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By R. F. Mehl, B. Lustman

THE formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.1 It is necessary here only to enumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type-i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained-the isothermal growth of the phase follows a simple parabolic equation: [1 = ki [I]] where X is the thickness of the alloy layer, k the reaction rate constant, and [t] the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.3 In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varies with temperature according to the Arrhenius equation: [k = Ae-QIRT [2]] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. All phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By R. F. Mehl, B. Lustman

The formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.' It is necessary here only to cnumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type—i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained—the isothermal growth of the phase follows a simple parabolic equation: X2 = kt [i] where X is the thickness of the alloy layer, k thc reaction rate constant, and t the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.$ In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varics with temperature according to the Arrhenius equation: k = Ae-Q/RT [2] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. Ali phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By Robert Henderson

Several very interesting articles have been written on the caving system of mining, but most of these papers have dealt separately with the slusher system or the chute and grizzly system. In this paper, a comparison will be made of the two methods, both of which are being used at the Climax mine. The mine is on the Continental Divide, in central Colorado, at an altitude of approximately 11,500 ft. above sea level. The long, cold winters, characteristic of the high Rockies, create a number of operating problems not usually found in other mining areas. The Ore Body The Climax ore body is just east of the Mosquito fault. This structural deformation has brought the granite on the east against the sedimentary rocks on the west. The ore occurs in an intensely altered granite and schist around a silicified granite core. The ore is in a highly fractured zone of moderate silicification. The principal mineral, molybdenite, is found in these fractures. Barren dikes of granite porphyry cut through the ore body and core with no apparent regularity. The grade of the ore is fairly uniform and gradually decreases toward the footwall core and also into the hanging-wall granite. The footwall and hanging wall are determined entirely by assays. The ore body is roughly dome-shaped, with the apex truncated at the surface. It is covered to varying depths with talus. A horizontal section of the ore body on the Phillipson level appears as an annular ellipse surrounding the footwall core. The ring of ore varies in width from 300 ft. to as much as 800 ft. The north-south axis of the core is about 1200 ft. and the east-west axis is about 1800 ft. In the ore zone, the rock is sufficiently strong to maintain reasonably large openings, and openings larger than haulage drifts usually have to be supported. The ore is cut by a great many fractures and shears and breaks into rather large blocks when caved, necessitating considerable secondary blasting. The waste that overlies the ore body breaks relatively fine in comparison with the size of the blocks of the caved ore and tends to run through the broken ore in the cave, causing dilution unless the draw is carefully controlled. Mining Systems For several years the ore was mined by the chute and grizzly system, a system that differs from that used in other caving mines only in the size of openings and equipment. In the chute and grizzly system, main haulage laterals were driven along the footwall core and also along the hanging wall. Between these laterals, at

Jan 1, 1946

By Otto H. Henry, J. J. Cordiano

Though powder metallurgy is one of the oldest of metallurgical processes, it is in its infancy as a branch of the modern field of metallurgy. As early as 3000 B.C., the ancients produced implements and weapons of iron by reducing iron ore in a charcoal fire and forging the resultant sponge while still hot into the desired shape. Melting and casting soon superseded the powder metallurgy practice, and it was not until the turn of the twentieth century that powder metallurgy was applied to the commercial manufacture of tungsten lamp filaments. From this beginning, the use of the powder metallurgy process spread" to the manufacture of porous oil-impregnated bearings, cemented carbide tools, contact points, diamond grinding wheels, clutch facings, starter brushes, resin-bonded radio cores, magnets, metallic filters, and other parts. More recently, and particularly during the present war, there has been a definite trend toward the manufacture of machine parts by this process in competition with the more conventional fabricating methods. Notwithstanding these many developments, scientific progress has been slow. While many articles on powder metallurgy have appeared in the press and various publications, there have been too few contributions to our technical societies, with the result that there is a dearth of the type of information necessary for the full development of this science. It is of primary importance that the results of research and development be freely disseminated if powder metallurgy is to realize its fullest potentialities. Purpose of Investigation Excluding the refractory metal field, all commercial powder metallurgical products made by a cold compressing and sintering operation contain voids. These voids can be substantially eliminated by subsequent severe working and heat-treatment, but ' such practice has not proved economical in most applications. By applying heat during the compressing operation, plastic deformation of the powder particles is substantially increased, and the resultant compact or briquette is practically free of voids. However, hot-pressing has many attendant problems, which at present preclude its use in the manufacture of precision parts. The more important of these are to devise: 1. A die steel capable of withstanding high pressures at elevated temperatures. 2. A high-temperature lubricant capable of preventing excessive die wear and welding of the compact to the die walls. 3. A method of retaining a neutral or reducing atmosphere in the compacting zone of the die assembly. 4. A means of ejecting the hot-pressed specimen into a neutral atmosphere until reasonably cold.

Jan 1, 1946

R. F. McELVENNY.- The next item is: "Center and other methods, vs. side charging." That was all discussed in the Carson case, and I do not know but what many of the plants are still using center charging. Some are using side charging. Did I understand that where you use the wet charge it is all side charging on the wet ore? B.-G. C. HONEYMAN.- We were on center charging for about a year with wet ore. R. F. McELVENNY.- Then you went to side charging. Has anyone any remarks to make on side versus center charging? E. A. BARNARD.- We have one side and one center, both on deep bath. It is an experimental proposition so far, but the side charge looks very favorable.. R. F. McELVENNY.- This is with calcine? E. A. BARNARD.- This is with calcine on a floating charge proposition.. They are both water jacket. The charge acts very similar on both center and side charging. The calcine spreads much the same as it does on the center charge. It will run down 75 ft. on the furnace side as well as the center. The advantage is in taking care of secondaries and things of that nature. C. BARDWELL.- Do you get any side wall protection from it? E. A. BARNARD.- No. R. F. McKENZIE.- Do you not project the side wall up to protect the skewback? E. A. BARNARD.- There is a slot projection down around the top of the bath; but the repairs on the side wall have been practically the same; that is, they, have been practically the same as they have on the center charge. A. H. RICHARDS.- A point I would like to make is that if you have any doubt about the center charging, we feel that we get better tonnages and lower fuel ratios and better slags with center charging than we ever got with side. Different kinds of charges would, of course, vary, and I could readily see that if you had the same advantage with deep bath smelting that you mention you would probably get just as good a slag and as good fuel ratios. E. A. BARNARD.- In fact, I think the calcine charge spreads more on the side than on the center charge. A. H. RICHARDS.- If you maintain a deep bath. E. A. BARNARD.- That is one thing we have to be careful about, to hold the charge back.

