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By William L. Fink, Dana W. Smith

In parts I1 and II2 of this series, there were presented results of investigations on the age-hardening of an aluminum-copper and an aluminum-magnesium alloy. It was shown that the simple precipitation theory of hardening3 adequately explained the aging phenomena, including certain so-called "anomalous" behaviors which had caused other investigators to reject or modify the precipitation theory. However, these papers did not discuss the double aging peaks, which have been stressed in recent articles by Dr. M. Cohen4 and Dr. M. L. V. Gayler.6 The present paper is devoted to an explanation of this "anomaly." Fig. 1 is a generalized schematic representation of aging curves at different temperatures. Curve A corresponds to the aging at the lowest temperature, and D at the highest temperature. Certain previous investigators have explained curve A and the initial peaks

Jan 1, 1938

Jan 1, 1967

By H. R. Peiffer

The increase in electrical resistivity, ?pT,at 78°K was measured as a function of elongation, E, at 78°K for a 2 pct (approximately) by weight finely divided alumina in silver material. The amount of increase in electrical resistivity (?pT) is a function of the amount of alumina present and can be represented by: ?pT = cen where c and n are constants. The constant c increases and the exponent n decreases with increasing alumina content. Approximately 33 pct of the resistivity increase is recovered upon annealing at room temperature. RECENTLY, dispersed phase alloys' have shown promise for use at elevated temperatures. These materials have a high creep resistance, a high-temperature strength considerably above that of the pure matrix, and a high electrical conductivity. These materials also show other properties such as retardation of re crystallization and resistance to flow even above the melting point of the matrix.' It is believed that high-temperature creep is retarded in these materials because the dispersed phase blocks the motion of dislocations. According to schoeck3 and also Weertman,4 the rate controlling process is the climb of dislocations around the dispersed phase particles. Any mechanical property of these materials, or any other material for that matter, can be explained on the basis of defect structures and their interrelations. It would certainly be interesting to learn something about the effect of a dispersed phase on dislocation densities and also their effect on point defect concentrations following cold work. This is the purpose of the research discussed herein. The method used was the measurement of the electrical resistivity as a function of elongation at low temperatures. This scheme has already been applied to the studies of pure metals.5 Electrical resistivity measurements conducted on pure metals such as copper, silver, gold, and so forth, have indicated that defects such as vacancies and dislocations are formed during deformation.5 It has been shown by van Bueren6 that the resistivity change, ?p, should increase with elongation, E, according to the following relation: Ap=Al/2 + B£3/2 where A and B are constants of the system; ?p is in µ? cm. The first term refers to the amount of resistivity change associated with line defects and the second term with the change associated with point defects. A later calculation yielded exponents of 3/4 and 5/4, respectively.6 Manintveld7 has shown that the resistivity of copper increases with strain according to a 3/2 power law, whereas van Bueren has shown that the resistivity of silver increases according to a 5/4 power law. Assuming then that van Bueren's calculations are correct, it appears that line defects contribute very little to the electrical resistivity. There is some doubt, however, as to the validity of van Bueren's expressions for all cubic metals.' In fact, the data on copper and silver are not conclusive. In this in-

Jan 1, 1962

By J. B. Austin

IT is now well established, chiefly through the work of Davenport and Bain,1 that the influence of temperature upon the rate of transformation of austenite to ferrite at constant temperature is represented by a curve of the type shown in Fig. 5 of Tech. Pub. 589; and the reasons for this general shape have been discussed by them in a qualitative way. Thus, the upper part, or nose, of the curve is the resultant of two factors of which the rate of change with temperature is not the same, and by analogy with other like cases it is almost certain that these factors are: (1) the chemical potential, or driving force, of the transformation, which is zero at the equilibrium temperature and increases rapidly as the temperature falls below this point; and (2) a factor analogous to viscosity, or resistance of the crystal lattice to a change in structure, which also increases as the temperature is lowered. Just below the equilibrium temperature this virtual "viscosity" of the metal is relatively low-that is, the metal offers little resistance to a change in lattice-but the driving force is also small, and the net result is that the reaction proceeds slowly. As the temperature is lowered the magnitude of both factors increases; but at first the driving force increases more rapidly than the resistance and the reaction is observed to proceed more rapidly. At lower temperatures, however, the resistance begins to increase faster than the driving force, and eventually, at the nose of the curve, overbalances it, causing the reaction to proceed more and more slowly thereafter. This concept is somewhat, though not completely, analogous to that employed in certain electrical cases where the precise factors are known and are separately measurable. The current I (in amperes or coulombs per second) flowing through a given wire is proportional to the impressed potential, or driving force E, and is inversely proportional to the resistance R of the wire; that is, I = E/R. Stated in a slightly different way,

