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By K. J. Rosengren

INTRODUCTION Mount Isa Mines Limited operates a major mining complex at Mount Isa in northwest Queensland, Australia. The location is arid and remote, some 600 miles distant from the nearest port of Townsville on the eastern coast (Fig. I). Current mine production is 6 million long tons per annum comprising 3.8 million tons of copper ore and 2.2 million tons of silver-lead-zinc ore. Copper ore production is scheduled to increase to 5.8 million long tons per annum by 1973 and a new silver-lead-zinc mine is being developed at Hilton, 13 miles north of Mount Isa. The Mount Isa and Hilton orebodies occur in a single stratigraphic member, termed the Urquhart Shale. This shale is conformable with several other sedimentary formations striking north-south and dipping approximately 65º west. The silver-lead-zinc orebodies occur in bands conformable with the shale bedding and tend to be of tabular shape, varying in width from a few feet to nearly 200 ft. The copper orebodies occur in breccia bodies, locally known as "silica-dolomite", within the Urquhart Shale and tend to be more irregular and massive with widths up to several hundred feet. The detailed geology is described by Bennett (1 2). At present, production comes almost entirely from underground operations with only about 25,000 tons per year of carbonate ore from open pit operations. The mining method used in the copper orebodies is sublevel open stoping with pillar recovery by pillar blast before stope filling or by sublevel caving after stope filling. A large primary sublevel caving operation was also carried out until recently in one of the orebodies. The wider lead orebodies are mined by sublevel open stoping, with or without pillar recovery, while cut and fill stoping is used in the narrower orebodies. Details of the mining methods are given by Davies (3). The company's interest in open pit mining stems from a large open pit which was mined out in 1965 and a further large open pit planned for future production. In addition, the company is currently evaluating several large ore deposits in Australia and New Guinea. All of these orebodies would be mined by open pit methods and rock mechanics studies of slope stability are now a standard feature of all open pit evaluations.

Jan 1, 1972

By B. A. Cheadle, K. P. Steward

Axial tensile, ring tensile, closed end burst, and free end burst tests were done at room tempe.vature and 300°C on three batches of Zircaloy-2 sheathing zuith different textures. Knoop hardness tests were also done on all batches. The mechanical properties of the tubes were largely dependent on the percentages of cold work, but were also markedly affected by the textures, particularly with respect to deformation behavio'r. The deformation behavior observed confirmed Picklesimer's predictions, zuhereas Knoop hardness results could be correlated with texture and yield strength anisotropy after the ,method of Wheeler and Ireland. From the mechanical properties, and from efjectiue strain values deterrlzined at the fractures using a photoqid technique, it zuas concluded that tubing witlz a single preferred orientation of radial basal poles best combines strength and ductility for any given deqee of cold work. THE mechanical properties required in collapsible Zircaloy-2 fuel sheathing for water-cooled power reactors are strength to resist wrinkling deformation by coolant pressure and ductility to accommodate a small amount of deformation in service without rupturing. Zircaloy-2 tubing during fabrication develops pre- ferred orientations of the a Zr grains due to aniso-tropic deformation behavior, and these textures markedly affect mechanical properties. Picklesimer' had predicted the deformation behavior of tubes with various textures, but the texture required to provide the optimum strength and ductility for a given degree of cold work has not been reported. To investigate this problem, tests at three transverse to axial stress ratios were done at room temperature and 300°C on three batches of Zircaloy-2 tubing covering a wide range of textures and percentages of residual cold work. Knoop hardness values were also measured to correlate with preferred orientation and yield strength anisotropy after the method of Wheeler and relland.' 1) MATERIAL For this investigation, three batches of tube-reduced tubing were chosen from the Zircaloy-2 sheathing produced for the Douglas Point Reactor. Individual tubes were 191/2 in. long, 0.600 in. OD, and 0.0165 in. nominal wall thickness. The identities of the batches, together with their textures, are shown in Table I. The tubes had the normal Zircaloy-2 composition3 of 1.5 wt pct Sn, 0.3 wt pct Fe, Ni, Cr combined with the following oxygen concentrations: Batch VII 1140 to 1390 ppm 0 Batch VIII 1400 to 1750 ppm 0 Batch IX 880 to 1320 ppm 0

