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By Ali M. Heidarieh Zadeh, Raghu N. Singh

The paper presents a stability investigation of shaft intersections and pit bottom roadways in the vicinity of upcast and downcast shafts at a colliery in the U.K. Aschemeof instrumentation was aimed at monitoring the strata displacement surrounding the pit bottom roadways and shaft intersections with a view to ascertaining the origin of the strata movement and effectiveness of the control measures. The bore- hole instrumentation results together with a theoretical analysis suggested that the cause of instability could be attributed to the drivage of a roadway within the shaft pillar. A semi-empirical technique was used to calculate the amount of support resistance required to reinforce the pillar to take additional abutment load. A rock bolting system was designed to provide a required increase in thrust capacity of the roadway support. The results indicated that roadway closure was effectively controlled after installation of bolts indicating efficacy of the control measures adopted.

Jan 1, 1982

By I. R. Kramer

The stress associated with the surface layer was deter-minedfor iron and molybdcnum. These measurements show that the surface layer plays a very important role in the plastic deformation of bcc metals. From the relationship between strain arui the surface layer stress and the back stress imposed by the internal obstacles, it is Proposed that the term of of the Hall-Petch equation is related only THE large number of studies on plastic flow of bcc metals have failed to delineate clearly the nature of the obstacles influencing dislocation movement. Since there have been numerous articles which have reviewed the mechanisms proposed to explain various aspects of plastic flow of bcc metals (for example, conrad1 and Keh and weissmann2), no attempt will be made here to discuss their conclusions. However, it should be to the surface stress while the term Kfd is the stress required to move dislocations through internal obstacles. Further, it was possible to derive the well-known empirical equation C = , and it is shown that the terprz a is comprised of two terms: a term Cs associated with the surface layer stress and Ci related to internal dislocation obstacles. pointed out that in all of these publications it has been tacitly assumed that plastic flow occurred uniformly throughout the cross section of the specimen (except, of course, for the Luders band region), It has generally been further assumed that the nature and distribution of the obstacles opposing the motion of dislocations are of the same type throughout. The role of the surface layer in bcc metals has not, as yet, been considered even though its role in fcc metals has been shown clearly to be of primary importance.3-5 Investigations on fcc metals have shown that at the onset of plastic deformation a surface layer acts to

Jan 1, 1968

By C. R. Swarts

The use of compressed air or gas in oil wells for raising crude oil to the surface has, within the last year, become a dominant factor In production engineering. Previous application of this principle was largely confined to oil wells that had been pumping for a considerable length of time. In the Seminole area, the gas-air lift has been applied to wells imniediately after natural flow has ceased and in some cases while the wells were still flowing. This early application of the gas-air lift has been watchcd with intense interest by the petroleum industry, both with respect to methods of application and mechanical installations and to the effects on immediate and ultimate production. Methods of Application The Seminole pool at its inception contained sufficient gas associated with the oil to cause natural flow. As no frce gas was found in the main productive horizon, the Wilcox sand, all the gas present was dissolved in the oil, hence the natural flowing life was short, rarely lasting over 45 days. When natural flow ceased, high fluid levels were common, and as depth and crookedness of holes were obstacles to efficient pumping, the gas-air lift was used almost exclusively in raising the oil to the surface. Because of the high gravity of the oil, 41" A. P. I., and its high gasoline content, and also because of the desire to obtain production before offset wells became productive, quantity of production was the aim of the operators and a method of flow was used whereby this aim could be fulfilled. One of the outstanding features of this method consisted in flowing the wells through the annular space between the tubing and rasing. By this means a greater quantity of fluid could be handled than by flowing through the tubing of the size in ordinary use. Wells that would produce only a few hundred barrels on the pump were by this rnethod made to produce as high as 7000 bbl. on the lift. A few days or wreks of production at that rate meant a large recovery of oil. Casing of 636 in. diameter was commonly used as a production string with a 5 3/16-in. liner set on top of the oil sand. Upset tubing for irtro-

Jan 1, 1928

By G. R. M. Del Giudice

A survey of the flotation literature of the past 10 years indicates an increasing use of the microscope as a tool for investigation. Thus, the metallurgical microscope has been used by Tucker and Head;' Taggart, Taylor and Ince;2 Ince,3 and del Giudice4 to examine mineral surfaces that had been subjected to the action of various flotation reagents and to the action of slime pulps. It has also been used by Gaudin, Groh and Henderson;5 Martin;6 Morrow and Griswold;7 and others to examine bakelite briquets of mill products. The microscope with transmitted light, both with bright-field and dark-field illuminations, has been used by Taggart, Taylor and Knoll8 and by Ince9 to observe Brownian motrement and flocculation in flotation pulps. The use of the microscope at low-power magnifications with incident illumination for the examination of mill products has been known for years.10 Finally, del Giudice11 has used a relatively new type of illumination, the Ultropak, for the examinntion of slime-coatings.

