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By R. J. Linney

Reserve Mining Co. produces 5 million tons of iron ore pellets per year. The finished product runs about 65.50 pct Fe, with 7.75 to 8.00 pct SiO2. Less than 12 pct arrives at the blast furnaces smaller than % in. This plant was originally designed to produce 3.75 tons annually—not 5 million. To handle the increased tonnage a fifth fine crushing line was added, and some very minor changes were made. When production can be stepped up 33 1/3 pct without extensive additions or changes—within the short period of a year—basic engineering has been sound. Operators of the plant consider it the best design job they have seen or heard of, and competent authorities have said that start-up was quicker and easier than for any previous large-scale minerals beneficiation plant. One big advantage is the elbow room allowed. Generally speaking, there is an eternal conflict between operator and designer over space. The designer has his costs per cubic foot, and he is keenly aware that if he permits the number of cubic feet to rise unnecessarily, total costs will be too high. But this was a new operation, and on a large scale. There were no proven standards to go by. Realizing this, Reserve's engineers provided ample and efficient access to machinery, allowing extra space for unanticipated situations. In three years of production this planning has paid off handsomely. Gravity Flow Saves Time and Money: This plant is on a rocky hillside, the car dumper about 270 ft above Lake Superior. In locating buildings and placing machinery the designers mad= good use of gravity flow, at considerable financial savings. In the concentrator building from rod mills to filters, gravity carries the material between all stages of the operation except one—the closed circuit pumping of concentrate between cone classifiers and ball mills. Since no machine is located directly above any other, an observer can stand on the truck ramp adjacent to the offices and laboratory and see practically every phase of activity in the huge building. The first mill section started in August 1955. After a day's run several modifications were made on auxiliary chutes and launders where spillage had occurred. This procedure was followed for the first

Jan 1, 1960

By J. E. Tobey

UNQUESTIONABLY, manufactured gas will stage a comeback of such huge proportions as to dwarf its previous history. Timing will depend on two things: the diminishing supply of natural gas and the perfecting of processes for large-scale production of high-Btu gas from, coal. What the timing will be, and how soon the new era will begin for manufactured gas, no one knows. It may be just around the corner and it may be several years, but it is certain to come. It will depend on economic changes, and any major world upheaval might accelerate it tremendously. Supplemental gas for pipelines will come no doubt from two sources at least: (1) synthetic-fuel plants of the coal-chemical group, which produce chemicals and liquid fuels with a tail gas high in methane as a by-product; and (2) large-scale gasification plants, which will produce high-Btu gas entirely or as a major product with chemicals and liquid fuels as by-products. There is important activity at the present time, in the development of new processes and the improvement of those now in existence. The first large-scale gasification plants of the second category probably will be strategically located in the coal fields on or near the long-distance transmission gas lines, and these plants probably will operate jointly with large natural gas storage fields. Inasmuch as virtually all the major gas-transmission lines cross one or more coal fields, such locations will not be difficult to find. It will be a practical necessity to produce a high-Btu gas -that is, 750 to 1000 Btu-in order to maintain the capacity of the main transmission lines and local city distribution systems and further to eliminate the problem of appliance changeovers in the cities. If gasification plants on a medium or smaller scale prove to be economical, local gas utilities no doubt will consider .the construction of such plants to supplement their supply of natural gas. If low-temperature distillation processes like those now being developed by the Pittsburgh Consolidation Coal Co. are successful, and there is reason to believe that they will be, utilities that supply both gas and electricity to communities would find this method particularly attractive, as they could burn the char product directly under power boilers, thereby minimizing thermal

Jan 1, 1953

By Ralph Hultgren, Prodyot Roy

Manganese vapor pressures from 1250° to 1500°K were measured by conventional Knudsen and torsion-effusion methods in twelve Fe-Mn alloys with compositions from 9 to 80 at. pct Mn. The Knudsen re-sults agveed approximately with previous measurements found in the literature which indicated the solutions were nearly ideal. However, except for the higher manganese compositions, the initial torsion readings indicated much (up to 50 pct) higher vapor presszcres than the Knudsen method. These high readings decreased steadily with time. The results are interpreted as due to depletion of surface concentration of manganese during evaporation. Thus the initial torsion readings are the most nearly correct and Knudsen methods on alloys are to be regarded with suspicion unless it can be demonstrated that diffusion rates are rapid enough to replenish surface concentrations depleted by evaporation. For the lowest manganese contents and highest temperatures, depletion causes initial torsion readings to be too low. FEW thermodynamic data are available for alloys of the high-melting transition metals due primarily to experimental difficulties at the high temperatures involved. Measurement of vapor pressure is one of the most promising techniques to be applied to this problem. From the vapor pressure of a component of an alloy phase, its activity or its partial molar Gibbs energy can be directly calculated. From measurements over a sufficient range of temperatures and compositions the partial and integral Gibbs energies, enthalpies, and entropies may be determined through Gibbs-Duhem integration. For solid phases of variable composition, which commonly are found in alloys, measured vapor pressures are low because of depletion of the surface concentration of the more volatile component as it is selectively vaporized. Diffusion from the interior tends to restore the depleted concentration. The seriousness of the effect depends on the relative rates of diffusion and vaporization. Although depletion has been recognized as a factor,' direct measurements of its rate are lacking and quantitative estimates of its effect on measurements are uncertain. In the present work the vapor pressures above a series of Fe-Mn alloys have been measured by the torsion-effusion method. This method permits a measurement of the vapor pressure of manganese as soon as the sample comes to temperature and continuously throughout the run. The rate of decline of the apparent vapor pressure measures the rate of depletion and the torsion reading at zero time should be correct. At high manganese concentrations (70 and 80 at. pct Mn), the torsion reading remained nearly constant; surface depletion was negligible. There was a slow drop in measured pressure due to bulk loss of manganese from the sample. However, for lower manganese contents, especially at high temperatures, the depletion effect was considerable and the apparent vapor pressure decreased steadily with time. For these alloys the Knudsen method should give pressures which are too low. The measurement of pressure in the Knudsen method cannot be made until enough manganese has been vaporized to be weighable. The Knudsen result is therefore an integrated average between the initial and final vapor pressures. To verify this, conventional Knudsen measurements were also made with results in approximate agreement with previously published Knudsen measurements for these alloys. As expected, for the lower manganese contents the initial torsion readings of pressure were as much as 50 pct higher than the Knudsen. THE APPARATUS The apparatus, shown in Fig. 1, is capable of operating to temperatures up to 2000°K. A vacuum of 5 x 10"6 mm Hg can be maintained. Temperatures were measured to +3° by a W-Re thermocouple placed in the dummy cell, N. The torsion cell consisted of two alumina crucibles with holes in their covers. They were placed in the molybdenum holder shown suspended from the torsion wire. Rectangular torsion wires (1 by 4 mm) were found to have superior sensitivity and less residual distortion than circular (2-mm-diameter) wires. The precision of angular measurement was found to be *0.025 deg; the variation is no doubt due to temperature fluctuation and vibration. For the Knudsen experiments the alumina cell was set on the support, N. SAMPLE PREPARATION 800-g samples were prepared by melting together electrolytic iron and electrolytic manganese and pouring the melt into a water-cooled copper mold. Melting and pouring were done under a helium at-