Jan 1, 1930

By R. W. Hyde, S. E. Eaton, B. S. Old

One of the most important problems facing the steel industry at the present time is that of maintaining at a minimum the sulphur content of many grades of steel where sulphur is known to have harmful effects On both quality and yield. The present outlook in this struggle to reduce the amount of sulphur in steel is rather gloomy since the sulphur content of the raw materials available in the United States is gradually rising, with little relief in sight. A flow sheet of sulphur in the steel process is shown in Fig I. The values used here were obtained by averaging coke oven and blast furnace data at No. 5 furnace in Cleveland and are considered typical for high top pressure practice. The sulphur evolved in the blast furnace top gas was obtained by difference and since the amount is relatively small, little significance should be attached to this particular value. From Fig I it is apparent, however, that coals used in the production of metallurgical coke represent by far the largest single source of sulphur in steel-making. As an indication of the decrease in quality of these coals as regards sulphur content the weighed average annual sulphur analysis of the coals supplied to two different steel plants, since 1925, is plotted in Fig 2} The sharp rise since 1940 is strikingly apparent. Another indication of this trend is found in estimates of coking coal reserves. Thus in the case of Pittsburgh seam coals available in Allegheny, Fayette, Greene, Washington, and Westmoreland Counties in Pa. as of Jan. 1937 only 25 pct of the coal reserves would contain less than 1.50 pct sulphur after washing.2.3 Many of these lower sulphur reserves have been seriously depleted in recent years because of accelerated war demands. still another demonstration of the increasing sulphur content of coals on a country-wide basis is found in a report by the Bureau of Mines4 which shows a steady increase in the sulphur content of coke made in the United States. It should be noted that this increase continues in spite of the wider use of coal washing in recent years. Sulphur occurs in coal in three forms, pyritic (FeS2), organic sulphur, and a small amount of sulphate sulphur (CaS04). The sulphur is subsequently found in the coke in combination with carbonaceous material of is composition and as calcium and iron sulphides' In considering the general problem of sulphur elimination, the Republic Steel Corp. was interested in determining which, if either, of the two major forms of sulphur in coal contributes the greater portion of sulphur to the coke. Since the ratio of pyritic to organic sulphur varies widely in different coals, it was thought that if it could be shown definitely that the major part of the sulphur occurring in coke originates from one of the two ""jar forms of sulphur in the coal, it would then be possible to select with confidence coal which, although high .in total sulphur, would yield coke of fairly low sulphur content. Using the new

Jan 1, 1949

By D. A. Dahlstrom

WITHIN the past decade, certain economic, legal, and technological changes have intensified the necessity for an efficient classifier or deslimer of particles at and below the 200-mesh point. First, mechanization of mining has increased the percentage of clays, silts, refuse, and high-ash material in the run-of-mine coal. Second, many washing plants must rely on smaller percentages of fresh make-up water because of shortages, economic factors, or legal restrictions on waste water disposal. Finally, the crushing of middlings and coarse refuse plus the trends toward the finer sizes in sales has further increased the amount of fines produced per ton of mine-run coal. A joint consequence of these circumstances has been the augmented percentage and build-up of —200-mesh material in the finer coal fractions and tipple circulating water. This results in the following disadvantages to the operator: (1) Higher ash percentages in the fine coal caused in large measure by the greater ash content of the —200-mesh material, (2) more difficult or expensive recovery of the fine coal from plant slurries, (3) lower filtration, drainage, and drying rates caused chiefly by lower permeability and the greater surface exposed per unit mass of the finer particles, (4) greater difficulty of beneficiatiing the fine coal because of lowered equipment efficiency and the partial "coating-out" of the —200-mesh fraction on the coarser coal particles. Obviously some cheap but effective fine-size classifier must be developed to aid in solving the above problems. To eliminate the generally unwanted —200-mesh fraction from coal slurries, several methods are in use. Probably the most popular with coal operators is the settling cone wherein the larger particles settle downward to the apex of an inverted cone while the slimes and fines are carried upward by vertical fluid currents caused by the overflow of the bulk of the water at the outer rim. The main advantage of the unit is the low initial and operating cost since no moving parts are involved. Disadvantages are primarily low capacity per square foot or floor space and the loss of good coal in the overflow above the 100-mesh size due to localized, high-velocity gradients and nonuniform, fluid-flow patterns, especially at high loadings. Also, when high slime concentrations are present, desliming efficiency is severely injured.', ' Other methods employed are the drag and spiral classifiers and the hydroseparator.' These involve mechanical separations achieved by moving parts and naturally result in higher initial costs. As they are all based on the settling velocity of the particles at the mesh of separation under operating conditions, area requirements are again large per gallon of throughput if they are to classify at the 200-mesh point. Usually the selection is made to operate at a higher throughput and thus sacrifice some coarser coal in the slime overflow. Cyclone Possibilities in Desliming To overcome the disadvantages of present deslirning methods, it is necessary to use a device that exhibits a very stable and uniform flow pattern while greatly increasing the settling velocity of

