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By M. Gensamer

A RECENT paper1 described, by means of stereographic pole figures, the preferred orientations produced by cold-rolling low-carbon steel of automobile-body grade. It was found that the surface of the sheet exhibited a deformation texture significantly different from the texture possessed by the inside of the sheet. Efforts to produce the surface texture by buffing a sample exhibiting the normal or inside texture, using a copper lap, have not been successful. In view of the data collected, by Kurdjumow and Sachs2, it was suggested that the surface texture might be the result of partial recrystallization of the normal or inside texture. The recrystallization texture of cold-rolled mild steel was studied by Goss3, but he did not use the pole-figure method, so that his conclusions were in need of verification. For these reasons the work reported in the present paper was undertaken. It had two objectives: (1) to study the general behavior of cold-rolled mild steel on recrystallization below the critical temperature A,, and (2) to attempt experimentally a demon-stration of the genesis suggested above for the surface texture in cold-rolled steel. The material was that used by Gensamer and Mehl, cold-rolled to 97.5 per cent reduction in thickness. Fig. 1 is an X-ray pinhole photo-gram of this material, taken with the beam transmitted perpendicular to the plane of the sheet, using a molybdenum target at 35 kv. with no filter. It is typical of the inside texture, but in it the deformation texture is better developed than in the samples that showed a well developed difference between the inside and surface samples. Specimens from this sheet, which was 0.005 in. thick, were annealed for 5 min. at various temperatures in a lead bath. After about 0.0005 in. had been etched from both surfaces, X-ray photograms were prepared, using the technique described in the earlier paper'.

Jan 1, 1936

By H. A. Baumann, A. J. Rostosky

EVER since the first installation of wet-washing methods of coal preparation, the removal of the water added by the washing process has created serious technical and operating problems. The rapid development and widespread adoption of wet washing has necessitated a corresponding development of dewatering methods and equipment. The amount of water retained by coal varies with the size of the coal. The moisture that is largely on the surface of the particles is easily shaken off coarse coal; thus coarse coal can be dried comparatively easily and quickly. Fine coal presents a larger surface area than does coarse coal, so its capacity for retaining moisture is greater. In fine coal, moisture below about 5 per cent is held between the coal particles and its removal is difficult. Draining and drying of the finer sizes is a major problem at many washeries. Two common problems of coal-washing practice that are intimately connected with dewatering and drying are the clarification of washery water and the prevention of stream pollution. The first field has been studied from many angles, including the use of coagulating and settling agents followed by vacuum filters to remove the solids, and the use of sludge tanks with dewatering screens incorporated therein. In many districts, the disposal of sludges into streams has been stopped by law. The lack of space for impounding sludges has created problems of disposal in other districts. Reduction in moisture means a saving in freight costs as well as the elimination of difficulties in unloading and storing. Excess moisture in coal causes it to freeze in localities where severe climatic conditions pre¬vail. Excess water in coals to be used in the production of coke and manufactured gas has a chilling effect on the walls of the oven or retort. Dryness of coal is important in producing good briquettes.

Jan 1, 1943

By H. l. Burghoff, J. S. Porter

This paper presents the results of an investigation of the effect of cold-working and annealing treatments upon the occurrence of preferred orientation in annealed brass wire. The subject has received less consideration than has the same phenomenon in annealed brass sheet or strip, and perhaps very properly so in view of the obvious and undesired results obtained in the forming or drawing of strip having preferred orientation, which results are in contrast with the lack of any spectacular visual evidence in wire. The factors of cold-working and annealing that control preferredness in strip are naturally expected to function similarly in wire. Indeed, one might expect the condition to be commoner in annealed wire, because the severity of the cold-working between anneals in commercial Practice is usually much greater for wire than for strip. For example, a wire that is to be finished in the annealed condition on a diameter of 0.040 in. is commonly subjected to a final reduction of 90 per cent between the last two anneals, the large reduction being accomplished in the successive drafts of a multiple-die machine. Wire for rivets, for instance, on 0.125-in. diameter, although given a slight reduction of about Io per cent after the final anneal, may have been given a prior reduction of 75 to 80 per cent. Barrettl states the fiber axis of annealed 70-30 brass wire to be [111], with some indication of [IOO] as a secondary fiber axis. Croft and Sachs2 have reported briefly on some differences in brass wire with random and with preferred orientations. They showed statistical plots of the twin-band angles with respect to the wire axis or direction of drawing as observed on an axial plane. They also pointed out that the resistance of the wire to corrosion-cracking when externally stressed and exposed to a mercurous nitrate solution decreased as the degree of the preferred orientation increased. Material and PRocedure All the wire for the investigation was processed from one portion as cut for extrusion from a cast billet of the following analysis: 70.13 per cent copper; 0.01 lead; 0.01 iron; 0.02, nickel; 29.83 zinc (by difference). The billet section, 8 in, in diameter, was extruded hot to 3/4-in. diameter, after which it was processed by alternate cold-drawing and annealing treatments as indicated in Fig. I. The earliest anneals in process were at about 1100°F. and the next to the last reductions by drawing were 58 per cent. The diameter of the finally annealed wire was 0.132 in. Semifinal anneals were at 800°F., 950°F. and 1100°F. and reductions of 47.5, 74, 83.5 and 89.5 per cent were employed in drawing to 0.132 in. The final anneals were at 87s°F., 1050°F. and 1250°F. and were