Jan 1, 1965

By T. C. Atchison, W. I. Duvall

Over the past ten years a series of investigations have been conducted to determine some of the pnysical processes involved in breaking rock with confined concentrated charges. Detailed discussions of many of these investigations have been published elsewhere.1-6 Laboratory experiments made by other investigators using Hopkinson pressure-bar techniques have shown that solid materials are fractured in tension by the reflection of an incident compressive stress pulse at a free surface.7-12 In these tests a small charge of explosive is placed in contact with one end of a bar. Detonation produces some plastic flow and crushing of the bar near the charge and generates a compressive stress pulse that travels along the length of the bar. At the free end of the bar the compressive stress pulse is reflected back into the bar as a tensile stress pulse. If the tensile strength of the bar is exceeded during this reflection process, a tensile fracture normal to the length of the bar is produced, and the broken end of the bar moves forward with a constant velocity equal to the average particle velocity trapped in the broken fragment. The new surface formed by the fracture becomes the new free end of the bar that reflects the remaining portion of the incident compressive stress pulse. This process is repeated any number of times until all of the incident stress pulse is reflected. Hino has demonstrated this kind of breakage for three rock types—marble, granite, and sandstone." He has defined a blastibility coefficient, B, as the ratio of compressive strength, C, to tensile strength, T, thus: C The quantity B is the maximum number of slabs that can be produced by reflection breakage. Normally fewer slabs are produced because of loss of energy as the stress pulse travels through the rock. Fig. 1 illustrates reflection-type fracture for a triangular compressive stress pulse. The number of slabs produced by the reflection breakage process is the first whole number less than the ratio of the peak stress of the incident pulse to the tensile breaking stress of the solid. Thus the number of slabs is given by the thickness of each slab is given by and the total length of rock broken is given by N = number of slabs S - peak stress in incident pulse T = tensile strength of the rock F = fall length of incident stress pulse h = thickness of each slab D = total length of rock broken During the reflection process the particle velocity at the free surface is twice the particle velocity in the incident stress pulse. Thus the velocity with which the broken fragments move forward is given by where v, = velocity of broken fragment, and v = average particle velocity contained in that portion of the incident pulse trapped in the broken fragment. Results of these laboratory experiments cannot be applied directly to rock blasting where the explosive charge is placed in a drillhole. In laboratory tests the charge is unconfined and in contact with the rock in only one direction. In a drillhole additional confinement is offered by the rock surrounding the charge and by the stemming placed above it. This additional confinement may be enough to allow the explosive gases to do additional work on the rock during their expansion. Other writers have discussed possible effects of gas expansion'on rock breakage.13-10 However, very few experimental data are available to determine to what extent expansion of the gases is responsible for rock fragmentation. The USBM has studied the physical processes involved in breaking rock with confined concentrated charges by using simple crater tests breaking to one free surface. Crater tests have been performed in four rock types: granite, sandstone, marlstone, and chalk. Table I gives some physical properties of these rocks. Fig. 2 shows plan and section drawings of two typical crater tests and illustrates some of the test variables measured. For these tests the charge was placed at the bottom of the drillhole and primed with an electric cap. The hole was stemmed to the collar with sand and the charge detonated. Size and shape of the crater were measured after it was cleared of broken rock. As a given charge size was buried deeper in a drillhole, the crater depth usually was equal to or