Jan 1, 1952

By A. D. Hughes

A relatively small area in Malaya, about 200 miles long by 40 miles wide, is the most important source of tin in the world. Some tin is recovered in other parts of the peninsula. Of the tin mined, 98 pct is recovered from alluvial deposits. From 1935 to 1941 the average annual world production of tin was 190,000 tons. The average annual production from Malaya during the same period was 62,000 tons or about one third of the total. Other producing countries, in order of importance, were the Netherlands East Indies 34,000 tons, Bolivia 30,000, Belgian Congo, Nigeria, Siam, Burma, China, and a few others with smaller amounts. The serious shortage of tin during the war period was due to the fact that the Japanese were occupying Malaya, Netherlands East Indies, Siam, Burma, and China which, together, formerly were producing 65 pct of the world supply. Because of the importance of tin in the world economy, and because of the fact that little is generally known in this country regarding the methods of recovering the tin in Malaya, it is believed that a short description of the industry, as carried on there, may be of interest to many of the readers. In addition you may be interested in the effect of the Japanese occupation, subsequent recovery of the properties and conditions existing at that time. The Malay Peninsula lies at the southeast tip of Asia. Singapore, a British colony, is situated on a small island at the southern end of the peninsula. It is a city of nearly a million population, an important world port, the site of a large British naval base and of one of the tin smelters. The Federation of Malaya consists of nine states, plus Penang, Malacca, and other small areas formerly part of the Straits Settlements, and it now covers the entire peninsula. The civil administration is controlled by the British. A constitution was adopted recently after reaching agreement with the Malay Sultans of the various states, who retain control of religious matters. The Capital is at Kuala Lumpur, a city of about 200,000 population, 250 miles north of Singapore and about half way to Penang. The country covers an area of 51,000 square miles, an area about equal to that of Florida and about one third that of California. It has a population of about seven million consisting of Malays, Chinese, East Indians, and a relatively small number of Europeans. The principal products are tin and rubber. There are over three million acres of planted rubber. The country is not self-supporting agriculturally as about one third of the necessary food supplies is imported. Rice is the principal food of the Asiatic population and some of the recent unrest is caused by a shortage of rice and the consequent high price. Good highways have been built through the settled part of the country. A railway, Government owned, extends from Singapore northward through the entire peninsula. The climate is tropical but health conditions are good for a tropical country. I was in Malaya from 1939 until January 1942, during the time of the simultaneous air attacks on Pearl Harbor, Manila, Hongkong, and Singa-

Jan 1, 1950

By John C. Calhoun, Alfred Chatenever

An exploratory study wap made to examine the possibilities of a visual approach in investigations into microscopic mechanisms of fluid behavior in porous media. Appropriate apparatus and techniques were developed so that microscopic phenomena could be recorded on color movie film as well as be observed visually. The observation flow cells in which tlie fluid behavior studies were made were essentially single-layered matrices of spheres between plates. sometimes all-glass, sometimes all-Lucite and sometimes a combination of the two. The fluids were limited to water and a filtered crude oil. Two flow regimes were observed during the flow of the immiscible liquids: channel flow and slug flow. In the former, transport was effected through stable networks of interconnecting channels; and in the latter, part of the movement took place in the form of slugs. Under certain conditions, flood-front patterns were found to be different depending upon which liquids were the displacing and displaced phases and not depending upon whether the matrix was water-wet glass or oil-wet Lucite. Residual formations of oil and water were observed and are described. Some of the ramifications and significance of the ohservetl phenomena are discussed. INTRODUCTION In recent years considerations of microscopic mechanisms of fluid flow in porous media have taken on greater significance. Much needs to be learned before the fundamentals of petroleum technology are completely established. For example, many unanswered questions exist in connection with relative permeability, displacement phenomena, residua! fluid formations. flow structure, etc.; and further analytical mathematical formulations are seriously indicated. It is hoped that systematic investigations into the microscopic mechanisms connected with the behavior of fluids in porous media will shed some light on some of the problems extant. Until recently microscopic mechanisms have been considered almost exclusively as speculative hypotheses. Within the past few years, however, the problem has been submitted to a limited number of experimental investigations. Nuss and Whiting' made some studies on the pore-space geometry of sandstones and limestones by impregnating cores with an inert plastic and leaching the solid matrices to leave behind plastic models of the pore spaces. SchaeferZ traced pore spaces microscopically through lengths of limestone cores by cutting away thin sections from the exposed faces normal to the line of view. In 1949 two projects were organized in which dynamic flow phenomena were examined microscopically to uncover microscopic mechanisms. One was set up at the Pennsylvania State College where Lowmanb bserved heterogeneous fluid flow phenomena in capillaries. The second was the American Petroleum Institute Research Project 47B at the University of Oklahoma where microscopic studies of dynamic fluid phenomena in synthetic porous matrices have been made by visual observation and cinephotomicrography.' It is with the latter that this paper is concerned. treating the techniques involved and the observations made. TECHNIQUES Observation Flow Cells The observation flow cells formed a focal point in the techniques employed. Essentially, these were matrices composed of a single layer of spheres sandwiched between two flat plates. This design was arrived at after a series of pre-