Jan 1, 1935

By Thomas Brownfield

Development and production activity in Oklahoma during the year 1940 was of routine nature. Production, according to the Corporation Commission's figures, averaged 409,100 bbl. daily as compared with 421,000 bbl. for the year 1939. Discoveries were of minor importance except for the Cumberland pool in Marshall and Bryan Counties, in the southern part of the state. Maintenance of a relatively stable producing rate is attributable to the drilling of new wells and the recompletion of many old wells in the previously established producing areas. During the year 1785 new wells were drilled, a decline of approximately 10 per cent as compared with the previous year. Of the wells drilled, 962 were oil wells with a combined initial production of 241,000 bbl. daily, 172 were gas wells having aggregate capacities of 1205 million cu. ft., and 651 were dry holes. Wildcat activity increased 20 per cent over 1939 and 227 such wells were completed during the year; that isl 43 oil wells, 16 gas wells, and 168 dry holes. In addition to the new work completed, 603 wells were recorded as having been drilled deeper or plugged back to test new horizons; included were 334 producing wells with total initial production of 65,000 bbl. daily, 37 gas wells with initial aggregating 305 million cu. ft., and 232 abandonments. Footage drilled amounted to 4,730,000 ft., an average of 2650 ft. per well as com-pared with an average depth of 2600 ft. recorded the previous year. The principal new pools discovered as a result of the exploratory drilling were Cumberland; East Cromwell, in Okfuskee County, and Prague, in Lincoln County. At the end of the year Cumberland had 13 completed wells, which averaged 700 bbl. initial through tubing from the Simpson Bromide formation (Ordovician) at 4750 ft. East Cromwell had 10 wells with average initial of 435 bbl. in the Cromwell sand (Pennsylvanian) at 3460 ft. Prague had II wells with an initial average of 220 bbl. from the Senora sand (Pennsylvanian) at 3260 ft. There were notable extensions to the Dill pool, Okfuskee County, and to the Hewitt pool, Carter County. At the end of the year, 19 producing wells had been drilled in the former, with initials averaging 1000 bbl., and 63 wells averaging 150 bbl. daily in the latter. There were no notable changes in the policy of State conservation authorities with respect to proration. The Bureau of Mines recommendations for the year averaged 413,000 bbl. daily; the State author-ities fixed allowables at an average of 406,000 bbl. daily, while, as noted above, production averaged 409,100 barrels. The most important development in the older areas occurred in the following pools: Billings.—Seven oil wells with an average initial production of 2500 bbl. and two dry holes were completed during the year. Production from the Simpson horizon averaged 6025 bbl. daily as compared with 5950 the previous year. Production from this field has been almost steady since reaching its peak early in 1937. The major portion of the pool is efficiently operated as

Jan 1, 1941

By Thomas Brownfield

Development and production activity in Oklahoma during the year 1940 was of routine nature. Production, according to the Corporation Commission's figures, averaged 409,100 bbl. daily as compared with 421,000 bbl. for the year 1939. Discoveries were of minor importance except for the Cumberland pool in Marshall and Bryan Counties, in the southern part of the state. Maintenance of a relatively stable producing rate is attributable to the drilling of new wells and the recompletion of many old wells in the previously established producing areas. During the year 1785 new wells were drilled, a decline of approximately 10 per cent as compared with the previous year. Of the wells drilled, 962 were oil wells with a combined initial production of 241,000 bbl. daily, 172 were gas wells having aggregate capacities of 1205 million cu. ft., and 651 were dry holes. Wildcat activity increased 20 per cent over 1939 and 227 such wells were completed during the year; that isl 43 oil wells, 16 gas wells, and 168 dry holes. In addition to the new work completed, 603 wells were recorded as having been drilled deeper or plugged back to test new horizons; included were 334 producing wells with total initial production of 65,000 bbl. daily, 37 gas wells with initial aggregating 305 million cu. ft., and 232 abandonments. Footage drilled amounted to 4,730,000 ft., an average of 2650 ft. per well as com-pared with an average depth of 2600 ft. recorded the previous year. The principal new pools discovered as a result of the exploratory drilling were Cumberland; East Cromwell, in Okfuskee County, and Prague, in Lincoln County. At the end of the year Cumberland had 13 completed wells, which averaged 700 bbl. initial through tubing from the Simpson Bromide formation (Ordovician) at 4750 ft. East Cromwell had 10 wells with average initial of 435 bbl. in the Cromwell sand (Pennsylvanian) at 3460 ft. Prague had II wells with an initial average of 220 bbl. from the Senora sand (Pennsylvanian) at 3260 ft. There were notable extensions to the Dill pool, Okfuskee County, and to the Hewitt pool, Carter County. At the end of the year, 19 producing wells had been drilled in the former, with initials averaging 1000 bbl., and 63 wells averaging 150 bbl. daily in the latter. There were no notable changes in the policy of State conservation authorities with respect to proration. The Bureau of Mines recommendations for the year averaged 413,000 bbl. daily; the State author-ities fixed allowables at an average of 406,000 bbl. daily, while, as noted above, production averaged 409,100 barrels. The most important development in the older areas occurred in the following pools: Billings.—Seven oil wells with an average initial production of 2500 bbl. and two dry holes were completed during the year. Production from the Simpson horizon averaged 6025 bbl. daily as compared with 5950 the previous year. Production from this field has been almost steady since reaching its peak early in 1937. The major portion of the pool is efficiently operated as

