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By R. S. Rickard

Chemical processing of ores has gained new im¬petus in recent years. The reasons are many. They range from the need to process ores that are difficult to beneficiate to the avoidance of pollution. Although many think of chemical processing as a hydrometallurgical operation there are other techniques. An example is chlorination. Chlorination, although examined and discarded by many investigators, is again being considered as a means of extracting uranium1, treatment of silver-lead ores2, and the recovery of base metals from pyrite cinder and ores3. Segregation roasting of copper and nickel ores, a process similar to chlorination, is another chemical treatment being revived.

Jan 1, 1970

By C. H. Chou, Albert Sauveur

The following experiments were conducted in order to study the influence of the rate of cooling through and below solidification on the dendritic structure (macrostructure) and microstructure of some hypo-eutectoid steel. The steel selected was of commercial grade and had the following composition: C, 0.40 per cent.; Mn, 0.85; Si, 0.70; P, 0.099; S, 0.043. After melting in vacuum in an Arsem furnace, the various samples were allowed to solidify and to cool to room temperature as indicated in Fig. I. Samples were thus obtained representing all possible combinations of slow and fast cooling through the various ranges of temperatures indicated, namely: (I) zone of solidification or primary crystallization, (2) zone of granulation, and (3) zone of secondary crystallization. The location of the different temperature zones in the iron-carbon equilibrium diagram is shown in Fig. 2. The authors adopted Belaiew's notations. The designations of the various samples readily indicate their treatment, as will be apparent from Table 1. Sample SSS.—This sample was slowly solidified and cooled to room temperature in the crucible in which it was melted. The dendritic (macro) structure is shown in Fig. 3. The dendrites an: sharp and dis-

Jan 1, 1930

By H. F. JR. Miller

(Butte Meeting, August, 1913.) THE major cause of the deterioration of the open-hearth furnace as its length of service increases, is the melting down, or rather the slagging, of the checker-brick, together with the deposition of dirt in the form of iron oxide, etc., which helps to close the openings, as well as to slag the brick by chemical action. Any construction that will do away with the necessity of having the waste gases come down through the checkers will eliminate the main reason for their deterioration. There are some other well-defined reasons which are subordinate to the main one given above. Some of the defects of the present type of regenerator chambers are as follows: 1. The checkers cannot be cleaned while the furnace is in operation, nor can they be cleaned at the end of the run without taking out all of the checker-brick. This causes high costs for labor and brick. The labor cost is high because all checker-brick have to be handled twice. The brick cost is high because many of the bricks are spalled in the double handling, rendering them useless because a spalled brick will not stand up. 2. The top courses of brick become coated with iron oxide, etc., melt clown, and large amounts of dirt are deposited throughout the checkers, especially at the bottom. The draft of the furnace is decreased by the closing of the top and bottom openings, especially the top ones, and the entire working of the furnace is affected. If an effort is made to clean the checkers the dirt and brick falling down into the holes still further diminish the draft. 3. The distribution of the air or waste gases through the checkers is in many cases uneven, resulting in a lower temperature of pre-heated air and therefore a slower working furnace. Also, the passage of air and waste gases is so crooked that sometimes the chimney is not powerful enough to overcome the friction.

Jan 6, 1913

By John C. F. Randolph

(Read at the Amenia Meeting, October, 1877.) Tits establishment being now in full working order, it has seemed of considerable professional interest to collect together, in a concise form, the various points as to its plan, method of dressing, and equipment. The data contained in this paper have been largely drawn from the able paper of E. Kutscher, constructing engineer. of the works, contained in the Zeitschrift fur Berg-Hütten-und Salinenuesen im Preussischen Staate, 1873, supplemented by some personal memoranda made while the works were under construction and by memoranda on the works appearing in various German technical papers from their completion up to date. This is probably the largest dressing works in the world devoted to the beneficiation of argentiferous lead ores, and it is doubtful if any establishment for the concentration of mineral of any description can compare with it in size. As showing the final practice adopted in an old and very conservative mining region, in which the concentration of ores has been a matter of constant practice and experiment for a very long period, these works are of peculiar interest. The fact that the Clausthal ores strongly resemble a very large and abundant class of ores found in the United States has always attracted the attention of American mining engineers and mine owners to the methods employed in dressing and smelting them. The study of their methods of concentration of ores has, however, always been full of difficulty,