Jan 1, 1952

By M. C. Flemings, P. J. Ahearn

Dendvite morphology of unidirectionally solidified Sn-12 pct Bi alloy was determined with the aid of X-ray and macroetch techniques. Columnar growth direction (growth direction of primary arms) in this alloy is [110]; secondary arms grow in the [lii], [111), and [112] directions. Interstices between [112] dendrite arms fill in during early stages of solidification so that well-defined (110) planes are seen in the final structure (parallel to the heat-flozo direction). Similarly, interslices betweex the [111] secondary arrlls fill in to form (112) planes, and interstices between [1111 ] arms fill in to form (112) planes. DENDRITE morphology in alloys is conveniently studied in unidirectionally solidified castings. In this type of solidification, heat is extracted from a single chill surface of the casting while other surfaces are insulated. Solidification progresses from the chill and results in cast grains that are columnar with the long axis of the grain perpendicular to the chill. Dendrite morphology is conveniently studied by examination of etched surfaces parallel and perpendicular to the chill, as previously described.'" Experimental studies on the growth direction for tin are in general agreement. The major growth direction is [110]:-' although this is altered somewhat by supercooling. In one study, tin dendrites pulled from a supercooled melt had a growth orientation 12 deg away from the [110] direction toward the [002] direction.' This orientation could be changed back to the [110] or close to the [110] direction by changing the tempera- ture gradient in the melt. In a study using autoradio-graphic techniques, (111) directions were shown to be directions of preferred growth in addition to the [110) direction.7 PROCEDURE The samples employed in this study were cut from 12 pct Bi-88 pct Sn castings, 1.5 in. in diam and 3.5 in. tall. The casting procedure consisted of heating the charge to 390°C and then pouring the molten alloy directly into a gypsum sleeve mounted on a massive copper chill. Specimens were cut from the ingot, mounted, polished, and etched with Taffs reagent [FeC13 .6H2O, 2 g; HC1, 5 cu cm;H20, 30 cu cm; CzHaOH (95 pct), 60 cu cm].' The dendritic pattern was clearly visible after etching. Photomicrographs at about 8 and 35 times were taken on surfaces parallel and perpendicular to the chill. Laue back-reflection patterns were obtained from three different columnar grains in a singIe polished face 2 in. from the chill. The cut face was polished and positioned in the beam of a Laue camera, so that diffraction occurred from a single dendritic grain. The resulting diffraction pattern was interpreted to determine crystal log raphic orientation in relation to the heat-flow direction and in relation to microstruc-ture of the given grain. RESULTS Fig. 1 shows a horizontal and vertical section of the columnar structure, at low magnification. Light regions are rich in tin, and darker regions tin-poor; the primary phase is tin-rich a phase. The two sections shown were taken orthogonally from the same metallographic specimen. It is readily seen from Fig. 1 that the dendrites have

Jan 1, 1968

By C. C. Clark, J. S. Iwanski

The purpose of this investigation was to study mi-crostructural changes that take place in a commercial nickel-chromium-iron alloy, such as Incoloy "901," over long periods of time at temperatures up to 13 50°F and to correlate such changes with creep-rupture properties. of the alloy. In the course of the investigation, some microstructural changes were observed which correspond to microstructural alterations found in previous studies of Inconel "X." Microstructural phases have been identified in both alloys with the aid of electron and X-ray diffraction and an electron probe microanalyzer. The materials used in this investigation were from commercial heats of the following chemical composition: Pct Cr Pct Ni Pct Mo Pct Fe Pct Cb Incoloy "901" 12.51 43.67 5.72 Bal. -Inconel "X" 14.61 73.44 - 6.61 1.02 Pct A1 Pct Ti Pct Mn Pct Si Pct C Incoloy "901" 0.10 2.46 0.46 0.24 0.05 Inconel "X" 0.70 2.43 0.51 0.36 0.04 Long-term creep-rupture tests were conducted on Incoloy "901" at temperatures of 1000°, 1200°1 and 1350°F. A summary of these results is shown in Table I along with the results of a long-term creep-rupture test conducted on Inconel "X" at 1500°F. The heat treatments given the specimens are also shown in Table I. When the creep-rupture results on Incoloy "901" are compared with shorter-tertn data, there is no evidence of any undue deterioration of the creep-rupture strength with time, nor is the elongation decreased more than would be expected from the influence of time alone. INCOLOY "901" PHASE IDENTIFICATION Microscopic examination of the Incoloy "901" specimens reveals a dark etching grain boundary constituent in the specimen which was under test for about 11,500 hr at 1000°F. This grain boundary constituent was seen to increase in size as the test temperature was increased to 1200" and 1350°F, Figs. 1, 2, and 3. Simultaneously, an acicular structure of definite crystallographic orientation appears within the grains of the 1350°F specimen, Fig. 3. Under examination with the electron microscope, a fine precipitate is observed in the 1200 °F specimen. Fig. 4. It becomes considerably larger in the 2850-hr 1350°F specimen, Fig. 5. In a few areas the precipitated particles have been replaced by, or transformed to, small needles or platelets. After 7380 hr at 1350°F, Figs. 3 and 6, the needles are much larger and have replaced nearly all of the fine precipitate. X-ray diffraction studies detected the presence of hexagonal Laves phase and hexagonal n phase (Ni,Ti) in the 1350°F specimens, Table 11. Only the Laves phase was detected by X-ray diffraction in the 1200°F specimen and none was detected in the 1000°F specimen. In this latter specimen, however, the small quantity of precipitate in the grain boundaries (presumed to be Laves phase) precludes its detection by X-ray diffraction. Composition of the hexagonal Laves phase is not yet known, although its diffraction

Jan 1, 1960

By A. P. Woods, J. A. Elias, A. J. Heckler

A method is described by whichX-ray pole figures and axis density figures may be plotted automatically. The X-ray data are obtained using a Siemens texture gonionleter and the Schulz reflection method. Composite sampling methods are used to obtain a full quadrant of the pole figure. The contour lines of the pole figure and axis density figures are drawn using a computer-controlled x-y plotter. The computer program used to draw the contours was obtained from ZBM. POLE figures used to describe crystallographic orientations of poly crystalline sheet materials are usually plotted manually from X-ray diffraction output in the form of a strip chart recording of the intensity distribution of a given crystallographic pole in physical space. Today's computers and associated plotting equipment now make it possible to plot pole figures and axis density figures automatically. Inverse pole figures have been determined by mathematically "inverting" X-ray pole figure data.'-' In general, these methods require complicated, time-consuming numerical calculations. A more economical but less accurate method is to determine the axis densities of low-index crystallographic poles using an X-ray diffractometer. When these axis densities are plotted in a unit stereographic triangle contour lines can be drawn to represent the axis density distribution. This can now be done automatically. Computers were used to plot pole figures by a method developed by Holland, Engler, and powers.' In their method intensity ratios based on a random standard sample were obtained from a strip chart recording, and the stereographic (x, y) coordinates of these ratios were determined by a computer. Symbols characteristic of different intensity ratio levels were then plotted using an automatic x, y plotter and intensity contours were drawn manually. The present paper describes a method by which pole figures and axis density figures have been automatically plotted from digital data obtained from a Siemens X-ray unit. Plotting was accomplished using an IBM 1620 computer and a Calcomp 563 digital plotter. COMPUTER PROGRAM The computer program was obtained from IBM Systems Reference Library, No. 1620-CS-05X, and was designed to plot contour maps from randomly distributed data. It consists of a set of twelve separate subprograms, four of which were used in this work. The program takes a given distribution of data points and by a numerical method determines the values at mesh points of a square grid system superimposed over the input data. The output data from this program is in a form suitable for input to the contour plotting program. A smoothing program is also available which calculates new mesh point values from a continuous function fitted to neighboring mesh points. The degree of smoothing depends on the number of points around a given grid point which are used to adjust or smooth the grid value. The contour plotting program is designed to allow the user to specify the interval, scale, and annotation of the contours to be plotted. EXPERIMENTAL PROCEDURE Pole Figure Data Points. Diffracted X-ray intensities were determined using a Siemens texture goniometer and the schulzs reflection method. Due to geometric