Jan 1, 1960

By R. J. Burgess, A. R. Ramey, A. R. Adams

During interpretation of pressure buildup tests on gas wells in a tight dolomite gas reservoir, peculiar behavior was noticed. Two straight lines were apparent. Effective permeability to gas taken from either straight line was about the same, and the Miller-Dyes-Hutchinson dimensionless time check for the straight line was proper for both straight lines. Geological data indicated the likelihood of scattered trending fractures in the reservoirs. Since the first straight Iine yielded permeability values close to the geometric mean permeability from core analyses, it was postulated that the reservoir model was that of an acidized well completed in the tight dolomite, but that widely scattered hairline fractures caused the mean permeability of the reservoir distant from the well to be higher than the matrix permeability. Because all other studies of fractured reservoirs to the authors' knowledge assumed that the fracture matrix was dense enough to communicate directly with the well, no interpretative methods were available. The Hurst line-source solution for a radial change in permeability for interference between oil reservoirs was adapted to pressure buildup testing. The result indicated that the first straight line should yield the proper matrix permeability and wellbore skin effect. The second straight line may be extrapolated to obtain static pressure. The time of bend between the straight lines was used to estimate distance to a fracture. Application to field test data is shown. It is believed that the methods developed and the case history presented will add to present tools available for pressure buildup interpretation. Introduction Since the pioneer studies by Miller, Dyes, and Hutchin-son1 and Horner' in 1950 and 1951, well test analysis has become recognized as one of the most powerful tools available to both production and reservoir engineers. Well test analysis serves as a logical basis for well stimulation and completion analysis, and for long-term reservoir engineering. Since the early 19501s, much effort has been placed on the development of well-test analytical methods. Reservoir and well conditions of increasing complexity have been considered systematically to provide the analyst with a catalog of causes and effects. Matthews and Russella state that some 200 papers dealing with this subject have been published in the last 35 years. Developments in well test analysis appear to have originated in one of two ways. Either a physically realistic field condition was anticipated and analytical solutions for the condition achieved, or anomalous field test behavior was recognized and interpretative methods sought for the anomaly. In recent years, it has appeared that the latter has inspired an increasing number of studies. The analyst today finds an increasing number of known cause and effect studies available for well test analysis, the classic of which is that of finding the specific flow problem that generated the answer — the well behavior. Although it may be impossible to achieve this goal uniquely, the analyst often is able to select a useful interpretation that combines all known performance and geologic data — or to show that various logical alternatives would not significantly affect the interpretation. During a recent reservoir study, we observed gas well test behavior that did not appear to fit behavior described previously. Although it cannot be said that we have found a unique interpretation, we shall present in this paper the peculiar behavior observed, and describe the reservoir and interpretative methods developed. Reservoir Description The subject gas reservoir is a 9-mile-long, narrow dolomite reservoir lying within a limestone of Ordovician age. (See Fig. 1.) The dolomitized rock in the field consists of dark brown to buff, dense to coarsely crystalline, vugular dolomite containing numerous hairline fractures, many of which may have been closed in the reservoir and parted when cores were brought to the surface. Larger fractures are also apparent in core, but usually are filled and sealed with euhedral dolomite crystals. Portions of the north flank of the reservoir are known to be cut by a sealing fault downthrown to the north. Gas wells located near the fault have higher open flow potentials than those more distant from the fault. This is believed to be a result of higher permeability near the fault due to more extensive and open fractures. Detailed coring and core analysis have been performed on several of the wells in this reservoir. Fig. 2 presents permeability variation' plots for both horizontal and vertical

Jan 1, 1969

By R. W. Fountain, John Chipman

The solubility of nitrogen in Fe-B alloys (0.001 to 0.91 pet B) is determined by the Sieverts' technique for temperatures of 950° to 1150°C. The activity coefficient of nitrogen is decreased by boron. The three-phase equilibrium between ? iron, BN, and gas is established and also the four-phase equilibrium between iron, BN, Fe2B, and gas. The above equilibria are calculated for a iron. The relation of these data to hardenability and strain aging of boron-treated steels is discussed. BORON additions are known to enhanbe the hardenability of heat-treatable steels and to assist in the control of strain aging in sheet steel for deep drawing. The increase in hardenability is explained by the theory that adsorption of boron on austenite grain boundaries reduces their free energy and thus retards ferrite and upper bainite nucleation.l,2 Digges and Reinhart3 have shown that the full effectiveness of boron in commercial steels is achieved only when strong nitride formers such as titanium and zirconium are also present. The influence of nitrogen on eliminating the boron contribution to hardenability was also demonstrated by Shyne and Morgan.4 These workers prepared Ni-Mo steels containing either nitrogen or boron or nitrogen plus boron. The nitrogen-plus-boron steels showed the lowest hardenability which was attributed to the presence of stable nucleating particles, presumably nitride. Morgan and Shyne5-7 have shown that boron in the amount of 0.007 pet will completely eliminate strain aging due to nitrogen in low-carbon, open-hearth steels. In addition, by proper control of the boron additions, a rimming steel can be produced. Since the effectiveness of boron on hardenability and eliminating strain aging is influenced by the amount and distribution of the nitrogen in the steel, the present study was. undertaken to determine the influence of boron on the solubility of nitrogen in iron. EXPERIMENTAL PROCEDURE The solubility of nitrogen in Fe-B alloys was measured by the method of Sieverts, which consists of determining the amount of gas dissolved by the metal in a constant volume system. The apparatus employed in this investigation and the experimental details have beendescribed previously.B AMcLeodgage was added to the apparatus to allow measurements at very low pressures. The alloys were melted at reduced pressure in a basic-lined induction furnace using electrolytic iron and ferroboron. Ferroboron was added after the primary deoxidation of the iron with carbon. Since it was difficult to attain a constant low level of oxygen by this procedure, silicon was added after the carbon deoxidation and prior to the ferr obor on addition. The alloys were castas 2-in. sq ingots, heated in argon at 1050loC, and forged to 1/4-in. plate. After forging, 1116 in. was machined from each side of the plate to remove any possible contamination, and it was then cold-rolled to 0.010-in. sheet. The sheet was cut into approximately 1/4-in. squares and pickled in an inhibited H2SO4 solution to ensure a clean surface. In the case of the boron alloys, a hydrogen treatment could not be used for surface cleaning because boron losses resulted. The composition of the alloys is given in Table I. For a solubility determination, a 75-g sample was inserted in a quartz tube and sealed in place in the apparatus. The entire system was evacuated at room temperature and leak tested for 24 hr. If no leaks were observed, the system was heated to the temperature of measurement and again leak tested for 24 hr. If no leaks were detected, the hot volume and solubility determinations were begun. The hot volume was determined at a constant temperature for each run by admitting successive amounts of argon and recording pressure vs volume, which, in all cases, resulted in a straightline relationship. The argon was then removed and the procedure repeated with nitrogen. Successive additions were made until the desired nitrogen content of the metal and equilibrium pressure of the system were obtained. The

