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By R. D. Heidenreich, R. E. McNulty, C. H. Gerould

Jan 1, 1946

By R. E. McNulty, R. D. Heidenreich, C. H. Gerould

Jan 1, 1946

By Hal M. Scrugham

UNITED States Steel Co.'s Tennessee Coal & Iron Div. Wenonah mines present definite materials handling problems arising from the natural features of the operation. Trackless equipment went a long way toward supplying the answers-but at the same time gave birth to several new posers. Machines-trackless or otherwise-require maintenance and Wenonah's experience may do much to add to the body of information already available on this type of equipment. Let's look at the mines themselves. Ore is of sedimentary origin, extending over an area of several square miles. A thickness from 8 to 14 ft is mined. Bed dip varies from the horizontal to 20 pct in local rolls. Practice is to mine across the dip at 14 pct or less. A parting forms a smooth footwall in some of the mines while in others the footwall must be blasted smooth. Ore weighs 215 lb per cu ft in place and is extremely abrasive.

Jan 6, 1953

R. V. NorHis, Wilkes-Barre, Pa. (communication to the Secretary*) : The electric-haulage plant of the Short Mountain Colliery of the Lykens Valley Coal Co., mentioned by Messrs. Stoek and Harris as the earliest underground electric plant in the United States (and, I believe, the second in the world), was started July 23, 1887. The plant, designed by W. M. Schlessinger, consists of two motor-cars, each weighing about 5 tons and equipped with a 32-h.p. Union Electric Go. motor. The original general construction of the motor-cars is shown by Mr. Stoek; but they were rebuilt, the same year, with some important improvements in design; and, except for strengthening the frames and replacing the original pig-iron weights by a casting, they have not been greatly changed since that time. The generating-plant consists of two Union Electric Co. dynamos of 65-h.p. each, driven by an old 18- by 48-in. plain slide-valve engine; the ordinary voltage is 450 and the amperage varies from 40 to 200; the average indicated h.p. of the engine is about 75, with a steam-consumption of about 75 lb. per i.h.p. per hour; and as the cost of steam at this colliery is 8.11 cents per 1,000 lb.,the steam-cost per day is about $4.56.

Jan 1, 1904

By G. C. Fryburg, H. M. Murphy

ThE rates of oxidation of metals are usually obtained by heating the metal specimens in furnaces. Such a procedure is satisfactory for most metals. However, there are several metals that oxidize according to the reaction.

Jan 1, 1959

By Peter M. Fozzard

The San Bartolomt silver deposit was discovered by a United Nations team of geologists working with a counter- part team of staff of the Ecuadorian Government's General Directorate of Geology and Mines (DGGM). The Phase I project over five areas of operation during which this discovery was made was financed through a United Nations Development Program contribution of $860,000 and an Ecuadorian Government participation of about $680,000 equivalent. Existence of mineralization at San Bartolomé was first recognized in 1966 when a reconnaissance geochemical stream-sediment program was carried out over a 10 500 km2 (4,054 sq mile) area centered around the city of Cuenca in southern Ecuador. Over the course of this project more than 10,000 samples of stream-sediment, soil, and rock materials were collected. Average costs per sample were $10.00, as follows: collection, $5; sample preparation, $1.60; assay work, $3.40. Initially in the program (1965-1966) sediments were collected along all motorable roads and tracks. Routine analyses, originally by colorimetry and later by AAS, were for Cu, Pb, Zn and occasionally As, Ni, and Co. Discovery geochemical samples from the San Bartolomé drainage area were among the first to be taken in 1965. As luck would have it, the road along which this traverse was taken passes only some 100 m (328 ft) downstream from the mineralized suboutcrop. The relevant two streams sampled are of inconsequential size, some 1 m (3.3 ft) in width, with a limited flow volume throughout the year. Original anomalies were recognized through cold-extractable Cu/Zn analyses. The pH of all river waters was also recorded at sample sites. Resampling the discovery sediments when AAS became available showed total extractable values of between 150 ppm-300 ppm Zn, 550 ppm Pb, and 10 ppm Ag. In 1967 the first followup was by rough-and-ready means. Dithizone field-kits (THM) were used to rapidly test soils from the surrounding area. The area has no outcrop. This work allowed the definition of an area of interest of some 2 km (1.2 miles) x 500 m (1640 ft). Six approximately 1 km (0.6 mile) to 1.5 km (0.9 miles) lines spaced at approximate 250 m (820 ft) intervals were established and used for IP surveys and soil sampling at 50 m (164 ft) intervals. Where one of the lines crossed the westernmost geochemical discovery creek a first-priority geophysical anomaly coincided with a major Zn/Pb (and later Ag) soil anomaly. A pit was sunk and encountered mineralized vein material at a depth of 1.5 m (5 ft). This lucky glory hole confirmed the geochemical discovery and prompted systematic followup. Immediately, costeaning of the west bank of the discovery creek, the Quebrada Ocashuaico, was carried out and exposed weathered and leached mineralization. Nearly 100 mineralized veinlets ranging in thickness from 0.5 cm (0.2 in.) to 8 cm (3 in.) were exposed across the 180 m (59 1 ft) costean. Sixty mineralized veinlets were determined over a 90 m (295 ft) wide zone. Sampling delineated minable widths averaging between 0.16 and 0.31 kg/t (5 and 10 oz per st) Ag with associated copper (very sporadic) lead and zinc. Over the period 1968- 1972 a considerable amount of detailed work was completed: detailed IP, EM Turam, magnetic and mise-a-la-masse geophysics, very detailed soil- sampling, trenching, drilling and glory-hole drifting, and cross-cutting. Numerous problems were encountered: the area was found to be a most difficult geoelectrical target; zero outcrop; pyrite (nonargentiferous zones) associated with faulting; mineralized groundwater; extensive clay development; loss of diamond drill-core, and no two-dimensional surface information. As the program developed the complexity of the structure was slowly unravelled, using a degree of good guesswork. Apart from photogeological and ground geological mapping at various scales, the following