Jan 1, 1968

By R. W. Hyde, B. S. Old, S. E. Eaton

One of the most important problems facing the steel industry at the present time is that of maintaining at a minimum the sulphur content of many grades of steel where sulphur is known to have harmful effects On both quality and yield. The present outlook in this struggle to reduce the amount of sulphur in steel is rather gloomy since the sulphur content of the raw materials available in the United States is gradually rising, with little relief in sight. A flow sheet of sulphur in the steel process is shown in Fig I. The values used here were obtained by averaging coke oven and blast furnace data at No. 5 furnace in Cleveland and are considered typical for high top pressure practice. The sulphur evolved in the blast furnace top gas was obtained by difference and since the amount is relatively small, little significance should be attached to this particular value. From Fig I it is apparent, however, that coals used in the production of metallurgical coke represent by far the largest single source of sulphur in steel-making. As an indication of the decrease in quality of these coals as regards sulphur content the weighed average annual sulphur analysis of the coals supplied to two different steel plants, since 1925, is plotted in Fig 2} The sharp rise since 1940 is strikingly apparent. Another indication of this trend is found in estimates of coking coal reserves. Thus in the case of Pittsburgh seam coals available in Allegheny, Fayette, Greene, Washington, and Westmoreland Counties in Pa. as of Jan. 1937 only 25 pct of the coal reserves would contain less than 1.50 pct sulphur after washing.2.3 Many of these lower sulphur reserves have been seriously depleted in recent years because of accelerated war demands. still another demonstration of the increasing sulphur content of coals on a country-wide basis is found in a report by the Bureau of Mines4 which shows a steady increase in the sulphur content of coke made in the United States. It should be noted that this increase continues in spite of the wider use of coal washing in recent years. Sulphur occurs in coal in three forms, pyritic (FeS2), organic sulphur, and a small amount of sulphate sulphur (CaS04). The sulphur is subsequently found in the coke in combination with carbonaceous material of is composition and as calcium and iron sulphides' In considering the general problem of sulphur elimination, the Republic Steel Corp. was interested in determining which, if either, of the two major forms of sulphur in coal contributes the greater portion of sulphur to the coke. Since the ratio of pyritic to organic sulphur varies widely in different coals, it was thought that if it could be shown definitely that the major part of the sulphur occurring in coke originates from one of the two ""jar forms of sulphur in the coal, it would then be possible to select with confidence coal which, although high .in total sulphur, would yield coke of fairly low sulphur content. Using the new

Jan 1, 1949

By F. R. Zachar

IT has always been understood, in northern West Virginia where both the Pittsburgh and Sewickley seams are mined, that pillaring or splitting in the lower Pittsburgh seam could break the interval strata and make mining in the overlying Sewickley difficult or impossible. In some instances, however, mining methods practiced in the overlying Sewickley have reversed the problem, resulting in a shifting of the intermediate layer and destroying valuable acreages of the Pittsburgh seam below. The Pittsburgh seam in this area is, on the average, 102 in. thick. About 18 in. of low-quality head coal are left for roof protection as it is mined. Immediately over the coal are two draw slates, two rider 'seams, and a good hard black shale, locally called black rock, which serves as a permanent roof where draw slates and riders are taken down on certain main haulroads. In most areas mined in this seam in the past the bottom has been satisfactory but soft. However, in areas now being mined by the Christopher Coal Co. in Monongalia County the bottom is very hard and unyielding. The Sewickley seam, lying 85 ft above the Pittsburgh, will average nearly 70 in. in thickness and is overlain by massive shales and sandstones. Much of the seam is mined only down to the "sheep skin," a hard band about 4 in. above the bottom, which is composed of relatively hard shale. Fig. 1 shows a typical cross-section through the Pittsburgh and Sewickley seams in the area being discussed. The thin Redstone seam is not deep-mined but is stripped in some locations where it outcrops. Most of the Sewickley seam in the Morgantown areas has been mined out from 10 to 30 years. There are at present only two large mines and five or six others of small production operating in that seam. Mining systems in the past were generally of the room and pillar type with some full pillar extraction. This seam in the Scott's Run area was operated by as many as thirty or forty different companies at one time, during an era beset with strikes, market failures, and depressions. Most of the barrier pillars along the many main haulroads were abandoned, and blocks of Sewickley coal that would be fully recovered with today's machinery were left unmined when conditions became anything less than favorable. Consequently the mined-out Sewickley is spotted throughout with solid blocks varying in size from 100x100 ft to 200x400 ft and larger. It is these unmined Sewickley blocks surrounded by worked-out portions that have caused transmissions of roof stresses to underlying Pittsburgh mining areas, see Fig. 2, resulting in untold difficulty. As the Christopher Coal Co. operates both the Pittsburgh and Sewickley seams, accurate maps of workings in both seams are readily available and are regularly consulted. The first Pittsburgh squeeze attributed to overlying Sewickley blocks occurred in the Arkwright mine, where a shuttle car crew was developing a section consisting of seven panel headings. These entries were being driven in solid coal 3400 ft from the nearest worked-out Pittsburgh area. As mining advanced it was noticed that certain ribs began to slough and certain areas to show signs

