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By A. S. Yue, A. G. Guy

A study was made of the effects of a prolonged flux of zinc atoms through the a solid solution of zinc in copper. The experimental arrangement consisted essentially of a copper disk about 0.01 in. thick, at one of whose surfaces a gaseous atmosphere containing zinc atoms was maintained, and at the other surface a gaseous atmosphere with a minimum of zinc atoms was maintained. During prolonged theothersurfaceexposure at high temperatures the zinc content of the copper disk gradually built up to the steady-state concentration distribution and then remained at this value. The concentration-distribution curves for various conditions were determined by chemical analyses. The results showed that the condition of steady-state diffusion was achieved. The diffusion coefficients calculated from the experimental data, although not of high precision, agreed with the values obtained by other workers using unsteady-state methods. Relatively slight porosity developed in the specimens in the course of diffusion. A LTHOUGH most diffusion studies have been made under unsteady-state conditions, it is known' that the steady-state method is often superior with respect to the directness and accuracy of interpretation of the data. Steady-state diffusion of gases through metal diaphragms is well known. Also, Harris' and Smith" have used the steady-state method in studying the diffusion of carbon in aus-tenite. The accepted mechanism in this system involves the motion of the interstitial carbon atoms in the rigid framework of the lattice of iron atoms. Thus, there is little difficulty in visualizing the steady flow of the small carbon atoms through the austenite. The situation in substitutional diffusion is quite different. Here the atoms are comparable in size, and it is not evident how a steady flow of one of the atoms through the solid solution might be achieved. At the time the present research was started, it was known that a previous exploratory attempt to produce steady-state diffusion in a substitutional alloy, the Au-Ag system,' had been unsuccessful and had indicated that perhaps there were basic difficulties that could not be ovei-come. Therefore, the present research began as a study of the effect of a prolonged flux of metal atoms through a substitutional solid solution. Eventua.lly, it was possible to produce actual steady-state diffusion in the system chosen for study, the a Cu-Zn alloys. Experimental Procedure The aim in the experiments was to maintain a high zinc content, about 30 pet, at one surface of a copper sheet, and to maintain a low zinc content, near 0 pet, at the opposite surface. The zinc would then diffuse into and through the copper, first building up to the steady-state concentration distribution and then maintaining this distribution. The three types of specimens that were used are shown in Fig. 1. In type A specimens the copper disk through which diffusion occurred was welded to the top of a cylindrical molybdenum tube, the bottom of which also was sealed by welding. At the diffusion temperature the brass chips in the molybdenum container were the source of the zinc vapor which maintained the lower surface of the copper disk at 30 pet Zn. The upper surface was maintained at 0 pet Zn by the vacuum in which type A, and also type B, specimens were diffused. Since the molybdenum container was impervious to zinc vapor, it was intended that the only path of escape for the vapor from the brass chips would be through the thin copper diffusion disk. However, it was found that small leaks often developed at the welded joints during the diffusion treatment, and in most specimens some of the zinc was lost in this manner. Although even small losses of this kind were a serious handicap in attempting to determine the flux through the disk, they did not prevent the maintenance of satisfactory boundary conditions for the attainment of the steady-state condition. Type B specimens differed from type A in having a weight of about 300 g supported on the copper disk by 15 to 20 short quartz rods. This change was made when it was observed that the copper disk was being bowed upward by the difference in the pressures acting on its two surfaces. Since the grain-boundary cracking which occurred in the bowed specimens could be attributed largely to the accompanying creep,3 it was desirable to minimize this effect. The counterweight was effective in significantly decreasing both bowing of the disk and cracking at grain boundaries. Type C specimens differed considerably from the others in that the low-zinc atmosphere at one sur-

Jan 1, 1959

By David Burgess, Hershiel H. Hayden

Experiments at the Somerset mine, Colo., under an agreement between US. Steel Corp. and the US. Bureau of Mines are described. A test was made of the tube bundle method of mine air sampling which was developed for European longwall mines; some 300,000 running feet of tubing provided continuous monitoring at 38 locations. Carbon monoxide concentrations were obtained with standard deviations of less than 1 ppm and oxygen concentrations with standard deviations of less than 0.2%. A base level of CO index (ppm CO evolved per percent 0, removed) was determined to be zero to 20 through most of the passageways of the mine. However, in one working section where the coal was initially hot (about 180°F within a pillar) the CO index was demonstrably higher, 120 trending upward to about 60 when smoke appeared and the section was sealed. The data are discussed in terms of laboratory experiments on CO evolution from coals.