Jan 1, 1985

By L. A. Roe

The flotation of fine particles less than five microns in diameter and the flotation of liquids from liquids generally requires bubble generation methods different than methods used in dispersed air type machines used in mineral flotation. Conditions in the separatory zone in mineral cells are generally more dynamic as compared to the quiescent conditions often absolutely necessary for the flotation of fine particles and liquids. An example of quiescent flotation with very fine bubbles is the lithium flotation plant which operated at Trona, California for 34 years, until it ceased operations in 1978. A review of the process development and the commercial flotation operations at Trona is given in this paper. The clarification of oil field brines by flotation of the oil from the brine has been used for over twenty-five years. Recent installations related to the Prudhoe Bay oil field and the Alaska pipeline are described.

Jan 1, 1980

By O. B. Buchlen, J. W. Smith

The Coal Research Bureau of the School of Mines at West Virginia University, using an experimental flotation cell designated an airlift-cyclone was able to obtain a clean coal product containing 7.64% ash with 94% yield and 97% coal recovery. This favorable performance was obtained with the experimental flotation cell operating as a simulated three-stage unit on slurry taken from the fine coal circuit of a coal preparation plant. This experimental device, consisting of a sheet metal cyclone-like unit mounted on a U-shaped uplift pipe, uses a combined flotation and cyclone action to beneficiate the minus 14 mesh partially cleaned feed product. In addition to providing comparable analytical results, the airlift-cyclone possesses other attractive features among them being a low capital expenditure, utilization of moderate plant floor space, efficient operation on high density feed slurry, and absence of moving parts. The primary shortcoming of the experimental cell is its limited capacity. The Coal Research Bureau presently has under construction a larger unit which, it is hoped, will provide the capacity and quality to establish the airlift-cyclone as a commercially feasible unit. Froth flotation of fine coal is a practice which has only recently gained wide acceptance in this country. Various explanations can be put forth for this delayed acceptance of a very selective and efficient system of coal preparation. Among these reasons would be the advent of continuous mining machines resulting in the increased production of coal fines, the change in market patterns from domestic and rail consumers who did not want fines to a predominantly utility market which normally consumes fines, and also the imposition of legal restrictions in regard to stream pollution. However, the major detriment is probably the high cost involved both in installation and operation of the flo- tation unit and auxiliary systems. These facts assume greater emphasis when considering that froth flotation installations normally process a low quality feed product. A recent estimate' of installation costs including dryers, filters, and other auxiliary equipment for a flotation system was $5000 to $7000 per ton of capacity while the operating costs, exclusive of auxiliary equipment, were estimated at 10 to 306 per ton of feed. The Coal Research Bureau of the School of Mines at West Virginia University is currently developing a simplified froth flotation cell, designated an airlift-cyclone, which may provide considerable savings in capital and operating costs without sacrificing product quality or recovery. This experimental cell consists of three primary components: 1) a vertically mounted U-shaped pipe; 2) an air injector device; and 3) an integrally mounted cyclone-like unit (Fig. 1). A feed slurry is introduced at the top of one leg of the U-pipe while compressed air is injected near the base of the other leg. The air serves both to aerate the pulp and to cause it to flow upward into the base of the cyclone unit where the floated clean coal is separated from the reject material and unfloated coal which remains in slurry. The Coal Research Bureau's experimental airlift-cyclone is somewhat similar in principle to a flotation device developed by Russian engineers in the late 1950's. In tests upon a two-stage pilot-size device, the Russians obtained very favorable cleaning efficiencies.' However, later experience with production models demonstrated that rated capacities and acceptable product quality could not always be maintained.3 Because of these limitations, Russian engineers subsequently recommended that conventional, mechanical cells be used when cleaning difficult to float slurries. Engineers at the Coal Research Bureau felt that such a device utilizing the combined actions of a cyclone and a froth flotation machine offered numerous attractive features and merited investigation. Accordingly, a small capacity experimental airlift-cyclone was designed and, with the permission of the Christopher Coal Company Div. of Consolidation Coal Co., installed in Christopher's Humphrey preparation plant near Morgantown, West Virginia.