Jan 1, 1962

By E. Martinez

Samples of chrysocolla, a hydrated copper silicate, from several sources were submitted to differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). Pure samples of chrysocolla are difficult to obtain, but comparison of the thermograms revealed that certain reactions occurred in all the samples and it is believed that these are due to chrysocolla. Endothermic reactions occurred at 50' to 175°C, 350° to 650°C, and 980° to 1100°C each of which caused a weight loss. The first was due to loss of absorbed water, the second to a dehydroxyla-tion, and the last to conversion of cupric oxide to cuprous oxide. In addition, two exotherms were detected at 685° to 695°C and 935° to 950°C. Infrared spectra of heated samples indicated the exotherms were due to changes in the Si-O bonds leading to the formation of cristobalite. The results suggest that thermoanalysis may be a more sensitive and reliable method for detection and identification of chrysocolla than X-ray diffraction, infrared spectroscopy, or optical techniques. The recovery of copper from oxide ores has been the subject of much research in recent years. One of the principal oxide copper minerals is chrysocolla, a hydrated copper silicate. The information available indicates that it has widely varying properties depending on the origin of the sample. Chrysocolla usually is found associated with cuprite, malachite, azurite, and native copper. Most of these other minerals are recoverable by present day flotation practice, but chrysocolla is lost in the tailings.1,2 Reagent combinations that are successful in laboratory chrysocolla flotation with ore from one source have been found to be ineffective with another. 3 The copper segregation process offers an altemative to beneficiation of oxide copper ores.4'5 The process is of particular interest in processing ores that cannot be treated by conventional hydrometal-lurgical methods because of high acid consumption.6 Fuller understanding of the properties of chryso- colla may prove of value in the search for improvements in both the flotation and segregation processes. Chrysocolla samples from Arizona, Nevada, Chile, Australia, and South Africa were studied by differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). In addition, a sample from Miami, Ariz., was submitted to X-ray diffraction, infrared spectrophotometry, and surface area determination. EQUlPMENT Differential thermal analysis (DTA) detects, amplifies, and records exothermic-endothermic reactions occurring in a sample as its temperature is raised at a constant rate, usually 10°C per minute. A unit made by the Robert L. Stone Co. was used in this study. The tests can be run if desired with a gas streaming through the sample. A thermobalance records weight losses or gains in a sample as its temperature is raised at a uniform rate. The gravimetric analyses (TGA) were run on a Chevenard thermobalance converted electronically for graphic recording. A heating rate of 5°C per minute up to 1100°C was used in these tests. A Perkin Elmer Infrared Spectrophotometer, Model 221, was used with sodium chloride optics obtaining IR spectra in the 2 to 15 region. A pressed pellet technique with potassium bromide was used in preparing the samples. DESCRIPTION OF SAMPLES Chrysocolla is found in the oxidation zones of copper deposits commonly associated with malachite, azurite, and limonite. It is described as varying in composition and in color from bluish green to brown or black. Inclusions of other minerals are usual so chemical analysis of chrysocolla samples may be suspect. However, it is considered by many to be a solid solution of CuO, SiO2 and H2O with a general formula of CuO.SiO2.2H2O or 2CuO.2SiO2. 3H20. Chukhrov7 has described a sample from the Urals as CU3,5(OH)2 (A1Si3) O10.nH2O and stated that chrysocolla is a montmorillonite-type mineral. On the basis of X-ray analyses, DTA, and infrared spectra of chrysocolla from the Inspiration Mine, Ariz., Sun8 concluded that there was no substantial evidence to classify it as a montmorillonite mineral. Chrysocolla samples from many sources throughout the world were used in this investigation. The following is a brief description of each:

Jan 1, 1963

By Earle C. Smith

The Chairman.—Mr. Earle Smith has kindly offered to make some remarks in connection with segregation in the product, Mr. Smith: E. C. Smith,* Cleveland, Ohio—I will start this Off by a story oF the code days of the American Iron and Steel Institute. In those days, Republic did not have a big strip mill, and the question came up of the check analysis of rimmed steel. I suggested that they let me be the chairman of the Committee on Accumulating the Information on the Variation of the Composition of the Ingots of Rimmed Steel. Somebody wanted to know why I wanted to be the chairman. I said, "we don't make any of the big ingots of rimmed steel, and no matter who makes them they are so bad that you don't dare publish the information. So if 1 collect it and hide it you can't charge me with having done anything that really disrupted the commercial situation." So, everybody furnished me with a rather complete story as to the horrible variations in big rimmed ingots. I took it out to my house and put it away, and it is still there. Now, segregation in the big ingot is no longer an "academic " matter as far as I am concerned. I am in a situation like that of the German who was told in 1956 about the coming war. He said: "until it is your throat that is going to be cut, you don't pay any attention to what is happening to the otherman." 'That is the way with the problem that we have in front of us. Recently I have been told that the 'Omptroller was questioning the payment for certain articles of stamped steel that had been made from rimmed steel, because upon check analysis of the rimmed steel it had been determined that these stamped articles were nut within the compositions that were included in the specification, and therefore he as the camptroller had no alternative. It was not meeting the specification; therefore, no payment. So I I say to all of you: You can very seriously consider this matter of segregation now and on into the future on the basis of the fact that it is actually going to cost your companies, which are making these products, money unless there is some new idea about the infallibility of quantitative , chemists who analyze some of these products or lawyers who read specifications, I don't know which man is going to be the major factor in the future. if the National Bureau of Standards could in some way show the specification writers the variation between good chemists analyzing for That they expect to be umpire eel. the writers would certainly realize that some of the to to which we have calmly signed our names as being O.K. are— well, as one man said to me, they might be filled by the devil, and they certainly could be filled by the Lord, but they could not he me by mankind. I would like to inject two or three things into a segregation study which I Want you to think about, because 1 would be a little surprised if there is very much discussion of them, In the first place, we generslly make steel in the United States in the basic open hearth, and I do not think there has bee,, nearly enough consideration given to segregation German the bath before it moves into the ladle. I am sure that any of the people who handled the 9400 series of the NE series when it contained the 0,60 per cent silicon have more respect than they had previously for the segregation that is within, the ladle; that is, before the metal reaches the ingot mold, the frozen ingots and the segregation in them. Another pint to which I think We ought to sis serious consideration is the segregation of iron oxide in the ingot-iron type of material, where the distinction between that and the steel segregation is that it is actually segregat. ing iron oxide, Normally we are segregating some form of carbon or sulphur, or something like that, with the stamping steel industry now coming down into the ranges of chemistry, where the segregation of iron oxide will be just