Jan 1, 1977

By Waynw P. Myers

Electricity, as normally thought of by a layman's definition, is a man- made 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 Mine Safety and Health Ad- ministration (MSHA), 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, 1981

By Rossiter W. Raymond

As I have attempted briefly to show you, gentlemen, the present position of the mining and metallurgical industries of this country offers in several respects most important indications of radical change. This is an epoch for more than one branch of these industries. We are commencing again to export copper; we have shifted the main production of lead from the Mississippi Valley to the far West, besides developing a new production of that metal in Missouri; we have seen the price of quicksilver go up, and the price of iron go down to such an extent as to affect profoundly, on the one hand, the great business of extracting silver by amalgamation, through the Washoe process in this country and the patio process in Mexico, and, on the other hand, the various manufactures employing iron as a raw material; above all, the manufacture of steel. But the epoch which has occurred in the relative value of gold and silver, in consequence of causes which I shall attempt to explain, and among which the extraordinary increase in the silver product of Nevada is not the least; this epoch is, perhaps, the most striking feature in the review of our situation. Since my official duties in connection with the mining industry of the Pacific slope and the Great Interior Basin have led me to pay particular attention to this subject, I have thought it not inappropriate to lay before you a somewhat extended account of its history. It is a topic of peculiar interest, because of the general use of these two metals as standards of value in the exchange of commodities. Neither of them is suitable to be, for the political economist, a real standard of value. That standard is rather to be sought in some more universal product of labor, such as wheat—the relation

By V. R. Garflas, J. W. Ristori, R. V. Whetshel

Preliminary estimates indicate that world consumption of petroleum products and related fuels in 1937 shattered previous records with a figure of 1,920,000,000 bbl.; that is, 124,000,000 bbl. more than the 1936 total. The writers, as in previous years, have been unable to account for all the available supply in 1937. This "unaccounted-for" supply, which formerly was thought to go largely into storage in foreign countries, was close to 53,000,000 bbl. in 1933; 93,000,000 in 1934; 111,000,000 in 1935; 75,000,000 in 1936 and 148,000,000 in 1937. As this discrepancy between supply and demand continued year after year, it became evident that other reasons than additional foreign stocks were responsible for it. It can now be stated that the "unaccounted-for" supply (see Table 1) goes to take care of: (1) consumption of petroleum products and related fuels for military purposes, the figures of which have been and are kept confidential by foreign countries, (2) additions to stocks to be consumed for military and nonmilitary purposes in foreign countries on which likewise no information is available, (3) errors incurred in the conversion of figures of production of crude oil, its products and related fuels from "weight" units, as used in Russia, for instance, to their American or "volume" equivalents and vice versa, and (4) to the lack of reliable statistics on production and consumption, particularly from Russia, the

Jan 1, 1938

By L. H. Robinson

A proposed method of drilling utilizes sequential detonation of two types of explosive charges delivered to the hole by a conventional drilling fluid through pipe. A shaped charge first produces a long thin hole. A second charge, called a gauging charge, is pumped into the thin hole, explodes, and enlarges it to full gauge. In one suggested configuration, the explosives are contained in cylindrical capsules 4- to 5-ft long. A drilling head is positioned 2- to 3-ft off bottom. When a capsule is pumped to the bottom of the hole and stops, pressure inside the drill pipe increases and differential pressure detonates the explosive. Primacord along the length of the capsule disintegrates the capsule. The debris circulates out of the hole with the drilling fluid. The gauging-charge action was examined using 2-ft cubes of Berea sandstone. The sandstone (18 per cent porosity) was vacuum-saturated with water and surrounded by concrete. To prevent reflected tensile pulses, the acoustical impedance of the concrete matched that of the sandstone. A 750-psig pressure was applied to a drilling fluid within a shaped-charge-formed hole before detonating the gauging charge. In these tests, 190 gm of rock were removed for each gram of explosive detonated. A similar series of experiments on low-porosity (0.40 per cent) metamorphic limestone provided a more rigorous test. Extensive fracturing from the gauging-charge action prevented an estimate of the volume of the expanded hole. The diameter of the hole was irregular, ranging from about 2 to 4 in, or about fivefold larger than the hole created by the shaped charge. INTRODUCTION In the past, explosives have found a varied but somewhat limited use in the oil field. An early well stimulation technique, still in use today, in vo lves shooting ni troglycerin to en large the borehole and to increase matrix permeability near the wellbore. Bullets and jets are now the conventional method of perforating casing and tubing. Detonations are frequently used to "back off" or "shoot off" stuck pipe and, of course, seismo-graphic work has long depended on explosive-generated pulses to find attractive earth structures. Efforts to use explosives in drilling operations have received limited examinations1-3 which, in one respect, is surprising because explosives offer one way to transmit large amounts of energy directly to the bottom of the hole. Recently, Ostrovskii l described a Russian method of drilling with explosives that utilizes small capsules containing explosives which are pumped into the mud stream to the bottom of a borehole. As the capsules leave the end of the drill pipe, a detonation mechanism is armed. Impact detonates the explosive. In another configuration, two liquids (an oxidizing agent and fuel) in the capsule are separated by a frangible membrane. Separately, the liquids are nonexplosive. Near the bottom of the drill pipe, the capsule passes through a narrow constriction which ruptures the membrane. The mixing of the liquids produces an explosive. Impact is again used to detonate the explosive. About the time Ostrovskii was developing his method, Humble Oil & Refining Co. was independently doing research on another explosive drilling concept based on the sequential detonation of two types -of explosive charges. The proposed technique consisted of alternately pumping a shaped charge and then a "gauging charge" down a well. The shaped charge should drill a long, tapered hole, and the gauging charge should expand it to full gauge. This paper presents the visualized drilling concept and gives results of laboratory work which showed that sequential firing of charges can form hole at an attractive charge-to-rock removal ratio. An important finding was that increased environmental pressure, which is to be expected in wells, increases rock removal efficiency of the gauging charge.