Jan 1, 1964

By J. B. Dorsey, T. W. Brinkley

Performance of a high-pressure, vaporizing gas-drive project in a volatile oil reservoir is discussed. The project has been in operation for over 8 years. Present recovery from the over-all displaced portion of the reservoir is 40 percent, and an ultimate recovery of 60 percent is indicated. Calculations reflect an over-all displacement volume of 50 percent for the entire reservoir; therefore, ultimate oil recovery will be 30 percent of the entire reservoir oil originally in place. Laboratory vaporization tests conducted prior to project initiation also are presented and discussed, along with an analytical method of determining stock-tank oil production and gar injection requirements related to over-all volumetric displacement efficiency from these data. Introduction The Shoats Creek field is located in Beauregard Parish, La., in the extreme western part of the state (Fig. 1). Discovered in 1956, the field is productive in three Cockfield sand zones, ranging in depth from 8,000 to 9.000 ft. The upper two zones, 1st and 2nd Cockfield, are condensate-bearing gas reservoirs. The lowest zone, the 5th Cockfield, is a volatile-oil reservoir. Laboratory work conducted on crude oil from the 5th Cockfield zone shortly after field discovery demonstrated that, when contacted with dry gas, signidcant volumes of the oil could be vaporized at reservoir temperature and at an appropriately high reservoir pressure. Further study led to the conclusion that early initiation of a crude vaporization project in the 5th Cockfield zone would be superior economically to other methods of reservoir depletion. Consequently, the zone was unitized and gas injection operations started late in 1958. This paper discusses laboratory work performed in conjunction with the project, and project performance to the present. History of Development The 5th Cockfield zone in Shoats Creek is composed of a thin, very shaly, low-permeability sandstone. Oil accumulation is controlled by a structural trap bounded by faults along the north and west and by a water contact on the southern boundary (Fig. 2). The zone covers a productive area of 1,550 acres at an average depth of 9,000 ft. The net sand section is thin, having a maximum thickness of 10 ft and an average thickness of 5.5 ft (Fig. 3). Average reservoir rock properties, as determined from core analysis are presented in Table 1. Shaliness of the zone is illustrated by the typical electric log of the 5th Cockfield section in Fig. 4. Because of the thinness and poor quality of the sand, the 5th Cockfield was developed on a wide spacing. Eleven completions were made in the zone between 1956 and 1961 for an average density of 140 productive acres per completion, with the majority of wells being dually completed in the 2nd and 5th Cockfield. Average initial potential for producers in the 5th Cockfield was 130 BOPD. Oil from the 5th Cockfield has a stock-tank gravity of 50.5" API; with a bubble-point pressure of 3,515 psia, the oil was highly undersaturated at the original reservoir pressure of 4,675 psia. Pertinent properties of the oil as determined in the laboratory are presented in Table 2. Because of the volatile nature of the crude, laboratory studies of its susceptibility to vaporization, as well as a vapor-liquid phase study, were conducted in addition to a standard PVT analysis. The vaporization study was conducted in a visual cell; a stepwise illustration of this work and laboratory measurements are presented in Fig. 5. Field

Jan 1, 1969

By M. A. Mahtab, J. D. Dixon

The results of a parametric study of the influence of natural features (stress field, rock strength, and strength and orientation of fractures) as well as the influence of induced features (undercut span, boundary slot, and other boundary-weakening measures) on the cavability of an undercut block of ore in mining by the block- caving method are presented. The two-dimensional finite-element analysis technique was used for this study. A coarse "mesh," along with linear homogeneous assumptions for rock properties, was used to model the problem of initiation of caving in a block of ore. Interpretation of the test results suggests that weakening the "abutments" of the block as well as certain orientations of natural fractures exercise significant influence on cavability. These findings hold promise for immediate application to known situations in block-caving mines.

