases involving displacement by the nonwetting phase.For these reasons, a test of the two-dimensional method for a case in which these factors are included would be very desirable. The test selected was a comparison of calculated results with those from a carefully controlled laboratory experiment on a model with measured physical properties. The model selected was one in which gas displaced oil down a tilted, rectangular sand pack. The model can be thought of as representing a vertical cross-section taken parallel to the dip of a reservoir. The displacement thus simulates gas displacing oil downdip that might result from gas-cap expansion or gas injection. This report outlines the calculation method used

By D. G. Oss, S. E. Erickson

An automatic control method for the ferrosilicon heavy media process maintains media density within 0.01 specific gravity points. Continued demands for higher grade, competitive products from the Mesabi Range have resulted in experimental work such as that detailed for one concentrator. Various methods, step by step procedures and instruments used at an iron ore beneficiation plant in the development of an automatic control system are described. Work continues and it is hoped that further applications of control instrumentation can be made in the next operating season. The need for instrumentation and automatic control of the various parameters in the heavy media process of iron ore beneficiation has been apparent for some time. Continued demands for higher grade, competitive products from the Mesabi Range have made it necessary to increase the efficiency of the process in every possible way. In a typical heavy media flow scheme for iron ore beneficiation (Fig. 1) a sized, prepared feed (generally about —1% in. to +% in.) is fed to a heavy media separatory vessel, along with a ferrosilicon slurry. A separation of the feed is made on the basis of specific gravity. Low density particles overflow a tailings discharge weir, while high density ore particles sink to the bottom of the high density pool and are moved away to the concentrate discharge chute. Both products are passed over drainage screens and then are cleaned thoroughly of attached ferrosilicon on wash screens. Float material is generally stockpiled, while the sink product is shipped as a final concentrate. Undersize from the drain screens is returned directly to the circulating media sump. Wash screen undersize is cleaned of contaminating ore particles and slimes by passing through magnetic separators. Provision is also made for splitting a portion of the tailings drain undersize into the cleaning circuit if necessary for control of depth of tailings overflow, or for additional cleaning as required. Cleaned ferrosilicon is stored in a densifier and returned to the Circulating media sump as make-up material. Dilution water is also added to this sump to maintain a desired specific gravity of the circulating media. As in any process, operational intelligence is secured only by keeping records of the process variables. Generally apeaking, plant operators have neither the inclination nor the time to keep complete and detailed records of these variables over the course of their shift. Before instrumentation was added to aid the operator, specific gravity was measured by weighing a given volume of pulp at intervals of from 30 to 60 min. Scale readings were made at the beginning and end of each shift. No records were kept of operating conditions, such as rpm of the separatory ves-sel, media level in the machine, tons per hour of the products, and so forth. These items were recorded only when spot checks were made by the metallurgical staff. CONTlNlJOUS DENSITY RECORDING The first process instrument used, other than the usual ammeter on the drive motor of the separatory vessel, was a nuclear density gauge and its associated circular chart recorder. These instruments were used to indicate and record specific gravity of the circulating media. This was a tremendous aid to the operator in that tie was able to observe and correct the specific gravity at any time. There was also added incentive to make frequent corrections because of the permanent record made by the recorder of the densities. The addition of the nuclear density gauge was influential in securing optimum quality and recovery of the heavy media product. Manual control was improved, and it became possible for a good operator to main control within f.05 specific gravity units. This compares with an unknown quantity, estimated at f0.15 gravity units, when manual measurement and control was used. An example of the improvement in manual control over the course of one season's operations is shown in Fig. 2. Chart A is typical of the records made shortly after the gauge was installed. Needless to say, it was difficult for operators and foremen alike

