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By Abner Dixon

INTRODUCTION. IN India the production of mica, which in other countries is of very minor importance, is one of the staple, long established industries, and ranks high in the statistics of mineral products. Nearly two-thirds of the mica of commerce comes from India. The Indians have used mica for glazing and decorative purposes through many centuries. About 14,000 men are employed in and about the mines, and the indigenous and primitive mode of mining is still followed; but, by reason of the exhaustion of the surface supply hitherto won without intelligence or capital, it will not be many years before the present interesting and casual methods will be replaced by a less archaic and more profitable system. India on the whole has little mineral wealth, but the unique resources of its mica fields, cheap labor, and favorable natural conditions render it unlikely that any other country can ever more than temporarily contest her leadership in the production of this one minor but essential mineral. Mica plays a small but indispensable role in a variety of fields of dissimilar application. Its use and value depend upon characteristics which different kinds of mica have in varying degrees, each kind being adapted to 'its own special purpose. Its well-known characteristics of transparency, flexibility, elasticity, toughness, high dialectric, strength, perfect flatness; ease of splitting into thin films, ability to stand high heat and sudden changes in temperature, give it value in many industries. No other substance, natural or artificial, has this combination of qualities. The oldest use of mica is in glazing. By reason of the improvements in annealing glass, this is not now of great importance, but mica is still employed for the covers of ikon images in Russian churches, the windows of anthracite stoves, compass

Jan 5, 1913

CORPORAL SHEPPARD B. GORDY Sheppard B. Gordy, a brief biography of whom was printed inn the January Bulletin, entered the employ of the Braden Copper Co. immediately on his graduation from the Sheffield Scientific School in 1912. He remained with this company four years, working up through the various grades to assistant foreman and foreman to one of the individual mines. The last year he was in its employ, he acted as general mine foreman. He was for a short time with the Chile Exploration Co. and then went with the Andes Exploration Co. (Anaconda) and remained with CORPORAL SHEPPARD B. GORDY. the latter, doing mine exploration and development work, until he sailed for home in June, 1918, to give a more personal and active service to his country in her need. He declined a tender of induction into an officers' training camp, at the urgent request of Professor McClelland supplemented by Mr. Potter, because they demonstrated to his satisfaction that he could give more valuable service to his country in helping out with the aircraft production. Being within the draft age, in order to carry out this plan, it was necessary for him to be called by his Local Board and sent to camp. This call came Aug. 26. Two weeks before that time lie had gone to Dayton, Ohio; to begin the study of aircraft production, and was sent by the Dayton Board to Camp Sherman, Chillicothe, Ohio, where he died of pneumonia on Oct. 9.

Jan 3, 1919

By F. C. Newton

RefineRs of lead by the Parkes process have always been solicitous of recovering the zinc used in the desilverization, and justly so, as the loss in zinc constitutes one of the heavy costs in this method of refining. Part of this loss is due to the absorption of zinc by lead, and in the present state of knowledge is not recoverable as metallic zinc. The remainder of the zinc, which finds its way into the precious-metal-bearing crust, is recoverable and naturally engages the operators' most exacting attention. Careful elimination of the impurities in base bullion has enabled the refiner to produce a zinc crust better adapted to retorting, which reflects favorably in the zinc recovery;- and to produce a richer crust, thereby lowering the zineking cost, as the increased efficiency of the zinc results in less of it being in circulation. It is obvious that if the ratio of concentration be increased, a lessening of the amount of crust formed will ensue, throwing less work on the retorts and diminishing the amount of retort metal sent to the cupels, thus making an actual money saving in all these operations. In the effort to obtain a rich crust, the metallurgist has increased the heat to a considerable degree, upon the assumption that at the higher temperature the zinc-dver alloy could be squeezed free from the adhering lead. A further possibility for improvement suggested itself in the freezing-point curve of Prof. H. C. Carpenter, upon zinc and silver. Study of this curve disclosed the existence of a definite chemical compound, Zn3Ag2, with a freezing point of 665" C., a promising compound for practical application. In the experiment undertaken it was endeavored to force this compound into the crust, hoping thereby to obtain a higher concentration than formerly. It was recognized that in bringing a large kettle of lead to such a heat, more fuel would be used, the life of the kettle would perhaps be shorter, and other disadvantages would be experienced. AS a commercial operation, the project would have to stand on its own feet,

Jan 1, 1915

By E. C. Pechin

Secretary's Note.—Mr. Bramwell was born in 1846, at Liverpool, England, his father being English, and his mother American, of Scotch ancestry. Brought to the United States in early childhood, he was educated at the public schools and graduated from the College of the City of New York. He subsequently studied his profession as a mining engineer at the Royal School of Mines, Berlin, Prussia, and was for a short time in the service of the Prussian government at Konigs hutte. Returning to this country in 1871, he was employed during succeeding years as mining engineer, chemist, and manager at various fnrnaces and iron works in Pennsylvania and the Southern States until, in 1883, he became actively engaged in the development of the Flat-Top coal-field of southwestern Virginia, in which region the town of Bramwell was named after him, in recognition of his services as a pioneer of the great industry which he did so much to promote. After prolonged and fluctuating ill-health, he died, July 13, 1894, at Paris, France. At the opening session of the Bridgeport meeting, the Secretary announced his death, and Mr. Pechin, being called upon, made the remarks reported below.— R. W. R. Widely as Joseph Herbert Bramwell was known, I. think I knew him somewhat better than any one else. After finishing his studies abroad, he came to this country, a very young man, seeking an engagement. This was about the beginning of 1871, as I remem ber, and I was then trying to make iron at Dunbar, at the foot of the Allegheny mountains, in Fayette county, Pa. His engaging manner and charming personnel, combined with his letters of intro duction, made me more than satisfied in securing his services as my chemist. At the outset we lived a sort of pioneer life, and for many months he was practically a member of my family, and the affection then formed remained unbroken to his dying day. I vividly recall the circular of April, 1871, signed by Eckley B. Coxe, R. P. Rothwell and Martin Coryell suggesting a meeting at Wilkes-Barre, Pa., for the purpose of forming the American Institute of Mining Engineers. At the last moment, prevented from going, I sent Bramwell; and I am more than glad that his name appears among those whose sagacity established an Institute that has become illustrious by reason of its numbers, the character of its members, its invaluable papers and its enormous influence for good