Jan 1, 1966

By J. H. Hensley

The mine of the Miami Copper Co. is in the Miami district, Gila County, Ariz., approximately 7 miles west of Globe. In 1906, the General Development Co. secured the ground now owned by the Miami Copper Co., and about a year later discovered ore in a prospect shaft at a depth of 220 ft. The Miami Copper Co. was organized in 1907, the claims held by the General Development Co. were transferred to it, and an active development campaign was inaugurated. The railroad was extended from Globe to Miami in 1909, a concentrating plant was constructed, and the company began producing early in 1911. The unit size of mineral tract in the district is the standard lode claim 600 ft. in width by 1500 ft. in length. Ownerships of land are held in fee. The geology of the district has been described by F. L. Ransome.' The formations of local importance are: The pre-Cambrian Pinal schist, which consists mainly of metamorphosed sedimentary rocks and is commonly of a thinly laminated sericitic variety; the diabase, which is thought to have been intruded in late Paleozoic or early Mesozoic times; the Schultze granite and granite porphyry, considered early Tertiary; the dacite of late Tertiary time; and the Gila conglomerate of early Quaternary. General Items Influencing Mining Methods The bodies of disseminated ore in the district are flat lying masses of irregular outline and variable thickness. As a rule, these masses lack definite boundaries; the orebody follows a curve along one of the main ridges, approximately 5500 ft. in length with a maximum width of 1600 ft. The minerals occur as finely divided and uniformly disseminated chal-cocite in the Pinal schist and Schultze granite. The typical overburden or capping is a barren rusty brown, very friable, highly siliceous, leached schist, or granite-porphyry. The topography of the district is fairly rugged and irregular; the altitude ranges from 3400 ft. above sea level, at the town of Miami, to 3900 ft. on the hills above the Miami orebody. The climate is mild; the mean annual temperature is 63.°F.

Jan 1, 1925

G. F. COMSTOCK (author's reply to discussion *).-The discussion of this paper has been of such volume and interest as to constitute in itself a sufficient excuse for the paper, even though the paper itself may have been as much in error as some of its critics have maintained. Mr. Howard does not appear to realize some very practical facts that the opponents of his theory have advanced. Among these are: the coarsely crystalline fracture of the nucleus of a transverse fissure, so different from the smooth fatigue break around it; the occurrence of fissures in large numbers in certain heats or rollings of rails, while other heats or rollings do not develop them; and the much smaller proportion of transverse fissures found in rails rolled .from reheated blooms as compared with direct-rolled rails. These facts are not explained by Mr.

