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By David N. French

In a recent paper, Miyoshi, Hara, and sugimotoL have shown that hardness increases and crack resistance decreases with polishing time in tungsten car-bide-cobalt alloys. They attribute the changes in hardness and crack resistance to cold working in these alloys. More recently Exner2 explains the decrease in crack resistance with the amount of material removed (polishing time) by suggesting that polishing removes a high compressive residual surface stress due to the initial grinding operation. He cites previous work on steel to show grinding can induce surface compressive stresses but offers no direct experimental measurements to support this in cemented tungsten carbides. In recent work we have observed changes in residual stress in the W C phase as measured by X-ray diffraction techniques with changes in polishing conditions.3 As a result of the work of Miyoshi et al.,L a brief study was undertaken to investigate the effects of polishing and grinding on the residual stress in the WC phase and have been reported.4 A single composition of tungsten carbide —10 wt pct Co was used. Two initial conditions were studied: an annealed condition with about -30,000 psi residual stress from the differences in thermal coefficients of expansion of WC and cobalt and, on the same specimen, a surface ground with a 150 grit diamond wheel. Stress was measured in the WC phase using X-ray diffractometry as a function of the amount of material removed by metallographic polishing with 6 diamond paste. The results are shown in Fig. 1. Two things are noted, 1) polishing with 6 p diamond paste has little effect on the annealed sample and 2) the magnitude of the grinding stress is markedly reduced as material is removed. By the time 0.1 mil is removed the surface has a metallographic polish satisfactory for light microscopy examination. Thus the surface, even though polished, can still retain most of the stress due to grinding. Since WC is itself slightly ductile, it seems reasonable that high compressive stresses can be generated in the surface by the plastic deformation accompanying grinding. Exner2 suggests, by analogy with steel, that as a result of grinding both WC and cobalt in the

Jan 1, 1970

By Hugh D. Pallister, Richard W. Smith

The Alabama flake-graphite industry has flourished only in times of war when importations of foreign graphite for crucible use have been greatly curtailed or cut off. World War I was a boom period and in 1918 some 30 plants produced 7,795,475 lb. of flake graphite. The industry languished following the war and no graphite was produced from 1929 to 1939. The Federal Bureau of Mines began investigating the Alabama graphite deposits in 1940 and worked out modern recovery methods that were applied to production during part of World War II. A prospecting program disclosed reserves of over 25 million tons of graphitic schists. In 1942 the War Production Board authorized the enlargement of the only plant then producing flake graphite and the construction of two new plants. Production of flake graphite from these three plants in 1943 is estimated at 8,100,000 lb. Increased imports from Madagascar late in 1943 shut down one of the new plants and curtailed production at the other. Alabama flake graphite has not yet been able to compete with Madagascar graphite for use in the manufacture of any but small graphite crucibles. The future of the industry must depend on meeting the higher carbon content demanded for other uses.

Jan 1, 1945

By J. W. Spretnak, D. A. Chatfield, G. W. Powell, J. R. Eifert

In nzost cases, the driving force for a lattice transformation is produced by supercooling below the equilibriunz transformation temperature. The interfnce reaction in isothermally annealed, multiphase diffusion couples may involve a luttice transformation which also requires a driving force. Direct experinzental evidence has been obtained for the existence of the driring force in the form of a supersaturated phase at the aocc)-0@cc) interface in Cu:Cu-12.5 ult pct A1 couples; the super saturation is equivalent to an excess free energy of approximately 3 cal per mol at 905. A tentatiue interpretation of the dynanzic situation a1 the interface based on the free energy-composition diagram is proposed. THE presently accepted theory of diffusion in multiphase couples1 states that there will be a phase layer in the diffusion zone for every region which has three degrees of freedom and which is crossed by the diffusion path in the equilibrium phase diagram. For binary systems, this restriction excludes all but single-phase fields and, for ternary systems, only one- and two-phase fields are included. In addition, Rhines"~ as well as other investigators3 6 have reported that the compositions of the various phases adjacent to the interfaces are, for all practical purposes, the compositions given by the intersections of the diffusion path with the solubility limits of the single-phase fields of the equilibrium phase diagram. Some studies of the rate of thickening of these intermediate diffusion layers indicate that the thickness of the layer changes para-bolically with time, or: where x is the position of the interface relative to an origin xo, t is the diffusion time, and k is a temperature-dependent factor. crank7 shows mathematically that, if the compositions at an interface are independent of time and the motion of the interface is controlled by the diffusion of the elements to and from the interface, then the segments of the concentration penetration curve for a semi-infinite step-function couple will be described by an equation of the form: hence, Eq. [l] follows from Eq. (21 if the interface compositions are fixed and if the motion of the interface is diffusion-controlled. Although the concept of local equilibrium being attained at interfaces has assumed a prominent role in the theory of diffusion in multiphase couples, experimental evidence and theoretical discussions which challenge the general validity of this concept have been reported in the literature. arkeen' has stated that strict obedience to the conditions set by the equilibrium phase diagram cannot be expected in any system in which diffusion is occurring because diffusion takes place only in the presence of an activity gradient. Darken also noted that it is usually assumed that equilibrium is attained locally at the interface although the system as a whole is not at equilibrium, the implication being that the transformation at the interface is rapid in comparison with the rate of supply of the elements by diffusion. ISirkaldy3 indicates agreement with Darken in that he believes the concept of local equilibrium is at best an approximation because the motion of the phase boundary requires that there be a free-energy difference and, hence, a departure from the equilibrium composition at the interface. Seebold and Birks9 have stated that diffusion couples cannot be in true equilibrium, but the results obtained are often in good agreement with the phase diagram. The initial deviation from equilibrium in a diffusion couple will be quite large because alloys of significantly different compositions are usually joined together. Kirkaldy feels that the transition time for the attainment of constant interface compositions (essentially the equilibrium values) will be small, although in some cases finite. Castleman and sieglelo observed such transition times in multiphase A1-Ni couples, but at low annealing temperatures these times were quite long. Similarly, ~asing" found departures, which persisted for more than 20 hr, at phase interfaces in Au-Ni and Fe-Mo diffusion couples. Braun and Powell's12 measurements of the solubility limits of the intermediate phases in the Au-In system as determined by microprobe analysis of diffusion couples do not agree with the limits reported by Hiscocks and Hume-Rothery13 who used equilibrated samples. Finally, Borovskii and ~archukova'~ have stated that the determination of the solubility limits of phase diagrams using high-resolution micro-analyzer measurements at the interfaces of multiphase couples is not an accurate technique because of deviations from the equilibrium compositions at a moving interface; diffusion couples may be used to map out the phase boundaries in the equilibrium diagram, but the final determination of the solubility iimits should be made with equilibrated samples. The purpose of this work was to investigate the conditions prevailing at an interface in a multiphase diffusion couple and to compare the interface compositions with those associated with true thermodynamic equilibrium between the two phases. Microanalyzer techniques were used to measure interface compositions in two-phase Cu-A1 diffusion couples annealed at 80@, 905", and 1000°C for various times.