Jan 1, 1941

By Hermann Wedding

It is now fourteen years since we German ironmasters, in considerable number, visited the United States on the occasion of the Philadelphia Exposition, and found the iron metallurgy of this country, as must be frankly confessed, in an advanced stage of development not previously suspected by us. At that time the United States already occupied, as now, the second rank, with Germany in the third, the product of pig-iron for that year being, in Great Britain, 6550, in this country, 2093, and in Germany, 1850 kilotons.* This relative position has not been changed. The present annual product of the three countries is, in round numbers, Great Britain, 8380, the United States, 7790, and Germany, 4530 kilotons. But the proportion of the United States, which was, in 1876, but 15 per cent. of the world's product, has now advanced to 30 per cent. When we left America in 1876, it was not only with gratitude for cordial hospitality and for the liberality with which our professional colleagues here had opened to our inspection whatever was worthy of notice in our special field, but also with the conviction that we had collected a great treasure of new and interesting information which we could utilize for the benefit of our German Fatherland. Particularly the achievements of the never-to-be-forgotten Holley in the field of Bessemer practice, set us an inspiring example for imitation in our own country. As an expression of our thanks in more practical fashion, I attempt in this paper to sketch what we have done in Germany since

Jan 1, 1891

By Walter R. Hibbard, Walter L. Finlay

INTRODUCTION THE key feature of the lattice coherency theory of precipitation hardening1-6 is the forced coherence between matrix and precipitate which elastically strains both lattices and is believed to be the major source of strengthening in precipitation hardening. In systems exhibiting age hardening, the atom movements leading to precipitation are not at all extensive and are such as to require the minimum amount of energy to produce the interface; that is, the new lattice forms in such a way as to be as nearly as possible a continuation of the old with a matched, coherent plane at the interface at least during the initiation of the precipitation. The crystallographic sequence whereby regions of the matrix change to the precipitate lattice usually can be resolved into a set of shearing operations.5,6 Conversely, the perhaps novel speculation is made that solution of a second phase is accompanied by shearing movements which are possibly the reverse of the precipitation shearing movements. A basic premise of the investigation reported in this paper is that precipitation and solution shearing movements constitute structural weaknesses which might cooperate with applied stresses to facilitate plastic deformation. Another basic premise of the investigation is that the application of hydrostatic pressure to a precipitation hardening system will significantly alter the degree of disregistry across the matrix-precipitate interface and thereby significantly affect the course of age hardening. Two binary precipitation hardening systems were investigated: 12 pct zinc in aluminum which undergoes transformations, both precipitation and solution, by a simple crystallographic mechanism; and 4 pct copper in aluminum which undergoes a complex transformation in precipitating and dissolving a second phase. The effects of the application of uniaxial tensile creep stress during elevated temperature aging of both systems and of hydrostatic pressure during the elevated temperature aging of 12 pct aluminum-zinc were then investigated. Previous Investigations Van Wert in 1935,7 studied the effect of hydrostatic pressure on the room temperature age hardening of a few precipitation hardening systems. The latter were rather unfortunately selected since none is known to exhibit any marked volume change on aging and the majority were complex commercial alloys the precipitation mechanisms of which are not known. Jenkins, Bucknall and Jenkinson,8 in 1944, applied tensile creep stresses to a complex coppernickel-silicon alloy at various temperatures. The complexity of the alloy and the industrial objective of the work did not permit an appreciable addition to the theoretical understanding of either deformation or precipitation hardening.

