Search Documents

By B. H. Sage

AN apparatus is described for the measurement of the pressure-volume-temperature relations of pure substances, simple mixtures and complex mixtures with an over-all absolute uncertainty, which is usually not more than 0.2 per cent. The equipment is suitable for studies in the gaseous, two-phase, and liquid regions. The behavior of such systems may be investigated at pressures as high as 10,000 lb. per sq. in. for temperatures between 70° and 600° F. The methods of measurement and the construction of the apparatus are described in some detail. The measurement of the volumetric behavior of multicomponent systems requires the simultaneous measurement of the pressure, volume, temperature and weight of each component of the system. In the present apparatus a sample having constant weight is investigated at a number of independently controlled pressures and temperatures, there-fore it is necessary only to establish the weight of each component added before a given set of measurements. This method is in distinction to that in which the total volume remains constant and the pressure is varied by addition or removal of material, the system having variable weight. An objective in the design of the apparatus to be described was to develop equipment that would yield results involving no uncertainties larger than 0.25 per cent throughout the range of pressures from 150 to 10,000 lb. per sq. in. at temperatures between 70° and 600° F. Although this over-all absolute uncertainty of measurement may not appear to be small, it necessitated care in the plans for control and measurement of each of the fundamental variables. In general, any uncertainty greater than 0.05 per cent in the pressure, volume, absolute temperature or weight of each component was considered undesirable; therefore the attempt was made to obtain a precision of measurement in each case such that the absolute uncertainty would be only half this amount except in certain regions near the ends of the experimental range of the variable under consideration.

Jan 1, 1939

Overview of Presentation ?About MiHR ?Human Resources Challenges in the Minerals and Metals Industry ?Getting the Facts -Sector Study Project ?Key Findings ?Recommendations ?Conclusions ?MiHR?srole

May 1, 2006

By Norihiro Murayama

The hydrothermal syntheses of zeolites from coal fly ash were carried out using NaOH and KOH as an alkali source. The cation exchange capacity (CEC) and the ion exchange selectivity were investigated for the zeolites synthesized by a hydrothermal treatment. The effective usage of the zeolite as a cation exchanger was considered from the viewpoint of engineering. Zeolite P, HS (hydroxysodalite) and K-CHA (potassium-chabazite) are mainly formed as zeolite species in NaOH or KOH solution at 393K. The zeolite P and K-CHA have a large exchange capacity as a cation exchanger. The cation exchange isotherms of various monovalent and divalent cations with various zeolites are investigated. The order of selectivity of the zeolites is as follows, NH4+> K+> Li+.For the divalent cation, the largest removal amount is obtained for Pb2+ in the low equilibrium concentrations below 0.2mmol/dm3, and almost perfect removal can be achieved for Pd2+. The order of selectivity of zeolites in low concentration is expressed in the following order; Pb2+> Co2+> Cd2+> Ca2+> Mg2+> Ni2+. Ii is considered the zeolites obtained from coal fly ash can be used as an excellent cation exchanger.