Jan 1, 1944

By H. l. Burghoff, J. S. Porter

This paper presents the results of an investigation of the effect of cold-working and annealing treatments upon the occurrence of preferred orientation in annealed brass wire. The subject has received less consideration than has the same phenomenon in annealed brass sheet or strip, and perhaps very properly so in view of the obvious and undesired results obtained in the forming or drawing of strip having preferred orientation, which results are in contrast with the lack of any spectacular visual evidence in wire. The factors of cold-working and annealing that control preferredness in strip are naturally expected to function similarly in wire. Indeed, one might expect the condition to be commoner in annealed wire, because the severity of the cold-working between anneals in commercial Practice is usually much greater for wire than for strip. For example, a wire that is to be finished in the annealed condition on a diameter of 0.040 in. is commonly subjected to a final reduction of 90 per cent between the last two anneals, the large reduction being accomplished in the successive drafts of a multiple-die machine. Wire for rivets, for instance, on 0.125-in. diameter, although given a slight reduction of about Io per cent after the final anneal, may have been given a prior reduction of 75 to 80 per cent. Barrettl states the fiber axis of annealed 70-30 brass wire to be [111], with some indication of [IOO] as a secondary fiber axis. Croft and Sachs2 have reported briefly on some differences in brass wire with random and with preferred orientations. They showed statistical plots of the twin-band angles with respect to the wire axis or direction of drawing as observed on an axial plane. They also pointed out that the resistance of the wire to corrosion-cracking when externally stressed and exposed to a mercurous nitrate solution decreased as the degree of the preferred orientation increased. Material and PRocedure All the wire for the investigation was processed from one portion as cut for extrusion from a cast billet of the following analysis: 70.13 per cent copper; 0.01 lead; 0.01 iron; 0.02, nickel; 29.83 zinc (by difference). The billet section, 8 in, in diameter, was extruded hot to 3/4-in. diameter, after which it was processed by alternate cold-drawing and annealing treatments as indicated in Fig. I. The earliest anneals in process were at about 1100°F. and the next to the last reductions by drawing were 58 per cent. The diameter of the finally annealed wire was 0.132 in. Semifinal anneals were at 800°F., 950°F. and 1100°F. and reductions of 47.5, 74, 83.5 and 89.5 per cent were employed in drawing to 0.132 in. The final anneals were at 87s°F., 1050°F. and 1250°F. and were