Jan 1, 1968

By David B. Scott

The Mogollon mining district, New Mexico, has received little public attention, although for 15 years it has been the leading silver producer of the state; it is situated in a region remote from the principal lines of travel, and its activities have usually been limited to the operations of two or three companies. The value of the total production of the district in the 44 years of its history has been estimated at $15,000,000. For the years 1904 to 1917, inclusive, the output was: gold, $4,370,000; silver, 10,042,000 oz.; copper, 874,862 lb.; total value, approximately $10,500,000. In 1913 the district contributed 80 per cent. of the total silver production of New Mexico, but in 1917 only 41 per cent., due to serious interruption in the operations of the leading producer. Since 1914 the silver output has diminished one-half, and the present high value of silver is nearly offset by the increase in cost of production. The output of gold has rarely exceeded 35 per cent. of the total for New Mexico. The ratio of silver to gold, by weight, has averaged 46:1 based on the whole output of the district. Location and Topography The town of Mogollon is 75 mi. (121 km.) by a poorly located highway ,. from the nearest railroad terminals, at Silver City and Tyrone. All supplies are transported by motor trucks and teams. The area, sometimes called the Cooney Mining District, lies on the western flank of the Mogollon Mountains, which occupy the western part of Socorro County. The elevations drop steeply on the west to the valley of the San Francisco River, adjacent to the Arizona boundary. The topography is very rugged, the whole area being sharply dissected; deep canyons with steep gradients and rugged walls are characteristic of the whole western slope of the Mogollon Range. The main canyons i run east and west, and usually maintain a flow of water during the entire year. As would be expected in a region of such deep dissection, the mines are generally dry. The mountain ridges between the canyons have altitudes varying from 7000 to 10,000 ft. (2130 to 3050 m.) and drop sharply, on their western face, to the floor of the San Francisco Valley at an elevation of 5000 ft. (1525 m.). Erosion has been rapid, and the

Jan 1, 1920

By Gerhard Derge

THE chemical and physical properties of slag systems are of special interest to metallurgists, for nearly all metals are in contact with molten slags during the primary reduction from their ores and then during the subsequent refining and alloying processes that determine their ultimate use, These processes are carried out at high temperatures and involve such complex chemical systems that fundamental scientific knowledge of the properties and behavior of these slags is inadequate. Various hypotheses have been proposed to explain known slag characteristics. The commonest of these regard the molten slag as constituted of compounds that are dissociated in varying degrees into their constituent oxides, as illustrated by Schenck1 and the recent papers of Chipman and co-authors.2-5 Another proposal is that these compounds dissociate by completes or partial ionization, the evidence for which has been reviewed by Martin and Derge.7 Whatever hypothesis is favored, the exact formulation of these compounds is incomplete. It is based on three principal types of information: I, Studies of solidified slag samples by X-ray diffraction, petrography, and similar methods that can be used at room temperature, The correlation of this information with the high-temperature properties of the molten slag is uncertain, 2. Studies of slag-metal equilibria, which have the advantage of providing observations on the molten slag at high temperature, However, even these data present problems of interpretation because they require a complete knowledge of the metal phase, 3, Direct measurements of properties of molten slag at the temperature of greatest metallurgical interest. Viscosity, electrical conductivity, specific heats, and similar properties have been measured, but the data of this type are widely scattered and frequently difficult to interpret, Additional direct measurements of properties of molten slag that can be interpreted in terms of chemical behavior are required, and this paper shows that the standard physical-chemical measurement of reversible electrode potentials, which measure the activity of specific constituents, is a fruitful source of such information, The purpose of this investigation, therefore, was to find an electrode combination that would yield reversible electromotive force measurements when dipped into the molten slag to be studied. Slags of the systems CaO-SiO2 and CaO-A1203-Si02 were chosen for study because graphite containers could be used and the data could be correlated with those for viscosity, conductivity, and other proper-

Jan 1, 1946

By A. E. Lehman

A RECENT demand for some form of panoramic display of an important railway line, showing its branches, connections, and terri tory controlled by it, revealed to the writer the advantages of' a topographical model or relief map fix this purpose. Hitherto, maps of this nature have been used chiefly for scientific and geographical purposes, and confined to a comparatively narrow field of service. They deserve to become more popular and to have their advantages better understood. Much has been written and accomplished in this direction by Prof. Lesley, Messrs. Harden, Moulten, de Mendonca Cortez, and others; but I believe their pub lished descriptions of the methods employed in the construction of these models are confined to those used by themselves. It is the writer's aim to present in condensed form these various methods, and some suggestions of practical value as to the most economical course of procedure, as well as to mention some of the uses that may be made of the results obtained Methods of Construction.—Many different materials have been prepared and used in the preparation of relief maps, such as metal, clay, plaster, gypsum, wax, putty, Card-board, papier-mache, wood, and compositions of varions kinds, with results more or less success ful : wood, however, in the writer's experience, has been found to be by far the most satisfactory, combining the advantages of stability, accuracy and ease of handling. The following is a brief description of several of the methods used in constructing topographical models : When clay, wax, putty, compositions or materials of a plastic nature are used, the operator carries his work up from its base by means of measurements or by the eye, manipulating and shaping the material as best he can, ac cording to such features of his subject as he wishes to delineate. This process requires remarkable skill, and given this, will probably fall short even then of an approximation to accuracy; lacking essential elements of detail nil over the work and exactness, particularly in position and elevation of the most important points in the territory mapped. When either of the above mentioned materials or compositions are used, metal or wooden pins are sometimes driven into the base or level datum plane of wood, the top of these pins giving the eleva-