Jan 1, 1895

By John E. Miller

Unit Rig & Equipment Co., manufacturer of Lectra Haul trucks, is continually studying methods of reducing the operating costs of large haulage trucks. Reduction of haulage system operating costs is an important goal that equipment operators and equipment manufacturers constantly try to improve on. One of the most variable and important factors affecting operating costs is actual truck operating practices. An examination was centered on methods to optimize truck utilization. It was found that a very effective method of accomplishing this goal would be an automatic truck control (ATC) system to automatically control a fleet of haulage trucks in a predetermined pattern. Economic studies were conducted which showed a very favorable reduction in mine operating costs by use of an ATC system. In 1970, Unit Rig & Equipment Co., in conjunction with SAAB-SCANIA began preliminary development of adapting, for truck use, a proven automated control system, previously used for train systems, small trucks, and military target vehicles. In 1974, the first prototype system was installed on a Lectra Haul M-100 and tested extensively at Unit Rig's test track in Tulsa, OK. This truck and system were then displayed publicly at the 1974 convention in Las Vegas. In 1976, the system was redesigned for production to maximize reliability, ease maintenance, and to accommodate future control and-status reporting developments proposed for haulage trucks. The new design equipment was manufactured, and a full system test will be conducted in an actual open-pit mine for an extended period to evaluate reliability, compile economic data, and obtain application information to evaluate complete mine haulage system conversions to ATC. System Description The ATC system is designed to provide automatic control of all the vehicle functions normally accomplished by the vehicle operator. The basic system consists of the on-board control equipment and the wayside control equipment. The on-board equipment receives commands from the wayside equipment and controls all the truck functions. In addition, on-board sensors monitor all critical truck functions and provide instructions to the truck and system to assure safe operation. The wayside equipment consists of a buried guidewire, block control units and a central controller which provides predetermined signals to the on-board equipment for speed control, steering, and for auxiliary functions (dumping, horn, etc.) through the guidewire located in the truck's path. The wayside equipment also controls vehicle separation, system status, and provides truck location to a central display panel. The central control panel can vary the speed level signals over any segment and can also command an emergency stop to halt all the units. [Fig. 1] illustrates a typical ATC installation. If ATC is used in operations which require flexibility and mobility at the end of the ATC guidance network, the trucks can then be operated by either radio remote control or manually to complete their assigned functions.

Jan 1, 1982

By E. W. Davis

If the tonnage of merchantable iron ore remaining in the Lake Superior district is divided by the average of the annual shipments for the past 20 years, it will be found that this ore supply will be exhausted in approximately 35 years. This computed exhaustion period would be an indication of the future activities of the iron-mining industry if it were not for the fact that merchantable ore is being manufactured from low-grade ore, of which there is an almost inexhaustible supply in the Lake Superior district. It is true that at present only the simplest of these low-grade ores are being concentrated to any considerable extent, but progress is being made with the treatment of the more complex ores, and now, in addition to 20 washing plants on the Mesabi Range, three plants are equipped with jigs for the treatment of ore that cannot be concentrated simply by washing. The latest addition to the ore-treating plants of the Mesabi Range is a magnetic roasting and concentration plant at Cooley, Minn., in which ore that cannot be concentrated either by washing or by jigging is roasted to the magnetic state and concentrated on magnetic separators. This plant is beginning its third season of operation, and while it is too soon to make definite predictions, there are strong indications that this new process may make commercially possible the manufacture of high-grade, merchantable iron ore from large quantities of low-grade ore now considered worthless. After the iron oxide contained in an ore has been converted to magnetite, almost any desired grade of concentrate can be produced, using magnetic-concentration equipment of the types now in general use for the concentration of the natural magnetites of New York, New Jersey and Pennsylvania. The conversion of hematite (Fe203) to magnetite (Fe3O4) is easily accomplished by heating the ore to a dull red temperature in a reducing atmosphere. The reaction is slightly endothermic, and while it requires 200 B.t.u. to heat to 900' F. one pound of hematite ore containing 45 per cent Fe, it requires only 100 B.t.u. to convert the oxide into magnetite. In the laboratory, using small quantities of ore, this conversion is very simple, but large furnaces suitable for commercial