Jan 1, 1962

By R. L. Slobod, H. A. Blum

A semiquantitative method for measuring the wettability of reservoir rocks has been developed. These data are needed for reservoir analysis and for interpretation of laboratory displacement studies. The wettability of a core sample is measured by the contact angle for the system oil-water-solid. These contact angles are calculated from the displacement pressure (threshold pressure) obtained by use of the centrifuge, using first oil-water and second air-oil in the same core sample. This method is based on the assumption that the air-oil and oil-water interfaces occupy similar positions in the porous medium when desaturation of the wetting phase is initiated. The assumption is also made that the Contact angle for the air-oil-solid system which is close to zero in value does not change appreciably even when the contact angle for the oil-water-solid system experiences marked changes. "Apparent contact angles'' for five different solids ranging from 31" to 82" have been determined, and changes irr the "apparent contact angle" of a given sample with laboratory use from 33" to 53' {lave been observed. INTRODUCTION Reservoir rocks vary in their wettability, 1,2,3,4 some being preferentially water wet while other are apparently preferentially oil wet. The degree of wettability, in theory, is measured quantitatively by the contact angle for the system solid-oil-water, hut in 1)practice this quantity is extremely difficult to determine." The need for obtaining some measure of this quantity has become obvious in recent years as a result of both laboratory. and field observations. Several reservoir.: such as the Bradford Sand in Pennsylvania and the Wilcox' at Oklahoma City are reported to be oil wet. If these report:: correctly reflect the true nature of the surface of the rock in the ground, then these reservoirs probably will not perform as predicted on the basis of a water wet rock. In the laboratory many core samples have been Observed to be oil wet. These samples, while perhaps not correctly representing the reservoir, have markedly different properties from water wet rock. The location of the phases is different (oil is in contact with rock instead of water), and other quantities such as the connate water, the capillary pressure curve; residual oil. relative permeabilities. and the recovery of oil by water flooding are markedly affected by the value of the contact -4 A further complication observed in the laboratory is the chang-ing of the wettability of a rock specimen with use. such changes mean that repeat runs on the same core are not the duplicate tests desired, but represent new experiments on a more oil wet material. The changes in surface characteristics are sometimes so rapid that by the time an experiment requiring several days is completed, the results may not be representative of the core as originally described, The, rock material itself (Silica. carbonates. etc.), whell Clean and uncontaminated, is water wet. There seems b( : little evidence of the presence of oil wet minerals such as heavy metal sulfides. The oil wetness of reservoir samples, therefore, is believed to be caused by the accumulation of an adsorbed film in which the polar group of a large organic. molecule is adsorbed on the surface leaving the organic or hydrocarbon part of the molecule projecting out from the solid. Such a surface is much more readily wet 17" oil than by water. These considerations indicate the need for a method which will provide some measure of tile wettalbility (Contact(angle if possible) for reservoir rock ..samples) The method should be capable of (1.1 distinguishing between tile wettalility of dif. ferent formation,.. (2) detecting (change. ill wettalbility of a core with use. and (3) measuring the changes in Wettability which may be accomplished with cleaning operations. such as the use of sodium silicate for increasing water wrettalbility." A preliminary report on such a method is preseted below. not with the idea that this procedure alone will Solve the wettabil-ity problem. but rather that it may provide encouragement to