Jan 1, 1886

By C. E. Lesher

THE Disco* process for the production of low temperature coke and its immediate predecessor, the Wisner or Carbocite process have been described in the voluminous literature of low temperature carbonization.1-4 This paper will describe the development of the process from the first attempt at commercial operation by the American Gas and Electric Co. at Philo, Ohio,' in the 1920's to the successful operation in 1949 by the Disco Co., a division of the Pittsburgh Consolidation Coal Co., of the 1000-ton per day Disco plant near Pittsburgh, see Figs. 1-2. In the 1924 coal industry depression following the hectic post World War I expansion, the northern Appalachian, unionized bituminous coal fields were affected first and foremost, and Western Pennsylvania as hard as any. Competitive market pressure was heaviest on the lower grades of steam coals, notably those from the Panhandle district where ash and sulphur are inherently higher than in the same Pittsburgh coal bed to the east along the rivers. The firm structure of Panhandle coal while favoring the prepared sizes, depressed the usefulness and value of the finer sizes. Panhandle slack and nut slack were marketed with difficulty at consistent, and at times considerable, loss. Many solutions were suggested, and the Pittsburgh Coal Co. investigated all. Lower delivered prices through lower mine costs and more advantageous freight rates were obvious goals, but equally obvious were the difficulties of self attainment of either in any substantial measure. Selling Btu's in pipes was abandoned as an idea after a thorough study of the economics of distribution of what was then, and is even now, the only developed continuous process of complete gasification of bituminous coal-producer gas. Although the coal company purchased huge blocks of electric power, it sold not a car of coal to the central power stations. Public utilities controlled the markets for electric current, and it was found that no matter at how low a cost current might be put on the bus bars by the coal company, distribution to its widely scattered coal mines made such an enterprise practically impossible. Consolidation of underground operations and a huge modernization program of mining operations in the 1920's were but preparation for the introduction of mechanical cleaning of the coal for market, particularly the smaller sizes of steam, gas, and by-

Jan 1, 1952

By G. W. Crane

When ore was discovered on the Tintic Standard property in the spring of 1916, new developments were immediately started both north and south of that property, on the supposition that in East Tintic the ore would be found to occur in northerly trending channels, similar to those so characteristic of the older camp. But 9 years of developments have failed to establish the existence of such a channel. This is due undoubtedly to important differences in the geology of the two camps, that were not recognized, and is indicative of the danger in the general tendency toward interpreting the geology of East Tintic too strictly in terms of that of the older camp. It should not be forgotten that while the two sections have had practically the same geological history, the net results of a long series of geologic processes have developed in them conditions that differ so widely and in so many particulars that the necessity of regarding them as essentially different districts seems apparent. In an effort to emphasize this fact, this paper is devoted chiefly to a comparison of the geological conditions as found in the two camps and is addressed more particularly to those familiar with the geology of the Tintic district. Following a short description of the several ore discoveries and of the Tintic Standard mine is a brief discussion of the evidence of ore channels in East Tintic. For my information regarding the Tintic Standard mine, I am indebted to the courtesy and generous assistance of Messrs. Wade and Snow of the Tintic Standard Mining Co. East Tintic District The Term East Tintic district is here used to represent that eastern part of the Tintic mining district lying between the productive portion of the old camp of Tintic on the west, the foot hills of Goshen Slope, on the east, the Denver and Rio Grande Railroad on the north, and Silver Pass on the south, all in Utah County. As represented by the geological map, Fig. 1, it includes an area about 4 miles wide, east and west, and 5 miles long, north and south, within which the Tintic Standard mine is about centrally located. The map is a compilation of data supplied, for the most part, by the Chief Consolidated Mining Co. and represents the