Jan 1, 1939

By E. W. Davis

If the tonnage of merchantable iron ore remaining in the Lake Superior district is divided by the average of the annual shipments for the past 20 years, it will be found that this ore supply will be exhausted in approximately 35 years. This computed exhaustion period would be an indication of the future activities of the iron-mining industry if it were not for the fact that merchantable ore is being manufactured from low-grade ore, of which there is an almost inexhaustible supply in the Lake Superior district. It is true that at present only the simplest of these low-grade ores are being concentrated to any considerable extent, but progress is being made with the treatment of the more complex ores, and now, in addition to 20 washing plants on the Mesabi Range, three plants are equipped with jigs for the treatment of ore that cannot be concentrated simply by washing. The latest addition to the ore-treating plants of the Mesabi Range is a magnetic roasting and concentration plant at Cooley, Minn., in which ore that cannot be concentrated either by washing or by jigging is roasted to the magnetic state and concentrated on magnetic separators. This plant is beginning its third season of operation, and while it is too soon to make definite predictions, there are strong indications that this new process may make commercially possible the manufacture of high-grade, merchantable iron ore from large quantities of low-grade ore now considered worthless. After the iron oxide contained in an ore has been converted to magnetite, almost any desired grade of concentrate can be produced, using magnetic-concentration equipment of the types now in general use for the concentration of the natural magnetites of New York, New Jersey and Pennsylvania. The conversion of hematite (Fe203) to magnetite (Fe3O4) is easily accomplished by heating the ore to a dull red temperature in a reducing atmosphere. The reaction is slightly endothermic, and while it requires 200 B.t.u. to heat to 900' F. one pound of hematite ore containing 45 per cent Fe, it requires only 100 B.t.u. to convert the oxide into magnetite. In the laboratory, using small quantities of ore, this conversion is very simple, but large furnaces suitable for commercial

Jan 1, 1939

By J. H. Swisher

In measuvements of the solubility of nitrogen in fer-rilic Fe-P alloys, tile nitrogen solubility is found to be Less in pIrospliorus-bearing alloys than in pure iron. The reduction in solubility is about 20 pct in a 1.0 wt pct P alloy at 1300°C and about 30 pct in a 0.23 wt pct P alloy at 440°C. Diffusion coefficient measurements at 1150 and 585°C show that phosphorus also decreases the nitrogen diffusivity in iron. In previous work on the Fe-P-N system, phosphorus was found to reduce the nitrogen solubility in liquid iron slightly.&apos; Indirect evidence for similar behavior in a Fe at low temperature was obtained by Dickenscheid and Brauner.&apos; These authors found that phosphorus reduces the height of the internal-friction peak due to dissolved nitrogen. The results of Dickenscheid and Brauner were confirmed by J. C. Swartz of this Laboratory in a single internal-friction experiment using the same specimen stock as in the solubility measurements described below. In the present investigation, the solubility of nitrogen in a fer rite-stabilized Fe-1.0 wt pct P alloy was measured in the temperature range from 800" to 1300°C. Additional experiments were performed in the temperature range from 440° to 585°C, using an Fe-0.23 wt pct P alloy and NH3-H2 gas mixtures. EXPERIMENTAL The experiments were performed in a vertical tube furnace wound with platinum wire. For experimental temperatures of 800°C and above, a mixture of 5 pct Hz in N2 was used as the reacting gas. The gas mixture was prepurified from oxygen by passage over platinized asbestos at 450°C, and subsequently over anhydrone to remove water. Flow rates of the gases were measured with capillary flow meters. The temperature was measured before and after each experiment with a Pt/Pt-10 pct Rh thermocouple. The specimens used for the high-temperature solubility measurements were in the form of rectangular plates, 0.534 by 1.6 by 3.8 cm. The specimens were cleaned in trichloroethylene and annealed for 2 hr in hydrogen at the beginning of each experiment. In measuring the nitrogen solubility, the specimens were held in the reacting gas until equilibrated, then cooled in a water-cooled copper block at the bottom of the furnace. The time needed for equilibration at 1150°C was determined by measuring the average nitrogen content of the 1.0 pct P alloy as a function of reaction time. As will be described, the nitrogen diffusivity in the alloy at 1150°C is only slightly less than its calculated diffusivity in pure iron. At temperatures other than 1150°C, the reaction time used in measuring the nitrogen solubility was about twice the calculated equilibration time for pure iron at the same temperature. With a few exceptions, the procedure for the low-temperature solubility measurements was the same as that described above. The compositions of the NH3-H2 gas mixtures were determined by collecting gas samples from the gas train and analyzing them for NH3 by titration with HC1. The specimen thicknesses were less than those used for the high-temperature experiments, eg., 0.124 and 0.051 cm for measurements at 585° and 440°C, respectively. Nitrogen concentrations were obtained by chemical analysis, using the Kjeldahl method. The Fe-P alloys were made by adding ferrophos-phorus to electrolytic Plastiron (Type 104 A). Commercial ferrophosphorus, containing 3 pct Mn and 0.35 pct Si as the major impurities, was first purified by melting under an FeO slag. In a separate heat, the electrolytic iron was melted and vacuum-carbon-deoxidized prior to making the ferrophosphorus addition. The principal impurities and their concentrations in weight percent in the 1.0 pct P alloy are as follows: Mn, 0.01; Si, <0.01; C, 0.01; 0, 0.003; and N, 0.0012. The impurity levels in the 0.23 pct P alloy are con-