Jan 1, 2006

By Raymond B. Ladoo

Wollastonite is a calcium metasilicate, with the formula CaSiO3; containing theoretically 48.3 pct CaO and 51.7 pct Si02. It is one of many natural and synthetic silicates with varying CaO/SiO2 ratios, with and without water of crystallization. While it is a very common mineral, deposits of sufficient size and purity to be of commercial interest are unusual. There is only one producer (1958) of wollastonite for industrial use in the United States, Godfrey L. Cabot, Inc. at Willsboro, New York. There has been a small production of surface material for ornamental use from near Blythe, California. Carload tests have been made on California wollastonite for making mineral wool and a commercial plant for this purpose was projected in 1957. Properties Wollastonite is monoclinic and commonly occurs in masses or aggregates of bladed or needle-like crystals. It has a perfect cleavage parallel to the long prismatic axis. It is rather brittle and some types grind easily to a very finely fibrous product, but other types, due to interlacing of fibers, are tough and difficult to grind. Mobs hardness is 4.5 to 5; specific gravity 2.8-2.9; index of refraction 1.616 to 1.631; melting point 1,512°C. Color when pure is a brilliant white, but when less pure it may be gray or brown. Luster is vitreous, transparent to translucent. Common mineral associates are garnet (several varieties), diopside, calcite and quartz. The nature of the mineral impurities determines to a large degree the commercial value of a deposit. At Willsboro, New York, the impurities consist chiefly of iron garnet and iron diopside which are both magnetic and so are easily removable by magnetic separation, yielding a nearly theoretically pure product. Some deposits in California contain calcite and quartz which cannot be removed cheaply, thus limiting market possibilities. Occurrence Wollastonite is a contact metamorphic mineral occurring in most places within or associated with impure limestones. The deposits at Willsboro, New York1,2,3,5 consist of two or more beds dipping 15-50°E and striking NW-SE. The main bed, 30 to 70 ft thick, may be traced on the surface for at least 2 ½ miles. In this belt, the Pre-Cambrian Grenville limestone has been injected and partially replaced by the more liquid portions of an anorthositic magma. Buddington and Whitcomb3 have described the rock as "Mixed gneisses, pyroxenite and garnetiferous gneisses and skarns." Prospecting revealed the wollastonite at ten different places in the belt, overlain in most places by a garnet rock. Diamond drilling has proven several million tons with probable reserves around 15 million tons. Interbedded with the wollastonite are beds of garnet from a few inches to several feet in thickness. In the wollastonite ore itself the chief and almost only associated minerals are garnet (mostly almandite but some andradite and grossularite) with small amounts of green hedenbergite. Inasmuch as the almandite and diopside are magnetic they are easily separated from the wollastonite in high intensity magnetic separators. If grossularite should occur in quantity other means of separation would be needed. Wollastonite has been reported at 35 localities in California12 but only those in the Big Maria and Little Maria Mountains, 16 to 20 miles north of Blythe, Riverside County, are

Jan 1, 1960

By Wilbur C. Helt, Joseph J. Yancik

Throughout the history of mankind, the principal use of coal has been to produce heat through combustion. The heat is used in many ways: to warm air space for our comfort; to provide heat or energy to power industrial processes, such as cement and steel production ; and to produce electricity. Because it is our nation's most abundant fossil energy fuel, coal in the late 20th century is on the threshold of becoming a significant source for synthetic liquids and gas energy fuels for this country. This is made possible by conversion processes which can change solid coal into various synthetic gases and liquids. These coal-derived fuels are nearly identical to the processed fuels and chemicals provided by natural gas and crude oils, which presently provide almost all the petrochemical feedstocks and energy fuels needed for the residential, light commercial, and transportation markets. A revolution is beginning to take place, not only in the United States, but in many other countries with a return to a coal-based energy economy. Also, new combustion and conversion technologies which are compatible with national health and environmental goals are rapidly emerging. These technologies will allow coal's use to be expanded not only in its traditional markets, but also to supply markets held by natural gas and crude oil. With the worldwide decline in natural gas and crude oil reserves, coal is being looked upon to meet the energy demand. Because of these new coal conversion technologies, coal will no longer be only a combustion fuel, but a valuable raw material for production of a variety of clean fuels and chemicals. MARKETS FOR COAL: PAST AND FUTURE A simplified diagram of the marketing network for coal is shown in Fig. 1. As shown in this figure, coal is transported to its traditional

Jan 1, 1981

By Pengle C. H.

El presente trabajo señala los beneficios de la explotación del mineral encontrado en las minas de Carahuara, Junín, de la Compañía volcán Mines S. A. El tratamiento del mineral logra superar las dificultades de separación cobre- plomo mediante la planta concentradora del Marh Tunel, Cerro de Pasco Corporation y permite recuperar el valor principal de la plata-dentro de los concentrados de zinc-, así como del plomo.