Jan 6, 1919

By B. G. Reisdorf

This paper describes the microstructural changes that occur when quenched ultrahigh-strength steels containing OA pet C and various amounts of nickel, silicon, and cobalt are tempered. The changes that occur in hardness, yield strength, and martensite diffraction-peak widths when these steels are tempered are related to the precipitation of the carbide phases. An unea$ectedly high silicon content (about 30 pct) was found in the E -carbide phase in a steel containing only 1.5 pct Si. TEMPERED martensitic steels have such wide-spread utility that they have been the subject of numerous investigations, and a sizable amount of literature has developed on this subject.M This investigation, which is a part of a larger program to correlate microstructure with mechanical properties at a variety of strength levels, is limited to the microstructural changes that occur when a quenched 0.40 pct carbon steel (USS Airsteel X-200 steel) is tempered, and to the effects of the alloying elements—nickel, cobalt, and silicon—on these microstructures. Used in this investigation were electron microscopy, electron-diffraction identification of the carbide phases, electron-probe micro-analysis of the carbides, X-ray determinations of retained austenite, and measurements of martensite X-ray diffract ion-peak widths. MATERIALS AND METHODS The chemical analyses of the eight heats examined eats No. 30 through 37) are shown in Table L Heat No. 30 has the chemical com~osition of Airsteel X-200, and the remaining seven heats contain various amounts of nickel, chromium, cobalt, and silicon. The heats were air-melted in an induction furnace and cast into 8 by 8 in. ingots that were subsequently heated to 2300 and rolled to 1-in.-thick plate. Oversize 0.505-in.-diam tensile specimens were rough-machined from the plates and austenitized in air at 1700° F for half an hour and oil-quenched. The specimens were then tempered in air at temperatures of 400° to 1000 for tempering times of 1, 4, and 16 hr, and finish-machined to 0.505-in.-diam tensile specimens. Electron micrographs were prepared from Formvar replicas of the midthickness of tensile-specimen shanks that had been electrolytically polished and etched in nital. Electron-diffraction patterns were obtained from carbon-extraction replicas. The replicas were prepared by etching the sample surface in the same manner as for microscopy, evaporating carbon on the etched surface, and re-etching the sample to free the carbon film and the precipitate particles. Electron-probe microanalysis was performed on some of the extraction replicas. To obtain adequate fluorescent X-ray intensities, several thicknesses of replica were exposed to the electron beam so that the results represent an average composition of the extracted particles rather than an analysis of single precipitate particles. The retained austenite contents of the specimens were determined by an empirical X-ray diffraction

Jan 1, 1963

By R. H. Wightman, G. H. ADAM

In order to secure good results in the prevention of accidents, it is generally recognized that the desire for such accomplishment, as well as the aggressive and constructive action to achieve it, must emanate from the Top Management and permeate successively down through the "Chart of Authority" to the workmen. Several years ago, with the above as a basis and with full support of the Top Management, the Mining Department started a program of selling the foremen and bosses the idea that safety could be achieved and that it was desired and required. Using psychology, persistence and numerous other methods, the foremen and bosses were finally impressed with the idea that "It can be done" and "It will be done." With this in mind, new ideas were brought forth by the foremen and bosses regarding the caving operation and the specific jobs in the operation. These new ideas were taken up in round-table discussions and resulted in certain changes in the undercutting method and the actual drawing of the blocks. These changes resulted in increasing fragmentation of the blocks which prevented the usual hang-up areas in the blocks. With the rock smaller in size and within reasonable reach from the tapping drifts, accidents were prevented in the tapping section. At the same time, an enforced campaign of housekeeping throughout the mine was undertaken with very beneficial results. The foremen and bosses then, in turn, educated and trained the workers themselves to become safely conscious. In so doing, a constant re- minder was given on all jobs assigned that the job was to be done safely as well as efficiently. No man is assigned a job who is not qualified for the type of work required. Efficiency and safety go hand in hand.