Jan 1, 1968

By S. J. Matas, R. F. Hehemann, R. H. Goodenow

The hot-stage metallographic method has been employed to determine radial growth rates of upper and lower bainite. Lower bainite appears to grow as individual plates that increase in both length and thickness while upper bainite grows as sheaves of closely spaced plates or needles. A discontinuity in the temperature dependence of the growth rate appears to be associated with the transition from upper to lower bainite and stepped quenching experiments suggest that lower bainite will not continue to grow when the temperature is raised to the upper range. Thus, a single process does not appear to control the growth of both upper and lower bainite. A tentative model based on the forces acting on a dislocation interface is proposed to account for the slow growth of bainite. It has been recognized since the early studies of Davenport and Bain that a close relationship exists between the martensite and bainite transformations in steels. However, diffusion of carbon during the transformation has lead to considerable controversy concerning the reaction mechanism.1-7 Many studies4,5,7-9 have emphasized the structura and kinetic aspects of the bainite reaction and, in particular, the difference observed between the two forms of bainite—frequently termed upper and lower bainite. A kinetic difference between the two types of bainite has been revealed in the activation energy determined from the overall reaction;4,5 however, many difficulties arise in an interpretation of these activation energies since a number of temperature dependent factors contribute to the kinetics of the overall reaction. The displacive surface relief10 accompanying the bainite reaction permits a separation of the nuclea-tion and growth contributions to the reaction and allows the kinetics of the growth process to be examined. Several investigations of this type have been conducted; however, they have been restricted to the low temperature range.3&apos;6&apos;11 Here, bainite plates are observed to grow slowly in both length and width. The present investigation extends such studies to include the upper bainite range. MATERIALS AND PROCEDURE Materials. The composition of the steels studied in this investigation are presented in Table I. The range of composition permitted a study of the effect of carbon content on the growth rate of upper bainite in the 9 pct Ni steels and consideration of both upper and lower bainite in the higher carbon steels. These steels were received as hot-rolled rounds and were forged to approximately 1/2 in. thick plates for preparation of metallographic specimens. In order to produce an essentially zero carbon steel, Steel A was decarburized in wet hydrogen at 1550°F for 15 days with the result tabulated as Steel AD. Experimental Procedure. In order to study the slow growth of the displacive transformation product, a commercially available Leitz hot stage was modified to permit heating of the specimen by its own resistance in a manner similar to that employed by other investigators.6 The furnace chamber was maintained at a pressure of 2 to 3 X 10-5 mm Hg prior to austenitizing at 2000° ± 12° F for 5 min. Samples could be cooled from the austenitizing to the transformation temperature in approximately 15 sec and the progress of transformation was recorded with a 9 cm by 12 cm single frame camera or a 16 mm movie camera. RESULTS AND DISCUSSION Growth Characteristics. The general growth characteristics observed in this investigation were analogous to those reported previously.3,6,11 Typical growth sequences for the high temperature and low temperature forms are illustrated in Figs. 1 to 5. In both temperature ranges, bainite plates increase in length at slow, temperature dependent rates until interrupted by a grain boundary, another plate, or

Jan 1, 1963

By Robert Abbott

THE influence of various elements in retarding or accelerating the absorption of carbon during the process of carburization is fairly well known. In general those elements which forth carbides accelerate the absorption, while those which do not retard it. It has sometimes been wrongly stated that those elements which raise the temperature of the critical range increase the absorption, while those which lower this temperature decrease it. Silicon is a notable exception to this rule, for its influence is to raise the critical range but to lower the absorption of carbon. Some elements which do not form carbides have no apparent influence upon the absorption rate. Carbon itself retards the absorption rate. With a view to obtaining more exact data upon the subject the following experiments were undertaken : 208 steels of different chemical composition were selected to represent most of the types of modern constructional steels. Specimens 3 in. in diameter and in. in length were weighed to milligrams. They were then packed in the special carburizing box shown in Fig. 1, and kept in .the furnace for 10 hours at a temperature of 900° C. A duplicate experiment was conducted at 1,000° C. At equal&apos; intervals of time the box was rotated in the furnace so that. two complete revolutions were made in the 10 hours. This precaution was taken to neutralize as much as possible any effect of unequal heating. At the end of the 10 hours the box was allowed to cool in the furnace with the doors open. The specimens were then weighed again and the increased weight (carbon) determined. In. the following table are given the analyses of the various steels, together with the. increased weight of .carbon expressed in milligrams.

Jan 10, 1913

By C. C. Templeton, S. S. Rushing

Methods previously developed for the study of air-liquid displacements in microscopic capillaries (inner diameters of 3 to 40 microns) have been used to investigate oil-water displacements in capillaries initially filled with water. Displacement calculations assuming perfect displacement and no capillary pressure hysteresis yielded oil effective viscosities smaller than the macroscopic viscosities. For a given liquid pair, the oil effective viscosity decreased both with decreasing capillary size and with increasing oil-water viscosity ratio. This behavior can be explained by the existence of an annular water film (20 A to 260 A thick) on the capillary wall. When the capillary was first filled with oil, the ratio of the oil effective viscosity to the normal oil vircosity was highest for the first water displacement and decreased with subsequent displacements. Sometimes the oil effective viscosity ratio during the initial water displacement was greater than unity. INTRODUCTION In a previous paper1 a technique was described for studying air-liquid and liquid-liquid displacements in very small capillaries of uniform diameter, in the hope that such microscopic data would further the understanding of the nature of multiphase fluid flow through porous media. That paper contained comprehensive data for air-liquid displacements in Pyrex capillaries, with a few data for oil-water displacements in capillaries initially filled with water. The purpose of this paper is to present more complete results for oil-water displacements in capillaries initially filled with water, and to describe for the first time such observations in capillaries initially filled with oil. In this way the effect of the wetting history of the system upon the displacement process may be studied. METHODS The basic techniques employed were described in the previous paper.1 The measuring procedure and the working equations will be briefly summarized here and a few modilications will be pointed out. For the present study, temperature control within 0.l °C was obtained by placing the microscope and its immediate accessories in a thermostated air bath made of a steel frame covered with plexiglas. The water and oils used in this work were the same as in the previous paper,1 with the addition of "Medium Mineral Oil, U.S.P. supplied by the Harshaw Scientific Co. When the first liquid was introduced into the horizontal capillary, the air-liquid static capillary pressure Poc was measured along the observable length of the capillary. From the relation Poc = 4y cos 0/d, the capillary diameter d could be calculated from Poc if the "microscopic" air-liquid boundary tension, To = y cos On, was taken as equal to its known "macroscopic" value. This calculation involves assuming that cos 6 = 1 and that capillary size or the resulting high interfa-cial curvature has no effect on surface tension, or y cos 6, as was verified by our work, and also by that of Cohan and Meyers on air-liquid-solid systems. For several capillaries these calculated diameter values were compared with values measured visually with a filar micrometer eyepiece. For a given capillary the average values for the two methods agreed within 1 or 2 per cent, but the visual values were less reproducible than the calculated values. Further the calculated values were much less subject to personal bias and took into account any slight ellipticity that might be present. Hence diameters calculated from air-liquid Poc data were used throughout this paper. The second liquid was introduced in such a way that a single spherical interface separated the two liquids. Displacements were always made with a constant pressure, Pt, between the ends of the capillary. The times (t) at which the interface passed certain