Jan 1, 1948

By H. W. Morse

The experimental work on the oxidized copper ore at the New Cornelia mine at Ajo, Ariz., ended on Jan. 12, 1916. On that date final decision was made on the general nature of the process to be used in the 5,000-ton leaching plant, and on many of the details, as far as experience on a 40-ton scale could decide them. With the approval of the Board of Directors and the General Manager, John C. Greenway, we have compiled what seem to be the most interesting data on the results obtained during the experimental period. The most important part of the data resulted from the operation of a 1-ton and a 40-ton plant at Ajo. Experimental work on Cornelia oxidized ore dates back to April, 1912, and has been going on nearly continuously since that time. A good many variations from the original idea have been tried, but the process finally decided upon is in principle and in all of its details a simple one. The history of the leaching work on this ore has been brought down to about a year ago in papers presented to this Institute by Stuart Croasdalel and Dr. L. D. Ricketts.2 The present paper will, therefore, deal principally with the results obtained during the last year of the work. Preliminary Tests by Mb. Croasdale Preliminary tests were begun by Stuart Croasdale in July, 1912. A number of important points were definitely decided by his work. Among these were: 1. New Cornelia oxidized ore, not very finely crushed (to about 2-to 3-mesh) showed good extraction with 5 per cent. sulphuric acid. It appeared that better than 80 per cent. extraction could be expected. 2. The consumption of acid for this extraction was not prohibitive. It was apparently 3.5 to 4 1b. gross per pound of copper recovered.

Jan 1, 1917

By C. B. Alcock, M. G. Hocking

The kinetics of the growth of sulfate layers on blocks of Cu20 has been studied between 688" and 800°C. At 788c the over-all weight increases followed the parabolic rate law, with k = 216 30 sq mg per cm4 min, using a 1:1 entering gas mixture of SO2:02. At 757 after an initial linear period the parabolic rate law was followed, with k = 57.8 10 sq mg per cm4 min. The gas mixture required a platinum catalyst to produce the maximum SOs pressure. The sulfation rate at 757' and 788c was high until all the CUZO had changed into a core of CuO, when it became very much lower. At 757°C marker experiments showed that the sulfates (CuO. CuS04 and CuSO4) grow outwards from the oxide surface, but CuO. CuS04 mixed with CuO was found beneath the markers. At 688 markers were found at the CuO. CuS04/CuS04 interface. Visual observations at 757 showed a liquid eutectic moving beneath the sulfate surface. causing very rapid sulfation and extruding to solidify as thick 'needles" up to 8 mm long. Marker experiments have shown conclusi.cely that CuO grows on Cu20 in air by the outward migration of copper. ThermODYNAMIC measurements on the sulfate and basic sulfate of copper, reported recently,' are followed here by measurements of the rates of formation of these sulfates on cuprous oxide, in order to provide a background for the understanding of roasting processes. peretti2 and McCabe and Morgan3 have shown that the phase Cu20 lies next to Cu2S when the sulfide is roasted under conditions where sulfates will be formed. Since this would present too complex a system for kinetic study, the present work4 has been based on the kinetics of sulfation of the oxide phase. The results of a study of the kinetics and mechanism of the sulfation of cobaltous oxide have recently been reported.4,5 Results on the sulfation of cuprous oxide have also appeared,6 but are at variance with those to be reported here. This seems to be because the previous workers6 did not obtain constant SO3 pressures from the SO2/O2 sulfating gas mixtures used, as will be discussed later. Wadsworth, Leiter, Porter, and Lewis found that the sulfates produced when SO2/O2 mixtures are passed over Cu20 at red heats are CuS04 and the basic sulfate CuO.CuSO4. When the decomposition of CuS04 was followed' by differential thermal analysis, a stage corresponding to CuO .CuS04 was reached before decomposition into the oxide occurred. APPARATUS The vertical furnace used for quantitative studies was a conventional resistance-heated and propor- tionately controlled furnace with an even zone (1 deg) which was 4 cm long. The gas mixtures of SO2 and 02 were made by mixing measured flows from capillary flowmeters and drying over phosphorous pentoxide before passing them into the Pyrex top-piece of the furnace assembly. A mullite tube of bore 2% cm was used as reaction vessel and at the bottom of this tube was a trap for SO3, which condensed as a colorless liquid. The residual gas was led into a fume cupboard for ventilation to the atmosphere. The furnace used for visual observations of needle growth and other phenomena consisted of a transparent silica reaction tube of bore 3 cm, having an optically flat silica window sealed into its wall. The reaction tube was clamped vertically, inside a mullite tube of bore 4 cm and length 42 cm which was heated by Kanthal windings. The window in the silica reaction tube was arranged opposite a hole 3 cm wide and 2 cm tall which had been cut in the wall of the mullite winding tube 19 cm from its top end. A binocular microscope was used to look through the window, illumination being provided by a focusing microscope-lamp offset sideways and downwards. The oxide block to be sulfated was suspended from the removable Pyrex top-piece to the reaction tube, by means of which it was inserted at the start of the experiment, and through which entered the S02/02 gas mixture. The variation of the temperature inside the reaction tube with horizontal and vertical displacement from the window was investigated, and, while it can be said that the temperature was constant 1 deg, its value at a given position was known only to 12 deg. In both furnaces, the oxide block to be sulfated was suspended from a small silica hook immediately downstream from a platinum thimble used as catalyst, which was held on a long silica rod from a Pyrex spring attached to the removable Pyrex top-piece of the furnace. The spring was only included in the quantitative sulfating furnace; its sensitivity was 1.4 cm per g and it was found to be free from creep in a 16-hr test when carrying the working load. The extensions were followed by a cathetometer which could be read to 0.001 cm, corresponding to i0.7 mg. Extensions of the spring were measured on adding weights between 5 and 500 mg to the working load (thimble + oxide block), and Hooke's law was closely obeyed. SAMPLES Cuprous oxide blocks were prepared by oxidizing Johnson Matthey "Specpure" copper sheet of 1 mm thickness (impurities: iron at 3 ppm, silver at 2 ppm, lead, nickel, sodium, and silicon each at 1 ppm, calcium, chromium, magnesium, and manganese each at less than 1 ppm) for 6 days in air at 1000°C in a re-crystallized alumina boat. It has been reported7 that when Cu20 is prepared by heating copper sheet for 1 day the central plane of the blocks produced consists