Jan 1, 1949

By R. F. Stahl, W. A. Martin, R L. Huntington

A marked gravitational segregation of liquid has been observed to take place in a number of volumetric fields toward the later stages of their oil-producing periods. This phenomenon has been pronounced in thick, highly permeable sand formations such as those of the wilcox zone in Oklahoma City. This observation has prompted considerable research directed toward the semiquantitative determination of the equilibrium saturation distribution of oil vertically throughout a formation at final depletion. In this paper, data are also presented showing the transient distribution of liquid at different stages of the depletion period. Other experimental results show the effect of temperature on the drainage rates of water, Wilcox crude oil, and a close-cut heptane fraction. Intermittent drainage of liquid produced saturation gradients that might well be expected from the flow theories involved, Yields of the various liquids varied from 50 to 75 per cent of the original fluid content of the sand-packed (4 in. by 8 ft.) vertical tube. Introduction In certain volumetric Oil fields the performance of the reservoir during the latter part Of its producing life is governed to a large extent by the downward movement of liquid due to the force of gravity. This is especially true of formations having thick or tilting beds of uniformly high permeability, free of shale breaks. Laverett4 and Katz3 have presented original data and discussed the theory relating to the capillary and gravitational forces acting On liquids contained in a sand body. These investigators have pointed out the importance of such studies in the estimation of future reserves as well as the original fluid content of a reservoir. In this previous work, no data have been reported showing the history of saturation distributions during the drainage period. Since a knowledge Of these transients is helpful in obtaining crude Oil from such a reservoir, the authors have obtained these data during this investigation. Experimental Apparatus The drainage tests were carried out in two vertical tubes, 8 ft. high and consisting of 2-in. and 4-in. standard wrought-iron pipe, respectively. Each tube was equipped with a water jacket, which could be kept virtually isothermal ( ± 1.0ºF.). A diagrammatic sketch of the 4-in. tube and its auxiliaries is shown in Fig. 1. At 6 in. above the base of the tube, and at every foot above this point, core nipples were inserted through the water jacket. These nipples were closely fitted with steel-plug inserts during each drainage run. At the end of the run, these inserts were removed so that cores could be obtained from the sand-packed tube.

Jan 1, 1943

By R. F. Stahl, W. A. Martin

A marked gravitational segregation of liquid has been observed to take place in a number of volumetric fields toward the later stages of their oil-producing periods. This phenomenon has been pronounced in thick, highly permeable sand formations such as those of the wilcox zone in Oklahoma City. This observation has prompted considerable research directed toward the semiquantitative determination of the equilibrium saturation distribution of oil vertically throughout a formation at final depletion. In this paper, data are also presented showing the transient distribution of liquid at different stages of the depletion period. Other experimental results show the effect of temperature on the drainage rates of water, Wilcox crude oil, and a close-cut heptane fraction. Intermittent drainage of liquid produced saturation gradients that might well be expected from the flow theories involved, Yields of the various liquids varied from 50 to 75 per cent of the original fluid content of the sand-packed (4 in. by 8 ft.) vertical tube. Introduction In certain volumetric Oil fields the performance of the reservoir during the latter part Of its producing life is governed to a large extent by the downward movement of liquid due to the force of gravity. This is especially true of formations having thick or tilting beds of uniformly high permeability, free of shale breaks. Laverett4 and Katz3 have presented original data and discussed the theory relating to the capillary and gravitational forces acting On liquids contained in a sand body. These investigators have pointed out the importance of such studies in the estimation of future reserves as well as the original fluid content of a reservoir. In this previous work, no data have been reported showing the history of saturation distributions during the drainage period. Since a knowledge Of these transients is helpful in obtaining crude Oil from such a reservoir, the authors have obtained these data during this investigation. Experimental Apparatus The drainage tests were carried out in two vertical tubes, 8 ft. high and consisting of 2-in. and 4-in. standard wrought-iron pipe, respectively. Each tube was equipped with a water jacket, which could be kept virtually isothermal ( ± 1.0ºF.). A diagrammatic sketch of the 4-in. tube and its auxiliaries is shown in Fig. 1. At 6 in. above the base of the tube, and at every foot above this point, core nipples were inserted through the water jacket. These nipples were closely fitted with steel-plug inserts during each drainage run. At the end of the run, these inserts were removed so that cores could be obtained from the sand-packed tube.