Jan 1, 1957

By Franklin J. Stermole

INTRODUCTION Economic evaluation of an open pit mine is similar to the economic analysis of any major investment project in any industry. It requires (1) taking into account all of the costs and revenues that are estimated to be incurred over the economic life of the project; (2) crediting the project with all the tax savings and tax credits that will be realized over the project life from tax deductions and credits related to various project costs; (3) charging the project with all taxes to be paid on taxable income over the project life; and (4) properly accounting for the time value of money for all project costs, revenues, taxes, tax savings, and tax credits when making the overall project economic evaluation. These considerations must be taken into account for any valid method of economic analysis such as discounted cash flow rate of return (DCFROR) or net present value (NPV) analyses. All economic analyses fall into one of two categories. ( 1 ) comparison of income-producing alternatives, or (2) comparison of service-producing alternatives. The analysis of alternatives in either of these categories can be made by using correctly any of five basic economic evaluation approaches which are. ( 1 ) present value, annual value, (3) future value, (4) rate of return (ROR) , and (5 ) break-even analysis. Of these evaluation techniques, DCFROR and NPV analyses are used most widely for evaluating income-producing alternatives while present worth cost and equivalent annual cost analyses are used most often for the evaluation of service-producing alternatives. In this chapter income- producing alternative analysis is emphasized, so DCF- ROR and NPV are utilized for evaluating the case studies presented.

Jan 1, 1979

By Carville E. Sparks, Rollin Farmin

TRIAL installations of rock bolts, of the slit-rod-and-wedge type, were under way at several units of Day Mines, Inc., when Korean hostilities interrupted the already slow deliveries of steel bars to the Coeur d&apos;Alene district. Factory-made bolts had not yet been put on the local market, so the program was halted for lack of supplies. Interest was revived by a visitor&apos;s description of wooden roof bolts. These were said to have been used briefly with apparent success in a coal mine, until apprehension voiced by the U. S. Bureau of Mines caused the practice to be suspended. To make wooden bolts for trial in ground support, Day Mines acquired a second-hand doweling machine equipped with two cutting heads, one to turn out the desired round rods of 2-in. diam, the other to turn out 1-in. rods to be used as powder-tamping sticks. This machine was installed in the all-weather sawmill of the Hercules mine unit at Burke, Idaho, where fabrication of the wooden bolts commenced early in 1951. Most of the mining in the Coeur d&apos;Alene district is along steeply dipping veins in shaly quartzite and argillite of Algonkian age. Ground support commonly is required in zones where the rocks have been sheared, brecciated, and hydrothermally altered. Pressure from the sidewalls is more troublesome than weight overhead, but both increase with the size of the mine opening. Caving may come from a progressive sloughing of irregular rock fragments or from an exfoliation and buckling of the layered wall rocks. The disintegration is thought to develop from an initial elastic expansion of the rock toward the newly-created mine opening, followed by the dilation of many tiny partings in the rock by absorption of water. As the partings widen, masses of rock develop weight and become free to fall. The function of rock bolts is to prevent or retard widening of partings in the rock supported. Wooden Bolts, Wedges and Headboards Bolt assembly used by Day Mines consists of a bolt 4 or 6 ft long, two wedges 16 in. long, and a headboard 30 in. long, Fig. 1. All four pieces are made of local red (Douglas) fir, either green or well-soaked in the mill pond before it enters the sawmill. Bolts are fabricated from cants, 2 1/4 in. sq, cut from relatively straight-grained timber with a minimum of knots and trimmed to 4- and 6-ft lengths. The bolt then is turned in the doweling machine from 21/4 in. sq to 2 in. diam round, except for a 4-in. length at one end which is left full square to provide the striking head and the shoulder that holds the headboard in position for wedging. The foot end of the bolt is slit with a thin saw for a length of about 16 in., thereby making a slot to receive the wedge against which the bolt is driven for anchorage at the bottom of the rock hole. A similar slit, 12 in. long, is made in the opposite (head) end of the bolt to receive the second wedge, which crowds the headboard against the ground at the collar of the rock hole and puts the bolt in tension. The second slot is aligned 90" from the plane of the first slot to avoid Longitudinal splitting and is notched out slightly to allow easier insertion of the collar wedge after the bolt has been driven to bottom. To prevent splitting the headboard by spreading action of the head wedge, this slot is oriented at 90" to the grain of the headboard when the pieces are assembled, Fig. 2. The wedges are similar to standard mine wedges, but more slender; they are cut 1 7/8 in. wide and 1 in. thick at the heel and taper out in 16 in. of length. The headboard, or bearing plate, is not necessary for some types of ground but generally is desirable because it helps the bolt to support an area of loose, friable rock and reduces the tendency for the rock at the collar of the hole to split away from the wedged head by distributing the pressure over a wider rock surface. The headboard may be a 24-to 30-in. length of 3-in. plank, 8 to 12 in. wide, but a similar length of rounded sawmill slab serves equally well at 20 pct of the cost. A hole of 2-in. diam is bored or punched through the center of the headboard, either at 90" or at various high angles to its surface. The bolt is inserted to its shoulder through this hole, then driven into the rock hole. Bolts, wedges, and headboards are given a full timber preservative treatment to inhibit rot. Bundles of each are immersed in a warm saturated solution of Osmose salts in water for 48 hr, removed, dripped dry, and stored in a relatively humid underground depot to cure. Most wooden rock bolts used by Day Mines are 4 ft long. Holes to receive them, about 42 in deep and 2 1/8 in. in diam, are drilled into the rock&apos; to be supported, nearly normal to the periphery of the mine opening. The type of drill used is dictated by convenience: stoper, jackleg, or jumbo-mounted drifter. Correct depth of the hole is assured by use of a measuring stick that has been cut to the proper distance from drill chuck to the ground at the collar of the hole when a standard length drill rod is at the bottom. The bolt is seated to the shoulder through the hole in the headboard, the foot-end wedge is placed in its slot, and the assembly is inserted into the rock hole. Then the bolt is driven until it is seated solidly on the wedge against the bottom of the rock hole. Driving may be by hand with a sledge, or