Jun 20, 1954

By Lyall Zickrick, R. S. Dean, F. C. Nix

The first attempt to establish an equilibrium diagram of the lead-antimony series was made by Roland-Gosselinl in 1896. This investigation classified the system as a purely eutectiferous one, with the eutectic at 12.5 per cent. antimony and 228" C. In the next year, Stead2 placed the eutectic temperature at 247' C. The error in temperature made by Roland-Gosselin, however, has been perpetuated in the literature with a remarkable degree of persistency; this value was accepted by Campbell (1902), and Ewen (1910),3 and will be found in the last edition of Desch's3 Metallography (1922). Gonterman's investigation, made in 1907, was the most complete one available at the time .the present investigation was started. He concluded4 that the system was a simple eutectiferous one and placed the eutectic at 13 per cent. antimony and 247° C. Other investigations by Tammann (1907),5 Garbow (1909),6 Rudolfi (1910),7 Loebe (1911),8 and Leroux (1913)9 added little, if anything, to Gonterman's diagram. A number of investigations have been made of physical properties of the alloys. The electrical conductivity of the series was studied by Matthiessen (1860)10 and by A. W. Smith (1921);11 the thermoforce by Rudolfi (1910),12 and Pelabon (1923) ;13 the specific heat by Durrer

Jan 1, 1926

By F. N. Kissell

The Bureau of Mines used sulfur hexafluoride (SF6) tracer gas to evaluate the effectiveness of gob ventilation and/or sealing practices at three coal mines, each having different problems associated with their mined-out areas. The purpose of these ventilation studies was to better understand whether current techniques employed for ventilation or sealing are successful at minimizing the potential for gob fires and explosions. The work performed at each mine is discussed: One is a long-wall operation that uses ventilation to carry off hazardous gases, and two are room-and-pillar operations, each with far different concerns, that seal off the gobs to isolate them from the main mine ventilation. In all cases employment of the Bureau's SF6 tracer gas technique resulted in answers to questions raised by the mine operators concerning the effectiveness of their gob ventilation or sealing practices in preventing mine fires.

Jan 1, 1986

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941

By E. M. Williams

The U.S. Bureau of Mines is investigating the use of in-seam seismic methods to monitor stress-induced changes in coal near the working face of longwall mines. Seismic surveys performed through a longwall panel and pillars near the face can provide valuable information on geologic anomalies, high stress regions, tailgate support performance and other conditions that could endanger miners or interrupt production. This paper describes the details of the equipment and data analysis techniques used, and the significant results obtained and their implications for ground control. Using seismic tomography, it is possible to conduct measurements on the pillar and reconstruct an image representing the internal velocity distribution. Successive measurements over several days identify changes in velocity attributable to changes in stress. Several field measurements were conducted at a western U.S. longwall mine to observe stress induced changes within the panel and pillars during mining. A permissible data acquisition system was designed to meet mine safety requirements for operation in gassy air. Certification from the Mine Safety and Health Administration (MSHA) was obtained, and this approved system was used to monitor stress changes in several pillars as the longwall face passed during first panel mining. Tomographic surveys were completed across the longwall panel to map the apparent abutment stresses ahead of mining. Velocity distributions show an increase in vertical stress across the panel from the headgate to the tailgate. Additionally. a yield zone along the face near the tailgate and the forward abutment approximately 100 feet outby the face in the tailgate side of the panel were detected. These results agree well with data obtained from other instrumentation emplaced in the panel near the tailgate. Using velocities for both compressional and shear waves, the Poisson's ratio was calculated for the panel.