Jan 1, 1969

By Thomas W. Wälde

BACKGROUND Foreign investment has been a major factor in bringing about the substantial mining industries of Chile, Peru, Bolivia, Venezuela, Brasil and Guyana. But economic nationalism and sentiment against foreiqn domination of vital national industries grew in the 1960s and most major mining projects were transferred into state owner ship. Among the state mining enterprises formed were CODELCO - Chile, MINERO-PERU/ CENTRCMIN - Peru, CCMIBOL - Bolivia (in 1952), Hierro-PERU, GUY-BAU/BIDCO - Guyana, etc. New investment during that time was discouraged because it was subject to the restrictive conditions of the investment regulations of the Andean-Pact, a grouping of Chile, Bolivia, Peru, Ecuador, Venezuela and Colombia. The philisophy was that mineral resources were to be developed exclusively by national enterprises. Essential foreign inputs had to be acquired "depackaged" as separate purchases of equipment and technical assistance services. As a result of the worldwide economic recession which hit the mining industries in 1980-1982, many projects that were viable in 1970 were not developed by the new state enterprises due to lack of capital, managerial and technical abilities and due to problems with marketing. As a consequence of the long-term decline of metal prices, governments experienced difficulty in getting investment organized through national or foreign enterprises and have had to face up to the trade-offs between national control and active mineral development. A change has since taken place in governmental policies. The 1981 Peruvian mining law, the 1982 mining law of Uruguay, the 1979/1980 mineral promotion laws of Argentina, all witness the gradual shifting of emphasis from restriction to promotion. The investment rules of the Andean Pact have been progressively softened through national regulation and today are more or less irrelevant. Nationalizations and forced renegotiations have not occurred in the last few years. Countries have gone to great lengths (without much success) to re-attract foreign investment on terms that accommodate the political sensitivities of the South American countries and the practical requirements of investors and financiers. For this analysis, three contracts have been selected which reflect this accommodation in three South American countries, where miner a1 production plays a major role in the national economy. These con tracts reflect both the attitudes and traditions of the individual countries, but also mark the shift in mineral investment policies that has taken place. EL INDIO AGREEMENT The 1977 investment agreement between Chile and St. Joe Minerals marked a dramatic relationship between Chile and foreign mining investor s. In Chile, mining of copper has played a major role in the country's history. Large scale copper mining was initiated and developed by Kennecott and Anaconda. The nationalization of these two companies under the Allende government in July 1971 started a wave of nationalizations of foreign-held mining and petroleum operations since then in many parts of the world. The military government supported the new Chilean state mining companies ((30DELCO and ENMI) , but it also attempted to accelerate mineral development by prom ting foreign private investment, thus reversing the nationalistic policies followed by the Allende and the preceding Frei government. The new policy by the military government is expressed in Decreto-Ley 600 (1974) which governs foreign investment in Chile. Decreto-Ley 600 is