Jan 1, 1952

By D. G. Westlake

Alloys of poly crystalline Nb-H have been tensile tested at 77" and 120°K after slow-cooling and after quenching from room temperature. A rationale has been developed to explain the effect of cooling rate on ductility in terms of microstructure. The inferior ductility of the slow-cooled alloys in this temperature range can be attributed to the precipitation of coarse hydride particles that fracture in the early stages of plastic deformation. Quenching Produced much smaller hydride particles and a decreased tendency for initia-tion and popagation of cracks. Prismatic dislocation loops, punched into the matrix of quenched alloys, eliminate the yield point and may Play some role in the low temperature ductility of the quenched alloys. The difference in ductility between quenched and slow-cooled V-H alloys was even greater than that observed in the N b-H alloys. It is well known that the ductility of Nb-H and V-H alloys decreases with increasing hydrogen concentra-tion and with decreasing temperature.1-l1 The follow-ing are some of the numerous mechanisms that have been adopted in attempts to explain these observations: 1) hydrogen-dislocation interarction,4'6 2) lowering of the crack surface energy by adsorbed hydrogen,9'10 3) localized lowering of the niobium bond strength,9 and 4) exertion of pressure inside voids by molecular hydrogen.6 A recent study1' indicates that, in some way, the embrittlement is related to the precipitation of a hydrogen-rich phase, because embrittlement and hydrogen solubility have the same temperature dependence. Most of the investigators observed that at very low temperatures there was a return of the ductility. Thus, hydrogenated niobium and vanadium may be said to exhibit a low temperature ductility minimum."1'8'9 It has been reasoned by most observers that diffusion is required for the embrittlement mechanism to be operative, and that as hydrogen becomes immobile at very low temperatures, the ductility increases. This investigation of the mechanical behavior of Nb-H al-loys under various conditions is an attempt to gain a better understanding of the low temperature ductility minimum. EXPERIMENTAL Tensile specimens, with gage length dimensions 20 by 3 mm, were machined from sheet stock" and both faces were ground on wet 600 grit Sic paper to obtain a final thickness of 0.5 mm. Annealing as described earlier12 resulted in average grain diameters of 0.3 mm. The recrystallized niobium tensile specimens were electropolished in 90 parts H2S04, 10 parts HF (48.9 pct) by volume, at 287°K and 30 v. Hydrogen, which may have been present in the starting material and/or added during specimen preparation, was removed by annealing at 1073°K in a dynamic vacuum of 2 X 10-6 torr. Hydrogenated specimens (1.15 at. pct H) were prepared by reaction with a known quantity of pure hydrogen (obtained by thermal decomposition of UH3) at 1073oK, followed by cooling at the rate of 100" per hr. These were vacuum encapsulated, homogenized at 573°K for 3 to 5 hr, and furnace-cooled. Tensile tests were conducted on an Instron machine at a strain rate of 4 x l0-5 per sec. The gripping device was such that the specimen was positioned below the crosshead. Thus, subambient test temperatures could be obtained by immersion of the device in a cooling bath of either liquid nitrogen or Freon-12. The temperature of the Freon-12 was controlled within ± 0.1°K of the desired temperature by automatically monitoring the flow of liquid nitrogen through a copper coil in the bath. Slow-cooling to 77°K was accomplished as follows. The testing device was surrounded by a rubber jacket, open at the top and with small holes in the bottom. Liquid nitrogen, brought up to the bottom of the jacket, entered the holes and vaporized quickly. The temperature was monitored at the specimen with a copper-constantan thermocouple, and a constant cooling rate of 2 deg per min was easily achieved by controlling the level of the liquid nitrogen outside the jacket. RESULTS AND DISCUSSION Low Temperature Ductility Minimum. Resistometric studies of both Nb-H12 and V-H13 indicated that at tem-peratures less than 150°K, virtually all of the hydrogen

Jan 1, 1970

By P. B. Mee

The secondary re crystallization behavior of two vacuum-melted, nominally 3 pct Si-Fe alloys has been studied, one alloy being produced from pure electrolytic iron and semiconductor-grade silicon and the other from commercial-purity hot band. The vacuum-melted and vacuum-remelted alloys were found to develop {110}(hhl) and {lll)(hkl), respectively, on annealing in high vacuum and {100}(0kl) and {11l}(hkl), respectively on annealing in pure hydrogen of dew point, < — 60°C. H2S doping of the hydrogen or annealing in commercial argon was found to effect a reversal for the vacuum-remelted alloy from (111) to (100) secondary recrys-tallization, while prolonged vacuum annealing at 2 x 10-6 Tow resulted in a tertiary re crystallization from (111} to (110). The growth selection of the {lll}(hkl) component was found to be governed predominantly by the {111}/planar misorientation, the maximum deviation of the resulting secondaries being 5 deg. It is considered that the driving force for {111}(hkl) secondary recrystallization arises from the preferential lowering of ?111, possibly by phosphorus or nitrogen diffusion, just as oxygen and sulfur under certain conditions have been found to preferentially lower ?100. When heavily cold-rolled metals are annealed at high temperatures, primary recrystallization usually occurs rapidly and may be followed by considerable grain growth. However, in the presence of a fine dispersion of inclusions1"3 or with a strong matrix preferred orientation4&apos;&apos; the matrix may be stabilized and a secondary recrystallization may then be effected. Also, in vacuum-melted Si-Fe it has been shown possible to develop {100}(001) and {110}(001)6 surface energy driven secondary recrystallization textures. Further, it has been found that, on annealing very pure metals, grain growth normally ceases when a grain size approximately twice the strip thickness is acquired, due to the formation of V-shaped thermal grooves which result in an equilibrium being set up between surface and grain boundary stresses. If, however, a surface energy difference ??s, exists between adjacent grains (of the order of a few percent of the grain boundary energy ?b), then according to Mullins8 a secondary recrystallization may be effected, since the grains having lowest ?s would grow at the expense of their higher-energy neighbors. For clean bee metal surfaces ?110 should be lowest; however, for 3 pct Fe-Si (100) secondary structures have frequently been developed and have been attributed by Walter and Dunn9 to an alteration of the relative surface energies due to the preferential chemisorption of oxygen on (100) planes. Kohler,10 however, indicated that this reversal may be achieved by employing minute quantities of highly polar compounds in the annealing atmosphere, i.e., sulfur compounds, in par- ticular H2S being beneficial in (100) growth. This work has been verified by Kramer" using {100)/{110} bicrystals, while Mager12 demonstrated the importance of sulfur diffusion within the strip. Detert13 has intimated that carbon may be responsible for the preferential lowering of ?110 although no direct evidence has appeared yet to support this supposition. It must , be appreciated that the above-mentioned examples of surface energy driven secondary recrystallization were obtained with very pure vacuum-melted materials with oxygen contents (which is now known to be a critical factor") less than 35 ppm. During the course of a textural study on Si-Fe it has been found that under certain conditions (111) secondary recrystallization can be obtained by what is believed to be a surface energy growth selection mechanism. The purpose of the present paper is to briefly describe this result and to try and postulate the possible causes. EXPERIMENTAL Two vacuum-induction-melted, nominally 3 pct Si-Fe alloys were produced, one from pure electrolytic iron and semiconductor-grade silicon designated A and the other from commercial-purity hot band, designated B.