Jan 1, 1944

By John D. Hanks

INTRODUCTION Chevron's Uranium Mill is located near Panna Maria, Texas; 70 miles southeast of San Antonio. Designed by Kaiser Engineering, the Mill will process a nominal 2500 dry T.P.D. of uranium bearing ore containing 15% uncombined moisture. Earl Torgerson, San Mateo, California, is the consulting metallurgist on process design. Feed to the plant consists of a mixture of high, medium and low grade sandy day ore; the average grade of the ore will be 0.7% throughout the life of the project. The ore is delivered to the mill via truck and stored by type in individual piles on a flat storage area. The ore is fed by conveyor to a semi-autogenous grinding mill. The SAG mill discharge slurry is pumped either to a storage tank or to the first of five mechanically agitated leach tanks where both H2SO and NaC103 are added. Following leaching, the slurry is mixed with thickener No. 2 overflow before being pumped to a six-thickener, countercurrent decantation circuit where the solution containing uranium is separated from the leach residue. The residue is washed essentially free of solubilized U308 values at the sixth thickener and discharged to an adjacent tailings pond. The first thickener overflow, containing approximately 0.4 grams U308 per liter, is filtered for clarification and sent to the liquid ion exchange (solvent extraction) section. The pregnant aqueous solution is mixed with organic solvent containing amine on which the complex uranyl sulfate ions are absorbed. The immiscible aqueous and organic solutions are mixed and separated in each of the four stages of solvent extraction. The final pregnant organic is directed to a stripping section. A strip solution containing (NH4)2S04 (ammonium sulfate) and NH4C1 (ammonium chloride) is contacted and separated from the organic in each of the four mixer-settler units. The strip solution is mixed with NH3 and the uranium precipitates along with trace amounts of sulfate, chloride, and ammonia. After washing in a thickener, the uranium precipitate or yellowcake is centrifuged and dried in a multiple hearth roaster. Overflow from the yellowcake thickener is recycled back to the stripping section of the solvent extraction circuit. The dried yellowcake concentrate contains more than 98% U308; diluents include H20, ammonia, chloride, etc.. Impurity concentratons in the product are sufficiently low, after drying, to permit direct shipment to refinement installations. ORE RECEIVING Ore from one or more mines will be stored on a pad adjacent to the uranium processing mill. Ore stored in the area may total 200,000 tons or more, which is equivalent to over a two month treatment reserve for the mill. In addition to providing surge capacity, the proposed storage facility permits natural oxidation of the ore and affords an area which, in turn, improve plant U308 recovery and reduces consumption of oxidizing reagents. The uranium bearing ore is segregated at the storage area into several distinct types. One group can be identified by its sandy, clay-like matrix and will be distinguished by its U308 concentration of high, medium, or low. Other ores contain substantial quantities of carbonaceous shale, typical of ore in the area. Feed is recovered from any one or combination of piles, in accordance with operating requirements and recovery factors. The run-of-mine ore, at 15% moisture, is transferred to a stationary, 24-inch by 24-inch grizzly. Undersize material falls into a 280-ton surge hopper located below grade, while oversize material is removed for preliminary size reduction. A sump-pump is located at the reclaim hopper to recover excess mositure and ore spillage for processing. Plant feed is continuously drawn from beneath the hopper at an average rate of 120 tons per hour by means of an apron feeder. The hopper is equipped with a low level safety system to protect the apron feeder assemble. The ore is transferred to a belt conveyor, elevated and discharged into a semi-autogeneous grinding (SAG) mill. Water addition at the discharge point is automatically controlled by a feed rate, moisture analyzer system located on the belt conveyor. GRINDING Minus 24-inch ore, at a rate of 120 mosit tons per hour and cyclone underflow at a rate of 137 moist tons per hour are combined with a controlled 186 gallons per minute fresh, warm plant process water. The mixture, at an average 68% solids, is fed to the SAG mill. The viscous mass is subjected to grinding at a temperature moderately above ambient resulting from use of the 140ºF well water. The 16.5'x5.0' Marcy Mill is driven by a 500 H.P. A.C. Motor. The mill will rotate at 73.4% of critical speed or 14.06 R.P.M. Eight percent of the mill's volume will be occupied by steel grinding balls; 22% by pulp. The mill is designed to rotate in either direction, in order to obtain maximum lifter and liner life. The SAG mill is equipped with a trommel having ½ -inch slots for removal of oversize material at its discharge and the large or oversize material is collected and either recirculated periodically or discarded. The undersize slurry is diluted to 64% solids with the addition of hot well water or mine water to the mill discharge sump. The flow is automatically controlled utilizing data from a gamma density meter. The slurry from the mill discharge sump is pumped to hydrocyclones to classify the particles. Underflow from the cyclones, at 80% + 28 mesh, is recycled to