Jan 1, 1945

By W. O. Philbrook, H. E. Burner, F. S. Manning

The equation of continuity for the hydrogen reduction of hematite in a fixed bed of closely-sized particles is solved assuming a flat velocity profile, negligible temperature gradients, md negligible axial diffusion. A kinetic expression from the literature is used which assumes the reduction process is controlled at the oxide-metal interface. The integral fractional conversion is computed, and the importance of particle diameter, flow mte, temperature, bulk axial diffusion, and inter- and intra-particle mass trarnsfer is predicted. Comparison with experimental data suggests one or more additional undefined variable(s) is significant. Equipment modifications are suggested for fidture experimentcll work. WITH the increasing desire to "design" the ore feed of a blast furnace, it has become necessary to define more quantitatively the process variables and to evaluate the extent of their control upon the reduction process. The bulk of the work reported in the literature has centered about the reduction of single particles; however, the blast furnace process more closely resembles reduction of a fixed bed than that of single particles. To simplify this analysis, the isothermal reduction by hydrogen of a natural hematite in a fixed bed of closely-sized particles is examined. With appropriate modifications in the kinetic and flow rate expressions, the approach employed should be extensible to mixtures of carbon monoxide, hydrogen, and inert nitrogen, and to adi-abatic conditions, thus approaching the blast furnace process more closely. The fixed bed variables which are investigated in this study are particle diameter, flow rate, temperature, and bulk axial diffusion, as well as inter-and intra-particle mass transfer. Of particular interest is the effect of particle size upon fractional conversion for a bed operating under constant pressure drop. The constant pressure drop concept bears a close resemblance to the blast furnace process, where regions of larger particles may provide a greater permeability to divert most of the reducing gas flow from the regions of smaller ore particles. Under such conditions one would expect qualitatively that, for sufficiently small particle sizes where the flow rate is small and the total surface area is large, the reduction rate would be limited by the gas flow rate. Initially the gas entering the bed reacts very rapidly and the composition approaches the equilibrium conversion value a short distance from the reactor inlet. This concentration "wave-front" then moves up the bed as the flow of reducing gas is continued, leaving in its wake an ever increasing layer of reduced particles. Providing that the reducing gas leaves the bed at equilibrium concentrations, conversion is expected to increase with an increase in flow rate, and hence with an increase in particle diemater. Conversely, for sufficiently large particles the flow rate will be high but the surface area available for reaction will limit the reduction rate. Since the total surface area decreases with an increase in particle size, conversion, in this case, is expected to decrease as the particle diameter is increased. It is clear then that between these two extremes an optimum particle diameter must exist. THEORETICAL DEVELOPMENT Above the temperature where wiistite is stable (about 560°C) the reduction of hematite proceeds through the series Fe2O3/Fe3O4/FeO/Fe. On the basis of microstructural studies and earlier work, Edström1 has postulated a mechanism for the reduction of an ideal hematite lattice: 1) Iron phase formation at the boundary between wiistite, iron, and gas (for sufficiently porous iron). 2) Diffusion of iron across a wustite layer. 3) Phase boundary reaction of Fe3O4 to FeO. 4) Diffusion across a dense magnetite layer. 5) Phase-boundary reaction of Fe2O3 to Fe3O4. According to the mechanism postulated, gaseous reaction product has to be removed only at the boundaries between wüstite and iron or gas, the only possible exception being enveloped Fe3O4 specks. On this basis McKewan2,3 has proposed that one may consider the hematite reduction process as a simple two-phase system of oxide/metal. If, for FeO and Fe3O4 layers of negligible thickness, the hypothesis is made that the rate of formation of a

Jan 1, 1963

By Alan Stanley

THE Maclntyre Development of National Lead Co. is located at Tahawus, N. Y., in the heart of the Adirondack Mountains. Operations involve the mining and concentrating of a titaniferous iron ore to produce ilmenite and magnetite concentrates. A general description of the operation and metallurgy has been given by Frank R. Milliken.1 Pigment plant production demands that the MacIntyre mill produce a 44.7 pct. TiO2 ilmenite concentrate. To achieve the required ilmenite grade and tonnage it is important that the table concentrate grade be closely controlled. Unfortunately, however, the titaniferous orebody which feeds the Maclntyre mill is not uniform. Ore dressing characteristics vary from one end of the orebody to the other, and from one level to the next.. The changeable nature of the mill feed precludes a single adjustment of the equipment for long periods of time. Thus the operators must constantly watch the equipment to insure a uniform concentrate from the fine and coarse tables and Wetherills, or dry magnetic separators. Chemical assaying of mill products requires about 4 hr from the time the sample is taken until assay results are obtained, and this is available only on a two-shift basis. The ore may change rapidly, even several times during a shift, so that assay results lose most of their control value by the time they are reported to the mill operating crew. Members of the crew have therefore tried to evaluate the table and Wetherill concentrate by visual inspection, since through long experience the shift operators, under most circumstances, can gage closely the grade of the mill products. However, there are times when the, physical nature of the ore is radically different from normal. Under these conditions visual inspection is of no value, and at such times final ilmenite as low as 43 pct TiO2 has been produced and shipped before the assay results have been received. The specific gravity method of assaying for TiO2 has been attempted to eliminate the shipping of ilmenite below normal grade as well as to help control day to day and hour to hour mill production. Table I shows the minerals found in the Maclntyre ore along with their average weight proportions and specific gravities. The first two products considered for the specific gravity method were fine and coarse table concentrates. It was reasoned that these products were essentially ilmenite with the higher specific gravity gangue minerals. Since they were always produced the same way, and the desired grade of TiO2 was always constant, the specific gravity of these materials would increase or decrease as the amount of ilmenite increased or decreased. Thus for table concentrates which assayed 40 pct TiO2 a constant gravity would invariably be obtained, and as the TiO2 value changed the specific gravity would change in direct proportion. The third product considered was Wetherill ilmenite. It was assumed that a desired grade of 44.7 pct TiO2 would also always contain the same amount and type of gangue minerals along with the ilmenite, and thus would always have the same specific gravity. As the TiO2 value of the ilmenite concentrate changed so would its specific gravity. Dr. Kenneth Vincent, chief metallurgist of the Baroid Division of National Lead Co. at Magnet Grove, Ark., ran specific gravity tests on 17 samples of the desired products. The lowest specific gravity reading assayed the lowest in TiO2 and as the specific gravity increased the trend was for the TiO2 assay to increase, see Fig. 1. Since these results warranted further investigation, a 500-g capacity Torsion balance and 250 ml Le Chatelier specific gravity bottles were obtained. [ ] Shift samples of fine table concentrate, coarse table concentrate, and final ilmenite were tested. Each sample was split and 85 g weighed on the Torsion balance. The Le Chatelier bottle was filled with water to a zero mark. To avoid wetting the neck of the bottle it was found necessary to do this