Jan 1, 1943

By Akio Suzuki, P. G. Wahlbeck

AS a part of a study of the vaporization of transition metal-chalcogen systems, the vaporization reactions for the Ti-Se system have been studied. In order to establish vaporization reactions it is important to determine the identity of vapor species in equilibrium with the condensed phases. In some cases, it is possible to deduce the identity of vapor species through observations of composition change of the condensed phase with which the vapor is in equilibrium. Determination of vapor species in equilibrium with condensed phases should precede vapor-pressure measurements and is necessary for proper thermodynamic analysis of vapor-pressure data. Bear and McTag-gart' reported that vacuum heating ot TiSea at 950°C produced a residue with a composition of 1.7 Se/Ti atomic ratio units. Analyses of condensed phases existing for the Ti-Se system have been performed by Bernusset,2"4 Gron-vold and Langmyhr,5 Hahn and Ness,' and Ehrlich.~ Results and conclusions of two types of experiments are described herein: 1) experiments where samples of known composition were vaporized followed by chemical analysis of residues and 2) experiments where the vapor species were identified by means of a mass spectrometer. Experimental Section. Sarnple Preparation. Samples of TiSe2 were prepared in a sealed, evacuated quartz ampule by heating to 1000°C stoichiometric amounts of selenium of 99.999+ pct purity obtained from the American Smelting and Refining Co. and titanium of 99.2 pct purity obtained from A. D. Mackay, Inc. After heating, the sample was ground and reheated to insure homogeneity. Samples containing less selenium than TiSez were prepared by mixing amounts of titanium powder and TiSez appropriate for the desired composition; the titanium and TiSez mixture was heated in the same manner as described for TiSe2. Analyses of titanium selenide samples contained in quartz crucibles were performed by gravimetric oxidation in oxygen at 800°C; the products of the oxidation were solid TiOz and gaseous Se02. The mass of the original sample and the mass of TiOn determined the Se/Ti atomic ratio. The sample of TiSen used in these experiments had a composition of 2.04 Se/Ti atomic ratio units. The compositions for all samples reported were analyzed by this method. Va/!orization Experiments. Samples of titanium selenides were vaporized in tungsten Knudsen crucibles. Some vaporization experiments were carried out in glass vacuum lines followed by chemical analyses of residues, and some vaporization experiments were performed with a Bendjx mass spectrometer as described previously.8

Jan 1, 1967

By W. H. A. Timm

Lake Dufault Mines, Limited, is located ten miles north of Noranda, Quebec, Canada. Following discovery of a copper-zinc orebody late in 1961, metallurgical investigations of diamond drill core were conducted by Lakefield Research Limited during 1962 and 1963. These were followed by pilot-plant tests in May and June of 1964, utilizing underground development ore. Milling operations commenced on August 16, 1964, and reached rated capacity of 1300 tpd by October 1, 1964. Since that time, tonnage was gradually increased to a maximum of 1400 tpd and since January 1, 1968, gradually decreased to the present rate of 1100 tpd due to an increase in the hardness of the ore. The ore milled from start-up until January 1968, was mainly massive sulfides, consisting of a complex mixture of iron, Copper, zinc, and minor amounts of lead sulfides with important associated values in gold, silver and cadmium (average specific gravity of 3-8). From January 1968 until the present, the ore being processed is described geologically as a boxwork of sulfide stringers of chalcopyrite, pyrite, and pyrrhotite with some local dissemination in siliceous rhyolite (average specific gravity 2.9) supplemented by the massive copper-zinc ore. The limited size of the orebody and the mining method employed (open stoping by blasthole and slash benching methods) would have

Jan 1, 1970

By R. Stickler, A. Vinckier

An optical and electron microscope study was made on a commercial 302 stainless steel heat treated for massive carbide precipitation. Convincirg evidence was obtained that the grain boundary precipitate does not grow away from the grain boundary into the matrix, but grows as a network of large thin dendrites in between the grains. IN austenitic stainless steels the carbon in supersaturated solution precipitates when the steel is heated in the temperature range 450" to 1000°C. During such heat treatments the chromium-rich carbide occurs primarily at the grain boundaries and has adverse effects on the corrosion resistance and low-temperature ductility of the material. It has been shown that the morphology of the precipitated particles differs widely depending on the time and temperature of the heat treatment, the nature of the boundary, the misfit between the grains, and so forth.1"5 It was assumed by Mahla et al.,' Streicher,' and Mc Nutt' that the carbide particles which nucleate in the grain boundary grow in various geometric or dendritic forms away from the boundary into the matrix. However, Kinzel,' Hatwell et a, and Plateau et aL4 found that the particles nucleate in the grain boundary and grow as a network of thin dendrites in the grain boundary interface. We have made a comprehensive studyg of the precipitation occurring in a commercial 302 austenitic stainless steel heat treated for times ranging from 0.15 to 1500 hr at various temperatures from 480" to 1065"~. This study was made to elucidate the influence of heat treatments on both the mechanical and the corrosion properties of this steel. Part of this investigation which is pertinent to the morphology of the grain boundary carbides referred to above is separately reported here. We found that the particles which nucleated in the boundaries grew in the interface of these boundaries, thus supporting the viewpoints of Kinzel,' Hatwell et al.,3 and Plateau et al.4 Furthermore, when carbide particles nucleated in the matrix very close to the boundaries, they possessed a morphology distinctively different from the particles growing in the grain boundaries. MATERIAL A study of metallographic samples and of fracture surfaces of a 302 stainless steel is reported in this paper. The composition and heat treatments are listed in Table I. Polished and etched samples were examined und813r the optical microscope, and carbon extraction replicas of etched micrographic samples and various fracture surfaces3'8'9 were examined under the electron microscope. RESULTS AND DISCUSSION A representative optical micrograph of the 302 steel, condition A, is shown in Fig. l(a). Particles can be seen on the grain boundaries but no traces can be found of particles which grow from the grain boundaries into the matrix. A carbon extraction replica of this sample shows numerous large thin dendrites, Fig. l(b). The lateral dimension of such carbide particles vary up to 100 p, and their thickness estimated from the amoun! of electron penetration i:; between 500 and 1000A. Such large dendrites are extracted from almost all grain boundaries and, if they had grown into the grains, they would definitely be revealed by etching traces in the matrix, Fig. l(a). The reason why these large dendrites on the extraction replica appear to be grown into the grain is due to the mechanism of the extraction replica process. Thus, these dendrites are supported by the carbon replica film only at the edges originally along the grain boundary trace A-A, Fig. l(b), in the polished metal section and have subsequently fallen over onto the carbon replica film during handling. Although such dendrites generally fall only to one particular side of the grain boundary trace, one finds occasionally that parts of a dendrite have fallen to both sides, as shown in Fig. l(b). Further evidence for the growth of carbide in the grain boundary can be obtained from the appearance of fracture surfaces. A small impact specimen of the 302 steel, condition A, was broken at liquid nitrogen temperature. The fracture path follows the