Jan 1, 1979

By T. F. Bower, M. C. Flemings

Results are reported of a study of surface dendrilic structure of an Al- Cu alloy solidified against a chill wall. Most primary and secondary "arms " in the surface dendritic structure are arranged orthogonally, giving the impression of strong preferred orientalion on the surface. However, no such preferred orientation exists and it is therefore evident the arms do not represent (100) directions. The primary arms are shown to be interseclions of a (100) plane wilh the chill plane, or, equally often. the projeclion of a (100) direction on the chill plane. Secondary dendrite arms are usually within a few degrees of 90 deg to the primary arm, independent of grain orientalion. Prirary, secondary, and higher-order surface dendrite arms almost always represenl intersections of (100) platzes with the chill surace, or pvojections of (100) direclions. Growlh of secondary arms is favored on the side of the primary arm where a (100) direclion points toward the chill surfAce a1 a Lou, angle. Surface dendrile arms are often observed to be bent. In these cases, the crystal lallice changes orientation; bending is concave to the chill surface. In a previous paper,' a technique was discussed whereby large grains can be obtained at a chill surface. The technique used involves quickly drawing superheated liquid A1-4.5 pct Cu alloy into a thin copper mold, so that the mold is full well before solidification begins. The chill surfaces employed are polished copper blocks coated with amorphous carbon. Shrinkage during solidification between dendrite arms and grains delineates both, without the need for polishing or etching of the cast surface. The grain structure of the chill surface was discussed in a previous paper;' in this paper, the dendrite arms within each grain are examined. Previous work on surface dendrites includes that of Edmunds, who studied the development of preferred orientation in zinc, cadmium, and magnesium.' In zinc and cadmium, he found that the surface region has a (0001) texture (parallel to the chill surface). Walton and Chalmers reasoned that, since the fast growth (1010) directions are in the basal plane, nuclei which have this plane parallel to the mold wall would produce larger grains than nuclei with other orientations. Hence, the texture observed is as expected.3 The same authors, in measurements on aluminum ingots, found no preferred orientation at the mold wall. However, the X-ray technique they used measured the preferred orientation in terms of grain numbers, not grain areas; larger grains were weighted equally with small ones. No preferred orientation is expected on this basis at the chill surface. In a later paper,' Edmunds stated that experiments show a random grain orientation at the surface in die cast aluminum; his technique, also used in his earlier paper, takes account of grain area. Little work has been published on the dendritic structure of metal chill grains. Recent work of Biloni and Chalmers on "predendritic growth" shows the change in morphology from spherical to dendritic during the initial stages of freezing, 5 but this work did not include detailed examination of the fully developed dendrites. Other pertinent work includes that of Lin-denmeyer, who investigated the growth of ice dendrites. 6 When growth was on a substrate, the dendrite axes were bent. The bend corresponded to a change in orientation of the crystal lattice and occurred in such a way as to align the basal plane to the substrate. DENDRITE STRUCTURE Fig. 1 shows the chill surface of a typical casting poured above the critical temperature necessary to produce coarse grains. A cursory examination of these grains shows that the surface dendrite arms within most of the grains are oriented roughly perpendicular to each other. One is tempted to assume that these are (100) directions and that, therefore, marked preferred orientation exists at the chill face. This, however, is not the case. Each of the grains in the casting of Fig. 1 was separately identified, Fig. 2, and its orientation determined by the Laue back-reflect ion method. Results are given in Fig. 3 and it is seen there that no preferred orientation exists. Even when grain area is accounted for, there is no significant preferred orientation. The relationship between surface grain structure and crystal orientation was then obtained by assigning X and Y axes to the casting surface, Fig. 1, and assigning the same axes to the stereographic projections of each grain. Thus, the visible surface structure could be compared readily with grain orientation. This was done for fifty-five of the grains of Fig. 1. Results of this study on three typical grains are described below, and some general observations given subsequently. Fig. 4 shows the structure and stereographic projection of a grain which lies near the (100) zone (with respect to the casting surface). The X and Y directions are marked on the projection, and the photomicrograph mounted with the same orientation. Poles of the stereographic projection represent crys-tallographic directions in the grain which point out of the casting, toward the chill. Two (100) directions are shown in Fig. 4. A line joining the center of the projection and a pole represents the projection of the pole onto the X-Y plane (chill surface). Two such lines are shown in Fig. 4 (solid lines). A line joining the intersection of a great circle with the circumference of the projection gives the trace of a crystallo-graphic plane in the chill surface; two such traces are shown (dashed lines).

Jan 1, 1968

By Howard L. Hartman

There is reason to believe that ventilation systems so far devised for use with continuous mining machines fall far short of success. This is vividly demonstrated to anyone who has observed in a continuous miner section the localized ignitions of pockets of gas and the generation of dense clouds of dust by the cutting head of the machine. The alarming frequency with which major ignitions and disasters continue to occur in modern mechanical mining and the rise in incidence of pneumoconiosis serve as reminders that our ventilation systems are far from achieving the ultimate in providing protection from either short-term explosions or long- term dust diseases, both of which take lives. Human safety is the main concern in ventilation. But in this day of high-priced labor, let us not forget human comfort, either, for this is a major factor in motivation toward high productivity. The failure or inadequacy of most mine ventilation systems in providing the kind of working conditions at the face that are conducive to productive as well as safe operation is an indictment of our environ- mental control program in mining generally.