Jan 1, 1927

By P. W. Rainier

The Chivor emerald field is situated on the eastern slope of the Andes in the Department of Boyach, at an elevation of about 8000 ft. above sea level. It overlooks the Llanos (plains) of the Orinoco and is watered by many streams flowing into the Rio Meta, the Orinoco's largest tributary. The Rio Meta is navigable from the Orinoco to a point within about 50 miles of the Chivor district and may eventually prove to be the reasonable outlet for the future development of this part of the country. The topography of the district is extremely rugged and mountainous (Fig. I), the difference in elevation between two points on a mining claim 1 km. square being sometimes as much as 4000 ft. The ground is covered with dense forest growth and the available timber is suitable and sufficient for mining purposes, but it is becoming gradually depleted by Indian clearings as the country around the mines becomes settled. The many streams combined with the rough topography give good possibilities for hydroelectric power. The center of population nearest to Chivor is Bogoth, the capital of the republic and a city of some 300,000 inhabitants; the distance is two and one-half days' travel. The first stage of the journey from BogotB is accomplished by rail to Choconta, some 4 hr. travel. From Choconth the journey is made in the saddle, one night being spent in Guateque. The latter is a small town and the nearest post office to the mines, being some 10 hr. ride distant. The roads are mere bridle paths, in parts hazardous and almost impassable in the wet season. All supplies brought to the mines, other than those produced locally, are carried by pack mule; mule freight from Choconth costs 3 centavos1 per pound. The climate of the Chivor district is healthful and bracing. The wet season begins in March and concludes in November, the remaining months being dry. The annual precipitation is about 130 in. The temperature throughout the year is nearly constant, varying from about 45" F. to about 65" F. shade temperature. The rains are cold and unpleasant, and for the greater part of each day in the wet season the country is shrouded in dense mist. A fire can with comfort be kept burning in a living room all the year round. There are a few slight

Jan 1, 1931

By L. E. Young

The purpose of this paper is to start a discussion on: (I) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, park walls, and filling, there will be no danger to men, equipment, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movemerit of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on conveyors on break lines, the rate of retreat should be increased substantially During 1935 and 1936, the United States Bureau of Mines, under a cooperative agreement with the Pittsburgh Coal Co., carried on studies of roof movement at Montour To. 10 mine. The work war done urider the direction of Mr. H. P. Greenwald, Supervising En neer, Experi-

Jan 1, 1938

By L. E. Young

The purpose of this paper is to start a discussion on: (I) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, park walls, and filling, there will be no danger to men, equipment, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movemerit of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on conveyors on break lines, the rate of retreat should be increased substantially During 1935 and 1936, the United States Bureau of Mines, under a cooperative agreement with the Pittsburgh Coal Co., carried on studies of roof movement at Montour To. 10 mine. The work war done urider the direction of Mr. H. P. Greenwald, Supervising En neer, Experi-

Jan 1, 1938

By D. U. Deere, F. D. Patton

Introduction A close relationship exists between the geologic investigation and the stability analysis of the slopes of an open pit mine. One significant result of this relationship is that the stability analysis is no better than the assessment of pertinent geologic factors that enter into the analysis. In some slope stability problems the engineering solution becomes obvious once the geologic framework is established. In other cases, establishing the geologic framework is only the first stage in the process of analysis. However, even in these cases the geology should not be neglected once the analysis is made. The geology should be periodically reviewed when new slopes are excavated. This will help ensure that the basic assumptions for the analysis have not changed and will permit changes when new conditions are encountered. In recent years improved methods of stability analysis have been accompanied by advances in laboratory testing techniques and new knowledge of the shear strength of rock discontinuities. At the same time there have been improvements in field geological descriptions. As more experience is gained in analyzing and predicting the stability of rock slopes, the importance of certain geologic factors has become more apparent. Some of these factors were described in a paper given at the Open Pit Mining Symposium in Johannesburg, South Africa in September 1970 (I). This paper includes many of the points covered at that meeting but with additional emphasis on the significance of the major geologic structures. Other papers given at the South African symposium also considered geological and hydrogeological factors in slope stability analysis (2) (3) (4) (5) (6). This paper first describes the approach to a slope stability problem including assessment of the relative roles of field geology studies, laboratory testing, stability analyses, and continued slope monitoring studies. Next, is described a framework which has been found useful for classifying or separating the several types of slope stability problems encountered in open pit mines. The principal geologic factors in slope stability problems in rock are discussed and brief comments are made on how these factors distinguish stability problems in rock slopes from those normally encountered in soil slopes. The over-riding control of major geologic structures, especially faults, in most slope stability problems is emphasized. In this regard the relative importance of statistical studies is contrasted with knowledge of the positions of key structural