Jan 1, 1994

By J. A. Eisele, D. L. Pool

"The Bureau of Mines has developed a particle agglomeration technique to improve the flow of leaching solution through heaps of low-grade gold-silver ores which contain clays. Benchscale experiments and industrial practice have shown that the percolation rate of cyanide leaching solution is greatly enhanced by mixing the ore with Portland cement as a binder, moistening the mixture, mechanically tumbling to form agglomerates, and aging before heap building and leaching. A slight modification ofthe technique allows its application to precious-metal-bearing tailings, which cannot normally be treated by heap leaching because they are too fine. IntroductionMany low-grade gold and silver deposits and tailing materials from former mining operations in the western United States are potential sources for precious metals. These sources are too low grade or too small to support the capital cost of a conventional cyanidation plant but have stimulated the development of lowcost procedures, such as extraction of the precious metals by heap leaching with cyanide. The Bureau of Mines has investigated methods to improve the recovery ofgold and silver by heap leaching these low-grade materials.For heap leaching to be successful, the crushed and stacked ore must have good permeability so that uniform distribution of the cyanide leaching solution through the heaps can be achieved. Some of the most difficult gold and silver ores to treat by heap leaching are those containing excessive amounts of clays, or fines generated during crushing. Excessive amounts of slimes, generally minus 50-micrometre or 270-mesh Tyler sieve size particles, in the heap feed will slow the percolation of the leaching solution, cause channelling, or produce dormant or unleached areas within the heap, resulting in long leaching periods and low extractions. In extreme cases, the clays or slimes can seal the heap and cause the leaching solution to run off the sides of the heap rather than through it."

Jan 1, 1987

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941

By J. Boulton

"Nuclear energy is an established and proven energy source. Today, CANDU-PHW nuclear-electric generating stations produce over one third of Ontario's total electrical supply: safely and economically. In many parts of Canada, where economic hydro resources do not exist or are fully developed, coal and nuclear energy are the only alternatives for future large-scale electrical generating capacity.Recent analyses have suggested that, in the f ace of increasing energy demands and decreasing reserves of hydrocarbon fuels, Canada must depend on electricity to provide an expanded fraction of its energy budget. Nuclear energy is likely to play an increasing role in the generation of electricity; there are also potential applications as a supplier of process heat in industry and in the in-situ recovery of bitumen fro m tar sands.The future supply of nuclear fuel, reactor safety and radioactive waste management are briefly discussed. In each case, the benefits to be gained from a controlled expansion in the use of nuclear energy outweigh any uncertainties which may exist."

Jan 1, 1981

By Yanagase T, Nakamura T, Ueda Y

The possibility of removing the phos phorus and sulphur contained in steelmaking slag has been studied by observing directly through the microscope melts heated on Pt- filaments. After a CaO crystal was placed in the molten slag, distributions of P, S and other elements formed around the CaO crystal were determined with the aid of EPMA. The results indicated that a layer of 2CaO SiO2 is formed on solid CaO in CaO-Si02 melts. Then between CaO and the newly formed compound the molten slag tends to migrate through cracks. For higher Fe 2 03 contents, the layers of the compounds 2CaO.Si02 and 3CaO SiO2 formed around the CaO crystal are not continuous but look more like particles, which promotes the dissolution of CaO. Phosphorus in slag was found to be enriched in the 2CaOòSi02 layer. Phosphorus in the 2CaO SiO2 phase is not related to the primary slag composition, being about 5-7% P205.. Sulphur in slag,as well as the phos- phorus,was concentrated in the 2CaO.Si02 phase. Disintegration due to weathering observed for slags produced in these investigations appeared to be due principally to hydration of lime.

Jan 1, 1980

By C. P. Smyth

Large volumes of quantitative geochemical data, presenting a formidable interpretation task to geologists, are generated in the course of exploration drilling for new ore deposits. The incorporation of geological expertise into computer programs developed for the interpretation of this data would improve the speed and accuracy with which it is interpreted. A detailed analysis of the geochemical log interpretation problem, together with a survey of relevant research in Artificial Intelligence and petroleum well- logging techniques, confirms, that artificial intelligence, particularly as developed in the fields of expert systems and pattern recognition, provides techniques for implementing such data interpretation programs. In addition, it provides data analysis techniques significantly more powerful than those currently applied to geochemical data, and very appropriate to the hypothesise and test' character of mineral exploration problem-solving. The conversion of raw borehole log data to meaningful higher level geochemical entities, in terms of which geological reasoning may take place, is a critical step in applying these techniques to log data analysis. A method of achieving this conversion as an exercise in signal-to-symbol transformation is presented.1