Jan 3, 1962

By R. G. Gifkins

Mean boundary migration depended linearly upon creep extension under various conditions. Prolonged annealing or air-casting increased the proportion of immobile boundaries at a given stage of tests. Grain growth during annealing followed a power law. The linking of migration and sliding in creep and models for migration are examined; activation energies are calculated from these models. Segregation of oxygen to boundaries appears to be a controlling factor. THE idea that boundary migration and boundary sliding during creep are linked has often been suggested,'-5 especially when evidence has been obtained for an alternation between the two processes. In simple bicrystals sliding can occur without any migration6 but in more complex bicrystals7 it is observed. McLean' and Couling and Roberts 5 made measurements of both sliding and migration; McLean concluded that there was no linking of the two processes whereas Couling and Roberts supported the idea. McLean' also developed a model for migration during creep and annealing. The present work was initiated as part of a study of the recrystallization of lead during creep9 but has been extended to examine some aspects of the mechanism of migration. MATERIALS AND METHODS Specially refined high-purity lead* was used; the total of impurities, excluding oxygen, was 0.0008 wt pct. Oxygen was removed as far as possible by melting in vacuo, treating at 550" to 600°C with hydrogen and then casting at 450°C under a vacuum of 10-2 mm Hg; the oxygen was then believed to be 0.00005 wt pct. Specimens were made from extruded strip and then annealed at the required temperature in an air oven, controlled to 5 lac. They were then polished in a mixture of acetic acid and hydrogen peroxide. At this stage some specimens were etched to give grain contrast and their grain sizes determined by the intercept method. Migration of boundaries during creep was measured on the surface of polished (not etched) specimens, directly loaded at room temperature (22°C) or 50°C (52"C) to initial stresses of 300 to 700 1b per sq in. Twenty six vacuum-cast hydrogen-reduced specimens were used and, in addition, two specimens were from material air cast after hydrogen reduction ("partial" air cast) and two from air-cast material not treated with hydrogen ("full" air cast). Duplicates were made in the majority of tests. At intervals through the creep tests, specimens were unloaded and the migration measured, normal to the direction of migration at the point of measurement, for each boundary along standard traverses. Usually between 110 to 180 boundaries were measured at each of some twelve stages of the tests. Migration was measured on the projected image (X100) using prism illumination. Fig. 1 illustrates the method of measurement and shows the kind of variation of migration found from boundary to boundary and along particular boundaries. Fig. 2 gives an example of more extensive migration. The mean value of distance migrated was generally reproducible to *10 pct but occasional points gave a scatter of *20 pct. The correctibn applied by McLean8 to allow for the contribution sliding makes to the apparent distance of migration could not be used, for the sliding at most boundaries was too small to measure with the equipment available. There were two reasons for supposing the correction unnecessary in the present work;

Jan 1, 1960

By AIME AIME

WITH a brilliance undimmed by hard times, the annual dinner on Wednesday evening, Feb. 17, was a complete success. More than 600 members, friends and ladies gathered early and filled the anterooms of the grand ballroom of the Commodore Hotel, while the president's reception was in progress, and then at the sound of the gong and with the music of the orchestra, rising above the happy din of conversation thronged to their seats at the tables. Following the "potage Ambassadeur"-probably to eliminate a very real hazard-the usual toy balloons appeared and a gay and lively scene, punctuated by multitudinous explosions, ensued, as the hundreds, of variously colored spheres bounced yon and hither until their gaseous existence was ended on the glowing end of a cigar or cigarette. On the speakers' dais sat C. E. Beecher, Chairman Petroleum Division; J. Vipond Davies, representative of A. I. M. E. on the Alfred Noble Prize Committee; Corbin T. Eddy, Alfred Noble Prize recipient; A.' S. Tuttle, Vice-president American Society of Civil Engineers; W. C. Mendenhall, Director U. S. Geological Survey; George C. Bateman, representing the Canadian Institute of Mining and Metallurgy; Paul D. Merica, Institute of Metals lecturer and Chairman James Douglas Medal Committee; Champion Herbert Mathewson, James Douglas Medalist; Robert E. Tally; retiring President; G. Temple Bridgman, toast-master; Scott Turner, incoming President; F. W. Bradley, William Lawrence Saunders Medalist; Fred Searls, Jr., Chairman William Lawrence Saunders Gold Medal Committee; Arthur Notman, President Mining and Metallurgical Society of. America; Robert J. Grant, Director U. S. Mint; Landon F. Strobel, Chairman New York Section; Howard Scott, recipient of Robert W. Hunt Prize; George. B. Waterhouse, Chairman Robert W. Hunt Prize Committee; F. M. Becket, Chairman Iron and Steel Division; Ora E. Clark, recipient of the J. E. Johnson, Jr., Award; Richard Peters, Jr., Chairman J. E. Johnson, Jr., Award Committee; E. C. Bain, Howe Lecturer; Sam Tour, Chairman Institute of Metals Division; and H. Foster Bain, Chairman. Charles F. 'Band Foundation Committee. ' Each was heartily applauded when introduced by Mr. Bridgman, as was Mrs. Tally, who also made a bow. The toastmaster made graceful reference in introducing Mr. Strobel, to the large part the latter had taken in planning the meeting.

Jan 1, 1932

By John Dodd

This paper reviews advances in the technology of abrasion resistant iron and steels, which could help combat abrasion and wear in mining operations. With the recent progress in high chromium alloy iron development, high temperature heat treatment of massive castings can be eliminated, aloy cost reduced, and cracking problems avoided. Data on erosion-corrosion resistance of these irons; trends in the development of improved cast steels; and factors influencing toughness and abrasion resistance of manganese steels are all considered. The 7% Mn. 1% Mo manganese steels are shown to combine toughness and abrasion resistance, and composite castings are a means of combating abrasion in applications involving severe impact. A brief appraisal is given of recently developed martensitic wrought steels with improved weldability.