Jan 1, 1952

By W. B. Morrison

The principal factors influencing the total percent elongation of a lead-tin eutectic and several low-alloy steels which exhibit superplasticity were investigated. These factors are: a) Strain-rate sensitivity of the stress (m). b) Specimen geometry; in particular, diameter-to-length ratio (d0/l0), and surface irregularity (e.g. notches). A feature of the tensile deformation of a superplastic alloy is the early appearance of a neck which continues to extend throughout the test. As a result the total elongation is directly related to the diameter-to-gage-length ratio. The strain-rate sensitivity of the stress varies during extension, mainly because of microstruc-tural changes. A satisfactory correlation exists between the minimum strain-rate sensitivity and total elongation, as indicated in the equation shown below. Notches cause a considerable reduction in total elongation and their effect is greatest at high values of strain-rate sensitivity. An initial notch depth exists below which there is no appreciable effect on elongation. An equation relating elongation to strain-rate sensitivity and specimen geometry is proposed, THE total percent elongation of a tensile specimen is usually regarded as a measure of superplasticity. However, little attention has been given to the fact that total elongation is also a function of specimen diameter and gage length, even though the importance of geometry has long been recognized in the tensile testing of materials in which elongations are relatively small.* In the present study, the effect on superplas- tic extension of the ratio of specimen diameter to length was investigated and an analysis was made of strain distribution along the gage length. Superplastic alloys are characterized by having a flow stress sensitive to strain rate but relatively insensitive to strain.2"' In an earlier study,5 it was found that the strain-rate sensitivity of several low-alloy steels changed during the test and that the minimum value correlated best with total elongation. In the present study, the variation of strain-rate sensitivity during the straining of a lead-tin alloy was investigated. EXPERIMENTAL PROCEDURE Lead-tin eutectic alloy (32 pct Pb 68 pct Sn), made from high-purity lead and tin, was cast in the form of 1-in. diam rod. The rod was cold-rolled in stages to 0.25 in. diam and then swaged to 0.125 in. diam. Samples were cut from the rod at various stages of the mechanical working process. Tensile test specimens were then made by attaching threaded steel ends to the rods by an epoxy-base thermosetting adhesive which required a setting treatment of 2 days at room temperature. The rods were seated in the steel ends in holes approximately 0.01 in. oversize. The test pieces thus made were of various diameters and gage lengths. These were stored at a temperature of about -70°C (-94°F) until required for testing. The distribution of strain along the gage length of a specimen was determined at various stages of the tensile test. The lead-tin alloy was superplastic at room temperature and direct observations during testing were simple. The gage length was divided by reference marks into five initially equal units. These reference marks were made with ink and were reinforced during the test when the initial marks became faint. Photographs were taken, at intervals, of the deforming specimen and measurements of the elongation in each of the gage units were made on these photographs. Tests were also done on several superplastic low-alloy steels whose properties were described earlier.5 The chemical compositions of these steels are given in Table I. A diagram of the notched tensile specimen used in the steel tests is shown in Fig. 1. The specimens were tested at 900°C (1650°F) in a furnace through which a mixture of He + 2 pct H was continuously circulated.5 RESULTS Strain Distribution. Approximately 20 tests on lead-tin alloy specimens were conducted to determine the strain distribution during the test. An example is shown in Fig. 2 of the strain distribution in the gage