Jan 1, 1967

By G. V. Raymor, James T. Waber, I. Rex Harris

The lattice parameters of a series of fcc alloys of cerium and thorium were measured at 93 " and 298OK. Lattice parameters were also estimated for 171OK. Substantial deviations, y, from Vegard's law were observed. Although y was negative at the two higher temperatures, it was positive and large at the lowest temperature. A variety of models, which have been proposed in the past, were considered, and the calculated values of y were compared with the observed values. The best agreement was achieved with values computed with Friedel's equation. THE purpose of this investigation was to determine the effect of temperature on the lattice parameter and on deviations from Vegard's law of Ce-Th alloys. A large negative deviation from Vegard's law was first observed independently by Weiner, Freeth, and Raynor' and Van vucht2 in the room-temperature lattice parameters of Ce-Th alloys that form a continuous series of solid solutions. This observation was confirmed by Evans and Raynor. The allotropy of unalloyed cerium was reviewed recently by Gschneidner, Elliott, and McDonald. In two subsequent papers,5" these authors reported the influence of various alloying additions on the y= transformation, which occurs below room temperature. Although other rare earths tend to stabilize the double-hexagonal phase, thorium, plutonium, and scandium as solutes tend to stabilize the normal fcc phase. With addition of sufficient thorium as a solute, there is evidence that the formation of is suppressed and it becomes possible to pass continuously with decreasing temperature from the room-temperature phase to the fcc a phase. Thus there is a closed loop which is similar in many ways to the y loop well-known in ferrous alloys. A closed field also occurs in the pressure-temperature "equilibrium" diagram of unalloyed cerium. Because of interest in the effect of thorium additions and their influence on the a and phases, lattice-parameter measurements were made at low temperatures on the fcc phase for a series of alloys ranging from 10 to 90 at. pct Th. The results obtained at three temperatures are shown in Fig. 1. Evans and Raynors analyzed the deviations from Vegard's law in Ce-Th alloys in terms of changes in the occupancy of the 4f electron level in cerium,

Jan 1, 1964

By H. L. Couch, J. D. Lubahn

In decarburized mild steel, the strain hardening arising from 1/2 pct strain can he partly recovered by subsequent heating, even though re crystallization or grain growth does not occur. This recovery varies from 5 pct in an hour at room temperature to 70 pct at 800°C. The variation with temperature was qualitatively similar to that reported for copper, but occurred at lower temperatures. Except for the initial portion (Bazdschinger effect), the stress-strain curve following recovery can be superimposed on the original curve by shifting it to the left. In other words, the tensile behavior is essentially the same after straining and heating as if there had been less strain and no heating. The importance of this observation in understanding simultaneous deformation and recouery is explained. AN earlier investigation1 on copper showed that strengthening due to strain hardening was augmented by heating at moderate temperatures, but was diminished by heating at higher temperatures, Fig. 1. Auxiliary experiments1 indicated that recovery and strain aging are independent processes, which may proceed simultaneously, and whose effects are additive as indicated in Fig. 1. In order to study recovery by itself, similar tests were made on decarburized mild steel, where strain-aging effects are known2 to be absent. MATERIAL, TESTING PROCEDURE The specimens were made from rimmed, hot-rolled SAE 1020 steel 0.040 in. thick, by stamping out rectangular blanks and end holes, Fig. 2, and pack milling the reduced section. These were wet-hydrogen treated2 for 16 hr at 720°C to remove carbon and nitrogen completely and then heated 1 hr at 850°C in vacuum to stabilize the grain size. Auxiliary ex- periments showed that heating up to 800°C will not cause grain growth. They were prestrained 5 to 7.5 mils per in. using the special grips shown in Fig. 2. Such small strains are less than the "critical" strain for recrystallization and, therefore, will not cause recrystallization, even at high temperature. The recovery treatment after prestraining and before the retesting consisted of heating for 1 hr in wet hydrogen at the desired temperature. In one test, Huggenberger gages were used to define more accurately the loading and unloading curves. Fig. 3 illustrates the creep during the early stages of unloading, the hysteresis due to cold stretching, and removal of hysteresis by heating.3 RESULTS The load-deflection curves had ratner widely differing shapes for different specimens, both before and after the recovery treatment. Some specimens showed perfectly smooth curves, Fig. 4, while others exhibited an inflection more or less suggestive of a yield point (Fig. 4 shows all extreme case). Some curves were much steeper than others; Fig. 5 shows two extremes. Some additional ex-