Jan 1, 1982

By T. N. Dixon, J. E. Briggs

A study was made of numerical techniques for solving the large sets of simultaneous equations that arise in the mathematical mode ling of oil reservoir behavior. It was found that noniterative techniques, such as the Alternating Direction Implicit (ADI) method, as well as some other finite difference approximations, produce oscillatory or unsmooth results for large time steps. Estimates of time step sizes sufficient to avoid such behavior are given. A comparison was made of the Point Successive Over-Relaxation (PSOR), Two-Line Cyclic Chebyshev Semi-Iterative SOR (2LCC), and iterative ADI methods, with respect to speed of solution of a test problem. It was found that, when applicable, iterative ADI is fastest for problems involving many points, while 2LCC is preferable for smaller problems. INTRODUCTION With the advent of high speed, large memory, digital computers, there has been an increasing emphasis on the development of improved methods for simulating and predicting reservoir performance. Two-dimensional, three-phase reservoir models with various combinations of PVT effects, as well as gravity and capillary forces, are common throughout the industry. Such models are also available through consulting firms, to anyone desiring to use them. Three-dimensional models will probably be practical in only a few years. We conducted a study of some of the numerical methods used for solving the large sets of simultaneous equations that arise in such models. A typical set of equations for a reservoir model is shown below:

Jan 1, 1969

By G. L. Oldright

THE metallurgist is familiar with the rapid development of concentration -by flotation and smelting in the reverberatory in recent years, brought 'about chiefly by the exhaustion of' bodies of .rich, coarse, direct smelting ore. Geologically speaking, in many porphyry-copper districts, the richer contact or replace let deposits surrounding 'the main ore-forming igneous intrusion have been exhausted, and it is necessary to beneficiate the copper minerals disseminated throughout the mass of the intrusion itself. The organization of great companies to treat such low- grade ores on a large scale and the practices resulting from the necessity for an economic method of treatment 'are among the most prominent metallurgical developments of the past decade. It is interesting to note the effect of the present trend of practice on the inter-relationship of the concentrator and smelter, on the constituents of the smelter charge, and on smelting in general.

Jan 1, 1925

By Fred P. Peters

At first glance this paper may seem unique among those comprising this symposium on designing for powder metallurgy, since it is evidently concerned with everything but Powder metallurgy. This paradox mill be at once resolved, however, when the real Purpose of the symposium meeting is understood—to present factually and objectively the things that can and cannot he done with powder-metallurgy methods, and especially to set forth with brutal frankness the limitations of Powder metallurgy, so that costly over-enthusiasm and misapplication may be prevented. Since much of powder metallurgy's future development (and many of its present disappointments) has been in competition with other and long-established methods of fabricating parts, it is easy to see that its true competitive possibilities in any given case cannot be accurately appraised without rudimentary knowledge of what the competition can do. This paper, therefore, presents a few reminders of things you all know—a background to be kept in mind as you examine the data on each of their specialties given by the authors of the papers that follow. From the standpoint of the design engineer powder metallurgy is often in Competition with one or more of the following: sand casting, die casting, permanent-mold casting, precision investment casting, ma- chined bar stock, screw-machine parts, cold-heading, drop-forging, and stamping and drawing. We will here briefly discuss each of these individually, and set forth so, rough (and therefore dangerous) generalizations about its competitive position, especially with respect to powder metallurgy. Sand Casting Sand-casting of small parts is sometimes an inexpensive method of manufacture, for its raw-material costs (i,e., for gray iron) are the lowest of the various methods and it involves the use of no tools and dies of jewelry quality. its design flexibility— that is, the ability to make complicated, cored and undercut parts in one piece—is about the highest of the competing processes and in this respect it can do many things that are impossible by powder metallurgy. For small castings its production rates may be higher, by using multi-impression molds, than can be achieved with parts of the same size by powder metallurgy. But its labor charges for melting, pouring, patternmaking and molding are comparatively high and the waste it entails in gates and risers is always considerable. Tolerances of sand castings are wide (+1/6 to 1/32 in- per in.) and where precision approaching that of powder metallurgy is required sand castings must be machined to final size, thus increasing their cost. Steel sand castings are more expensive and less precise than iron, and nonferrous the most costly of all.