Jan 1, 1878

By Rudolf Kudlich

The problem of eliminating the hazards of hoisting in mines has been with us since the industry passed its earliest stages, when coal and ore could be won from surface working and tunnels. At first, safety devices were introduced as means of decreasing the amount of labor necessary to produce the mineral, or to increase the amount that could be obtained from a certain opening. For example, crude ladders replaced winding footpaths or steps cut into the walls of the pit or shaft, decreasing the distance it was necessary to carry the product to the surface and eliminating, to some extent, the hazard introduced by the precarious footing afforded by such paths and steps. Latcr, instead of being carried from the pit on the backs of men, the product was hoisted in buckets or baskets on a rope passing over a pulley or around a windlass. Thus the capacity of the pit was considerably increased, and the hazard due to making many trips up and down the shaft was eliminated. From such beginnings accident prevention in mine hoisting advanced with the importance of the industry, until at present hoisting compares favorably with other branches of the mining industry with reference to safe practices. As in the other branches, this progress has been accomplished along two general lines—by legislation, rules, and education, and by the installation of safety devices. Though due credit must be given the former, it is not so satisfactory as the latter. Legislation, to be effective, requires a policing and inspection system to guarantee enforcement, such as we cannot hope to inaugurate. Rules may be satisfactory so long as the employer controls the labor market, and dismissal or some other form of discipline is an effective means of insuring obedience to the rules; but where labor demand is in excess of the supply, or where labor organizations are in control, such measures are not effective. An educational campaign will draw attention to hazards and may awaken a desire to avoid accidents by exercising the proper care. It is necessary, therefore, to place our reliance mainly on mechanical devices to prevent accidents, and to depend as little as possible on laws,

Jan 1, 1923

By Rudolf Kudlich

The problem of eliminating the hazards of hoisting in mines has been with us since the industry passed its earliest stages, when coal and ore could be won from surface working and tunnels. At first, safety devices were introduced as means of decreasing the amount of labor necessary to produce the mineral, or to increase the amount that could be obtained from a certain opening. For example, crude ladders replaced winding footpaths or steps cut into the walls of the pit or shaft, decreasing the distance it was necessary to carry the product to the surface and eliminating, to some extent, the hazard introduced by the precarious footing afforded by such paths and steps. Latcr, instead of being carried from the pit on the backs of men, the product was hoisted in buckets or baskets on a rope passing over a pulley or around a windlass. Thus the capacity of the pit was considerably increased, and the hazard due to making many trips up and down the shaft was eliminated. From such beginnings accident prevention in mine hoisting advanced with the importance of the industry, until at present hoisting compares favorably with other branches of the mining industry with reference to safe practices. As in the other branches, this progress has been accomplished along two general lines—by legislation, rules, and education, and by the installation of safety devices. Though due credit must be given the former, it is not so satisfactory as the latter. Legislation, to be effective, requires a policing and inspection system to guarantee enforcement, such as we cannot hope to inaugurate. Rules may be satisfactory so long as the employer controls the labor market, and dismissal or some other form of discipline is an effective means of insuring obedience to the rules; but where labor demand is in excess of the supply, or where labor organizations are in control, such measures are not effective. An educational campaign will draw attention to hazards and may awaken a desire to avoid accidents by exercising the proper care. It is necessary, therefore, to place our reliance mainly on mechanical devices to prevent accidents, and to depend as little as possible on laws,