Jan 1, 1985

By Blake M. Caldwell, Thomas C. Poulter

A new approach to an old problem has made it possible to do in a a tively short period what has not been accomplished in the past three quarters of a century using strictly experimental methods. A theoretical study was made of the underlying principles whereby a jet is formed by a shaped charge and of the mechanism of the penetration of the target by that jet. It was found that there are more than 10, and perhaps as many as 15 variables affectin!? the performance of the shaped charge. Only a few calculations are necessary to show that it is physically impossible to investigate all of these variables experimentally. The shaped charge theory has been extended to include a previously little-understood mechanism in high explosive phenomena; namely, low order detonation. By superimposing a high order detonation on a zone already undergoing low order detonation, all appreciable improvement in performance is accomplished. The development of a design wherehy these phenomena are coordinated in such a way as to develop a jet which is tailored to meet the specific target requirement will be described in detail. The shortcomings or even impossibility of strictly experimental techniques will be illustrated by a discussion of the development of a special-purpose explosive charge. INTRODUCTION In an article appearing in the May, 1888 issue of Scribner's Magazine, Charles E. Monroe described his early experiments with gun cotton (Fig. 1) which led to his name being most fre-quently connected with our present-day shaped charge. Although the sunken letters or "cavities" in Mon- roe's gun cotton were not lined, they produced some penetration of an iron plate. The credit for the lined shaped charge, however, should rightfully go to Dr. R. W. Wood of the Physics Dept. of Johns Hopkins University, who was responsible for first discovering the fact that a metal liner in a cavity of explosive gave high velocity fragments and/or jets of metal. This discovery was made by Dr. Wood inadvertently while investigating an accidental death resulting from an electric blasting cap. He discovered that a jet of high velocity copper particles was ejected from the dimple

Jan 1, 1958

By Arthur F. Wendt

In the manufacture of charcoal-blooms, washing or cleansing of the ore from adhering gangue has been practiced for many years. A sluice-box is even to-day used for that purpose in the Southern Appalachian Mountains. For the Lake Champlain bloomaries hard magnetic ores are crushed with stamps and then sluiced or jigged in hand-jigs. The stamps used in the Lake Champlain region are of the most primitive kind. They consist of a trip-hammer, dropping on a perforated cast-iron plate, through which the crushed ore escapes. Only friable rock can thus be successfully treated. To render the raw ore friable, a calcining or burning in piles on a bed of cordwood is resorted to. An expense of 35 cents per ton of crude rock treated is thus incurred. The crushed ore is shovelled or otherwise fed into jigs without previous sizing, except such as is incidental to crushing through the perforated bottom of the stamping-machine. In jigging this ore, it is allowed to pass through the bedding into the "hutch." The tailings are scraped off and wasted. They contain a large percentage of fine ore. In many instances, this is regained by subsequent sluicing. Such was the condition of the industry, when the writer's attention was first called to it in 1882. No attempt had been made to introduce into thiS branch of ore-dressing the notable improvements adopted in concentrating the ores of other metals. The result of the writer's investigations was the building in 1882 of the "Crown Point Separator." At the Crown Point Mines, N. Y., lean ore unfit for the blastfurnace (containing less than 331/3 per cent. of iron), was concentrated and used in the bloomary connected with the mines. The ore was burned here as elsewhere, and treated as described. The plant designed by the writer for Crown Point, is nearly a counterpart of that since erected by Messrs. Copeland and Bacon, contractors, for the Theal mine, Putnam County, New York, which is illustrated by the accompanying plate. The only difference is in

Jan 1, 1885

THE Institute assembled on Tuesday evening, October 24th, in the hall of the Franklin Institute, Mr. Frank Firmstone, Vice-President, in the chair. Mr.. J. Price Wetherill, of Tremont, Pa., read a paper on An Outline of Anthracite Coal Mining in Schuylkill County, Pa. The paper was discussed by Messrs. Coxe, Rothwell, Heinrich, Harden, and Symons. The second session was held on Thursday evening. Mr. A. L. Holley, Chairman of the International Committee, appointed by the Institute to consider the nomenclature of iron and steel, offered the following report of the committee, signed by all the members: WHEREAS, The recent production of soft, cast, malleable compounds of iron by the Bessemer, the Siemens-Martin, and the crucible steel processes appears to demand a new nomenclature of iron compounds, for the following reasons : 1st. The term "steel," by which these soft products are commercially and professionally designated in England and in the United States, does not completely distinguish them from previously existing "steel" which would harden and temper. 2d. A nomenclature recognized in all languages seems desirable, as well for commercial as for scientific purposes, especially as lawsuits, already commenced, depend on the meaning of the term "steel." 3d. Although homogeneity, due to fusion, is usually recognized, and is by this committee recognized as the most definite characteristic of both bard and soft steel, this quality may be equally well expressed in other terms, thus leaving the old term, "steel," to define the malleable compounds of iron, which will harden and temper. Therefore, resolved, That this committee recommends the following nomenclature : 1. That all malleable compounds of iron with its ordinary ingredients, which are aggregated from pasty masses, or from piles, or from any forms of iron not in a fluid state, and which will not sensibly harden and temper, and which generally resemble what is called " wrought iron," shall be called WELD IRON (German, Sehweisseisen; French, fer soudé) 2. That such compounds, when they will from any cause harden and temper, and which resemble what is now called "puddled steel," shall be called WELD STEEL (German, Schweiss stahl; French, acier soudé).