Jan 1, 1945

By D. R. Bomberger, M. Deul

An automatic microscope has been developed to measure the size and populations of macerals and minerals in fine coal particles. Differentiations are made on the basis of reflectance. This study is concerned with the size distribution of pyrite inclusions. Most fine coal cleaning processes do not remove pyrite as completely as a straight density separation. Consideration of the pyrite size distribution is suggested as a more accurate method of predicting sulfur reduction by a cleaning process. Analyses of float-sink results and Deister Table operation in terms of pyrite particle sizes are made. Other potential applications of automatic microscopy are also discussed. In the study of coal cleaning by pseudo-gravity methods (tables, cyclones, hydrotators, etc.), it is customary to express the deficiency of the process relative to float-sink measurements in some form of "percent efficiency". These have been calculated in many different ways in order to provide a means of extrapolation of test data to untested coal feeds. This works quite well with coarse coal (here defined as larger than one-eighth in.). Large, heavy pieces of refuse are rejected rather thoroughly by many cleaning processes, and the efficiencies relative to float-sink results approach 100%. In coarse coals, the difference in the sizes of fine pyrite is masked by the averaging effect of the large coal envelopes. The existence and fate of fine pyrite is often hidden in the larger numbers representing coarse (and easily removed) pyrite. There are cases where it is desirable to subject fine coal (here defined as smaller than one-eighth in.) to cleaning processes. This is true of naturally occurring fie coal streams and in cases where comminution followed by cleaning is necessary to provide the quality desired. It is in this area that the use of process efficiency relative to float sink fails. Percent efficiencies decline to very low figures, and equivalent separation densities become a matter for conjecture. The net result is that an attempt to estimate product quality from float-sink data and a process efficiency figure often results in large errors. This work represents a new approach to the problem by observing the fate of pyrite particles, grouped by sizes, in a cleaning process. Examples are given which relate pyrite size measurements to float-sink washability and to a Deister Table operation. EXPERIMENTAL WORK The automatic microscope used here has been previously described.' Briefly, it is an instrument which measures the diam of particles (as defined by a range of reflectance) exposed on a polished specimen. The instrument scans a sample briquet, measures diam of exposed pyrite inclusions and records the data by size intervals. Preparation of the briquet is critical, due to the automatic nature of the process. The principal requirement is for an optically flat surface, so that focus will be maintained as the motorized stage moves the specimen under the lens. The various substances present must be polished to the same level in spite of the wide difference in hardness between coal substance and minerals. The polishing method must not pluck out small grains, which might be rather loosely held by surrounding coal. The procedure below was successful in producing all of these results. The coal sample (8 mesh or finer) was riffled (a micro vibrating riffle is essential) to obtain 15 g. One volume of Lucite powder (thermosetting plastic mounting medium) was mixed with three volumes of coal and mixed thoroughly. A briquet was formed using a cylindrical die (1 1/4 in. diam) at 3000 lb per in.* pressure and 150°C. Preparation of the optical surface was accomplished on automatic polishing equipment, according to the following schedule: 1) Grinding: 3 stages, using successively fine Carborundum grits of 180, 320 and 600 mesh. 2) Rough polishing: 2 stages, using 3µ alumina on cast iron, followed by 1µ alumina on lead. 3) Fine polishing: 2 stages, using 0.5µ alumina on napless broadcloth over bronze, followed by 0.1µ alumina on silk filament cloth over bronze. Raw data were corrected for the fact that the chords

Jan 1, 1964

By W. C. Kelly, E. J. Essene, A. M. Affifi

Occurrences and associations of natural tellurides are constrained by the relative fugacities of Te, in specific mineralizing environments. Some are rare (e.g., FeTe2) and others absent (e.g. MoTe , ZnTe) m nature because high f-Te2/f-S2 ratios are rare or unattainable , whereas others (e. g . , Ag2Te,HgTe) require lower ratios and are common. Complex and seemingly chaotic sulfide-telluride associations are, in fact, highly systematic and depend both on temperature and fugacity ratios. Some older sulfides act as buffers via reactions such as PbS + Te2 = PbTe + S2, thereby affecting the deposition and paragenesis of younger tellurides and the combined or uncombined mode of occurrence of precious metals. Thermochemical calculations of telluride-sulfide-oxide equilibria can have pragmatic value. The thermochemical approach tells us little about the Te "source", but is beginning to unravel the systematics of telluride mineralogy and controls at the precipitational end of the line.

Jan 1, 1985

By Raymond L. Jones

With the inauguration of open-pit copper mining in Bagdad, Ariz., plans were formulated for a large scale leaching operation. Dump stockpiling was started almost immediately, but actual production was not initiated until spring 1961.