Jan 1, 1923

By Herbert Kynor

BY THE term mechanical mining is meant that operation, or series of operations, that replace the hand methods of mining. The first undercutting machine to operate in anthracite was placed in the Butler mine of the Hillside Coal & Iron Co., Dec. 23, 1910, by the Sullivan Machinery Co. The first Jackhamer used in the anthracite field was installed at the Wadesville colliery of the Philadelphia & Reading Coal & Iron Co. in Oct., 1912, by the Ingersoll-Rand Co. The first longwall conveyor was installed at the Dodge mines of the Delaware, Lackawanna, & Western Coal Co. in March, 1912. The first mechanical scraper equipment was installed in the Seneca mines of the Lehigh Valley Coal Co. in January, 1914. The amount of anthracite mechanically mined since the first mining machine was installed in 1910a is as follows: PENNA. COAL Co. D. L. & W., SCRANTON TEMPLE HUDSON YEAR AND HILL- TONS COAL Co., COAL CO., COAL CO., TOTAL. SIDE COAL TONS TONS TONS TONS AND IRON, TONS 1920 372,737b 367,000d 322,892 74,127 371,878 1,508,634 1919 950,786 no record 306,616 81,575 319,356 1,658,333c 1918 917,778 744,966 24,880 44,756 288,781 2,021,161 1917 757,940 838,800 5,050 57,279 164,180 1,823,249 1916 286,780 860,663 13,960 114,173 101,475 1,377,051 1915 428,819 592,169 8,253 1,029,241 1914 219,188 153,896 373,084 1913 171,505 171,505 1912 124,267 124,267 1911 40,319 40,319 1910 1,184 1,184 a. A slightly greater production than shown was obtained as the tonnage from individual operations is not shown. b. Decrease due to strike conditions in 1920. c. Does not include tonnage of D., L., & W. d. D., L., & W. decrease in 1920 due to having less mining machines in operation. There are about 150 undercutters in use in the anthracite region, 80 mechanical loaders, and 10 longwall conveyors.

Jan 9, 1921

Jan 1, 1902

By AIME AIME

THE section delegates assembled Monday morning with the incoming president, W. H. Bassett, in the chair and F. W. Bradley as vice-chairman. The secretary called the roll and urged the delegates to become familiar with the activities of the Institute. He explained the allotment of funds to local sections and the uses to which these funds may be put. He also announced plans for travel by Mr. Bassett and asked the delegates to confer with him as to meetings en route. An invitation was extended for all section delegates to attend the Directors' dinner Wednesday evening. He suggested that local sections hold a meeting once a year under the auspices of each division of the Institute. He further explained the system of choice of publications by members. The question of licensing of engineers was brought up, and the consensus of opinion among the membership was asked for. Because the matter is controversial, no official action has been taken and it was suggested that the' local and State sections act separately in this regard. A. B. Parsons, the assistant secretary, next spoke. In his remarks he indicated surprise that many prominent mining men still did not belong to the Institute, and urged that section delegates make up a list of such prospective members and send it in to the office for study by the New York staff. He also asked that re- ports of all meetings be turned in for publication in MINING AND METALLURGY, and said that the reports

Jan 1, 1930

Fifty to 75 million years ago, hydrocarbon-bearing rocks were formed in the Green River formation of Colorado, Wyoming and Utah. The hydro- carbons can be extracted from these rocks, marl- stone but misnamed oil shale, after crushing and intense heating. At about 900°F the marlstone decomposes to produce liquid shale oil. A press release from the Colony Development Co. describes a process which may permit, for the first time, economically feasible access to shale oil. Shale oil has resisted economic extraction for almost three centuries. According to the USBM, a patent was issued as early as 1684 in England to produce "oyle from a kind of stone". France produced oil from marlstone in 1838 and a dozen years later, Scotland started an oil shale industry, producing kerosine, that lasted nearly 100 years. In both countries, the process involved crushing the stone and retorting it to decompose the kerogen-a long and costly process at that time. In 1859, Edwin L. Drake brought in the first oil well in Titusville, Pa., and shale oil faded into oblivion.

Jan 8, 1965

By Sidney Powers

CONTENTS PAGE Distribution of fields 4 History of development 6 Origin of oil 7 Structure, accumulation and migration 8 Reservoir rocks 9 Methods of drilling and exploration 10 Oil-field statistics : 12 Description by regions: United States: Appalachian region ; 12 East-central states 17 Kansas 18 Oklahoma : 19 Texas : 24 Arkansas : 32 Louisiana 33 Mississippi ....... 34 Rocky Mountain region : 34 California 37 Canada 41 Mexico 43 Cuba 46 Bibliography 46 THE purpose of this brief account- of the occurrence of petroleum in North America is to make available to those who have a knowledge of geology, but who are not engaged in the petroleum industry, a few salient facts about the location of oil and gas fields, their productivity, the important structural types of accumulation and the age of the rocks containing petroleum. A few useful data and statistics are furnished, yet not complete statistics that are available elsewhere. Geology has been treated in simple terms because the reader is presumed to have little interest in the names of formations and of oil sands. Mineral deposits are more or less analogous. Whether oil or metals, minerals are found in rocks, largely in sedimentary rocks which carry water or have at one time carried it. A genetic or accumula-