Jan 1, 1977

By G. R. Speich, Morris Cohen

The growth rate of bainite has been determined by hot-stage metallography in five hypereutectoid high-purity iron-carbon, iron-carbon-chromium, and iron-carbon-nickel alloys. The studies have been confined essentially to lower bainite. The growth rate is independent of time at constant temperature, but both the edgewise and sidewise growth rates increase with increasing temperature. Increasing the carbon content, or adding chromium or nickel, decreases the growth rate without greatly affecting the temperature dependence. The results lead to separate diffusion-controlled models for the edgewise and sidewise growth rates. ALTHOUGH bainite has been subject of many detailed investigations,1,2 the growth mechanism of this intermediate transformation product of steel remains unclear. One difficulty has been that practically all the kinetic measurements have been restricted to studies of the overall reaction rate. Only a limited amount of information3, 4-6 is available on the growth process itself. The purpose of the present work was to investigate the effect of time, temperature and composition on the growth rate of bainite using hot-stage metallography. This method makes it possible to observe continuously the isothermal growth of individual bainitic units because of the surface upheavals accompanying their formation.3 This information is needed to test the existing growth models and to obtain a better understanding of the factors controlling the bainitic transformation. EXPERIMENTAL PROCEDURE Alloys—The compositions of the alloys used in the present work are shown in Table I. The five alloys were vacuum-melted and cast, and were prepared from high-purity materials. The three iron-carbon alloys were available from the work of Roberts et al.7 in the form of 3/8-in. diam rods.* To facilitate machining, the rods were ing. The rods were then tempered for 3 hr at 650°C to allow machining. The iron-carbon alloys in Table I were selected for investigating the effect of carbon on the bainitic growth rate. Due to the rapidity of the transformations involved, it was not feasible to measure the growth rates in iron-carbon alloys having carbon contents much less than 0.9 pct C. The iron-carbon-chromium and iron-carbon-nickel alloys were selected to study the influence of chromium and nickel on the growth rate at a carbon level of about 1.1 pct C, since this carbon content was intermediate among the iron-carbon alloys. The concentrations of chromium and nickel were chosen to match isothermal trans formation diagrams in the literature.8'9 Hot-Stage—Since the iron-carbon alloys had such low hardenabilities, it was necessary to quench the hot-stage specimens drastically from the austentiz-ing temperature to the isothermal transformation temperature to prevent the formation of pearlite or proeutectoid constituents. A rapid-quenching metal-lographic hot-stage was built for this purpose. A maximum temperature of about 1100°C and quenching rates up to 500°C per sec could be attained with this equipment. The details of the apparatus are described in a recent publication. After being polished and mounted on the hot-stage, the specimen (0.020 in. thick) was protected from oxidation and decarburization during austenitizing by a vacuum of 10-4 to 10-5 mm. The quench to the reaction temperature was accomplished with a helium blast, and the isothermal run at this temperature was conducted in a helium atmosphere. A fine-wire thermocouple spot-welded to the sample and a high-speed

Jan 1, 1961

By W. A. Jr. Slippy, E. P. Dahlberg, R. B. Reed-Hill

A large room-temperature mechanical-hysteresis effect under cyclic tensile loading was observed in zivconium specimens prestrained at 77°K so as to form large numbers of (1121) twins. The observed hysteresis loss was a maximum when the prestrain was just under 1 pct It also depended strongly on the maximum applied cyclic stress, but only moderately on loading rate and temperature (-72°to 100°C). The phenotnena have also been studied in terms of the elastic aftereffect where the data has been found to cotlforln closely to the functional relationship between strain and time, c = -RT/a In tank ft. t to)/Zr, for strains cts large as about 10-4 This eyication can be derived directly from the strain-rate equation There may be important commercial implications to the present discovery since it appears that within rather wide limits it may be possible to obtain any desired magnitude of damping capacity in zirconium melal. The damping propevties may also be given directional characteristics. It is shown that the observed anelaslic phenomena can he explained on the assumiplion that they are the resuilt of stress-induced twin-boundary movements in which the average twin increases its thickness by only a few percent. In polycrystalline zirconium, a grain is least favorably oriented for slip when its basal plane, containing the (1130) slip directions, lies nearly perpendicular to the principle normal stress. Mechanical twinning is favored by this orientation and under simple tensile deformation at room temperature the primary twinning mode is {1012).' The (1012) twinning shear is small (0.17) so that, during deformation, twin growth does not greatly enhance ductility. At 77°K, on the other hand, the predominant twinning mode shifts to {1121), and many thin (1121) twins can form at small strains.' Twins thus nucleated can grow readily during subsequent room-temperature deformation and permit easy deformation in unfavorably oriented grains. In addition, the (1131) twinning shear is large: 0.63. These facts have lead to a process' for greatly improving the room-temperature ductility of zirconium when it contains a sizable fraction of grains with basal planes nearly normal to the stress axis. Optimum results are obtained by slightly less than 1 pct prestrain. The effect is large so that a 50 pct elongation increase is readily attained. A large room-temperature mechanical-hysteresis effect has also been observed in zirconium specimens prestrained at 77°K. The present paper is concerned with some aspects of this effect which the experimental observations strongly indicate is primarily the result of strain-induced {1121) twin-boundary movements. This clearly suggests that mechanical twins formed by plastic deformation can cause anelastic effects similar to those previously observed2 for annealing twins and twins associated with phase transformations. EXPERIMENTAL PROCEDURES All specimens were prepared from arc-melted sponge zirconium plate stock as previously described,3 which has a preferred orientation with basal planes aligned parallel to and uniformly distributed around the rolling direction. Both lonti-tudinal and transverse tensile specimens, with axes parallel and transverse, respectively, to the plate rolling direction, were cut from this plate. In a longitudinal specimen most grains are favorably oriented for slip, while in a transverse specimen a large fraction are unfavorably oriented. Prestraining at 77°K was performed in two ways. In one, annealed zirconium plate stock was cooled in liquid nitrogen and then rolled in the transverse plate direction to strains varying from 0.5 to 12 pct. Cylindrical 1/8-in.-diameter by 1-1/4-in.-gage-length tensile specimens were machined from this material. In the other, previously machined tensile specimens were prestrained in tension at 77°K between 0.2 and 3.8 pct. Type FA 25-12 SR4 strain gages were cemented to all specimen gage sections. All tests were performed on an Instron testing machine of 10,000-lb capacity. EXPERIMENTAL RESULTS Fig. 1 shows a typical two-cycle room-temperature stress-strain diagram for a specimen prestrained 0.65 pct by rolling at 77°K. The maximum stress in both cycles was 14,500 psi. Note that in the first cycle the loading and unloading curves are unsymmetrical so that a residual strain, er, remains after unloading. In the second cycle the stress-strain curves form a nearly symmetrical hystere-