Jan 9, 1977

By B. L. Landrum, P. B. Crawford

The rise of a new laboratory model for studying tran-sient fluid flow problems, is described. The theory of he model is based on the analogy between the equa-ions which describe the flow of compressible fluids in porous media and the conduction of heal m solids. The "thermal model" is used to study the Iransient Pressure distributions during fluid displacement in five Standard well patterns. The studies indicate quantita-ively how die pressures change with lane at any poit in the reservoir. It was found that, in general, the equipressure contours are more radial about the wells early in the program than after steady-state conditions are established. In addition two studies of fractured five-spot patterns are presented to illustrate the opplicability of the model for a wide range of reservoir conditions. INTRODUCTION In reviewing the oil recovery techniques involving fluid displacement it was found that a very considerable quantity, if not all of the fluid within the pattern, mav be displaced (during a time-dependent or transient period rather than the usually applied steady-state conditions. Since the oil is displaced during a transient period, it was believed desirable to study the nature of the transients for several of the commonly used fluid displacement patterns. A literature review indicated fairly complete studies of the streamlines and isopotentials for steady-state: yet few data were available on the transient displacement process. Several simulated steady-state multiwell displacement programs were carefully mapped by Foster and Lodge on an electrical conducting sheet as early as 1875, hut the more recent work of Muskat provides the best source for steady-state phenomena having direct petroleum production applications. In order to study the transient phenomena a new lab-oratory model was developed which is based on the similarity of the equations that describe the flow of fluids and the conduction of heal. The equations describing heat flow were developed early in the nineteenth century. Regorous solutions tor most transient problems are in gcneral complex and usually limited to fairly restricted houndary conditions.2 the thermal model may be used to obtain approximate solutions for many transient problems without some of the restrictions required for analytical solution. The application of the analogy between heat conduc-. tion in solids. electrical flow and fluid flow, in a porous media has long been recognised. Techniques originally developed for the solution of heat conduction prol?lems have in many instances proved useful in ohtaining solutions to fluid flow prohlcms. Ir is not surpri5ing then that a heat conduction or thermal model might bf usefull in sludying transient fluid flow. As an example ol the problems suitable for the study with the thermal model, transient pressure distributions during fluid displacement programs are studied for the five-spot, line-drive, staggered line-diibe. seven-spot 211 two fractured patterns. A model was constructed of an iron plate of geometry similar to the reservoir patterns under study. The principle of mirror images as suggested by Bryan was employed in shaping the model. A temperature differential was obtained by soldering two sections of copper tubing to the plate at points analogous to the well location in the field. Hot and cold water was passed through the tubing. The temperature distribution, analogous to the pressure distribution in the field. was obtained a a function of time from thermocouplcs distributed over the plate.

A filled stope is one in which the support for walls and men and, at times, for the back of ore, is furnished by waste rock or sand tailings. The filling may be rock sorted out in the stope or from the walls, develop-ent, or the surface. The orebody is mined in sections, each practically an open or timbered stope, filled wholly or in part before adjacent ground is attacked. As a rule, the filled-stope method is limited to overhand flat-back, stepped-face, or rill stopes. The examples given are Copper Range, Iron Cap, Verde district, Zaruma district, Lucky Tiger, and Silver King Coalition.

Jan 1, 1925

By Wayne P. Myers

Electricity, as normally thought of by a layman's definition, is a manmade force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by the U.S. Bureau of Mines, as well as the various state departments of mines. BACKGROUND Until recent years most underground coal mines used direct current exclusively for all movable and for some stationary equipment. Exceptions were for permanent pumps, tipple, fan, and outside buildings where alternating current was normally employed. However, over 60 years ago there were mines with dual systems. Alternating current was used for cutting machines, drills, and pumps, direct current for locomotives. There were no other machines as these were hand-loading mines. Later, during early mechanization in the 1920s, alternating current was also applied to loading machines at some mines. Use of dual electric systems then declined until fairly recently when

Jan 1, 1973

By Porter W. Shimer

Ox completing the filtration of a solution of pig-iron in hydrochloric acid, and after apparently everything had been transferred to the paper, a minute residue was observed remaining in the angle of the beaker in which the solution had been made. This residue had a steel-gray color and metallic luster and was hard and gritty when touched with a glass rod. Placed under a microscope and magnified 400 diameters, the substance was found to be made up almost entirely of opaque cubical crystals with some fragments having the same color and luster as the cubes. The appearance was strikingly like that of a collection of crystals of iron pyrites. The amount of material obtained from ten to twenty grams of borings by solution in dilute hydrochloric acid, and careful decantation from graphite, was barely sufficient for a microscopic slide. A qualitative test of the minute amount of material obtained in this way, showed the presence of considerable titanium. After many fruitless trials by decantation and other methods, sufficient material for quantitative analysis was finally obtained in the following manner: Two hundred and fifty grams of the coarsest possible borings were dissolved in seven liters of hydrochloric acid of sp. gr. 1.03. A solution by the aid of heat took four to five hours. It was allowed to settle, and the clear solution poured off. Great care was taken that none of the material which had settled to the bottom was lost. The graphitic residue was then completely transferred upon fine bolting-cloth, previously Stretched and fastened over the top of a beaker. All graphitic lumps were broken up by the finger while

Jan 1, 1887