Jan 1, 1962

By N. J. Grant, D. S. Bloom

THE development of high temperature, high stress alloys had proceeded with such rapidity during the war, and for a short time afterward, that our knowledge of the constitution of the alloys had become seriously inadequate. To interpret correctly alloy behavior it is not only necessary to recognize the phases present, but also to know the properties of the phases under all varieties of conditions and treatments. Chromium in these high temperature alloys holds the unique distinction of being the only one element which must be present when an oxidizing or generally corrosive atmosphere is present and when a long life is desired in service. Carbon and nitrogen must also be considered where chromium is present. Carbon is always present, either as an impurity in the raw alloying elements, or as a deliberate addition agent to increase the strength. Nitrogen is generally picked up from the atmosphere during melting or may be added as an alloying element. The effect of nitrogen additions is not too dissimilar to that of carbon additions. As such, chromium carbides and nitrides become of great interest since they are present in a very large number of alloys, including alloy steels, stainless steels, super alloys, and the like. In the chromium-carbon system there are three accepted, carbides: Cr,C, Cr7C8, and Cr3C2. The existence of one more carbide, a still higher carbon form CrC, has been advanced. The phase diagrams of chromium and carbon as published by Friemann and Sauerwald² and by Tofaute, Kuttner and But- tinghaus³ -do not extend beyond the carbide Cr3C2, which contains 13.3 pct carbon; but Hatsuta has extended the diagram up to 20 pct carbon, and in doing so hypothesized, with the use of some questionable experimental results, the compound CrC. This carbide would contain 18.75 pct carbon, 81.25 pct chromium, by weight. It is further known that as the chromium carbides increase in carbon the acid resistance increases but the oxidation resistance decreases4,5 This is of great importance in high temperature alloys where time-temperature stability, as well as oxidation resistance, is of prime importance. The possible existence of a carbide of the formula CrC thus becomes of prime importance and it was considered important to recheck the chromium-carbon binary constitutional diagram for such a compound. In view of the wide spread of values listed for the melting point of chromium (1500° to 1850°C) and 1930°C8, it was considered .that the liquidus temperatures might well be redetermined more ac-