Jan 1, 1965

By J. G. Y. Chow, S. B. McRickard

The tensi1e properties of Ferrovac iron have been studied from 4° to 300°K. The stress required for macroscopic yielding was found to he constant below approximately 50°K. The effect of mechanical twinning on this low -temperature stress plateau was investigated. The onset of twinning occurs in this iron between 130° and 150°K and depending on its previous thermal history the twinning-stress curue may drop below or remain above the vield-stress curves as the temperature is lowered. Twinning has been shown to initiate slip in quenclzed iron at low temperatures. In no instances, however, did the onset of twinning alter the continuity of the yield stress -tempwature curve. Our data shows that carbon inhibits twinning and slip at low tem-peratures. This observation nay be used to explain the ductile-to-brittle transition in iron. The effect of fast neutron irradiation on yielding and embrittlement in iron and Fe-C alloys is offered as supporting evidence for this viewpoint. THE mode of yielding in iron at low temperatures was studied in an attempt to find an expression based on a single mechanism to describe the thermal dependence of the yield stress of iron. There are two types of inflections observed in the variation of the yield stress with temperature in iron and Fe-C alloys. The first is associated with ductile behavior and consists of a region extending 50" to 100°K above absolute zero in which the yield stress is independent of temperature. The second is observed in more brittle materials such as Fe-C alloys and irradiated iron and consists of an abrupt discontinuity in the yield curve as the temperature is lowered through a ductile-to-brittle transition point. The temperature dependence of the yield stress for iron with four grain diameters as found in this study is shown in Fig. 1. To varying degrees all the curves appear to flatten or approach an asymptotic value as the temperature is lowered below 50°K. Several other investigators1,2 have observed a plateau in the yield stress of iron and steel at low temperatures and in 1956 Louat3 presented a theory which contained an explanation for this behavior. In a subsequent exchange with Erickson and Low4'5 who attributed the plateau to the onset of mechanical twinning Louat8 showed that twinning first occurs in iron and steel tested in tension at temperatures as high as 140°K which is well above the observed plateau in yield stress. Furthermore he pointed out that both twinning and slip are basically dislocation processes and that with modified parameters his original theory still applied when deformation is initiated by twinning. Variables which affect the ductile-to-brittle transition in iron are test temperature, strain rate, composition and grain size.7 LOW,8 Hahn et al.,9 and Hull10 have provided evidence which links brittle fracture at a given temperature with the specimen grain size and the onset of twinning. In fact, Hull equates the brittle fracture stress to the twinning stress. On the other hand brittle fracture has been observed in the absence of twinning and priestnerl1 has given a fracture criterion which is valid whether or not fracture is preceded by extensive twinning. The data presented here clarify the role of twinning in the low-temperature deformation of iron. Strong evidence is given that the amount and distribution of interstitial impurities such as carbon are of

Jan 1, 1965

By J. A. Retty

HOLLINGER CONSOLIDATED GOLD MINES LTD., through two subsidiary companies, has the exclusive right to prospect in two contiguous areas in central Labrador. This paper presents the results of the mineral exploration that has been conducted in these areas to date. One of the subsidiaries of Hollinger. the Labrador Mining and Exploration Co. Ltd., under an agreement with the Newfoundland Commission of Government, holds an area of approximately 20,000 sq.mi., which comprises the western portion of Newfoundland-Labrador and includes the upper basins of the Hamilton and Naskaupi Rivers. (The main area of the deposits so far discovered may be located on a map at about 67° west longitude and 55° north latitude.) The other subsidiary of Hollinger, Hollinger North Shore Exploration Co. Ltd., has licensed from the Province of Quebec an area of approximately 3900 sq.mi. lying directly north of the Newfoundland-controlled area at the headwaters of the George, Whale, and Swampy Bay Rivers. The M. A. Hanna Co., large iron-ore operators of the Lake Superior region, are participating in the project. With the exception of the years 1940 and 1941, field work has been conducted in the Newfoundland area since 1936, and in the Quebec area since 1939. Hollinger assumed the management in 1942. The field base is at Hollinger Lake, some 300 miles north of the tidewater base at Seven Islands, Quebec, which, in turn, is just west of the mouth of the Moisie River, on the Gulf of St. Lawrence. Air transportation is used exclusively to service the operation.