Jan 1, 1935

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By Harold L. Bare, Frank R. Barnako

Coal mining historically has been a hazardous occupation but, in recent years, tremendous progress has been made in reducing accidental coal mine deaths and injuries. The purpose of this chapter is to discuss the basic principles of accident prevention as they are related to coal mining. Accident prevention fundamentals are no different for coal mining than for any other type of work. The fundamentals apply to all industries. Construction workers may be struck by falling tools and materials, and miners may be struck by falling slate and coal. Sailors may be trapped by shipboard fires, and miners may be trapped by mine fires. Railroad brakemen may lose hands and fingers positioning couplers, and miners may lose hands and fingers positioning couplers. Many other examples could be cited, but the point is that accidents that happen in coal mines are basically similar to accidents that happen in other industries. Thus, the basic principles for preventing accidents apply in coal mining as they do in any other type of work. COAL MINE ACCIDENT EXPERIENCE The US Mine Safety and Health Administration (MSHA) is the main source for accident experience data in coal mines. Coal mine operators are required, by law, to forward to MSHA monthly the number of fatal and disabling injuries, man-hours worked, and tons of coal mined. This information is compiled and published quarterly, with annual summaries, by MSHA. Trends in the number of fatalities and fatal injury rates are shown in Fig. 1. Major coal mine disasters, with number of miners killed, and dates of coal mine safety legislation are shown in Table 1. The fatal and disabling injury frequency rates for the coal industry are shown in Fig. 2.

Jan 1, 1981

By T. A. Wright

THE SAMPLING of waste materials containing copper, lead and tin has taken on a new significance within recent years, and is of increasing importance, on account of the entry of some of the copper refineries into this field and the tendency towards consolidations among the smelters. In the past, such material was sold on the basis either of a rough or grab sample or of casual inspection of the lot. The two principal sources of this waste are the processes of fabrication and the scrapping of automobile, electrical, plumbing, railroad and other equipment. In both cases much material can be sorted, salvaged and sold by classification and grade to be melted "as is" or with the addition of new or virgin metal. The increasing care in classifying exercised in the large manufacturing plants tends to increase the proportion of this usable scrap; on the contrary, the increasing use of more complex and special non-ferrous alloys tends to make sorting and grading more difficult in turnings, borings, clippings, etc., and consequently is making sampling of more moment. In tin, lead, aluminum, and zinc furnace by-products such as ashes, drosses, skimmings, etc., the trade practice of evaluation has not varied much. For instance, tin drosses, battery lead, and aluminum skimmings are ordinarily sold on what is called "metallic button" or "metallic recovery" or "metallic yield." Copper and lead waste, however, is being sold more and more on actual copper and lead contents based on sample and chemical analyses. This paper will be devoted chiefly to the sampling of materials suitable only for refining and recovery of one or more of the metals present. The methods described are often based on the fact that but one metal, such as copper, is to be paid for. The loss of volatile constituents in melting does not appreciably affect the final copper result, as the "after-melting" assay can be readily calculated to the "before-melting" basis, but if smelter efficiency continues to increase, so that in time zinc, for instance, may be recovered on a paying basis, the method of sampling dirty brass, for example, will have to be changed also.

Jan 1, 1928

By C. W. Goodale

I. INTRODUCTION. In the summer of 1909 the Boston & Montana reduction department of the Anaconda Copper Mining Co. completed a new flue system, at a cost of about $1,100,000, and -is this includes the largest and highest chimney in the world, and some new features of flue construction, a description will be of interest. At the Spokane meeting of the Institute in September, 1909, a brief mention was made of this flue system, in discussing Mr. Brunton's presidential paper on the Progress of Metallurgy in the West, and a promise was given that when a long enough time had elapsed, so that operating results could be given, a paper would be offered. The smelting plant includes blast furnaces, MacDougall roasters, gas-fired reverberatories, and converters.

Jan 8, 1913

TO THE BOARD OF DIRECTORS, AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS: Gentlemen.-I have the honor to present the following report of the President for the year 1919. In order that this report may be printed and distributed to the members in advance of the February meeting, it is necessary that it end with the calendar year 1919. Any activities during the first six weeks of 1920 will be covered in the Secretary's report for the year 1920. VISITS TO MEMBERS Your President has visited each of the Local Sections of the Institute, with the exception of the ones at Washington, D. C., Tulsa, Okla., and the Nevada Section. These three sections have not arranged meetings at which the President could be present. In addition, your President, accompanied by President Jennings and Secretary Stoughton, in the year 1918, attended meetings of members in Minneapolis and Duluth, Minn., and Houghton, Mich. A dinner and meeting of the members in Pitts-burgh, Pa., was also attended, in company with the Secretary and your President also attended the meeting of Canadian Mining Institute in Montreal, in March, 1919.