Jan 1, 1971

CONTENTS PAGE. WHITE, DAVID.-Environmental Conditions of Deposition of Coal. Discussed by E. C. Jeffrey, George H. Ashley, Reinhardt Thiessen, S. W. Parr, David B. Reger, Wilbur A. Nelson, James F. Kemp, E. S. Moore, Homer G. Turner, David White, A. C. Noé, W. A. I. M. van Waterschoot van der Gracht 2 THIESSEN, REINHARDT.-The Constitution of Coal. Discussed by Edward C. Jeffrey, Reinhardt Thiessen, Ralph H. Sweetser, David White 12 TURNER, HOMER G.-Microscopical Structure of Anthracite. Discussed by E. S. Moore, Edward C. Jeffrey, Reinhardt Thiessen, H. J. Rose, James F. Kemp, David White, Clarence A. Seyler, A. C. Noé 14 JEFFREY, EDWARD C.-Coal in Relation to Coke. Discussed by H. J. Rose, David White, E. S. Sinkinson, S. W. Parr, James F. Kemp, Edward C. Jeffrey, Reinhardt Thiessen, Chas. R. Fettke 17 FRANCIS, W., and WHEELER, R. V.-The Resolution of Coal by Oxidation. Discussed by Edward C. Jeffrey, S. W. Parr, E. S. Sinkinson, Reinhardt Thiessen, David White 23 TIDESWELL, F. V., and WHEELER, R. V.-The Constitution of Coal. Discussed by David White, A. C. Fieldner 24 JOLLY, J., and WHEELER, R. V.-Organic Sulfur Compounds in Coal. Discussed by S. W. Parr 25 SINNATT, F. S.-Selective Combustion in Coal. Discussed by J. D. Davis, A. C. Fieldner, Geo. S. Rice, W. M. Grant, H. J. Rose, S. W. Parr, David White 25 COBB, JOHN W.-Nitrogenous Constituents of Coal. Discussed by S. W. Parr, H. J. Rose, Reinhardt Thiessen 28 PARR, S. W., and HOBART, F. B.-Coal and Oxygen. Discussed by J. D. Davis, W. T. Thorm, Jr., S. W. Parr, H. J. Rose, A. C. Fieldner, F. F. Jorgensen, David White, W. M. Grant 30 FIELDNER, A. C., and DAVIS, J. D.-Modern Views of Chemistry of Coals of Different Ranks as Conglomerates. Discussed by S. W. Parr, David White, Reinhardt Thiessen, A. C. Fieldner, Clarence A. Seyler 32 EBY, J. BRIAN.-Contact Metamorphism of Some Colorado Coals. Discussed by Geo. C. McFarlane, W. T. Thom, Jr 35 WHITE, DAVID.-Progressive Regional Carbonization of Coals. Discussed by A. C. Fieldner, Homer G. Turner, W. A. J. M. van Waterschoot van der Gracht, A. C. Noé 37 THOM, W. T., JR.-Moisture as a Component of the Volatile Matter of Coal. Discussed by A. C. Fieldner, S. W. Parr, Clarence A. Seyler, W. T. Thom, Jr., R. D. Hall 39

Jan 7, 1925

By Roman Šejnoha, Karel Mazanec

A pronounced tendency for delayed fracture zoas observed in the martensite structure of low-alloy steels in the as-quenched condition. Cracks of predominantly intercrystalline nature nucleated and propagated at stresses substantially lower than the short-titne tensile strength of- the steels, and were observed even in hydrogen-free speciunens. The occurrence of delayed fractures in the as-quenched condition is interpreted as a supevposition of the effect of free dislocations generated during the martensite transforlnation, and of a weakening of the prior austenite grain boundaries caused by dynamic shocks exerted on the boundaries by growing martensite plates. AN important metallurgical problem, connected with the production and use of high-strength steels, is delayed fracture in martensitic structures. Such fractures occur in quenched steels as a result of prolonged loading with external stresses far lower than the short-time tensile strength of the steel. The same effect can be produced by sufficiently high internal stresses: it is well-known that quenched structures will in some cases crack intergranularly at room temperature if not tempered quickly enough even in the absence of any externally applied stress. In Troiano's papers1,2 on delayed fractures in high-strength steels, the fundamental role of hydrogen migrating under the influence of multiaxial stress towards the nuclei of cracks was found. Fig. 1 shows the typical relationship between stress and the time to fracture found by Troiano in hydrogen-charged high-strength steels. On the other hand, Shurakov 3,4 explains the realization of delayed fractures in martensite as due to a "quasi-viscous" behavior of the austenite grain boundaries immediately after the martensitic transformation. 1) MATERIALS AND EXPERIMENTAL METHODS Two low-alloy steels of commercial purity were used for the experiments reported in this paper. Their chemical composition is shown in Table I. The heats were melted in a laboratory furnace, cast to ingots, forged to bars of 3/4 in. diameter, and annealed. Machined test pieces were heat-treated as follows: Ni-Cr-Mo steel held at 900°C for 30 min and quenched in oil; Mn-Si-Cr steel held at 900°C for 30 min and quenched in water. For the delayed-fracture tests, notched cylindrical test pieces, Fig. 2, stressed in torsion, and unnotched cylindrical tensile-test pieces, 1/4 in. diameter, were used. The specimens were normally loaded with a constant static load 45 min after quenching for the torsional tests and 10 min