Jan 1, 1952

By H. D. Keiser

Minor industrial minerals included in this chapter are: the alum minerals, bromine, calcium chloride, epsomite and other natural magnesium salts, iodine, meerschaum, quartz, industrial crystals other than quartz, and nonfuel gases (air, helium, carbon dioxide). Alum Minerals The natural alums comprise a group of hydrated double sulfates, the most important of which are potash alum, KAI(S04)2.12H20, the "alum" of popular usage; ammonium alum, (NH4)AI(SO4)2, known mineralogically as tschermigite; and soda alum, NaAI(SO4)2.12H20. Kalinite, KAI(SO4)2.11H20, and mendozite, NaAl(SO4)2, 11H20, are fibrous monoclinic alums, distinct from the isometric species potash alum and soda alum.4 Alunite, KAI3(S04)2(OH)6, also known as alumstone or alum rock, has been used as a raw material in the manufacture of alum since early times. All the natural alums are highly soluble and occur as surface evaporation products in arid regions or in sheltered places. Potash alum, together with the other natural alums, commonly occurs as an efflorescence or crevice filling in argillaceous rocks and brown coals that contain disseminated pyrite or marcasite. The mineral is derived by the action of sulfuric acid, formed during the weathering of the sulfide, upon alkali-rich aluminum silicates. Ammonia alum is found chiefly in lignite or broad-coal beds and bituminous shales. Alunite is most commonly associated with acid volcanic rocks, where the rock has been largely altered and alunite formed owing to the presence of sulfuric acid solutions or vapors. Aluminum sulfate, which for most uses is the essential ingredient of alum, may be found in saline residues resulting from the evaporation of natural water and may be formed by the action of acid waters upon aluminous rocks. A deposit of natural potash alum occurs in an irregular network of veins associated with sulfur in rhyolite in Esmeralda County, Nevada, about 35 miles west of Tonopah and 10 miles north of Silver Peak. Alum was recovered at a plant operated on the property between 1920 and 1923 by crushing the ore to ¾ in., grinding to minus 80-mesh, and counter-current leaching; the resulting alum solution was then filtered and crystallized. Alunite was of much interest during World War I as a source of potash and during World War II as a source of alumina. The wellknown deposits at Tolfa, Italy, are veins in trachyte and have been the basis of alum manufacture there since the middle of the fifteenth century. Pure alunite is insoluble in water and in common acids, but if it is heated to 500°C it loses its water of hydration, and the residue consists largely of anhydrous potash alum, part of which is readily soluble in water or acids. If the heat is increased beyond 500°C, most of the sulfur combined with the alumina is released as oxides and the residue consists of potassium sulfate and alumina. Thus, either potash alum (and aluminum sulfate) or potassium sulfate and alumina may be made. In the

Jan 1, 1960

By T. Glen Heslop, Dennis H. Laubscher

INTRODUCTION In all cave mining operations waste is drawn mixed in the ore, hauled, hoisted and milled. This waste usually contains some mineral which partly covers some of the costs of mining and milling it, but it still re- presents a loss of profits as the production rate from the mine is matched to the mill capacity - every tonne of waste milled replaces a tonne of profitable ore. Draw control aims to reduce the amount of waste drawn and to increase the amount of ore recovered. It is also used to regulate the grade of ore flowing to the mill and in block cave blocks to prevent potential stress build- up on the major apexes above grizzly drifts. This paper summarises what has been learnt about draw control in the forty years that cave mining methods have been used in the three largest underground chrysotile asbestos mines in the southern hemisphere. The four mining methods to which draw control has been applied are: a. Block caving. b. Shrinkage with overburden caving. c. Sublevel caving. d. Open stoping. Open stoping has been included because on a number of occasions severe falls from the back and side of these open stopes have occurred. Without full records of where and when ore is blasted, when and how much ore has been drawn from each of the drawpoints, it would be impossible to analyse the migration of ore and fallen waste in the stope. Several problems peculiar to chrysotile asbestos ore bodies affect the practice of draw control. Heterogeneous fragmentation, cavities, side pressures and the interaction of stresses in the caved ore affect the migration of ore under draw. Fibre is normally not developed uniformly throughout the ore bodies, values vary from place to place but there is usually a general decrease upwards and the hangingwall contact is an economic limit. The immediate hangingwall rock frequently looks like the ore body hostrock and is difficult to recognise in a drawpoint, and cannot be used as the marker for stopping draw. During caving or shrinkage, a large proportion of fibre becomes detached from the host rock and re- ports in the fines, which migrate differently to the larger rocks. The fines are not sticky, and flow easily if loose and dry, but compacted, the fibre and rock fines con- solidate the ore. During draw the proportion of fines in the ore varies considerably, as fines either flow relatively freely between the large rocks or become trapped and compacted above large rocks or hangups. This creates a large sampling error in drawpoint grade assessments, whether done visually or by bulk sampling, unless the assessments are done frequently. The method of draw control used is to regulate the draw rate in an attempt to lower the ore-waste interface as evenly as possible, and to finally stop working the drawpoint when a calculated tonnage has been drawn.