Jan 1, 1945

By W. J. Taylor

It is, perhaps, more important to put on record the particulars of experiments that are derided failures than those that are successful, as those of the latter class are certain to live, while the former may be lost sight of in a short time, and repeated by others. TO this end, I propose to give the particulars of a straight or no-bosh furnace just tried at the Chester (New Jersey) works, which was such a decided failure as to leave no doubt of the plan being wrong, and determining the necessity of a bosh of some kind, as of old. Some experiences during the past year led me to suppose that the bosh or belly of a furnace was unnecessary, and that the contraction of the walls toward the bottom for the stock to wedge in, in its descent, facilitated dirty walls and scaffolding; hence, irregularity and high fuel. I concluded, however, that a very shallow bosh for a skew-back support to the stock would be necessary, and that the proper place for this was in the tuyere-section, beginning just below the tuyeres and ending just above them, where there is nothing in the solid state but fuel, which is consuming, and no slipping or travel of stock takes place. The cubical capacity of a furnace of this design would necessarily be much less than in the old style, unless it was made very much higher. But I assumed that the loss of room for reduction could be overcome by making the size of the ore and stone charged much smaller, so that the gases would act more quickly. The next point was, what should be the size of the shaft, crucible, tuyere-circle, and tunnel-head for a given quantity of air? My first design was 12 feet diameter of shaft for 7000 feet of air, with a 9-foot crucible and 8-foot toyere-circle. This I soon reduced to 8-foot shaft diameter, which I concluded was large enongh for economical work, if regular travel of the stock on the walls could be maintained. I consulted with a number of experienced furnacemen and furnace-engineers, and the plan was well thought of by many of them; and, as I had also some offers of financial aid from them toward the risk of trying the experiment, my firm concluded

Jan 1, 1885

By A. J. Lena, M. F. Hawkes

Changes in hardness, tensile properties, microstructure, electrical resistance, and X-ray diffraction effects indicate that lattice strains are necessary for the embrittlement of ferritic stainless steels when heated for relatively short times at 475°C (885°F). It is suggested that 475°C (885°F) embrittlement is due to the accelerated formation of an intermediate stage in the formation of s under the influence of these strains. FERRITIC stainless steels (low carbon alloys of iron with more than 15 pct Cr) are subject to two forms of embrittlement when heated in the temperature range of 375° to 750°C. The embrittlement which occurs after long time heating between 565" and 750°C is well understood; it is caused by the precipitation of the hard, brittle s phase. Sigma is an intermetallic compound of approximate equi-atomic composition with an extended range of formation in Fe-Cr alloys. The maximum temperature at which this form of embrittlement can occur is dependent upon chromium content; and is approximately 620°C for a 17 pct Cr steel and 730°C for a 27 pct Cr steel. The other form of embrittlement occurs after relatively short heating periods in the range of 375" to 565°C; in the higher chromium steels, hours may be sufficient as compared to months for s embrittlement. This phenomenon is not at all well understood and several controversial theories have been proposed. The rate and intensity of embrittlement increase with increasing chromium content but the maximum rate occurs at 475°C re-gardless of chromium content. As a result of this, the phenomenon has been termed 475°C (885°F) embrittlement. The effect of 475°C embrittlement on the properties of ferritic stainless steels has been thoroughly reviewed by Heger.1 The embrittlement causes a pronounced decrease in room temperature impact strength and ductility, a large increase in hardness and tensile strength, and a decrease in electrical resistivity and corrosion resistance. Microstructural changes accompanying embrittlement are minor and difficult to interpret with a general grain darkening, appearance of a lamellar precipitate, grain boundary widening, and precipitation along ferrite veins having been reported at various times. With the exception of reported line broadening, X-ray diffraction studies by conventional Debye analysis of solid samples have been of little value. BY making use of electron diffraction methods, Fisher, Dulis, and Car-roll' have recently shown the existence of a chromi-um-rich, body-centered cubic phase in 27 pct Cr steels which had been aged at 482°C (900°F) for as long as four years. Two types of theories have been advanced to account for the embrittlement. The first of these requires the precipitation of a phase not inherent in the Fe-Cr system with various investigators suggesting a carbide,3 nitride,3 phosphide,4 or oxide." Theories of this type have difficulty accounting for the influence of alloying elements on the embrittlement and for the facts that a minimum chromium content is necessary for embrittlement and the intensity of embrittlement increases with increasing chromium content. The second type of theory that has been proposed relates 475°C embrittlement to s phase formation which is inherent in the Fe-Cr system. An assumption of this kind can adequately explain the influence of alloying elements, for they exert an effect on 475°C embrittlement similar to that on s phase for-mation as can be seen in Table I. The minimum chromium content is essentially the same for both phenomena and it has been shown12,13 that s is a stable phase in the embrittling temperature range. In addition, it has been reported14,15 that pure alloys embrittle to the same extent as commercial type alloys. There are, however, several factors which have prevented complete acceptance of a s phase theory. Foremost of these is that the embrittlement can be removed by reheating for short time periods above 600°C, which in the higher chromium steels is within the stable s region. No s has ever been observed after one of these curing treatments, nor has any s been found as a result of embrittlement at 475°C. In addition, the simple precipitation of s cannot explain the time-temperature relationships for reactions between 350°and 750°C. This behavior is shown schematically in Fig. 1. Newell 16 and Ried-rich and Loib4 have shown that 475°C embrittlement follows a C-type curve as illustrated, while Short-