Jan 1, 1969

W. N. Triplett (Geology of the Silver-Lead-Zinc Deposits of the Avalos-Providencia District of Mexico, P. 583) was born in Tecumseh, Mich., and attended the University of Michigan and Massachusetts Institute of Technology. From 1912 to 1917 he worked for Moctezuma Copper Co., a Phelps Dodge subsidiary at Nacozari, Sonora, Mex. He served in Army as Second Lieutenant Field Artillery from 1917 to 1918 and from 1919 to 1922 returned to Moctezuma Copper Co. From 1922 to 1952 he has been with Compania Minera de Penoles, S. A., a subsidiary of American Metal Co., Monterrey, N. L., Mexico in Unit Dept. as chief geologist and at present is consulting geologist. Mining geology and operation is of particular interest to Mr. Triplett. He presented a previous paper before with M. W. Hayward entitled, "Occurrence of Lead-Zinc Ores in Dolomitic Limestones in Northern Mexico." Besides being an AIME member, he holds membership in Society of Economic Geologists. Fishing, hunting and photography are his favorite hobbies.

Jan 1, 1952

By Jonathan G. Price

Silver-copper-lead deposits In Precambrian, Permian, and Cretaceous red-bed sequences near Van Horn, Texas, have the following features In common: (1) mineralization controlled by steeply dipping fractures in sandstones, (2) lack of ore in overlying and interbedded limestones, (3) absence of igneous intrusions, (4) sulflide ores without typical hydrothermal gangue minerals, and (5) associated arsenic, molybdenum, zinc, and cadmium but not gold. Ore was probably deposited along fractures by reaction between low-temperature, oxidizing, metal-rich ground waters and sulfide-bearing waters or rocks. Detailed mapping and studies of fracture patterns indicate that mineralization occurred during Basin and Range extensional deformation, thereby postdating major Trans-Pecos igneous activity.

Jan 1, 1984

By M. P. Board, M. J. Reus

Instrumentation was installed during construction of the Silver Shaft in northern Idaho to evaluate lining behavior and rock deformation. Rock mass displacements were monitored with multiple-position borehole extensometers. Liner stress and strain were measured with concrete pressure cells and embedment strain gages. Rock displacement data from the 5,955-ft level indicate rock mass anisotropy. Liner stress and strain data reflect high in situ stresses and nearby station and raise construction. Continued monitoring and preliminary analysis indicate that concrete-lined, circular shafts are stable for high, unequal stress fields and anisotropy in deep level mines.