Jan 1, 1969

By T. L. Chu, G. A. Gruber

Silica films hare been rleposited 011 silicon substmtes at 400° to 600°C by a chemical-transport technique using hydrogen fluoride as the transport agent ill a closed system. This transport takes place from a source materia1 1071: temperature to substrates at higher temperatures, as indicated by the thermochemistry of the transport reaction. The experimental variables of- the transport process, such as the substrate temperature, the pressure pi the transport agent, and so forth, have been studied. The rate -determining step of the transport process appears to he the ),ale of chemical reaction in the source region. The transported films are similar to thermally grown silica films in physical proper-ties with the exception of 'some what higher dissolrrtion rates. SILICA films deposited on suitable substrates serve many purposes in electronic devices. They are used for the fabrication of tunneling devices, the surface passivation of devices, and the shielding of devices from nuclear radiation: and as selective masks against the diffusion of specific impurities into semiconductors. Doped silica films can also be used as sources for the diffusion of impurities into semiconductors. Several oxidation and deposition techniques for the preparation of silica films have been developed to meet the requirements of these applications. The therma1 oxidation of silicon by oxygen or steam at temperatures above 900 C is commonly used in silicon technology. The deposition techniques are perhaps more advantageous since they usually require lower temperatures and are not limited to silicon substrates. Silica films have been deposited on silicon and other substrates by reactive sputtering and chemical reactions. The sputtering of silicon in an oxygen atmosphere is capable of depositing good-quality silica films on silicon' and gallium arenide. Many chemical reactions are known to yield silica at room temperature or higher. These reactions may involve intermediate steps. However, the final step yielding silica should take place predominately on the substrate surface in order to produce adherent films. When silica is formed in the gas phase by volume reactions, no adherent deposit can be obtained. Generally, the experimental conditions of a reaction can be varied so that the surface reaction predominates over the volume reaction. The chemical reactions which have been used successfully for the deposition of silica films are briefly as follows. The pyrolysis of alkoxysilanes in an inert atmosphere or under reduced pressure has been employed to deposit silica films on germanium3 and silicon4 at 650" to 750°C in a flow system. The deposition of silica films from alkoxysilanes has also been achieved at nearly room temperature by a low-pressure plasma. Device quality silica films have been deposited on germanium and gallium arsenide by the deposition of an amorphous thin silicon film followed by oxidation at 600" to 700" . Silica films for high-temperature capacitors have been produced by the hydrolysis of silicon tetrabromide at 950°C in argon and hydrogen atmospheres.7 We have developed a chemical-transport technique for the deposition of silica films on semiconductor substrates at relatively low temperatures. The thermochemistry of the transport reaction, the experimental variables of the transport process, and the properties of the transported silica films are described in this paper. THERMOCHEMICAL CONSDERATIONS The transport of solid substances by chemical reactions in the presence of a temperature gradient has been used for the preparation of films and crystals of many electronic materials. In this technique, a gaseous reagent is chosen so that it reacts reversibly with the solid substance under consideration to form volatile products. Since the equilibrium constants of most reactions are temperature-dependent, the transport of these products to regions of suitable temperature in the reaction system would cause the reverse reaction to take place. depositing the original solid. When the equilibrium is shifted toward the formation of the solid as the temperature is decreased, the solid is transported from a high-temperature zone to a lower-temperature region, and vice versa. This chemical-transport technique can be carried out in a closed or gas-flow system. In a closed system, chemical equilibrium is presumably established in the different temperature regions of the system, and the transport agent regenerated in the deposition region repeats the transport process in a cyclic manner. The local chemical equilibrium may not be approached in a flow system: however, this system offers a greater degree of flexibility. Silica reacts reversibly with hydrogen fluoride and this reaction was chosen for the transport process. The over-all reaction between silica and hydrogen fluoride may be written as: SiO2(s) + 4HF(g-) = SiF4Ur) + 2H2O(^)

Jan 1, 1965

By J. S. Vanick

AN extremely hard, tough, and strong, white or chilled cast iron has been applied for the past several years to industrial and mining services in which its unusual properties have been confirmed by its ability to deliver in many instances much better performance than plain chilled iron, or other wear-resistant materials. It is being produced regularly by alloying a good base composition of chilled or white cast iron with essentially 4 to 6 per cent of nickel and 1 to 2.5 per cent of chromium. Such a material can attain a hardness exceeding 600 to 750 Brinell as against 380 to 530 for corresponding grades of plain chilled iron. The strength is approximately doubled and the toughness significantly increased. These properties make it especially useful for many applica-tions requiring a high hardness for resistance to wear, abrasion, attrition, deformation; to some extent to high compressive loading and to a lesser but important degree to corrosive action. A wide variety of commercial castings is being successfully produced from this iron, ranging in size from the small-grain grinding plates or burrs through medium-sized castings such as sand pumps up to large, heavy castings such as rolls for metal rolling or cement grinding. The composition of this white cast iron may be roughly bracketed within the range shown in Table 1.

Jan 1, 1933

By J. S. Vanick

An extremely hard, tough, and strong, white or chilled cast iron has been applied for the past several years to industrial and mining services in which its unusual properties have been confirmed by its ability to deliver in many instances much better performance than plain chilled iron, or other wear-resistant materials. It is being produced regularly by alloying a good base composition of chilled or white cast iron with essentially 4 to 6 per cent of nickel and 1 to 2.5 per cent of chromium. Such a material can attain a hardness exceeding 600 to 750 Brinell as against 380 to 530 for corresponding grades of plain chilled iron. The strength is approximately doubled and the toughness significantly increased. These properties make it especially useful for many applications requiring a high hardness for resistance to wear, abrasion, attrition, deformation; to some extent to high compressive loading and to a lesser but important degree to corrosive action. A wide variety of commercial castings is being successfully produced from this iron, ranging in size from the small grain-grinding plates or burrs through medium-sized castings such as sand pumps up to large, heavy castings such as rolls for metal rolling or cement grinding. The composition of this white cast iron may be roughly bracketed within the range shown in Table 1.

Jan 1, 1933

By E. H. Dix, F. Keller

The use of magnesium as an alloying element in aluminum alloys has been limited, in general, to comparatively small quantities. In duralumin-type, strong aluminum alloys, magnesium is present to the extent of 35 to 3/4 per cent. and various grades of Magnalite and the "Y" alloy of the National Physical Laboratory of England contain up to 1 1/2 per cent. In this country small quantities of aluminum alloy sheet containing 4 per cent. magnesium are produced commercially. All commercial aluminum contains sufficient silicon to convert a portion of the magnesium added to the compound Mg2Si. It is well known that the solubility of both magnesium and magnesium-silicide decrease with decrease in temperature. It is, therefore, impossible to separate the age-hardening effect of the magnesium-silicide from that of magnesium, except by the use of aluminum of such high purity that the silicon content is negligible. The present paper is the fifth l, 2, 3, 4 of a series from the laboratories of the Aluminum Co. of America reporting the results of investigations of the equilibrium relations in aluminum-rich alloys made from the high-purity aluminum manufactured by this company. 5 Previous Investigations A number of investigations have been made of the constitution of the complete aluminum-magnesium system and several determinations made