Jan 1, 1955

By Charles Will Wright

ITALY is by- far the poorest in mineral resources of the so-called great pou7ers of Europe. Before the World War this shortage was not so serious as the essential minerals that could not be mined domestically at a profit were bought in the world markets. In those days tourist trade and remittances from Italians abroad helped to provide Italy with foreign exchange. During the World War, when certain mineral products were scarce and when prices rose in some instances to several times normal, the Italian Government began to regulate consumption and imports. It was not until later, when the Fascist regime established the corporate state, that Italy seriously considered adopting a of self-sufficiency. Private industry was grouped under separate corporations, for the principal industries; including mining and metallurgy and the heads of the large producing companies, became members of these corporations. Industrialists were thus able to regulate their own affairs and to advise the Government as to the measures necessary to meet domestic or foreign trade demands upon their industry. Labor was or-

Jan 1, 1939

By Fred C. Bond

AN improved method of measuring the surface area of a comminution product down to any desired particle size has been developed. The method is largely graphical, and requires relatively little calculation. It can be used with materials containing large amounts of clay, or excess fines of any kind. The surface area S is expressed in terms of square meters per100 c.c. of solids. This expression is based upon volume rather than weight, and is considered to be more suitable for crushing and grinding problems, where the machines ordinarily are operated under constant volume conditions. It has the advantage that surface areas of different materials can be compared directly, even though their specific gravities may be unknown. The "specific surface" of a material, or the number of square centimeters of surface area per gram, is equal to 100S divided by the specific gravity. Particle diameters are expressed in microns, K being the diameter of the largest particle present and L the grind limit, or lower size limit of the particles formed directly by grinding. The value of K does not always coincide exactly with the diameters of the largest particles retained on the coarsest testing sieve, since the largest particles formed in crushing and grinding are often slabby, or have other irregular shapes. L has been chosen as 0.700 microns, or number 27.5 in the size number series,1 for reasons to be explained later. S is the total surface area of all particles larger than L microns in diameter. When a homogeneous comminution product is separated into fractions whose diameters bear a constant geometrical relationship [p] to each other, and the log per cent weight retained upon each size and passing the next larger size is plotted against the log diameter, a straight line results, which is called the distribution line, and which has a slope in called the distribution modulus. The distribution line can be extended to any desired limiting size, and the total surface area of all particles larger than that size can be calculated. The equation of the distribution line is w = Cxm [I] where w is the per cent weight retained on each successive sieve; x is the particle diameter; and C is the per cent weight retained on an opening of unit diameter.2 Theoretically, the distribution line can be extended to include infinitely small particles. When it is so extended, and the assumption is made that no fine particles are present other than those accounted for by the equation; the log per cent cumulative weight passing any series of sizes, plotted against the log diameter passed, will result in a straight line lying parallel to and above the plotted distribution line.