Jan 1, 1965

By Allan J. Clark

It may be said that the history of gold in the Black Hills begins with one of South Dakota's most. interesting relics, the so-called Thoen Stone, now in the Adams Memorial Hall at Deadwood. This slab of reddish sandstone, about 14 in. square, was found in by Louis and Ivan Thoen, at the base of Lookout Mountain, near Spearfish, a town in the northern foothills of the Black Hills uplift. Both sides of the stone bear clearly legible inscriptions. One side reads: Came to these hills in 1833. Seven of us, De Lacompt, Ezra Kind, G. W. Wood, T. Brown, R. Kent, Wm. King, Indian Crow. All ded but me, Ezra Kind. Killed by Indians beyond the high hills. Got our gold June 1834. On the reverse side: Got all the gold we could carry. Our ponys all got by the Indians. I hav lost iny gun and nothing to eat, and Indians hunting me. Attempts were made to trace these men. Relatives of Brown were found in Missouri, and it was learned that he had left for the West in 1832, with one Kent. Kind's relatives were also found, and stated that he had started West the same year. None of them had been heard from since their departure. So Kind failed to get out with "all the gold we could carry"; 15 years later California became the center of the first great gold rush, and the Hills waited 40 years for their gold to be rediscovered. It is interesting to speculate on what might have been "the course of Empire" had this little group won through. The history of Dakota, of Montana, indeed, of all the Northwest, might have been very different. When, late in 1875, the goldseekers arrived, they passed quickly northward from the first discovery near Custer, and soon were established on Deadwood Creek, along which, as well as for short distances above the mouths of its tributary streams, Blacktail and Bobtail, placer operations went forward vigorously. These placers were near the northern outcrop of the Homestake ore-body. Their gold was partly derived from this, perhaps in greater quantity from the erosion of the conglomerate or cement deposits, of Potsdam time, themselves a "fossil placer" or beach deposit formed by

Jan 1, 1935

By T. R. Ingraham

The thermal decomposition of Nickel (II) sulfate was examined by determining the total pressure of SO3, SO2, and O2 developed over a sample when it was heated in an evacuated system fitted with a Pyrex-bellows mercury manometer. The equilibrium pressures were combined with previously published data on the oxide and sulfide systems to establish a predominance volume diagranz for the Ni-S-O system over the normal range of roasting temperature and gas composition used in the treatment of nickel minerals. The protective coating of NiSO4 which forms on the oxide during roasting, and which causes the sulfation reaction to almost cease, may be disengaged readily by temperature cycling. When nickel sulfide is roasted in air, either nickel sulfate or nickel oxide may be formed by altering the experimental conditions. Because of the differing stabilities of various metal sulfates and oxides, possibilities exist for separating some of the constituents of mineral mixtures by the technique of selective sulfation and oxidation roasting. The experimental information required to make reasonable predictions of the possibilities of this technique is incomplete and, in some cases, in conflict. As part of a general program of providing some of the required information, a study EXPERIMENTAL Materials, Apparatus, and Procedure. Fisher certified reagent-grade nickel sulfate hexahydrate was used in the source material for both nickel sulfate and nickel oxide. The manufacturer's analysis indicated: 0.001 pct Fe, 0.005 pct Cu, 0.003 pct Co, 0.001 pct C1, other 0.15 pct. The material was dehydrated, before use, by heating at 420°C for 5 hr. The oxide was prepared by roasting the sulfate in an open tray in a muffle furnace for 10 hr at950°C. Preliminary experiments which were made by thermogravimetric analysis and X-ray diffraction analysis established that only one crystal form of nickel oxide and one of nickel sulfate were involved in the equilibrium shown in Eq. [I]. The apparatus used in the experiments was described previously.1,3 The main feature is a corrosion-resistant, flexible Pyrex bellows which is used to protect the mercury in a u-tube manometer. Before a run was begun, the apparatus was washed thoroughly with hot hydrochloric acid and water and dried by heating under vacuum. The mixed sulfate -oxide sample was contained in a platinum bat rest-