Jan 1, 1877

THE Johnson award for 1926 was given to T. L. Joseph for his experimental work on blast-furnace operation. When the Bureau of Mines undertook its experimental blast-furnace investigation in 1919, a number of operators and metallurgists were doubtful as to the practicability of small-scale tests. Several pre-vious attempts, outside the Bureau, to operate small furnaces had been unsuccessful. However, pig iron was produced in three and four-ton furnaces during the first half of the nineteenth century. The operation of a small furnace did not therefore seem an impossible task. This point of view, together with a realization of the importance of problems connected with the pro-duction of pig iron, prompted the Bureau to undertake this work. Such problems as the feasibility of using charcoal briquets as a fuel, the application of oxygen enriched blast, and the use of new ores and raw ma-terials, in general, can be investigated only at consider-able cost on full sized furnaces, while with an experimental furnace they can be conducted at a com-paratively ;small, cost. The results of small-scale tests are sufficient to determine whether the problem. War-rants the expenditure required for a trial on a com-mercial scale. The accompanying photographs and chart show the various stages of the experimental furnace development. Some idea of the size and shape of furnaces which were tested can be had from the development chart. In oper-ating furnaces A to F, a series of changes were made to increase hearth temperature. Perhaps the most im-portant change was the position of the tuyeres with respect to the bottom of the hearth. The height of the tuyeres above the hearth was gradually increased and the hearth diameter decreased. It was shown by this series of furnaces that metal and slag are the chief source of heat supply to the crucible. For this reason there is a minimum rate at which these materials can be brought into the hearth of a small furnace if it is to function properly. The rate of slag "and metal fall are determined by the burden on the furnace and the rate of blowing. Due to lack of funds necessary to provide ample blowing equipment, hot blast stoves, essential mechani-cal features, and to meet operating expenses, it. was necessary to work with much smaller furnaces, such as G to K shown in the chart. The particular object of these tests was to study the extent to which reactions could be speeded up by decreasing the size of the stock. One decided change, noticed at the beginning of this series of tests, was the effect which coke size had on the production of a strongly reducing gas. Furnace G, 22 in. high, operating on coke crushed to pass 10 mesh, made a gas richer in carbon monoxide than did fur-naces A to F, operating on run-of-the-oven coke.

Jan 3, 1927

By Francois Clerf

IRON ORE fields are situated in both the East and West of France (see maps). The eastern deposit is by far the most important from a tonnage point of view, not only in France, but in all Europe. The ores of this region are known as minette, and are situated in the Lorraine ore fields and the Briey plateau. The iron ores of the West are those of Normandy, Anjou and Brittany. Before the war, a large number of important German companies had acquired considerable interests in these western fields and a heavy trade with Westphalia had begun. Recently, however, conditions have changed and some of the mines of Brittany and Anjou are now idle. From a geological point of view, in Anjou and Brittany, a series of synclines extends from the northwest to the southeast, containing a number of seams of varying thickness and generally intercalated in Silurian and sometimes in Devonian formations. The ore is generally a hematite or a magnetite. The composition varies from 48 to 52 per cent of iron and from 8 to 12 per cent of silica. Con¬servative estimates indicate a con¬siderable tonnage of workable ores (150,000,000 metric tons).

Jan 1, 1936

By H. Foster Bain

FROM time to time geologists and mining engineers, impressed by the heavy demands made on our mineral reserves' by modern industry, and particularly by the steadily mounting rate of production necessary to meet that demand, have issued warnings as to the danger of exhaustion. There can be no dispute as to the fact that mineral deposits are exhaustible. New mineral, is not created to replace that taken from the earth and when a crop of mineral is once harvested another cannot be grown in the same area. The evidence of exhaustion 'of particular oreshoots, deposits, or even of whole districts is familiar to all who have mined. If one were to judge solely from the abandoned mills and prospect holes he would rightly conclude that mining is but a short-lived industry. If one were, furthermore, to assemble the data as to known reserves of almost any of the commonly used minerals, and divide them by the annual tonnage mined, he would come to the same conclusion. If, again, one were to consider the most carefully made estimates of competent men seeking to measure the earth's reserves of minerals and plot against them a projection of the curve of past consumption, he would be justified in viewing the situation with alarm.