Jan 1, 1931

By Sidney Powers

CONTENTS PAGE Distribution of fields 4 History of development 6 Origin of oil 7 Structure,, accumulation and migration 8 Reservoir rocks 9 Methods of drilling and exploration to Oil-field statistics 12 Description by regions: United States: Appalachian region 12 East-central states 17 Kansas 18 Oklahoma 19 Texas 24 Arkansas 32 Louisiana 33 Mississippi -.. 34 Rocky Mountain region 34 California : 37 Canada 41 Mexico 43 Cuba 46 Bibliography 46 THE purpose of this brief account of the occurrence of petroleum in North America is to make available to those who have a knowledge of geology, but who are not engaged in the petroleum industry, a few salient facts about the location of oil and gas fields, their productivity, the important structural types of accumulation and the age of the rocks containing petroleum. A few useful data and statistics are furnished, yet not complete statistics that are available elsewhere. Geology has been treated in simple terms because the reader is presumed to have little interest in the names of formations and of oil sands. Mineral deposits are more or less analogous. Whether oil or metals, minerals are found in rocks, largely in sedimentary rocks which carry water or have at one time carried it. A genetic or accumula-

Jan 1, 1931

By George T. Wickes

(Washington Meeting, May, 1905.) SEVERAL years ago, Mr. Robert A. Cook described and illustrated in our Transactions 1 a mechanical coke-drawer, patented in 1891 by Mr. Thomas Smith of the Thorncliff Iron Works, Sheffield, England, and first introduced in the United States in, 1896, at the coking-plant of the Latrobe Coal Co., Latrobe, Pa. This machine has not received any very extended application in this country, although it was successfully used in two places for a number of years. The present. paper describes a new and simpler machine, containing few wearing-parts capable of withstanding continued rough usage. Anything which tends to prolong the general use of bee-hive ovens will be welcome to those who are interested in cheapen¬ing the cost of producing coke in such ovens, especially if it provides satisfactory mechanical means, replacing the hard labor involved in drawing coke by hand with the old-fashioned ?duck bill.? The difficulty of finding efficient coke-drawers, especially during the summer season, and in the South, is notorious. Yet, notwithstanding the great improvements that have been made in retort coke-ovens, new bee-hive ovens are continually constructed; and a machine which will successfully compete with hand-drawing, and, at the same time, add to the efficiency of the bee-hive oven, seems to deserve notice. The machine here described was put in operation at the Frick Coal and Coke Co.'s plant, known as Continental No. 1, at Uniontown, Pa., in October, 1904, and is reported to have met successfully all the tests to which it has been subjected. This trial has demonstrated that one of these machines, equipped with an electric motor, and operated by one mart with an assistant, besides two men to " water down " the

Jul 1, 1905

By Russell W. Dayton

The metallurgical polarization microscope has been utilized in several researches in the last few years, thus attaining a fair degree of prominence, but little has been written in a manner suitable to a metallurgist concerning the theory of this instrument. In this investigation the theory was carefully studied, and the results are presented here in a detailed manner, yet as simply as possible. The theory is discussed with particular reference to the three chief functions of the instrument: (1) determination of anisotropy; (2) effect of strain; and (3) identification of inclusions. Each of these is investigated experimentally, with especial attention to the mechanism of producing any effect. Where possible, the discussion is supplemented by photomicrographs. The instrument used had numerous defects as a polarization microscope; these and their remedies are discussed. In the microscopic study of transparent mineral sections (chalcography) the use of polarized light has aided tremendously in the identification of a mineral. The determination of strain in transparent substances (photoelasticity) by the use of polarized light has lately become a commercial process, used in testing finished glass articles. The success of the use of polarized light with opaque materials has not been so great. The magnitude of the effects obtained is much less than that of the corresponding effects with transparent materials, and the mechanical difficulties are much greater. Königsberger,"' i in 1909, was the first to apply polarized light to the microscopic study of opaque substances; Endell and Hanemann(2) were the next, in 1913. In 1919 and 1920, Wright(3,4) prepared two papers on the subject. In the first he developed the detailed mathematical theory from the viewpoint of the electromagnetic theory of light, and in the second described the various methods in use, giving improvements of his own. Schwarz(5)