Jan 1, 1954

By W. F. Rochow, W. C. Burke

Numerous designs of linings and accessories, including dams, lifters, and heat exchangers, contribute greatly to kiln efficiencies. Greater conductivity is achieved with basic brick than with fireclay and high-alumina refractories, depending largely upon the use of steel plates in radial joints between adjacent brick to increase heat transfer through the lining. Refractory lifters expose all portions of the load to radiant or convective heat and raise some portions to higher temperatures by cascading the load down through the path of the hot gases.

Jan 3, 1955

By R. W. Gurry

THERMODYNAMIC calculations indicate that boron is a better deoxidizer than silicon but probably is not quite as effective as aluminum. Boron should, therefore, be readily oxidized out of the open-hearth bath, which implies that it is not recovered in significant concentration from any scrap charged; also that, if added in the ladle, it tends to oxidize out during teeming unless protected by the presence of a. better deoxidizing agent. These conclusions do not apply to liquid cast iron, in which the oxygen content is much lower than in liquid steel. The possibility of conserving certain strategic alloying elements widely used in steelmaking, notably manganeie, chromium and molybdenum, by the use of boron, which in small concentration appears to be extraordinarily effective in promoting hardenability, raises a question as to what extent any boron present in the scrap charged into the open hearth is oxidized out during melting and subsequent refining. This question is significant because the optimum concentration of boron in the finished steel, which is fairly critical, would be very difficult to attain if the boron in the charge were largely retained in the metal. Moreover, unless boron is substantially eliminated in the open-hearth process its use on a large scale would eventually make it impossible to produce boron-free steel except by restricting the charge to virgin material. There is at present, unfortunately, virtually no satisfactory direct evidence to provide an answer to this question; but there are indications from practice that boron is oxidized out in the open hearth in the production of medium or low-carbon steel, although it may be retained if the carbon content remains fairly high; that is, if the oxygen is kept fairly low. In the absence of direct data, it is necessary to rely upon the indications of indirect evidence, the best approach now available being a thermodynamic calculation of the deoxidizing power of boron in liquid steel by the general method used so successfully by Chipman1 in his study of the reactions in the open-hearth process. The thermal data for boron, upon which such a calculation must be based, are reasonably satisfactory; the only quantities not directly determined are the entropy of melting of boron, the activity coefficient of boron in liquid steel, and the activity coefficient of B203 in an open-hearth slag; but these values may be estimated with ample accuracy. The results of this calculation, which is presented later, are given in Table I, together with corresponding data for other deoxidizing elements. This table shows the calculated residual content of oxygen in equilibrium with different residual concentrations of the deoxidizer in the metal;

Jan 1, 1943

By J. J. Fischer

COMPOSITES containing cold-drawn, high-strength steel wires have shown promise for normal and slightly elevated temperature applications, particularly where strength-to-weight ratios or corrosion resistance are important.&apos;-3 Although tensile strengths up to 500,000 psi may be obtained by cold drawing these wires, processing the composite at elevated temperatures will result in a rapid decrease of the wires&apos; strength. In wrought maraging steels, high-strength levels can be obtained by aging at 900&apos; . Because these alloys do not rely on heavy cold working to achieve their strength, and because they do not overage readily, they are of potential interest for use in composites. In view of this, the tensile strengths of composites containing The total heat effect thus represents the heat of formation, AHf of the compound at 273&apos; . Since the heat of solution of tin in the tin solvent bath is zero, AHz = 3( - H273)Sn and Hf is given by: For LaSn3, AH3 had a measured value of 11,285 i 380 cal per g-atom while for La2Sn, the corresponding value was 33,658 870 cal per g-atom. Using the measured data for the compounds and pure lanthanum, a value of -15,150 200 cal per g-atom was calculated for the heat of formation of LaSn, at 273°K, while Hf for La2Sn3 was found to be -28,090 400 cal per g-i&om. The authors would like to acknowledge the financial support of the Army Research Office, Durham, North Carolina. under contract No. DA-31-124-ARO-D-384.