Jan 1, 1930

By S. Arthur Krom

(New York Meeting, February, 1912.) THE James diagonal-plane slimer is specially adapted to handle the finest slimes, but it will also handle sands as coarse as 40-mesh. The saving efficiency of this machine is due to the original construction of the deck, and to the rapid reciprocating movement imparted to it by the head-motion. The deck consists of a plurality of connected planes, having a certain fixed ratio of inclination one to another. These planes intersect each other diagonally to the stroke-line of the table and are arranged so as to give the pulp on the table a double treatment. This double concentration performed by the diagonal-plane deck produces cleaner concentrates and tailings than those obtained by the operation of two separate machines. The action of the diagonal planes settles, combines, and holds all the concentrates in one compact mass, sharply defined from the gangue, and easily cut away without loss. Many slime-concentrating machines distribute the feed-pulp for a distance of 4 or 5 ft. only, and upon a very limited settling-surface. This results in a thick, heavy deposit, from which it is impossible to stratify the values and wash, away the gangue, the resulting products being dirty concentrates, and tailings carrying high values. The diagonal-plane slimer distributes the feed-pulp for a distance of 10 ft., and upon a settling-surface having an area of 40 sq. ft.; in other words, it spreads the pulp thinly on the table, which allows the metallic values to settle through the gangue quickly, forming a bottom stratum from which the thinly-distributed overlying stratum. of gangue is easily brushed away by the feed-water without disturbing the underlying concentrates. Referring to Fig. 1, plane A is the main settling-section, of the table. The feed pulp flows gently down this plane and is

Jun 1, 1912

By Persifor Frazer

During the Centennial year some of our leading geologists in the United States and Canada conceived the happy thought of calling an International Congress of Geologists for the purpose of agreeing upon such important though subsidiary matters as the colors by means of which the different geological formations should be expressed ; the terms that should be applied respectively to these formations; and also upon the far more important problem of the limits and values of these different formations. The first session of this Congress was held in Paris in 1878, the second session in Bologna in 1881, and the third session in Berlin in 1884. The third session found the preliminary difficulties so far cleared away that some definite and tangible results could be attained. After a great deal of free discussion had taken place at Paris and Bologna, during which every one's views were listened to with attention; and a great deal more painstaking scientific work had been accomplished by the International Committees, having before them the objects of unifying the nomenclature of the science, and of preparing a scheme of colors between the second and third sessions of the Congress; and after the provisional results had been subjected to a searching criticism by the Congress in Berlin; it was decided to make an attempt to embody these provisional results in some work which should include as many as possible of the difficulties to

Jan 1, 1887

By Charles MacDowell

Up to 1909 the American public had little knowledge of, or interest in, potash. Some remembered that it had to do with soft soap and sore throat, but further they knew not. In 1909-10, the German-American potash war, and the publicity attending hostilities, brought home to America the knowledge that potash was an important article of commerce; that Germany monopolized its production and distribution, and exercised all the prerogatives attending complete control. The present war, with its transportation embargo, has again directed attention to Germany's strength as a potash producer and her present unfortunate situation as a distributor. As a consequence, the search for potash takes on new life and it again becomes a subject of general interest. My first knowledge of potash came from a study of the German potash exhibit at the World's Fair in 1893. This investigation led to the recommendation that Armour & Co. engage in the manufacture of commercial fertilizers and the fertilizer branch was organized early in 1894. From then to now "potash" has been a live subject. Two and eight-tenths per cent. of the earth's crust consists of potassium oxide. It is an important constituent of feldspar, granite, and other igneous rocks. Potash is valuable commercially in a water-soluble form. In igneous rocks it is locked in so tight that it is of little value and no utilization in a commercial way has been made of these insoluble forms. Potash in water-soluble form is found in large deposits in Germany; in smaller deposits in Austria and Spain; and in brines in some of our Western arid basins. The deposits in Germany, Austria, and Spain are concentrations from sea waters containing potash derived from the decomposition of potash-bearing rocks.