Jan 1, 1960

By Tong Guangxu

INTRODUCTION Throughout the world, the caving mining methods of ore-draw under the overlying waste rock are sublevel caving in Sweden, block caving in U.S.A. and forced block caving and sublevel caving with sill-pillar in U.S.S.R. These caving methods are of high efficiency, low cost and large production (especially the block caving method) when compared to opencast mining. From the ore production of all under- ground mines, the largest annual production of underground metalliferous mines in the world is caving methods. The sublevel caving in Kiruna Iron Mine of Sweden has reached annual ore production over 20 million tons in 1974. The block caving in Climax Molybdenum Mine and San Manuel Copper Mine of U.S.A. both have produced about 40 thou- sand tons of ore per day in 1971. At the same time, the productivity of Kiruna was 12 thousand tons of ore per man-year, Climax 42.8 tons (48.3 short tons) per man-shift and San Manuel 29.01 tons (32.1 short tons) per man-shift. The main feature of this group of mining methods is the underground extraction of ore from beneath overlying caveable waste rock. Since the loss and dilution of ore are inherent (sometimes to a great extent), the control of ore-draw in these methods as com- pared with other methods is very important. Consequently, concerned Universities and Research Institutes have devoted great amounts of research on ore-draw theory and control management which has provided positive results to mine production, and has apparently promoted the development of the caving methods. During 1979 in China, metalliferous underground mines accounted for 15.22% of the total iron ore produced, while also accounting for 56% of total non-ferrous production. According to the mining methods, sub level caving in the principal underground iron mines counted for about 56.74% of total principal underground iron mine production, but only about 1% of total non-ferrous underground mine production. Relative to forced block caving and sublevel caving with sill pillar, the Chinese non-ferrous under- ground mines estimated about 35% of total non-ferrous underground mine production from these two methods, mainly from the latter. From the trend of development of underground metalliferous mines in China, the percentage of production in caving will be increased in the future, especially in block caving and forced block caving which have already been given great attention in the mining circle. In these types of mining methods the ore is drawn from the stope under a large area of overlying waste rock, which complicates the basic regulation and control of ore-draw, but provides lower loss and dilution than sublevel caving. Because of these reasons, the Kiruna Iron Mine in Sweden is intending to change its sublevel caving by testing a sublevel shrinkage caving method and considering a large area of ore-draw beneath the stope as an advantage. Therefore, the basic regulation and control management of ore-draw under a large area, as practiced in China, will be discussed in this paper. BASIC REGULATION OF ORE- DRAW FROM CAVING STOPE The aim of studying ore-draw under a large area of overlying waste rock is to se- cure a planned draw schedule that guarantees a certain plane of interface between ore and waste rock, and controls the change of its shape in spatial position for reducing ore loss and dilution during the draw process. Presently, the ellipsoid theory is comparatively near the actual attitude of ore-draw from the cave. 1. Ore Drawn Out from Single Drawpoint Laboratory testing and practical experience all show that after a certain amount of ore has been drawn out from a drawpoint, its original shape in the stope before drawing is more or less similar to an ellipsoid, hence the name "draw ellipsoid." This draw ellipsoid is cut at the bottom by a horizontal plane corresponding to the raise of the drawpoint, and its volume can be calculated by the following formula:

Jan 1, 1981

By R. M. Brick

Segregation can occur only in cast alloys that solidify over a range of temperatures with a difference in composition of liquid and solid phases within this range (ignoring monotectic systems and chemical reactions as in rimming steels). Thus a pure binary eutectic alloy should show no segregation unless undercooling occurs for one of the solid constituents of the eutectic; e.g., chill-cast Al-I2 per cent Si alloys. The phasial condition implicitly described above—solidification over a range of temperatures with a compositional difference between solid and liquid—is found in nearly all solid solutions or combinations of solid solutions and eutec-tics, Metastable conditions of solidification of these types of alloys cause coring; i.e., a difference in composition between the center of a dendrite and its periphery. This composition gradient can be detected usually only by microscopic examination of etched structures; it is a "micro" effect. The gradient of more immediate industrial concern is that between the center of a cast section and the surface layers. This gross (macro) effect is usually deter-minable only by sampling of the casting at different points, with chemical analyses of each sample. If the compositional difference is of the same type as in coring, the first parts to freeze being enriched in higher-melting-point constituents, and vice versa, the effect is called normal segregation. When what is apparently the first part of the casting to solidify shows a higher concentration of low-melting-point constituents, the effect is called inverse segregation. These macro effects are quite separate from the micro effect, coring, yet the latter must be described first because it is an essential part of the picture. Coring Solid Solution, Ni-Cu The nickel-copper phase diagram is reproduced in Fig. Ia, in which the solid lines represent the equilibrium liquidus I, 3, 7 and solidus 2, 5, 8, and where the vertical I, 4: 8 represents a 55 per cent Cu alloy. Upon moderately rapid solidification, the first dendritic axes of composition 2 (see Fig. Ib) start to form at a temperature somewhat under I. Solidification continues by growth of the dendritic nuclei, but at temperature 4 the increment solidifying is of composition 5. The rapidity of this crystal growth prevents diffusion of nickel and copper atoms from adjusting the composition of the entire dendrite at 5, which it would be under equilibrium conditions. The average composition of a specific dendrite, or the entire solid phase, at temperature 4 might be that indicated

Jan 1, 1945

PRESIDENTS DAVID THOMAS 1871 R W RAYMOND 1872-1874 A L HOLLEY1875 ABRAM S HEWITT 1876 T STERRY HUNT 1877 ECKLEY B COXE 1878 - 1879 WILLIAM P SHINN 1880 WILLIAM METCALF 1881 RICHARD P ROTHWELL 1882 ROBERY W HUNT 1883 JAMES C, BAYLES 1884-1885 ROBERT H RICHARDS 1886 THOMAS EGLESTON 1887 WILLIAM B POTTER 1888 RICHARD PEARCE 1889 ADAM S HEWITT 1890 JOHN BIRKINBINE 1891-1892 H M HOWE 1893 JOHN FRITZ 1894 J D WEEKD 1895

Jan 1, 1923

By William Waters Van Ness

The Pierrefitte mines, situated in the South of France, in the district of the Hautes-Pyrenees, owe their name to the fact that the first mining operations of any extent, and of comparatively reccnt date, were carried out in the neighborhood of the village of Pierrefitte, which is a branch terminus of the Midi railway. The Pierrefitte mines, however, embrace a wide extent of country and several different concessions, on most of which comparatively little exploration-work has been done. The portion of the property presently to be described is a zone running roughly E—W., over a distance of about 5 miles from the valley of Cauterets to the valley of Estaing, the ridge dividing these valleys being a spur of the main chain of the Pyrenees, and running more or less at right angles to it. According to local tradition, which various indications tend to confirm, these mines are of ancient date, the first workings being attributed to the Romans, who are supposcd to have sought not only the lead but also the silver which is contained in the ore. Old slags have been found in the neighborhood which might well have been produced from the cupellation of lead-ores. These old workings, while of considerable extent at times, do not seem to have extended beyond a depth of 100 ft., even this depth being somewhat exceptional. The old notarial records of the district show that mines were known to exist, and that they were even worked, in the sixteenth century, but since the mines were abandoned (by the Romans or others) considerably prior to this period, very little

Jan 1, 1909

By L. L. Wyman

THE resultant embrittlement caused by the exposure of oxygen-bearing copper when hot and exposed to reducing gases has been the subject of many studies.1 Little attention, however, has been given to the possible embrittling effects due to atmospheres or conditions that under some circumstances might be the source of a reducing gas. At rather infrequent intervals there occur reports of copper becoming embrittled during normal annealing cycles in commercial steam-atmos-hered furnaces such as customarily are used for this operation. As might be expected, several other factors exist-such as oil, dirt on the wire, or in the furnace, or metallic surface contacts that might produce reducing gases and be the source of the trouble. However, in consider-ation of the statement made by Ruder,2 it would seem that under some conditions steam itself might prove to be the source of trouble. A consideration of the amount of the dissociation of water vapor up to temperatures of the melting point of copper shows that' the amount of hydrogen that could come from this source is far too minute to account for any embrittlement. What such information does not tell is what will happen at the surface of copper when subjected to steam at elevated temperatures, for entirely different conditions may persist, which would account for Ruder's observation. Furthermore, there are no data as to what might happen at the surfaces of other materials present, the result-ant of which might affect the condition of the copper present. For this reason, it was decided to make a series of experiments com-parable to those previously conducted by the writer,1 which would clarify the effect of the steam on copper, and in copper in the presence of steel.