Jan 1, 1929

By F. Keller, E. H. Dix

The use of magnesium as an alloying element in aluminum alloys has been limited, in general, to comparatively small quantities. In duralumin-type, strong aluminum alloys, magnesium is present to the extent of 35 to 3/4 per cent. and various grades of Magnalite and the "Y" alloy of the National Physical Laboratory of England contain up to 1 1/2 per cent. In this country small quantities of aluminum alloy sheet containing 4 per cent. magnesium are produced commercially. All commercial aluminum contains sufficient silicon to convert a portion of the magnesium added to the compound Mg2Si. It is well known that the solubility of both magnesium and magnesium-silicide decrease with decrease in temperature. It is, therefore, impossible to separate the age-hardening effect of the magnesium-silicide from that of magnesium, except by the use of aluminum of such high purity that the silicon content is negligible. The present paper is the fifth l, 2, 3, 4 of a series from the laboratories of the Aluminum Co. of America reporting the results of investigations of the equilibrium relations in aluminum-rich alloys made from the high-purity aluminum manufactured by this company. 5 Previous Investigations A number of investigations have been made of the constitution of the complete aluminum-magnesium system and several determinations made

Jan 1, 1929

By B. Pitchumani, D. Venkateswarlu

INTRODUCTION The characteristics of feed and product of any size reduction operation are normally expressed as mean size, the size corresponding to 80 percent undersize or the percentage below a specified size or specific surface area. But the feed has a distribution of sizes and quite often it becomes essential to obtain a product of desired distribution. In such cases, size distribution of feed is related to product by matrix methods. The technique of matrix representation of crushing operation was proposed by Broadbent and Calcott (1 to 4). They divided the complete crushing mechanism of coal into breakage, selection and classifying functions for a closed-circuit system to establish relations between the feed and product distribution. Ellis, Ray and Venables (6) suggested an empirical method of determining the breakage matrix by combining the characteristic functions and proposed the following hypotheses: 1. The breakage of individual size fractions passing through the mill at a given rate is the same whether passed separately or as part of a mixed feed. 2. The breakage of a mixed feed may be estimated from the products of individual size fractions passed through the mill separately at a rate at which they would be crushed as part of the mixed feed. This method is stated to be applicable when there is no interaction between the individual sizes.

Jan 1, 1980

By S. Y. Han

INTRODUCTION More than 97% of the total uranium production of the United States comes from sedimentary deposits (1). These sandstone deposits were formed by reduction of migrating uranium-bearing solutions from volcanic silicate rock sources. Such deposits occur in two major forms, either as relatively flat, lens-like deposits or as crescent- shaped roll front deposits. The lens-like deposits are found as discrete masses enclosed in reduced sandstone which is generally surrounded by oxidized sandstone. The roll front deposits are found along crescent-shaped interfaces between reduced and oxidized sands tone (2). In-situ mining of selected sedimentary deposits has proven to be a viable method of extraction and competitive with conventional mining for relatively deep low-grade ores (2). In in-situ leaching, uranium is recovered by drilling injection and collection wells in the ore body, pumping a suitable lixiviant to dissolve the mineral, extracting uranium from the pregnant solution by ion exchange, and finally regenerating and recycling the lixiviant. Even though there is increasing interest and practice in developing the in-situ technique for obtaining uranium values from deeper, lower-grade reserves, there is a lack of knowledge of the basic leaching kinetics and combined transport processes. In-situ leaching operations, in general, appear attractive for the following three general types of deposits (2): (1) low-grade surface dumps or deposits which lie above the natural water table,

Jan 1, 1983

By R. G. Davies

THE effect of ordered structures upon steady state creep has not been extensively studied although it has been demonstrated that the brass,' ie,' and Fe3Al3 superlattices increase the creep resistance. Suzuki and Yamamoto observed an acceleration in the creep rate of Ni3Fe below the critical temperature for order, (T, - 505"), for both the ordered and disordered states, and that the activation energy for creep was independent of the applied stress. They concluded that a dislocation climb creep mechanism was operative down to 300°C which is - 1/3 TM where TM is the absolute melting temperature. This is quite remarkable in that it is usually observed that climb controlled creep in both pure metals and alloys ceases below - 1/2 TM (590" for ie). With this anomaly in mind it was decided to reinvestigate creep in a 75 at. pct Ni-25 at. pct Fe alloy. The creep apparatus and operating conditions have already been decribed. Since Ni-Fe alloys order very slowly, it is possible to have a disordered alloy at a temperature below T,. A long anneal at a temperature just below T, produces considerable long-range order;5 the ordering treatment in the present investigation was 150 hr at 485°C which gives an antiphase domain size of-SOW

Jan 1, 1963

By George J. Bancroft

INTRODUCTION. IT is unnecessary to repeat here the contents of many valuable contributions to this subject which have appeared in the Transactions and in the publications of the U. S. Geological Survey. As a basis for the further suggestions of this paper, the following are the most important: 1. The investigation of J. R. Don,1 showing the gold of certain Australasian veins to have been deposited by ascending solutions, and not by lateral secretion. 2. The theory of Prof. Posepny,2 distinguishing the vadose from the deep circulation, and ascribing the origin of certain classes of ore-deposits to ascending solutions of the latter class. 3. The theory of Prof. Van Hise,3 as to the underground circulation and the primary enrichment of veins thereby. 4. The paper of Prof. J. F. Kemp,4 showing that ore-deposits are largely the products of " expiring vulcanism." Many of Prof. Kemp's, ideas have been widely adopted by mining men. 5. The theory of secondary enrichment, so lucidly expounded by Mr. S. F. Emmons.5 This theory, dealing with, the rearrangement of ore-bodies after primary mineralization, has been generally adopted, and seems to me to have been as completely proved as the nature of the case permits. There are two facts which I think should be constantly borne in mind in formulating a theory of the genesis of ore-

Jan 1, 1913