Jan 2, 1915

By W. B. Lilienthal, J. C. Melrose

The application of Bingham's law to the behavior of drilling fluids in a rotational viscometer permits the expression of viscometric data in terms of plastic viscosity and yield value, the flow properties of a plastic fluid. A commercially available rotational viscometer is described, and when modified to a multispeed type viscometer, is shown to provide a simple and convenient instrument for the measurement of these properties both in the laboratory and in the field. The data obtained are shown to be useful in defining and understanding mud control problems relating to chemical treatment and to the hydro-dynamic behavior of muds. INTRODUCTION The highly complex drilling fluids which are required for deep drilling often give rise to new and unusual mud control problems. Rapid and economic solutions to these problems may require, on the one hand, better understanding of the changes which contaminants and chemical treating agents produce in the colloidal and inert solids of the mud, or, on the other hand, closer control of the hydrodynamic behavior of the mud. The latter objective obviously can be achieved only if a correct rheological analysis of the flow behavior of drilling muds is available and if this is accompanied by the appropriate rheological measurements. The purpose of this paper is to describe such measurements in the field, and to show how the resulting data can be of value in solving difficult mud control problems. It is now generally recognized that Bingham's law of plastic flow can be utilized in describing the hydrodynamic behavior of drilling fluids in the non-turbulent flow range. Beck, Nuss, and Dunn' have recently applied this law to the flow of mud in small pipes, and Rogers2 has reviewed the rather extensive literature on this subject. So far, however, the use of Bingham's law has been restricted to the analysis of mud flow in pipes or capillary tubes, and it has not been directly applied to the flow in rotational viscometers. In the work to be reprted, the Reiner-Riwlin3 equation for the flow of a plastic fluid in a rotational viscometer has been utilized to permit the expression of multispeed viscometric data in terms of plastic viscosity and yield value. the two absolute flow properties of a plastic fluid. With regard to the application of these measurements, the calculation of the relationship between pumping rate and pressure drop, both in the drill pipe and annular space, has long been a subject of interest. Beck, Nuss, and Dunn,' following Caldwell and Babbitt: base their calculations for non-turbulent flow on Buckingham's integration of Bingham's law for pipe flow and measurements of the plastic viscosity (rigidity in their terminology) and yield value. In the case of turbulent flow, Fanning's equation is employed, and the pressure drop is relatively insensitive to the flow properties of the mud. Since flow in the drill pipe is likely to be turbulent at usual circulation rates, the plastic flow properties will chiefly influence the pressure drop in the annular space. As pointed out by Beck,' the control of this component of the total pressure drop may be of special importance where lost circulation problems are encountered. Other hydrodynamic problems to which it should be possible to apply measurements of the plastic flow properties include predictions of the velocity distribution in non-turbulent flow and the critical velocity for transition to turbulence. Plastic viscosity and yield value. as abmlute flow propertie.;, will reflect the colloidal or surface-active behavior of the solids present in drilling fluids. Measurements of these properties should therefore find application in developing a better understanding of such behavior and in characterizing the type and condition of these solids. Garrison and ten Brink have utilized multispeed viscometric data in this manner. although their measurements were not expressed in terms of the absolute flow properties. In connection with the application of these measurements, it should be recognized that the presently used one-point viscosity measurements are relative in nature. The API Stormer 600-rpm measurement, for example. is a function of both plastic viscosity and yield value, as well as mud weight, and will often be misleading when its application to mud control problems is attempted. NOMENCLATURE, UNITS, AND DEFINITIONS In Fig. 1 an idealized plot is given of the flow variables involved in any viscometric measurement. It is seen that the flow behavior of plastic fluids is characterized by two constants — plastic viscosity, µp, and yield value, F. Other workers hate used the term rigidity for plastic viscosity or the term mobility for its reciprocal. The term plastic viscosity, however, emphasizes the close relation this property bears to the viscosity of a true fluid and is expressed in the familiar viscosity units of centipoises. The yield value is expressed in lbs/100 sq ft, the units adopted for gel strength measurements with the APT shearometer. Definitions of these properties based on rheological or macrc)scopic flow considerations follow from Fig. 1. The plastic viscosity of a substance obeying Bingham's equation is defined

Jan 1, 1951

By J. C. Melrose, W. B. Lilienthal

The application of Bingham's law to the behavior of drilling fluids in a rotational viscometer permits the expression of viscometric data in terms of plastic viscosity and yield value, the flow properties of a plastic fluid. A commercially available rotational viscometer is described, and when modified to a multispeed type viscometer, is shown to provide a simple and convenient instrument for the measurement of these properties both in the laboratory and in the field. The data obtained are shown to be useful in defining and understanding mud control problems relating to chemical treatment and to the hydro-dynamic behavior of muds. INTRODUCTION The highly complex drilling fluids which are required for deep drilling often give rise to new and unusual mud control problems. Rapid and economic solutions to these problems may require, on the one hand, better understanding of the changes which contaminants and chemical treating agents produce in the colloidal and inert solids of the mud, or, on the other hand, closer control of the hydrodynamic behavior of the mud. The latter objective obviously can be achieved only if a correct rheological analysis of the flow behavior of drilling muds is available and if this is accompanied by the appropriate rheological measurements. The purpose of this paper is to describe such measurements in the field, and to show how the resulting data can be of value in solving difficult mud control problems. It is now generally recognized that Bingham's law of plastic flow can be utilized in describing the hydrodynamic behavior of drilling fluids in the non-turbulent flow range. Beck, Nuss, and Dunn' have recently applied this law to the flow of mud in small pipes, and Rogers2 has reviewed the rather extensive literature on this subject. So far, however, the use of Bingham's law has been restricted to the analysis of mud flow in pipes or capillary tubes, and it has not been directly applied to the flow in rotational viscometers. In the work to be reprted, the Reiner-Riwlin3 equation for the flow of a plastic fluid in a rotational viscometer has been utilized to permit the expression of multispeed viscometric data in terms of plastic viscosity and yield value. the two absolute flow properties of a plastic fluid. With regard to the application of these measurements, the calculation of the relationship between pumping rate and pressure drop, both in the drill pipe and annular space, has long been a subject of interest. Beck, Nuss, and Dunn,' following Caldwell and Babbitt: base their calculations for non-turbulent flow on Buckingham's integration of Bingham's law for pipe flow and measurements of the plastic viscosity (rigidity in their terminology) and yield value. In the case of turbulent flow, Fanning's equation is employed, and the pressure drop is relatively insensitive to the flow properties of the mud. Since flow in the drill pipe is likely to be turbulent at usual circulation rates, the plastic flow properties will chiefly influence the pressure drop in the annular space. As pointed out by Beck,' the control of this component of the total pressure drop may be of special importance where lost circulation problems are encountered. Other hydrodynamic problems to which it should be possible to apply measurements of the plastic flow properties include predictions of the velocity distribution in non-turbulent flow and the critical velocity for transition to turbulence. Plastic viscosity and yield value. as abmlute flow propertie.;, will reflect the colloidal or surface-active behavior of the solids present in drilling fluids. Measurements of these properties should therefore find application in developing a better understanding of such behavior and in characterizing the type and condition of these solids. Garrison and ten Brink have utilized multispeed viscometric data in this manner. although their measurements were not expressed in terms of the absolute flow properties. In connection with the application of these measurements, it should be recognized that the presently used one-point viscosity measurements are relative in nature. The API Stormer 600-rpm measurement, for example. is a function of both plastic viscosity and yield value, as well as mud weight, and will often be misleading when its application to mud control problems is attempted. NOMENCLATURE, UNITS, AND DEFINITIONS In Fig. 1 an idealized plot is given of the flow variables involved in any viscometric measurement. It is seen that the flow behavior of plastic fluids is characterized by two constants — plastic viscosity, µp, and yield value, F. Other workers hate used the term rigidity for plastic viscosity or the term mobility for its reciprocal. The term plastic viscosity, however, emphasizes the close relation this property bears to the viscosity of a true fluid and is expressed in the familiar viscosity units of centipoises. The yield value is expressed in lbs/100 sq ft, the units adopted for gel strength measurements with the APT shearometer. Definitions of these properties based on rheological or macrc)scopic flow considerations follow from Fig. 1. The plastic viscosity of a substance obeying Bingham's equation is defined