Jan 1, 1987

By E. A. Reilly, G. R. Gardner, F. P. Lasseter

THE methods that may be applied to the treatment of slurries and water, as these are related to practical coal-preparation problems, are concerned essentially with the movements of solids suspended in water. It is assumed that there are no fundamental differences between the principles involved in the treatment of coal slurries and the phenomena encountered in general mineral-dressing practice, and the latter are presented in some detail. Basic principles are correlated with present practice for both the anthracite and the bituminous coal. fields, and meth¬ods are discussed which are designed to utilize best all the material subjected to treatment and suggest a sound approach to the solution of problems relating to the return of clear water to process or to streams. In order to approach the practical phases of the subject with sufficient understanding of the basic principles, it is necessary to discuss two types of phenomena that are applicable. The first is flocculation and the second is sedimentation. Descriptive matter is given covering the various meth¬ods and types of equipment employed to conduct these operations, with emphasis on their application to water and coal-slurry treatment.

Jan 1, 1943

By K. E. Gray, M. S. Seth

Equations of elasticity for transversely isotropic, axisymmetric, homogeneous, porous media exhibiting pore fluid pressure were formulated. Using an analogy between thermal and porous body stresses, it was shown that the solution for a transversely isotropic porous body may be obtained by incorporating body forces and the stresses due to a boundary load into the corresponding solution for the thermal stress problem. Equations of elasticity ad the thermal analogy method were used to determine transient horizontal, tangential, and vertical stresses and radial displacement in a semi-infinite cylindrical region when either a constant pressure or a constant rate of flow is maintained at the wellbore. The vertical and tangential displacements are zero from the conditions of the problem. A numerical analysis was made of the solutions obtained by using a digital computer to determine the relative influence of each system variable. Considering rock as a porous body with internal fluid pressure generally gives results significantly different than considering the rock to be nonporous; the directional character of rocks leads to significant differences as compared to results based upon the common assumption of isotropy. Stress gradients are high near the wellbore but die out away from the well. Radial stresses are compressive or neutral, whereas tangential stresses are tensile, neutral or compressive, depending upon the boundary conditions and physical properties of the system Vertical stresses are compressive for an unbounded system. For constant wellbore injection rate, the vertical stress is proportional to the rate of fluid injection and decreases with time, whereas the radial and tangential stresses increase with time. At a given location, the radial displacement generally is very dependent upon time. INTRODUCTION A realistic appraisal of the state of stress in subsurface rock formations would be of considerable interest and use to the petroleum industry. For example, knowing the state of stress in proximity to a wellbore would be of fundamental importance in designing a fracturing operation or, more important, of clearly understanding the conditions necessary to produce rock failure of desired dimensions and geometry. Understanding conditions necessary for rock failure at the wellbore would also be of utility in a preventive sense. For example, borehole stability is an important consideration for many rock formations, and knowledge of the stress state at and near the wellbore under conditions of substantial pressure gradient due to fluid flow would be of great value. When fluid flows through a porous body which is initially at some uniform stress level, the following forces generate stresses at any point in the body. (1) Forces due to nonuniform pressure distribution. With increasing pressure the elements of a body are compressed. Such compression cannot proceed freely in a continuum when the pressure is not uniform throughout, and thus, stresses due to flow of fluid are set up. (2) Pore fluid pressure. This gives rise to normal stresses whose value at any point is the product of areal porosity and the fluid pressure. Although the fluid exerts uniform pressure, the stresses it creates in an anisotropic body may not be the same in all directions since the areal porosity in an anisotropic porous body is a direction-dependent quantity. This consideration leads to the concept of directional porosity. (3) Body Forces. The flow of the moving fluid imparts a force to the rock matrix, the magnitude of which depends upon the pressure