Jan 2, 1920

By Eugene A. Smith

Geological Relations. In his second report upon the Geology of Alabama, Prof. M. Tuomey calls attention to a rock occurring near Florence, in the Tennessee valley, the composition of which is as follows: Per cent. Carbonate of lime,.. .. .. ..16.41 Phosphate of lime,.. .. .. ..14.19 Peroxide of iron,.. .. .. .. .36 Quartz and other insoluble matters,. .. ..68.72 99.68 This rock was referred by Prof. Tuomey to the Carboniferous, because he found the Carboniferous limestones always resting conformably upon it, whilst both rest uncomformably upon the underlying Silurian or Devonian rocks. The recent discovery in Tennessee of phosphate-rock of this age (or approximately so) has stimulated the search in Alabama for similar rich material; but our search has been, up to this time, unrewarded by the finding in quantity of anything of better quality than the rock whose analysis is given above. It is, however, in high degree probable .that the rich phosphaterock of Tennessee will at some time be found to have its counterpart in Alabama. Materials of several kinds, containing a notable quantity of phosphoric acid, have been found in Alabama in both the Cretaceous and the Tertiary formations, and for our present purpose they may be most conveniently considered in their geological relations.

Jan 1, 1896

By T&apos Ke, ing-sui

THE subject of recrystallization and grain growth has been much studied and the literature on this subject is numerous. Such studies have been mostly carried out by metallographic examination of X ray methods. Since recrystallization and grain growth involve elementary atomic processes, their mechanism can best be elucidated by a study of some properties which can be readily traced back in terms of such atomic processes. Prior to a detailed quantitative study, however, it is necessary to explore first the possibility and practicability of utilizing any particular property for obtaining the desired information. We have pointed out in a preceding article' that the internal friction of cold-worked metals is extremely high during recrystallization and it drops abru~tlv once the recrystallization is complete. ~reviois work has also shown that the viscosity of grain boundaries in a recrystallized specimen at a given temperature is raised by grain growth.' It seems thus that the measurements of internal friction may furnish a useful tool for the study of the mechanism of recrystallization and grain growth in terms of elementary atomic processes. The purpose of this paper is to report results of a study along this line. We will demonstrate that the internal friction method does give results in agreement with those furnished by conventional metallographic examinations. Once such a correlation has been established, we will be in a position to take further steps to achieve new information which cannot be achieved by conventional methods. The measurements of internal friction were made using apparatus and procedures similar to those used in the preceding article. All the measurements were made under such a small stress level that the internal friction is independent of stress level. The frequency of vibration is, unless mentioned otherwise, about one cycle per second in all cases. Internal Friction and Recrystallization Complete Recrystallization Temperature: Fig. 1 shows the internal friction curve during annealing of a few metals: aluminum, alpha brass and iron. These curves were determined in the following manner. In the curve for aluminum, internal friction measurements were performed upon. 99.991 aluminum subjected to 95 pct reduction area. The internal friction was first measured at room temperature. The specimen was then annealed at 50°C

Jan 1, 1951

By John Patek

KNOWLEDGE of the relative floatability of silicate minerals is increas-ing in importance as flotation is being applied to the concentration of nonsulfides. Many silicates are in themselves commercial products amenable to concentration by flotation. Moreover, the selective flota-tion of other nonsulfide minerals, such as cassiterite, depends largely upon the floatability of associated. gangue silicates. Differences in floatability existing between the various silicates have not been suffi-ciently appreciated; for example, the feldspars that differ greatly in floatability have generally been merely treated as "feldspar." It was the purpose of the work described in this paper to determine by experi-ment the differences in floatability between silicates; to investigate the causes for such differences, and to discover a means of predetermining approximate floatability without the necessity of experimentation.