Jan 1, 1951

By G. T. Lineberry, L. Adler

Due to safety-imposed constraints on clearances for mobile bulk handling equipment, it is necessary to optimally select a unit based on speed and size. The unit cannot be both large and fast. Since output is proportional to both size (or capacity) and speed, the combination must be carefully examined to maximize output. A simple graphical procedure and a calculus-based solution are presented to accomplish this. While the procedure applies to all mobile bulk handlers, as an example of the solution technique, attention is focused on shuttle cars. Background Major variables To fully define a bulk handling problem, the conditions, equipment, and activities must be characterized. The conditions and activities, when lumped together, are termed "encumbered space," since they "act to impede motion, as with a burden" (Lineberry, 1979). The insertion of mobile bulk handling equipment into what is already a difficult set of conditions and activities compounds the state of encumbrance, as limited space is competed for by many normal and life support systems. Long (1972) recognized the effects of design criteria, including road width, on haulage vehicle speed and, therefore, on production. Velocity-clearance curves Velocity-clearance curves are either available or can be constructed in the field. A preliminary set of curves for average conditions and activities is shown in Fig. 1, where clearances are only for the side of the vehicle (Lineberry and Adler, 1984). These curves set the safe speed limits for a vehicle operating at given clearances, under given conditions and activities. When feasible, velocity-clearance curves should be constructed through field measurement and observation. Curve construction should also consider haulway roughness, distances, and operator skill, as well as loading and dumping characteristics. It should be noted that haulage capacity determination is a total systems problem, not one just dependent on velocity and clearances. Production requirements and company capabilities also influence capacity determination.

Jan 1, 1986

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 10, 1913

By John Birkinbine

A RETROSPECT of the growth of the production of pig-iron for the past half century would be the history of the invention and introduction of heated blast as applied to the smelting of iron ores. As the apparatus employed was improved in conception and construction, the economical operation of the furnaces to which it was attached was the more marked, and the production correspondingly increased. To compare the original iron box placed over a coal fire with the modern hot-blast stove, with its combustion-chamber, gas-burners, and air-regulators, would be as unfavorable to the former as to contrast the product of the little Blauöfen with the yield of the improved furnaces of to-day. But, as these little Blauöfen were the germs from which the larger plants have grown, so from the crude apparatus invented and applied by Neilson has grown, in the face of great opposition, the more economical hot-blast stoves now in use. It is not surprising that an innovation like heated blast should have received a large amount of attention from metallurgists, nor that men of recognized ability should formerly have been found both among its champions and opponents, but it is remarkable that, at the present day, with the results of careful research and thorough experiment compiled in convenient shape for perusal, there are iron¬masters who still consider it economy to allow the products of combustion to escape into the atmosphere, rather than utilize them in heating the blast, because of a supposed injury to the quality of the product. In the present state of knowledge and practice, it is proper to express as an axiom, that a well-constructed hot-blast apparatus is essential to the economic operation of an iron-producing plant. Of the interpretation of proper construction there is of necessity a variety of opinions, and, with the view of solving the problem, the apparatus for heating blast has from time to time assumed various forms. Boxes, cylinders, and pipes, placed horizontally, vertically, inclined, or in circles and spirals, have been tried ; there have been pistol-shaped pipes, double pipes, divided or diaphragm pipes, siphon pipes, and as much variety in the mains, connections, flues, and setting. It is probable that, to the introduction of the bell and hopper in

Jan 1, 1876

By John Birkinbine

A retrospect of the growth of the production of pig-iron for the past half century would be the history of the invention and introduction of heated blast as applied to the smelting of iron ores. As the apparatus employed was improved in conception and construction, the economical operation of the furnaces to which it was attached was the more marked, and the production correspondingly increased. To compare the original iron box placed over a coal fire with the modern hot-blast stove, with its combustion-chamber, gas-burners, and air-regulators, would be as unfavorable to the former as to contrast the product of the little Blauöfen with the yield of the improved furnaces of to-day. But, as these little Blauöfen were the germs from which the larger plants have grown, so from the crude apparatus invented and applied by Neilson has grown, in the face of great opposition, the more economical hot-blast stoves now in use. It is not surprising that an innovation like heated blast should have received a large amount of attention from metallurgists, nor that men of recognized ability should formerly have been found both among its champions and opponents, but it is remarkable that, at the present day, with the results of careful research and thorough experiment compiled in convenient shape for perusal, there are ironmasters who still consider it economy to allow the products of combustion to escape into the atmosphere, rather than utilize them in heating the blast, because of a supposed injury to the quality of the product. In the present state of knowledge and practice, it is proper to express as an axiom, that a well-constructed hot-blast apparatus is essential to the economic operation of an iron-producing plant. Of the interpretation of proper construction there is of necessity a variety of opinions, and, with the view of solving the problem, the apparatus for heating blast has from time to time assumed various forms. Boxes, cylinders, and pipes, placed horizontally, vertically, inclined, or in circles and spirals, have been tried; there have been pistol-shaped pipes, double pipes, divided or diaphragm pipes, siphon pipes, and as much variety in the mains, connections, flues, and setting. It is probable that, to the introduction of the bell and hopper in