Jan 1, 1940

By C. R. Van Hise

[Concluding Contribution of Prof. Van Hise to the Discussion of his Paper, and Others on the Same General Subject, presented at the Washington Meeting, February, 1900 (see Trans., xxx., 27, 177, 323, 424, 5 S); also of the contributions of Vogt, De Launay, Beck, Lindgren, hemp, Rickard, Bain, Keyes, Collins and Adams, presented at the Richmond Meeting, February, 1901, and printed in the present volume.] IN June, 1900, shortly after my paper was published in the Transactions, I made a briefer statement* before the Western Society of Engineers covering the same `round, which, in certain respects, is somewhat of an improvement. For instance, instead of using the terms descending and ascending with reference to the waters resulting in the two concentrations, my modified statement is as follows " The first concentration of many ore-deposits is the work of a relatively deep water-circulation, while the reconcentration is the result of reactions upon an earlier concentration through the agency of a relatively shallow water-circulation. Commonly the deep water circulation is lacking in free oxygen, and contains reducing agents, and the shallow water contains free oxygen. The deep water is therefore a reducing, and the shallow water an oxidizing agent."† Of the papers upon ore-deposits which, in vol. xxx. of the Transactions, follow my own, or which were presented at the Richmond meeting, a considerable number are wholly confirmatory of the conclusions which I have presented. Among these are the Washington paper of Emmons upon the Secondary Enrichment of Ore-Deposits‡ and his discussion at Richmond of other papers,§ that of Weed upon the Enrichment of Gold and Silver Veins,[ ]the discussion of Emmons', and at Richmond of Weed's paper by Collinst and Prof. De Launay,† the paper of Lindgren on Metasomatic Processes in Fissure Veins,¶ that of-Rickard upon the Formation of Bonanzas in the Upper Portions of Gold Veins,** and the remarks of Bain upon the Mississippi Valley lead- and zinc-deposits.†† It is therefore un-

Jan 1, 1902

THE metal iron has physical and chemical properties which are somewhat different from those of steels, but a knowledge of the pure metal is a useful starting point in studying the behavior of steels. Solid iron exists in two different crystalline forms, called alpha (a) and gamma (?) iron, the former being the ordinary form at room temperature. When heated above the "A2 point," 1400°F. (760°C.), the metal becomes non-magnetic, and at the "As point," 1670°F. (910°C.), it undergoes a change in crystalline form to become gamma iron. In the range 1400 to 1670°F., it is sometimes called beta (0) iron to distinguish it from the magnetic alpha, but the two are identical in crystal structure. When gamma iron is further heated to 2550°F. (1400°C.), it changes into delta (d) iron, which is identical with beta or non-magnetic alpha iron. Pure iron melts (in a hydrogen atmosphere) at 2795°F. (1535°C.); the melting point is generally lowered by alloys or impurities. PROPERTIES OF IRON AT HIGH TEMPERATURES Many of the properties of iron undergo abrupt changes at the transition temperatures. (1) For example, in heating through the As point a sudden shrinkage in volume occurs. Similarly, melting is attended by sharp physical changes such as an increase in volume. Table 27 contains a summary of the measured physical properties of pure iron at several temperatures. Usually the properties change smoothly within the range of stability of a given form, but this is not always the case. For example, the specific heat reaches a sharp maximum at the A2 point although no transformation occurs. Solvent Powers of Liquid Iron. Liquid iron is capable of dissolving most of the other metals and many nonmetallic elements as well. Of the metals which are liquid at the melting point of iron only lead, silver, and bismuth refuse to dissolve to an appreciable extent. The non-metals presumably dissolve by virtue of the formation of an iron compound; for example, sulphur is thought to dissolve as the compound FeS. However, there is no satisfactory method of proving that this

Jan 1, 1944

By F. X. Tartaron

F. C. Bond (Consulting Engineer, Processing Machinery Dept., Allis-Chalmers Manufacturing Co., Milwaukee, Wis.) — Papers such as this one which deal in a lucid manner with the obscure fundamentals of comminution theory are always welcome. The author has attempted to bring together several diverse theories and handles them interestingly. However, some of the ideas expressed and conclusions drawn require critical reviewing, for which amenities alone will not suffice. The author points out that the theoretical energy required to break across crystal lattices is of the order of 1000 times the actual energy required to crush or grind, and that this energy in turn is perhaps 1000 times the measured surface energy of the new surface area produced. The energy required to grind commercially is controlled by flaws and dislocations, rather than by the inner strength of the lattice structure. The measured surface energy is only a slight residue left after the face atoms are adjusted to their new environment. The dislocations in the crystal lattice structure, with a spacing of about O.l,u, or

Jan 1, 1962