Jan 1, 1981

By C. L. Mantell

When considered from the viewpoint of world annual output, tin is one of the rarest metals. Its annual production is exceeded by that of iron, copper, lead, zinc. aluminum, magnesium; probably by that of the ferroalloys of manganese, chromium, and silicon, and possibly by the world production of sodium; while it exceeds only the output of such common metals as nickel, antimony, mercury, tungsten, molybdenum, silver, gold and the precious metals. Cassiterite, or tinstone, until the second World War was the only mineral that was an important source of tin. This mineral is frequently called "tin ore." The use of the term should be restricted to the ore containing the mineral, and not, in addition, to the concentrates of the mineral obtained from the ore or from stanniferous alluvial deposits. There is a general misuse of the term "tin ore" in the Malay Peninsula and adjacent localities, particularly where most of the mineral is obtained from secondary stanniferous deposits. The term "cassit-erite" is exclusively used in mineralogical, geological, and other scientific writings; it is unfortunate that it is not mole frequently used when referring to the occurrence of the mineral on an economic scale. Ores "Tinstone" js a very convenient old English term deserving a more frequent use. Tinstone is a dioxide of tin, or stannic oxide. When chemically Pure, as in the very rare transparent variety, it has a metallic content of 78.6 per cent tin. Frequently, however, the crystals and grains contain appreciable amounts of impurities, chiefly iron and tantalum. The impurities here referred to are those actually in the mineral itself. Tinstone usually has a deep brown or black color with an adamantine luster. Several other colored varieties are known, among them red ruby tin, yellow rosin tin, and yellow wax tin. the names jn each case being descriptive of the mineral's appearance. Ainalite is a variety of cassiterite con-taining almost g per cent of tantalum pentoxide. Sparable tin, tooth tin, and needle tin, as a result of their acute dite-tragonal pyramidal crystalline form, re-ceive their names from their crystallo-graphic appearance. Wood tin is a compact variety of cassiterite composed of radiating fibers resembling dry wood. Toad's-eye tin is a similar variety on a smaller scale in which the fibers appear to resemble the eye of a toad. Stream tin is water-worn tin-stone. Float tin is sometimes employed to describe the cassiterite occurring in soil derived from the weathered surface of a mineralized area. Stannite is an ore of tin of lesser impor-tance than cassiterite. It is a sulphide of tin, copper, and iron, sometimes known as tin pyrites or bell-metal ore. Its chemical com-position is sometimes expressed by the for-mula Cu,S.FeS.SnSz with zinc usually present in varying quantities. The tin con-tent varies from 22 to 27 per cent and there is about 29 per cent of copper, 13 per cent of iron, and 30 Per cent of sulphur.

Jan 1, 1944

By R. S. Goodrich, G. S. Ansell

The microstructure of three Al-Al2O3 SAP-Type alloys (containing 2.0, 3.0, and 5.7 wt pct alumina, respectively) was studied utilizing transmission electron microscopy. These alloys were fabricated from aluminum powders by powder-metallurgical techniques, cold-rolled into thin strips, and recrys -tallized. Thin foils suitable for an electron-transmission study were then prepared from the strip material by electropolishing. The microstructure of these alloys is shown to consist of small (0.1 mean diameter) plate -shaped alumina particles finely distributed in an aluminum matrix. In the higher-oxide content alloys the platelets are somewhat larger and more irregular in shape. The distribution of oxide particles is not uniform and there is an increasing tendency toward clumping SINCE the discovery by Irmann1 that aluminum alloys produced by compacting, hot pressing, and extruding fine aluminum powders possess remarkable high-temperature mechanical properties, the Al-A12O3 SAP-Type alloys have been utilized extensively as model dispersion-strengthened alloys in both experimental and theoretical invest igations.2-8 The use of the SAP-Type alloys as model dispersion-strengthened alloys implicitly assumes that their microstructure has been completely delineated. This is, however, not the case. with increasing oxide content. In all the alloys studied, the mean center-to-center spacing of particles was quite small (0.2 u) due to the very fine oxide debris present. Selected-area diffraction of the specimen identified the oxide as either y Al2O3 or y' Al2o3. The re crystallized MD-5100 alloy exhibited a mean grain diameter of only 0.7u, while the grain size of the other alloys was several hundred microns. Severe pinning of the grain boundaries by oxide particles was rarely observed, and the grain boundary triple points in the small-grained MD-5100 alloy were often particle -free. Diffraction contrasts visible around the particles are attributed to elastic strain fields set up by differential thermal contraction during cooling from the recrystallization anneal. Early investigation demonstrated that optical metallography did not possess sufficient resolution to observe the microstructure of the SAP-Type alloys.' Later, extensive use was made of replication techniques to study the microstructure by means of electron microscopy.7-9 These studies indicated that the SAP-Type alloys consist of a dispertion of irregular Al2O3 platelets, approximately 150A thick 9 and a micron or so on edge,9 distributed in a matrix of commercial-purity aluminum. These oxide platelets tend to be oriented in the aluminum matrix, with their largest dimension parallel to the extrusion direction. 8,9 A study employing polarized-light techniques1' indicated that the grain size of a series of as-extruded SAP-Type alloys was several microns in diameter, while the grain size after re-crystallization was several millimeters in diameter. A more recent study 12 utilizing surface-replication techniques examined the particle morphology,