Jan 1, 1934

By P. W. Bridgman

IT is characteristic of most scientific investigators that they are not satisfied with the discovery of new facts, no matter how curious or unexpected, but that along with the factual discovery there is a constant effort to understand It appears that. one's interest in, and satisfaction with, the discovery of an array of news experimental facts is enormously increased if one has at the same time a theory or hypothesis guiding one's expectation of what sort of new experimental discovery may lie around the corner Conversely, as a theoretical physicist one's satisfaction with his theory is greatly enhanced if along with the development of the theory can go the discovery of new experimental facts, confirming or perhaps modifying the theory as it grows Of course, there have been long and stretches in the history of physics in which new data of unquestioned ultimate importance ham e piled up, without much inspiration or illumination in the way of understanding For 50 years spectroscopy had such an and history, but how irksome this was felt to be is plainly shown by the almost audible relief that greeted the first success by Bohr in injecting understanding into the situation, and by the fresh rush of experimenters into this field when the prospect of understanding had once been offered The investigations in the field of high pressure, which have occupied me for a long time,1 until the last few years have been in very much the Same sort of situation as spectroscopy before the advent of Bohr A great many kids, of data were collected for a great many solid and liquid substances, and there could be no question of the importance of these data, because the uniform change of dimensions produced by hydrostatic pressure is perhaps the simplest conceivable type of alteration to which a body can be subjected But except for a few isolated flashes, there was no theoretical illumination, so that it had to be to a large extent the enthusiasm of the collector that kept me going However, within the last few years the wave-mechanics theory of solids has progressed so rapidly that

Jan 1, 1938

By Leo F. Reinartz

The history of steelmaking in the United States is a fascinating story of determination, sudden tragedy, exploitation, and inventive genius rolled into one gigantic plot. Mr. Reinartz' flowing interpretation of the progress made in the last one hundred years is being presented in a series of four articles. THIS is the Age of Steel. We live in a mechanized era. Our everyday lives--everything we see or do-are organized and influenced by this versatile metal. Our industries, our farms, our homes, and our transportation-yes, our vocations and avocations, or luxuries and necessities-all are dependent upon smelting iron and making steel. Take away iron and steel and soon our vaunted civilization would revert to a primitive existence. These metals, often in crude forms, have been known for thousands of years. Down through the ages, until about one hundred years ago, steel was made laboriously, and at high est, in small batches. During those years, methods of manufacture did not change very much. Over long periods of time only warriors, royalty, and wealthy people could afford to use articles made of iron or steel. History has recorded that the nations which were expert in iron and steel manufacture, and had access to rich iron-ore deposits, were the leaders in war or in peaceful pursuits. At the end of the 18th century, thirteen struggling American colonies had broken not only the political shackles that bound them to Great Britain, but also many of the economic bonds. They had showed their skill, Yankee ingenuity, and energy by making iron and steel articles for their own use. After the Revolutionary War, more and more hardy American pioneers pushed westward through the Allegheny Mountain passes and down the rivers into the fertile Ohio River and Kentucky country. Demands for articles made of iron increased. The iron industry on the east coast grew and prospered. As this trend continued, iron industrialists moved their plants westward to be near the large deposits of high-grade coal in western Pennsylvania, eastern Ohio, and nothern West Virginia. They also desired to use the local iron ores and water resources of those areas. Blast furnaces and ironworks were built in the Pittsburgh, Youngstown, southern Ohio, and northern West Virginia districts. In 1810, the United States produced 53,908 gross tons of cast iron and 917 tons of steel. Iron ore discovery A white man first discovered large deposits of iron ore in the northern Michigan and Lake Superior country in 1844. One year later, the Sault

Jan 1, 1961

By W. R. Ingalls

During the last two years, and especially during the last six months, a number of important articles upon the new methods for the desulphurization of galena have been published in the technical periodicals, particularly in the Engineering and Mining Journal and in Metallurgie. I proposed for these methods the type-name of " lime-roasting " of galena as a convenient metallurgical classification,'and this term has found some acceptance. The articles referred to have shown the great practical importance of these new processes, and the general recognition of their metallurgical and commercial value which has already been accorded to them. It is my present purpose to review broadly the changes developed by them in the metallurgy of lead, in which connection it is necessary to refer briefly to the previous state of the art.

Jan 1, 1907

By I. Fatt

Study of a model which contains "dead-end" pore volume indicates that pressure transients are influenced by the amount of dead-end pore volume and by the resistance of the flow path between the dead-end pore volume and the main flow channels. A semi-empirical method is demonstrated that makes possible measurenment of the volume in the dead-end pores and the total pore volume. The difference between these two volumes is the volume of the flow channels. An indication of the flow resistance between the dead-end pore space and the lain flow channels is also obtained. INTRODUCTION In some engineering calculations the distribution of pore volume in a petroleum reservoir need not be known. For example, a material balance calculation treats a reservoir as an oil-filled tank. In other calculations the distribution of pore volume appears implicitly through use of the porosity and the relative permeability and capillary pressure characteristics. It is the purpose of this paper to point out that under certain conditions the exact distribution of pore volume must be known in order to interpret correctly transient flow behavior. Pressure transients during single-phase flow in porous media are usually said to obey differential equations of the form