Jan 1, 1969

By R. I. Jaffee, F. C. Holden, H. R. Ogden

The effects of ternary and quaternary additions of aluminum, oxygen, and carbon on the mechanical properties of high-purity titanium-molybdenum alloys were studied for several microstructural conditions. Heat treatments were designed to produce 1) ß-quenched, 2) equiaxed ß) transformed (acicular) and 4) stabilized -P microstructures. Tension, impact, and hardness tests were performed. Transformations from the ß phase were followed by hardness measurements and metallography. The ß-to-w transformation was slowed by aluminum additions; carbon and oxygen additions increased the transformation rate. In addition to solid-solution strengthening, these solutes may increase or decrease strength by altering the /3 transformation kinetics. Aluminum additions promote the formation of strain-induced martensite, and lower yield strengths at compositions near 12 pct molybdenum.. a-P alloys are more ductile with equiaxed than with transformed microstructures. High strength levels can be reached by aging in many cases. Strength levels of the aged specimens usually are lowered slightly by straining prior to aging. ALLOYS of molybdenum with titanium form an iso-morphous alloy system which has been the subject of several investigations. Additions of substitu-tional and interstitial -stabilizing elements provide means of improving mechanical strength and con- trolling the heat-treatment response of the binary alloys. The work reported here forms a part of a continued study of the effects of microstructure on the mechanical properties of high-purity titanium alloys. Previous papers have considered the various binary alloys (Ti-Mo, Ti-Al, Ti-C, and Ti-0) that form the bases for the ternary and quaternary alloys included here. The compositions were selected to correspond with the previous binary alloys. Further, the high purity of the alloying components was maintained, so that direct comparisons with earlier work can be made. The total research program included a large number of compositional, microstructural, and testing variables. The data reported here have been selected to provide a reasonably complete and representative summary of the results. The reader is referred to the original Air Force Report for a complete tabulation of the results. EXPERIMENTAL PROCEDURES All the alloys used in this work were prepared from high-purity electrolytic titanium produced by the U.S. Bureau of Mines. A typical furnished analysis showed the following impurities in wt pct, balance This analysis is equivalent to that of iodide-refined titanium. In addition, hardness, tensile, and impact tests made using unalloyed electrolytic titanium showed it to have properties equivalent to those obtained with iodide titanium and suitable for these studies of high-purity base alloys.

Jan 1, 1962

By Robert Cefalo

Drill and Blast Engineer Abstract In 2019, the Bingham Canyon Mine, owned by Rio Tinto Kennecott Utah Copper Company, mined through the active underground that dewaters the pit. The active underground required the limitation of vibrations to avoid catastrophic damage or damage that would require work to the shotcrete and additional roof support. The surface design of the current sector next to and through portions of the active underground. The drill and blast group was required to test site law vibration parameters to ensure that vibration limitations were lower than limits set by the underground management team. Seismographs were used to validate the vibration prediction model and check performance of blast in areas of the underground. The bench conditions and limited pounds-per-delay created large obstacles for the blasting team, making it difficult for them to accurately load the pattern with the number of decks in the blast. Methods were used to improve the loading instructions and ensure that each hole achieved pound requirements based off of the distance to the underground that it was designed to protect. The project evolved from start to finish, and the process to estimate distances and loading improved to make the blast a more repeatable process for the size of the project.

By Gerald Edmunds

CASTINGS of pure metals and many alloys usually have a coarse-grained structure characterized by long columnar grains throughout the main body of the casting. Frequently, the surface exhibits finer, some-times nearly equiaxed grains, and such grains may also compose other parts of the casting. This paper deals primarily with determinations of the grain-orientation textures of the columnar and surface grains of polycrystalline zinc castings. It includes some results upon a cadmium casting and a magnesium casting. A hypothesis is devel-oped to account for the observations on columnar grains and to use as a basis for predicting orientations in other cast metals. A general description of the position of the columnar grains in castings is that their long axes are approximately parallel to the direction of the thermal gradient during crystallization. Thus, in cylindrical castings the columnar grain axes tend to be radial, and in large flat castings where most of the cooling is through one or both of the large mold surfaces they tend to be perpendicular to the mold surfaces. At the edges and corners the direction of heat flow and there-fore the position of the grains is more com-plex. Actually observation shows that even in castings made in flat molds the cooling seems to be somewhat irregular, since columnar grains tend to emanate from certain areas of the cooling surface, indicat-ing that thermal contact was better there than in neighboring areas.

Jan 1, 1940