Jan 1, 1951

By Ronald D. Irving

The object of the present paper is to give an outline account of the mineral resources of the State of Wisconsin, so far as they are now known, including both metallic ores and non-metallic useful mineral substances. Tl~e only previous publication making ally attempt at such an account is one of a popular nature, prepared by the writer for Snyder and Van Vechten7s Historicccl Atlas of Wisconsin, which was published at Milwaukee in 1878. The data upon which the statements of the following pages are based are chiefly from the

Jan 1, 1880

By N. Cabrera

IN a recent paper Kuczynski' studied the rate at which the crack between a metallic plane and a spherical particle of the same material is filled up gradually when heated at temperatures near the melting point. If x is the radius of contact between plane and sphere (fig. I), Kuczynski shows experimentally that x5 = At [1] where t is the time. Assuming that the mechanism of transport of matter is the volume diffusion of vacant lattice sites, he is also able to prove Eq 1 theoretically. The constant A contains as a factor the self-diffusion coefficient of the metal and he shows that the values for this coefficient deduced from his experiments yield the same activation energy as that calculated by other methods, which is a confirmation of this point of view. Kuczynski has also considered theoretically the law of growth of x which would be expected if surface diffusion were the important mechanism. He suggests that x should then obey a law of the form x7 = At, and claims to be able to decide the mechanism involved from the observed law of growth., The purpose of this note is to prove this incorrect. On the contrary, when the mechanism is surface diffusion Eq 1 is also obeyed, but with a different constant A. Following Kuczynski, we suppose the bottom of the crack (surface A A) to have an average radius of curvature p. As a result of this curvature the concentration of adsorbed atoms in this surface, n(p) per cm2, will be smaller, and the concentration of vacant lattice sites in the neighborhood, N(p) per cm3, will be larger than the corresponding concentrations, n(w) and N(w), for a flat surface. For all practical cases we can write Thomson's formula in the form n(co)— n(P) N(P)—N(cc) _ 2a-a" n(oo) JV(co) kTp [2] where u is the surface energy of the metal and a the interatomic distance. 1. Let us now consider the mechanism of surface diffusion. We suppose the concentration of ad-

Jan 1, 1951

By R. R. Sayers

TWO serious hazards from coal dust confront the bituminous-coal miner- -a physical or safety hazard and a physiological or health hazard. The first threatens the miner with loss of life from coal-dint explosions, and the second with loss of health and earning capacity from inhaling large quantities of the dust. Studies by the Bureau of Mines have shown that coal dust, except some grades of anthracite dust, is capable of initiating an explosion when no explosive gas is present and that its property of extending or propagating an explosion has been responsible for nearly all the widespread explosions that have occurred in bituminous mines in the United States in the present century. For years many mining people believed that low-volatile coal dust was not explosive but not only is it explosive but if the source of ignition is intense, it is as explosive as the dust of many high-volatile coals because the war is creating increased pressure for greater coal production and because of the trend toward greater mechanization in mines, explosion and health hazards from coal dust are likely !n increase considerably.