Jan 1, 1964

By Victor Formanek, Paul Chataignon, Maurice Rey

IT is found when floating oxidized lead ores by sulphidization, that the presence of calcium salts in the water, is usually detrimental and lowers the recovery. This effect is particularly marked in dry countries such as North Africa, where the waters often carry large amounts of calcium sulphate and where the ore may even contain gypsum. The effect of calcium salts is readily visible. Whereas in their absence cerussite is quickly stained brown and then black by sodium sulphide, in their presence the mineral remains very light in color. A similar effect is produced when barium sulphide is used as a sulphidizing agent instead of sodium sulphide. Magnesium salts have little or no effect and even tend to reduce the detrimental effect of calcium salts. A study of this phenomenon indicates that it is due to the precipitation of calcium or barium carbonate in contact with the mineral simultaneously with the formation of lead sulphide. The chemical reactions can be interpreted as: PbCO3 + Na2S = PbS + Na2CO3 CaSO4 + Na2CO3 = CaCO3 + Na2 SO4 They might also be written: PbCO3 + S = + Ca++ = PbS + CaCO3 The precipitation of calcium carbonate can be followed by the lowering of the pH with which it is accompanied. Magnesium carbonate is more soluble than calcium carbonate and usually does not precipitate under the conditions prevailing. It is interesting to note that calcium salts have no effect on anglesite (lead sulphate) because calcium sulphate is soluble, but barium salts hinder the sulphidization of anglesite because of the precipitation of barium sulphate. Remedies When calcium sulphate is present in large amounts, the softening of the water with soda ash is usually too expensive to be considered, but the precipitation of the objectionable calcium carbonate can be prevented in two different ways. One is the use of sodium hydrosulphide instead of sodium sulphide. This salt gives a lower pH than sodium sulphide and does not bring about the immediate precipitation of the calcium which remains in solution as calcium bicarbonate. The other procedure is to add ammonium salts such as the sulphate or chloride which have the property of increasing markedly the solubility of calcium carbonate. Ammonium salts have other effects such as cutting down conditioning time and accelerating flotation. They should be added to the flotation cells rather than to the ball mills. Table I. Effect of Sodium Hydrosulphide and/or Ammonium Sulphate on the Flotation of Two Oxidized Lead Ores Mibladen Ore4 La Plagne Ored Con- Tall- Con- Tail-centrate ing centrate ing Reagents Pb, Pct Pb, Pct Pb, Pct Pb, Pot Without addition of CaSO, NaS 56.0 0.68 43.4 0.65 NaSH 56.2 0.60 40.4 0.50 Na2S + (NH4)2SO4d 54.6 0.56 NaSH + (NH4)2SO4d 43.0 0.66 With addition of 40 lb/ton CaSO4 Na2S 39.4 3.85 34.0 3.21 NaSH 49.1 0.70 49.6 0.88 Na2S + (NH4)2SO4d 53.9 0.85 NaSH + (NH4)2SO4d 51.0 0.45 41.1 0.78 In table I are given the results of representative tests on two different oxidized ores. They show that the strongly detrimental effects of calcium sulphate can be offset by the two procedures outlined above. Sodium hydrosulphide is now used regularly on a mill scale on certain ores. Tests are being carried out with ammonium salts. It should be noted that malachite is subject to influences similar to cerussite. One final word of caution—when the ore is rich in primary slime, which is flocculated by the calcium salts, it may be indispensable to remove these by washing or precipitation with sodium carbonate instead of keeping them in solution by the above methods. Acknowledgment We wish to thank Socibtk Miniere & Metallurgique de Penarroya and Minerais et Metaux, for permission to publish these results.

Jan 1, 1951

By D. R. Hay, E. Scala

STUDIES of structure-sensitive properties, especially mechanical behavior, have shown that grain and subgrain structure play an important role. The mechanical properties of tungsten, in particular, are sensitive to the nature of the intergranular structure. Substructure and dislocation networks in single-crystal and polycrystalline tungsten have been studied by Nakayama et al.' Various orders of substructure were observed ranging from a microscopic first order (grain diameter: 2 to 8 mm) to a microscopic second order (grain diameter: 50 to 300 p), and, within the latter, dislocation networks forming an even smaller order of substructure. In their single crystals, grown by arc fusion, the degree of misorientation in each order was small: 16'3OU, -11, and -10" for the first-, second-, and third-order substructure, respectively. To study the properties of polycrystalline tungsten, powder metallurgy tungsten is generally used. However, in a mechanical property investigation, the zone-melted or arc-fusion crystals are more desirable than the powder metallurgy product due to their higher purity and absence of porosity and other defects inherent in consolidation by powder metallurgy. Grain boundaries can also be produced in melted stock by working and recrystallizing. However, material with subgrain mis orientations of the order of several degrees (high-angle substructure) has not been reported previously and is the subject of this communication. Crystals were grown by electron-beam, floating-zone melting. The starting material, Sylvania Pure-tung welding rod, was given one zone pass at a traversal rate of -2 mm per min. Through control of the zone temperature, it was possible to influence the degree of crystal perfection. By maintaining the zone at a high degree of superheat, high-perfection crystals could be grown. However, at temperatures only slightly above the melting point, the zone-melted crystals contained a high-angle substructure. A sensitive control of the zone temperature was not possible due to the difficulty of estimating the temperature of the zone and of providing a constant supply of power to the sample. Therefore, an empirical method, using the shape of the molten zone as a criterion, was adopted as an indication of temperature. At high degrees of superheat, the surface tension of the molten zone decreases and a neck forms at the top of the zone, whereas at low zone temperatures the diameter of the zone remains reasonably uniform. Although it was not possible to obtain a continuous variation of misfit angle, the conditions could be directed toward the growth of either high- or low-angle substructure by maintaining only a slight neck in the zone (sufficient to establish that it was molten) or a well-necked zone, respectively. Mass spectrographic analyses of both types of material revealed no significant differences in the concentrations of their impurities. The degree of misorientation at high angles was obtained by measuring the angular spread of spots corresponding to a single reflection on a Laue back-reflection photograph. Fig. 1 shows a typical Laue back-reflection photograph of a crystal with a 3-deg spread. By measuring the angular deviation of the spots corresponding to a single reflection from the mean center of the spots around which constant angular deviation contours were drawn, an average angular spread of misfit could be calculated. The angular average was weighted by the number of spots observed in each angular interval. At angles greater than 5 to 6 deg the spots from different reflections begin to overlap, and cannot be associated with a particular reflection. Laue back-reflection photographs taken at different locations on samples .with approximately 3-deg spreads showed only a small difference in angular misorientation, less than 8' of arc, within individual specimens. The microstructure was examined using Berg-Barrett X-ray extinction contrast microscopy. Berg-Barrett photographs taken directly on the as-grown surface, Fig. 2, show an essentially equiaxed subgrain structure of -0.1 mm in average grain diameter in both high- and low-angle crystals. Fig. 2(a) is a photograph of a sample with a low misfit angle and Fig.

Jan 1, 1968