Jan 1, 1969

By J. R. Cahoon, H. W. Paxton

The possibility of using unidirectionally solidified, two-phase alloys as an approximation to fiber composite materials is investigated. The short-term me.chanical properties and failure modes of unidirectionully solidified A1 (rich)-Cu alloys containing ap -Proximately 0, 17.5, and 27.7 vol pct of 0 phase &apos;fibers" are determined at temperatures from 25" to 500" and compared with those obtained for conventionul SAP alloys. In a previous publication,&apos; hereafter referred to as I, the possibility of understanding some of the room-temperature mechanical properties of unidirectionally solidified castings was explored. For Al(rich)-Cu and Al(rich)-Mg two-phase alloys over a substantial range of compositions, the yield and ultimate strengths and common ductility measures were very adequately predicted from the principles of fiber strengthening4 and the analysis of ductility outlined by Gurland and Plateau." The results obtained in I suggest the possibility of using unidirectionally solidified, two-phase alloys to simulate fiber composite materials where the inter-dendritic second phase or constituent acts as the reinforcing material. Recent attempts concerning the fabrication of fiber conlposites have concentrated on producing composites with a good bond between fiber and matrix and with very long fibers so that their maximum contribution to the strength of the composite may be realized. However, these objectives are difficult to attain in practice and present fabrication processes are either extremely laborious or costly.13 The slow, unidirectional solidification of eutectics has received considerable attention as a method for producing composite materials. 5,6 This method can fulfill both of the above objectives but it is currently laborious, expensive, and has the additional disadvantage that the volume fraction of reinforcing phase cannot be easily varied. On the other hand, unidirectionally solidified, two-phase alloys, also with a good bond between the phases, are relatively easy to make and the volume fraction of reinforcing "fibers" can be easily varied by changing the average composition of the alloy. The disadvantage of the cast alloys is that the mechanical effectiveness of the "elongated interdendritic reinforcements" (EIR)* may be reduced due to their rela- tively short lengths, the w factor in Eq. [2] of I. However, if the EIR have a high strength their contribution can be considerable. For composite materials containing discontinuous cylindrical fibers of various lengths the ultimate strength is given by1 where it is assumed that the composite fractures when the fibers fail. In Eq. [I], a, is the stress in the matrix just prior to failure of the composite, Vf is the total volume fraction of fiber reinforcing constituent, Vf(l+) is the volume fraction of fibers whose lengths exceed the critical length, I,, which is defined as the shortest length of fiber in which the stress can build up sufficiently to break the fiber. af is the fracture strength of the fiber material, w is a factor accounting for the discontinuity of those fibers whose lengths exceed I,, 1-/d is the average aspect ratio of those fibers whose lengths are shorter than I,, and t is the shear stress in the matrix at the fiber-matrix interface. The factor w is dependent on the length of the fibers and also on whether deformation of the matrix occurs plastically or elastically. However, for a given length of fiber, w is smaller when elastic deformation of the matrix is assumed.&apos; It is of interest to consider the properties of simple unidirectionally solidified, two-phase alloys at elevated temperatures in view of the possibility of using suitable modifications for high temperature service. Knowledge of the creep behavior of these materials is still rudimentary (although under active investigation) and the present paper concerns itself with short time tensile properties of some alloys similar to those investigated in I (i.e., unidirectionally solidified Al(rich)-Cu alloys). Unidirectionally solidified alloys containing 5.6, 17, and 23 wt pct Cu were tested parallel to the direction of solidification at temperatures from 25" to 500°C. In the present investigation, the alloys were homogenized for 2 days at 535°C giving a matrix of homogeneous a phase (5.2 wt pct Cu) and an interdendritic constituent (EIR) which was completely Q phase (53 wt pct Cu). EXPERIMENTAL Alloys of nominal composition 5.6, 17, and 23 wt pct Cu (containing approximately 0, 17.5, and 27.7 vol pct 8 phase, respectively, after homogenization at 535°C) were prepared by melting 1200 g of A1 (99.99 pct) in a high purity graphite crucible and adding the appropriate amount of freshly cleaned copper chips (99.9 pct). The molten alloy (at 700°C) was poured into a preheated graphite mold (also at 700°C) and the ingot unidirectionally solidified by impinging water on the steel baseplate of the mold. The alloy was degassed immediately