By David Browne

THE use of coal-dust fired reverberatory furnaces, or indeed of reverberatory furnaces of any description, was for the Canadian Copper Co. a matter of necessity, and not of choice. For 20 years smelting had been done in blast furnaces alone, and with the Herreshoff furnaces used prior to 1904 there was no trouble in treating fine ores. But little flue dust was produced, and this, following the time-honored custom, was wetted down and put back with the charge. Whether the flue dust really smelted, or whether it was worn out by being chased around in a circle, was a problem that troubled no one. With the installation of modern blast furnaces and high-pressure blowing engines, in 1904, flue dust commenced to assert itself. Evidently more dust was made than could be smelted, but so many vital problems engaged our attention at that time that this minor question was pushed to one side. In 1906, the details of blast-furnace smelting and the conversion of matte had been worked out to a satisfactory conclusion, and the ever-increasing piles of flue dust and fine ore on the stock yard demanded serious consideration. Numerous experiments in sintering, briquetting, mixing with converter slag, forming blocks of flue dust with green-ore fines and cement, and so on, were undertaken. None of these showed much promise. Our problem, was still further complicated by the question of treating converter slag. The ore was basic, the slag was not needed as a furnace flux, and it was felt that under these conditions the old method of pouring slag in molds and resmelting in the blast furnace was an unnecessary expense. If the converter slag could be settled in basic-lined reverberatory furnaces, in which at the same time flue dust and green-ore fines could be smelted, two problems might thus be solved.

Jan 1, 1915

By Arne Westgren

ONLY in exceptional cases can the ordinary methods of chemistry be used for determining the constitution of compound metallic substances. Recourse has therefore been taken to special methods, the main expedients of which are, as we know, thermal analysis and metal microscopy. To these may be added-though more accessory-the determination of electric conductivity, specific volume, hardness or other properties. The information obtained by these methods has been compiled in equilibrium diagrams. Naturally, the technically most important alloys, such as steel, bronze and some others, have been subjected to very close study, and many investigators have devoted themselves to the solving of their problems of constitution. The equilibrium diagrams of these systems are therefore known today with a comparatively high degree of accuracy, even though it must be admitted that many details regarding their transformation reactions still remain to be completely explained. The equilibrium diagrams of the other alloys as a rule have not been determined so accurately. Most of them are based only on approximate determinations of the homogeneity ranges of the various phases. Thus extensive, detailed studies remain before these diagrams may be considered as established. Unfortunately, it must also be admitted that many of the alloy diagrams given in the present handbooks are as a whole very dubious. As a matter of fact, many of them may really only be viewed as the results of rather superficial, orientating investigations. In fact, there also seems to be a general opinion prevailing in our day that much work still remains to be done before the equilibrium conditions of the alloys may be considered as fully explained. At present, in almost all institutes for research on metals, as well as in many university laboratories, investigations to this effect are being carried out. As a rule, the classical methods of metallography, the thermal analysis and metal microscopy are applied.

Jan 1, 1931

By C. R. Kuzell

Although furnaces constructed of refractory brick have been operated for many decades, there has always been an unfulfilled desire by the operators for a less arduous and more satisfactory method of patching weak spots and burned-out zones in order to postpone and to effectively extend the termination of a furnace campaign. Not only has this desire frequently arisen when small spots have approached incipient failure while the furnace structure as a whole was still in good condition, but also when larger areas showed signs of needing replacement. The available methods have been arduous, sometimes dangerous, inefficient with respect to the life of new refractory material used, and nearly always have necessitated interruption of the continuity of the furnace operations and therefore reduction in furnace production during the period of time required for the repair work. Most of these older methods have involved the replacement of masonry by refractory shapes in the weakened areas. Many attempts have been made to develop a method of patching the burned-out areas by spraying granular refractory material upon old surfaces. While some success has been attained in attempts to renew the grooved, corroded side walls and fettling, and the edges of hearths, there have been no known successful applications of the spraying method in patching the underside of arches of operating furnaces. The method developed recently at the Clarkdale smelter of the United Verde Branch of Phelps Dodge Corporation, at Clarkdale, Aria., and described in this paper, has been found to be not only convenient and successful with respect to patching vertical or inclined surfaces, but has met with a marked degree of success in patching the parts of furnace arches that are exposed to flame, the successful result being obtained without interruption or interference with the continuity of furnace operations. It may be described as a method of renewing the interior refractory surfaces of operating furnaces by pneumatic spraying of an aqueous suspension of finely divided. particles of refractory material. It has been used

Jan 1, 1944