Jan 1, 1984

Jan 1, 1941

By E. W. Stewart, G. P. Conard, J. F. Libsch

The effects of several additives upon the reduction characteristics of hydrogen-reduced ferrous formate are described. The various additives inhibit sintering of the reduced iron particles by apparently different mechanisms. The magnetic properties of the low density compacts produced from the resulting ultra-fine iron powders were improved markedly. THE permanent magnetic characteristics of ultra-fine iron powder prepared by various means have been a subject of considerable interest and experimentation in the past few years. When such particles are small enough to show single domain behavior, they possess&apos; 1—permanent saturation magnetization, and 2—high coercive force. In the absence of domain boundaries, the only magnetization changes in a particle occur through spin rotation which is opposed by relatively large anisotropy forces. With decreasing particle size, the coercive force tends to increase to a maximum and then decrease because of the instability in magnetization associated with thermal fluctuations. Kittel&apos; has calculated the critical diameter at which a spherical particle of iron can no longer sustain domain boundaries or walls to be approximately 1.5x10-&apos; cm. Stoner and Wohlfarthr in England and Neel4,6 in France have shown from purely theoretical calculations that the high coercive force expected from single domain particles is dependent upon crystal anisotropy, shape anisotropy, or strain anisotropy contributions. Further work by Weil, Bertaut,&apos; and many others has contributed much to the understanding of fine particle theory. Neel and Meikeljohn" have demonstrated that a decrease in particle size below a critical value of approximately 160A leads to a quite rapid decrease in coercive force because of the prevention of stable magnetization by thermal agitation. Lih1, working with powders prepared by the reduction of formate and oxalate salts of iron, has shown the marked influence of powder purity upon magnetic properties. Maximum coercive force was obtained in powders of approximately 65 pct metallic iron content while the maximum energy product, (BxH) occurred in powders of 85 pct metallic iron content. Careful consideration of the preceding theoretical considerations and experimental results has led to the manufacture of permanent magnets from ultra-fine ferromagnetic powders by powder metallurgy techniques. Such work has been done by Dean and Davis," the Ugine Co. of France, and Kopelman." The aforementioned work of Kopelman and the Ugine Co. was concerned somewhat with the effect of various additives upon the properties of hydrogen-reduced ferrous formate. Virtually no work, however, has been published on the effects of additives on the reduction rates of metal formates, although unpublished work by Ananthanarayanan16 howed promise of improved energy product in ultra-fine iron compacts prepared by the hydrogen reduction of a coprecipitated mixture of magnesium and ferrous formate. After consideration of the preceding information, it was hoped that a better balance between the metallic iron content and particle size of the reduced iron powder could be accomplished by a prevention of the attendant sintering of the partially reduced iron powder during the reduction reaction. It appeared possible that magnesium oxide might interpose a mechanical barrier between adjacent iron particles and prevent their sintering together, while metallic cadmium and metallic tin would interpose a liquid barrier which might accomplish the same purpose. The degree to which these materials were effective in accomplishing the foregoing objective and the experimental details associated with the work are reported in the following sections of this paper. Experimental Procedure Preparation of Formate and Oxide Mixtures: To obtain ferrous formate of reproducible reduction characteristics, a slight modification&apos; was made in the technique of Fraioli and Rhoda." A supersaturated solution of ferrous formate was mixed with an equal volume of 95 pct ethyl alcohol and the formate crystals precipitated by stirring and screened to —325 mesh. These crystals were in the shape of elongated hexagons, approximately 4x10 micron in dimension. Various preparations of such ferrous formate, designated as lot 111, were reduced for 2 hr, yielding ultra-fine iron particles of exceedingly reproducible size, metallic iron content, and magnetic properties. The magnesium and cadmium formates were prepared by the reaction of dilute formic acid with their respective carbonates, while the tin formate was prepared by the reaction of dilute formic acid with stannous hydroxide. To evaluate the effect of metallic formate additives in intimate mixture with the ferrous formate, varying amounts of magnesium, cadmium, and tin formates were coprecipitated with the latter. The designations of these materials and their chemical compositions are given in Table I. Due to the differing solubilities of the various formates in aqueous media,

Jan 1, 1956