Jan 1, 1970

By M. J. Blackburn

The phasal equilibria in TI&apos;:Al alloys has been studied Ry transmission electron microscopy, electron diffraction, and X-ray diffraction. It is shown that three-phase fields exist below the transformation, viz.: a disordered hexagonal solid solution a; an ordered hexagonal phase based on Ti3Al, aa; and a two-phase region. (a + (YZ) , occurring between the single-plzuse fields. The size. disiribution, and morphology of- the a, phase in the two-phase region is shown to be dependent upon the alloy composition and heat treatement. The ordering process in the a, phase leads to the formation of anliphase domain boundary networks; the contrast and stability of these networks is shown to be dependent on alloy composition. A new and relatively simple phase diagralil for the systemm is constructed. The phasal equilibrium at the titanium-rich end of the Ti:Al system has long been the subject of considerable controversy. crossleyl has recently reviewed the phase diagrams that have been advanced for the system and in his turn proposed yet another one. There would seem to be general agreement that a phase exists at a composition at or near Ti& with an ordered hexagonal DO,,-type structure. However, several other phases have been proposed; for instance, Ence and ~ar~olin&apos;s&apos; diagram includes two phases, Ti2A1 and Ti3A1, in the region up to 25 at. pct Al. The position of the proposed phase boundaries varies over a considerable compositional and temperature range, a point graphically illustrated in Fig. 1 of Crossley&apos;s paper.&apos; It is perhaps germane to briefly examine the techniques used by other workers in the establishment of the phase structure. These fall into three categories: 1) X-ray diffraction, the only limitation of which is the rather low intensity of superlattice reflections in this system.3 Thus, superlattice reflections become increasingly difficult to detect in the more dilute aluminum alloys. 2) A considerable amount of optical microscopy has been performed"2&apos;4 and it will be shown in a later section that many of the obscure mi-crostructures that have been observed can be attributed to hydrogen contamination. It is concluded, therefore, that such observations should be interpreted with considerable care. 3) The variation of some physical property with aluminum content has been measured.5"7 These methods are a useful indication of the existence of a transformation, but are usually insufficient in themselves to identify the transformation. The results using these techniques will be considered in more detail in the discussion. In this paper, the phase structure of alloys containing up to 25 at. pct A1 has been studied by transmission electron microscopy and X-ray techniques, and the results are used to generate a new and relatively simple diagram for the titanium-rich end of the Ti:Al system. EXPERIMENTAL A series of alloys containing 5.05, 10.16, 13.39, 13.99, 14.40, 20.83, and 25.05 at. pct A1 were obtained in the form of hot-rolled sheet 0.02 in. thick. These alloys contained 0.10 to 0.15 pct 0. Thirty-gram arc-melted buttons were prepared from iodide titanium and 99.99 A1 which contained 16.1, 16.9, 18.2, 19.0, 21.6, 22.2, 23.0, and 23.9 at. pct A1 and had an average oxygen content of 0.03 pct 0. The differences in oxygen content did not appear to influence the nature of the phase transformations which were found. Oxygen content may affect the temperature of these transformations, but insufficient samples of the high-purity alloys were examined to answer this question. The heat treatment of alloys was performed in dynamic atmosphere and vacuum furnaces or in helium -filled silica capsules. A special vacuum furnace was constructed to provide a high quenching rate in which rates of 4000°C per sec were obtained using water as the quenching medium. As pointed out by Crossley,&apos; it is important to avoid heat treatment in the a - [} phase field as the resultant segregation of the alloy into the two phases containing different amounts of aluminum can persist through subsequent treatments leading to ambiguous results. It will be demonstrated later that step cooling of specimens from the a phase region can also lead to anomalous effects. Thus, all solution treatments were carried out in either the a or 3 phase fields followed by water quenching and subsequent isothermal annealing at various temperatures. X-ray analyses were performed on a diffractometer on fine-grained bulk specimens. The value of long-range order parameter, S, wa_s calculated from the integrated intensity of the (1211) reflection. In general, the intensity of the (1011) superlattice reflection was compared with that of the (2021) fundamental reflection to correct for experimental differences between measurements. Thin foils for electron microscopical examination were produced by electropolishing using the technique described in an earlier paper.8 Dark-field techniques were employed to a large degree in this investigation using the gun-tilt method. Finally it should be noted that the lattice parameters of the D01,-type superlattice are approximately related to the disordered hexagonal phase parameters by Crf - c, and 2ad - a, where the subscripts s and d refer to the ordered and disordered unit cells, respectively.

Jan 1, 1968

By Richard W. Lodge

Several methods, both wet and dry, for the assay of zinc-box residues from the cyanide process, have been described in recent years, and each of them has been claimed to be superior to all others. In the year 1901, a paper, entitled "Assay of Zincy Precipitates," was published ill the School of Mines Quarterly to the purport that the scorification method for the assay of zinc-box residues was absolutely unreliable. In order to shed light on this matter, the following experiments were undertaken by Messrs. C.B. Hollis and F. D. Kehew, undergraduate students at the Massachusetts Institute of Technology. The zine-box residues used were obtained through the courtesy of Mr. H. R. Batcheller. The samples were very rich and varied greatly in the fineness of their condition. SCORIFICATION-ASSAYS. In the preliminary tests, the charge, which was weighed on a chemical balance, consisted of 0.1 Assay Ton of residues mixed with from 30 to 35 grammes of test-lead and placed in a 3-in. scorifier, over this an additional quantity of test-lead (from 30 to. 35 grammes) was placed for a cover, and borax-glass, varying in quantity from 3 to 15 grammes, was sprinkled over the top of each charge of the various assays for a cover. The charges were scarified in a muffle-furnace heated to the ordinary temperature which is used in scorification; in some cases the door of the muffle was left open, while in others it remained closed. Generally, the charges spit badly, especially in the assays that were made with door of the muffle left open, or in those in which the door was opened too quickly. The results of the preliminary assays showed: 1. That in order to obtain approxi-

Jan 1, 1904

By A. B. Kinzel

MUCH work has been done recently in an attempt to analyze the physicochemical mechanism involved in the production of steel by the open-hearth process. . This has resulted in reducing the process to a series of interrelated phenomena obeying the usual laws of mass action and diffusion. Of these, the reaction of the iron oxide and carbon in the molten steel is of most interest from a technical point of view as it con-stitutes the main action in the usual steelmaking processes. A. L. Feild1 has formulated a basic differential equation expressing the open-hearth reactions and Hefty has done considerable experimental work on the determination of a number of constants involved in the basic open-hearth reaction. In considering the application of the law of mass action. to the reaction FeO +C ?? CO +Fe, the iron will be taken as constant, as is the case in the open hearth and the carbon monoxide pressure will be assumed&apos; constant at one atmosphere. From this xy = m at equilibrium, where x is the percentage weight of carbon, y percentage weight of iron oxide and m the weight-concentration equilibrium constant. While it is customary for physical chemists to express equilibrium constants in terms of molar concentrations, the constant is here expressed as the product of the percentage-weight concentrations for ease of comparison with the constants quoted by Herty and by Feild, and for more ready applicability to the open-hearth reactions. Herty and his associates have attempted to calculate the value of this constant from data on open-hearth heats. So many variables affect these results that an adequate calculation presents very great difficulties. A value of 4 X 10-2 was first arrived at, but this was later changed to 1.6 X 10-2. Feild, in order to illustrate the operation of the differential equation of the open hearth, has assumed a value considerably lower than Herty&apos;s, namely, 1.0 X 10-2, the largest value consistent with certain theoretical

Jan 1, 1929