Jan 1, 1943

By R. C. Ku, A. J. McEvily, T. L. Johnston

The microplastic response of a series ofas-quenched Fe-Ni-C martensites has been measured at 77°K. At strains less than JO'3 the flow stress is governed primarily by the transformation-induced dislocation structure of the martensite. Only at strains in excess of 10-3 is the influence of carbon manifested in the flow stress. At these macroscopic strains, typically 10-2, the solid-solution hardening is proportional to (wt pct C)1/3, and, in an alloy containing 0.39 wt pct C, amounts to 50 pct of the flow stress. THE technological significance of high-strength ferrous martensite has stimulated many investigations of its structure and properties. Although our knowledge of the characteristics of martensite has increased immensely, especially with the advent of high-resolution techniques, an understanding of the basic strengthening mechanism still remains elusive. The purpose of the present paper is to consider certain aspects of micro-plastic behavior of Fe-Ni-C martensite which we feel can help to resolve this important problem. Such alloys are particularly suitable for experimental investigation because their compositions can be adjusted to reduce the M, to a temperature low enough essentially to eliminate the diffusion of carbon in the freshly formed martensite.1 The mechanical properties in this condition are of interest inasmuch as they reflect a state that is free of the important but complicating influence of precipitation processes. In this virgin martensite the carbon is distributed as it was inherited from the parent austenite; i.e., it is present interstitially, and gives rise to tetragonality through strain-induced ordering.' In order to determine the source of strength of such alloys, Winchell and Cohen1 investigated the low-temperature macroscopic stress-strain behavior of a series of virgin martensites of increasing carbon content but of common M, temperature (-35°C). They found that the flow stress increased rapidly with carbon content up to 0.4 wt pct; beyond this point the flow stress increased at a much slower rate. It was concluded that martensite is inherently strong. To account quantitatively for the strength of virgin or as- quenched martensite in terms of the role of carbon, Winchell and cohen3 suggested that the carbon atoms, trapped in their original positions by the diffusionless martensite transformation, interfere with dislocation motion according to a model akin to that of Mott and Nabarro. 4 In this treatment, individual carbon atoms are considered to constitute centers of elastic strain and thereby generate an average stress resisting the motion of dislocations throughout the lattice. The additional stress necessary to move dislocations, over and above that necessary for motion in a carbon-free martensite, is given by where L is an effective length of dislocation capable of motion. L was assumed to be limited to the spacing between the twins that are an essential structural element of Fe-Ni-C martensites. They assumtd the spacing to be invariant and of the order of 100A. However, recent work5 has shown that L is variable and can be in excess of 1000Å, so that the assignment of an appropriate value of L is not straightforward. In contrast to the above conclusion that there is an intrinsically high resistance to plastic flow, it has been suggested by Polakowski6 that freshly quenched martensite is in fact "soft" in the sense that dislocations are initially free to move upon application of stress. The high indentation hardness and macroscopic yield stress of ferrous martensites are then a consequence of rapid strain hardening that depends upon carbon in solution. Consistent with this point of view are the results of Beau lieu and Dubé who measured the rate of recovery of internal friction as a function of aging (tempering) temperature in a freshly quenched steel containing 0.90 wt pct C, 0.37 wt pct Mn, 0.1 wt pct Cr, and 0.07 wt pct Ni. The kinetics were clearly consistent with the idea that many dislocations are unpinned in the as-quenched state and that during aging they become progressively pinned by carbon at a rate controlled by carbon diffusion in the body-centered martensite lattice. In order to provide a basis upon which to distinguish between the "hard" and "soft" interpretations indicated above, we have made studies of the initial stages of plastic deformation in Fe-Ni-C martensites similar to those'used by Winchell and Cohen. It will be shown that the results support the contention that dislocation segments in as-quenched material are indeed

Jan 1, 1967

By B. O. Pickard

With more than a score of shafts and numerous stope openings to the surface, all inter-connected underground; with underground temperatures high, often exceeding 100' wet bulb; with an ore presenting a dust health-hazard; with certain rocks giving off inert gases; with an altitude of 6000 ft. above the sea level and a dry desert climate, the Tonopah mines offered an interesting problem to the student of metal-line ventilation. Tonopah is not an old mining district, relatively speaking. It was discovered in 1900 and Tonopah soon was a boom camp. Ry 1910 the mines of this district had paid many millions of dollars in dividends. At the time of the 1921 ventilation study, mining had passed its peak of production and the operators were striving to reduce costs, to discover new orebodies, and to attract desirable workmen. In 1925, the camp was operating on a still less prosperous basis, but the several managements had not relaxed in their efforts to keep the mines on a paying basis, neither had they lost their faith in the ability of the mines and the price of the silver to "come back." Early in the fall of 1921 the Bureau of Mines was invited by the mine operators at Tonopah, Nev., to make a detailed study of the underground air conditions in the Tonopah silver district. D. Harrington, chief engineer of the Safety Service Division of the Bureau, who was then directly supervising the ventilation studies, detailed district engineer B. 0. Pickard, mining engineer E. D. Gardner, surgeon C. E. Kindall, and petrographer IT. Insley to carry on the study. G. S. Rice, as chief mining engineer of the Bureau of Mines, was in general charge of the work. Upon the completion of the study each operator was furnished a report on conditions in his mine. In 1925, a supplemental study at Tonopah was made by the district engineer at the request of several of the operators, and each operator advised on the changes in his respective air conditions and recommendations for improvements. Recently, several of the operators gave the

Jan 1, 1927