Jan 1, 1967

By W. H. McFarland

The mechanical properties have been determined for a large number of alloy-free martensitic steels with carbon contents ranging from 0.08 to 0.20 pct and with manganese contents of about 0.4 to 0.5 pet. These steels were tested 1) as water-quenched, 2) after quenching, temper rolling, and tinning, and 3) after tempering treatments which involved temperatures from 400o to 1300oF and times from 1 min to 8 hr. The majority of these tests represent steel from commercial-size coils, i.e., strip 32 in. wide, coil weights up to 20,000 16, and steel thicknesses from 0.0055 to 0.024 in. As a result of these treatments, it has been shown that as-quenched low-carbon alloy-free steels can be produced with tensile strengths ranging from 140,000 to 220,000 psi and tensile elongations from 3.0 to 4.0 pet in 2 in. The tensile strength of the as-quenched martensites can be represented by the equation, tensile strength (ksi) = 119 + 560 (wt pet C). The response to tempering of these steels is related to previous work by Muir, Averbach, and Cohen and by Grange and Baughman. Strain aging of low-carbon martensite has also been investigated. If low-carbon steels are defined as those steels with a maximum carbon content of 0.2 pet, it is found that the literature on low-carbon, alloy-free martensites contains little data on the mechanical properties of these steels. However, the following facts concerning low-carbon alloy-free martensites seem firmly established:'-' 1) The major factors in controlling the strength of the martensite appear to be a) fine structure, b) the internal strain resulting from the transformation, and, particularly, c) the amount of carbon in solid solution. 2) In low-carbon steels, the martensite is auto-tempered and is in the form of needles with only minor amounts of internal twinning, whereas the martensite in high-carbon steels forms as plates which are internally twinned on a fine scale. 3) Care must be taken in comparing the results of work that has been done on low-carbon steels with varying amounts of alloying elements to data on plain carbon steels. As has been noted by Irvine, Pickering, and Garstone,6 alloying elements generally lower the martensite start temperature and, thereby, decrease the amount of auto tempering obtained during the quench. This makes it difficult to

Jan 1, 1965

By C. R. Fulton

The idea of making permanent magnets by sintering is not a new one, but until the introduction of the iron-nickel-aluminum permanent-magnet alloys there was little need for such a process. Permanent-magnet alloys in use up to the time of this development could be forged and machined to the exact size or shape required without too much difficulty. These new Fe-Ni-A1 alloys, which have become known as Alnico in this country, soon became very popular because of their superior magnetic properties, but when they were made by casting they did have some disadvantages when compared with the older type of permanent-magnet steels. Among these disadvantages were the following: 1. It was almost essential that they be cast to size, since they could not be readily forged or machined. The material could be ground but this was quite expensive, particularly for small magnets in large quantities. 2. The material had a large grain size and was mechanically weak. 3. Close tolerances could not be held and on small magnets this meant grinding almost the entire magnet. Because of the brittle nature of the material, there was considerable loss due to chipping and cracking during these grinding operations. 4. Because of its high aluminum content, the molten alloy had a high surface tension. It was difficult to prevent loss of aluminum by oxidation during the melting operation. In view of these difficulties it is not hard to understand why a process for sintering alnico was developed, or why sintered alnico has come into such widespread use in recent years. It might be well to qualify this by saying that it has come into widespread use for small magnets weighing 2 oz. and less, of the type shown on Fig. I. In this size range, sintered alnico has been able to compete in price with cast alnico. Magnets larger in size, of the type shown on Fig. 2, can be made but they do not compare favorably in price with the cast material. An idea of the range of sizes that have been produced is given by Fig. 3, which shows a small magnet weighing 0.006 oz. and a large magnet with a steel insert weighing 4 lb., both made from sintered alnico. Magnets weighing more than 2 oz., however, should not be made from sintered