Jan 1, 1941

By F. S. Young, K. E. Gray

Drilling tests with a 11/4-in. diameter roller bit were performed on Berea and Bandera sandstones and Leuders limestone using water and two conventional drilling muds as circulating fluids to evaluate the influence of dynamic filtration on penetration rate. The muds possessed widely differing API fluid-loss properties. Mud filtrate was constrained to flow beneath the bit; no filtrate flowed radially through the borehole wall. Rock pore pressure at three different locations ahead of the bit, cumulative filtrate volume, borehole pressure and bit location were monitored during drilling. The rock samples, cored in three orientations with respect to bedding planes, possessed a wide range of liquid permeabilities. and were drilled at borehole-to-formation pressure differentials of 0, 250, 500 and 1,000 psig. The effect on penetration rate of API fluid loss, borehole pressure and rock permeability was studied. Rock permeability damage and pore pressure gradients beneath the bit were evaluated. The importance of borehole-to-formation pressure differential was illustrated for each drilling fluid and rock permeability combination. Penetration rates decreased with increased borehole pressure and reduced fluid loss. The observed penetration rate reduction due to changing fluid Ioss was attributed to decreased filtrate flow and improved mud cake plastering hy the low fluid-loss mud. The reduction in filtrate flow could not be related to spurt-loss phenomena. Rock permeability influences penetration rate through particle invasion ahead of the hit, which damage leads to high pressure gradients. Penetration rate variance with sample orientation was evident for water-drZled samples but less obvious for mud-drilled rocks. Permeability damage beneath the bit ranged from 1 to 3 cm. Maximum damage occurred in the first 0.1 cm. Pressure gradients varied with API fluid 10.s.s and could be correlated with penetration rate. The pressure gradient was found to influence penetration rare in rocks of all permeabilities tested. INTRODUCTION Early microbit and small-scale drilling experiments proved to be invaluable contributions to understanding the mechanics of drilling at depth. For example, the effect of borehole-to-pore pressure differential on drilling rate was demonstrated conclusively by Murray and Cunningham', Eckel' and others .' However, the effects of various drilling fluid properties on drilling rate, particularly filtration, have not been studied extensively on a laboratory basis. Microbit correlations of penetration rate with different viscosity and API fluid-loss muds led EckelV o conclude that viscosity and density. more than API fluid loss, were the most important fluid properties in controlling drill bit penetration rates. Ferguson and Klotz6 studied filtration beneath the bit and stated that the maximum amount of filtrate which could conceivably flow beneath a drilling bit could be described by a potential function associated with flow from a moving disc source. and be characterized by a depth-of-filtrate invasion. Invasion depth is a function of penetration rate, formation porosity and permeability, flooding efficiency, pressure difference between borehole and formation and borehole radius, assuming that no filtrate flows through the borehole walls. Electric analog and experimental measurements were obtained, assuming no plugging of the formation pores. Theoretically, filtrate invasion was predicted to extend from 1- to 15-hole radii beneath the cutting surface; experimental results indicated that the extent of invasion was only Y2 in. Comparing these data with results of core-plugging experiments by Norwak and Krueger' led Ferguson and Klotz to state that the drilling operation apparently contributes to higher filtration rates than are observed in nondrilling core filtration tests in which the core face is jetted and scraped. Glenn and Slusser: in describing a linear filtering system in which a rotating bit continuously scraped mud cake from the surface but did not penetrate Alundum cores, stated that mud-solids invasion and permeability damage of the cores were most severe in the first 2 to 3 cm. The filtrate flow rate through the core was found to stabilize after sufficient time had elapsed for the formation of an internal mud cake whose effective permeability was estimated to be 50 to 300 times as high as that of bulk filter cake. Krueger and Vogel reported core permeability damage depths up to 12 in. during a 5-day exposure period in which filter cake buildup was prevented. Havenaar pointed out that the discrepancy between reported and calculated values of filtrate volume obtained in the experiments of Ferguson and Klotz was due, among other things, to failure of the reported API fluid loss to truly represent filtration beneath the bit. Williams," Pro-koplz and others"" have shown that dynamic filtration tests (where a flow of fluid parallel to the filter surface continually erodes the deposited filter cake until a dynamic equilibrium between wall-shearing forces and normally directed compaction forces is attained) yield higher filtration rates than do static tests. Cunningham and Goinss reported results of drilling tests in impermeable shales. They found that by reducing

By Irwin Roman

NUMEROUS results and formulas have been published for analyzing seismic records, but most of them apply only to large-scale phenomena such as are encountered in studying earthquakes. In a few cases,1 formulas have been published for some of the simpler structures. In the present paper, an attempt will be made to analyze several types of struc-tures without using methods more advanced than those of a first course in calculus. In, tracing a disturbance through a medium, it is almost always possible to base the analysis on Fermat's Principle of Extreme Time, which states that waves of displacement travel between points in such a manner as to make the time of travel an extremum with respect to all neighboring paths. In the simpler cases, comprising most of those used in optics or geophysical prospecting, this time is a minimum and the principle is often referred to as the Principle of Least Time. Within a homogeneous medium, having a uniform speed of transmission of the disturbance in all directions and throughout the medium, the paths are straight and are refracted at the interfaces in accordance with the Snell law of refraction, which states that the ratio of the sine of the angle, made by the ray with the normal to the interface, to the speed of trans-mission is the same on both sides of the interface. Thus, in any medium composed of homogeneous sections, this same ratio has a constant value at all points. In particular, if all interfaces are horizontal, it is apparent that the angles of incidence are the angles made by the ray with the vertical direction. Furthermore, the incident ray, the refracted ray and the normal to the interface are all in the same plane at each refraction;

Jan 1, 1933