Jan 1, 1945

By R. Laird Auchmuty

The A. I. M. E. Subcommittee on Bituminous Mining has been trying for several years to secure the information that was collected by the Marquette Cement Manufacturing &. on the subsidence of its property caused by mining coal beneath it. The Marquette company was willing to have these data used, but it was impossible to obtain them because the records had been filed away. About two years ago these records became available and the engineering data presented herewith were compiled from them by R. L. Auchmuty, assisted by L. E. Young, who was connected with the collection of the information. On account of the cost, it is impossible to reproduce all of the data here, although the original information is on file with the records of the Committee on Ground Movement and Subsidence. The accompanying charts show representative and average data and give only the engineering information with enough description to tell how it was obtained. It is hoped that all of those connected with the original case will participate in the discussion that this will bring forth. Howard N. Eavenson, Chairman, Subcommittee on Bituminous Coal Mining. PRobably the most complete records of subsidence due to coal mining in the United States are those compiled by the Marquette Cement Manufacturing Co. at LaSalle, 111. These records, covering a period of more than three years, were compiled and used as evidence during the suit of the Marquette Cement Manufacturing Co. vs. the Oglesby Coal Co. at Oglesby, LaSalle County, Ill., in which the cement company successfully endeavored to stop the coal company from mining under its property. Fig. 1 shows a typical section of the geological formation. The cement company was mining the LaSalle limestone which lies about 125 ft. under the surface. The limestone is 30 to 35 ft. thick and underlain by about 15 ft. of shale. The cement company was mining about 20 ft. of the limestone, and in some places 10 to 12 ft. of the underlying shale, by the room and pillar method. The mining of the limestone always preceded the mining of the shale. The coal company was mining by longwall advance methods the NO. 2 seam of coal 42 in. thick underlying the limestone bed by 435 to 470 ft. The coal mine, a very old one, had largely mined out its original property

Jan 1, 1931

By D. L. McElroy

It is too broad a statement to say that the mine car is the most important unit in a haulage system, but almost every mining man will admit that it is one of the most important. The mine car is to the mine haulage system what the railroad car is to the railroads; the main purpose in each instance is to move the greatest number of ton-miles of material at the least cost. The data presented in this paper are taken from a study of mine haulage conducted by the School of Mines of West Virginia University at 42 mines in 8 coal fields of Wrest Virginia. The study was made possible by a graduate fellowship of the School of Mines and the cooperation of the mining companies of the state. Three important factors in the use of mine cars in West Virginia are: (I) the number of mine cars in use per loader; (2) the capacity of mine cars; (3) the distribution of mine cars. ("Loaders" in this paper refers to all men loading coal, whether manually or mechanically.) During the World War many mine managers were annoyed by the reduction of efficiency and production caused by railroad-car shortages. Today relatively little complaint is heard about a shortage of mine cars, yet possibly 50 to 75 per cent. of the mines in West Virginia are suffering from this cause of reduced production and increased costs. The railroads have solved their car shortage by placing in service more cars of larger capacity and better design. Many coal mines in West Virginia should solve a part of their cost problems by the same simple procedure. Such a procedure requires an initial outlay of capital, but there is little doubt that this will be repaid, with a good return on the investment. Determining Number of Cars Needed There can be no mathematical rule to determine the number of cars which should be in use per loader in a coal mine, because numerous factors such as concentration of mining, system of haulage, car capacity, speed of haulage, distance of working places from tipple, and so forth, affect materially the number of cars in use. These factors in turn are more or less determined by height of bed, character of roof and coal,

Jan 1, 1931

By C. D. Woodward

ThE subject of elcctric signals for the despatching of mining cagey through shafts has received cousiderable attention recently from various mining companies. The Anaconda Copper Mining Co. has found it necessary to develop a system that is rcliable, safe and simple in operation, and easy to repair. The movement of all mine cages or skips is under the direction of a station tender, who rides on the cages when men or supplies are being lowered or raised; when ore is hoisted, he is stationed at a skip pocket for loading and despatching the skips. For the station tender's use, two signal systems are installed in cach hoisting compartment, and he is the only employee authorized to use them. One system is known as the "AC " or station bells, as it is operated from the 110-volt, 60-cycle, power service; the other system, called the "DC" or shaft bells, takes its energy from closed-circuit primary batteries. As a supplemcnt to the two main signals, a buzzer system is installed The general arrangement is similar to the main signal, except that there is a mine buzzer at each station. When a signal switch connected into the buzzer system is pulled down, all buzzers arc operated, thus notifying the station tender that he is wanted at seine particular level. Placed on the station posts, and within easy reach of the men on the cages are the signal pull switches for the main signals. The station, or "AC," pull switches are furnished with a short rope as shown in Fig. I, while the shaft, or "DC," pull switches are equipped with ropes that extend down the shaft past the next station. To avoid all confusion in the use of the three signal systems, a standard arrangement has been adopted in all mines for the location of the pull switches. Fig 2 illustrates the position of the pull switch at the various mine stations for the main signal systems, but it does not show the buzzer pull switch; this is fixed to the roof timbers about 25 ft. back from the shaft. If the skip pockets are a considerable distance below the station, a pull switch for each main shaft compartment is connected to the "AC" system and placed at this point. However, if the distance is short, a light cord is attached to the station pull switches and dropped down to the skip pocket.

Jan 1, 1923