Jan 1, 1935

By Russell W. Dayton

The metallurgical polarization microscope has been utilized in several researches in the last few years, thus attaining a fair degree of prominence, but little has been written in a manner suitable to a metallurgist concerning the theory of this instrument. In this investigation the theory was carefully studied, and the results are presented here in a detailed manner, yet as simply as possible. The theory is discussed with particular reference to the three chief functions of the instrument: (1) determination of anisotropy; (2) effect of strain; and (3) identification of inclusions. Each of these is investigated experimentally, with especial attention to the mechanism of producing any effect. Where possible, the discussion is supplemented by photomicrographs. The instrument used had numerous defects as a polarization microscope; these and their remedies are discussed. In the microscopic study of transparent mineral sections (chalcography) the use of polarized light has aided tremendously in the identification of a mineral. The determination of strain in transparent substances (photoelasticity) by the use of polarized light has lately become a commercial process, used in testing finished glass articles. The success of the use of polarized light with opaque materials has not been so great. The magnitude of the effects obtained is much less than that of the corresponding effects with transparent materials, and the mechanical difficulties are much greater. Königsberger,"' i in 1909, was the first to apply polarized light to the microscopic study of opaque substances; Endell and Hanemann(2) were the next, in 1913. In 1919 and 1920, Wright(3,4) prepared two papers on the subject. In the first he developed the detailed mathematical theory from the viewpoint of the electromagnetic theory of light, and in the second described the various methods in use, giving improvements of his own. Schwarz(5)

Jan 1, 1935

By Eugene Coste

Although some of the observers who first paid especial attention to the occurrences of oil and gas in the strata (such as Hunt in 1859, Andrews in 1861; Winchell in 1865, Mendelejeff in 1876, Höfer in 1876, Minshall in 1881, and I. C. White in 1883) seem to have been impressed with the fact that oil and gas deposits were connected with the disturbances in the rocks caused by their upheavalll yet, with the exception of Mendelejeff, and possibly Andrews, these observers do not appear to have understood what is really the one essential factor in the occurrence of oil and gas in the strata: viz., the faulting, uplifting, fracturing, fis-suring, and jointing always accompanying even slight rock disturbances, and in certain districts (petroliferous provinces)2 allowing solfataric hydrocarbon emanations to force their way up from the interior and to reach and impregnate the porous portions of sediments subjected to the disturbances. Instead of this simple explanation to account -for the observed connection between petroleum deposits and rock disturbances, most of the observers mentioned above, and many others who have foliowed them on the same lines since, have entirely reversed the problem. To them, instead of the dissemination of gases from fissures into the sediments, it presented the accumulation and concentration, according to anticlinal or other geologic structures, of oil and gas originally present throughout the whole mass of the strata where they were produced by the decomposition or distillation of organic remains. Whether this important problem involves accumulation from sources within the strata themselves, or infiltration and dissemination from outside sources, may be easily determined if all preconceived ideas are put aside and the established facts only are considered. Physical Facts Sedimentary strata are composed of alternate beds of shales, sandstones, and limestones, most of which are sufficiently close-grained to

Jan 1, 1915

By H. E. Hostetter

GROSSMANN'S method1 for calculating the hardenability of steel from the composition and grain size has gained wide acceptance, and when properly used, has been well proved in practical application, both for estimating the hardenability of known compositions and for selecting compositions to meet known hardenability requirements. The Grossmann method uses as the criterion of hardenability the "ideal critical diameter," DI, which is the size round that will just harden to a structure of 50 per cent martensite at the center when given the theoretically fastest quench, or "ideal quench." The DI can be related to actual quenching practice if the severity of quench is known; or the DI can be correlated with hardenability as determined by the Jominy end-quench method.2 The effect on hardenability of each element present in a steel can be represented by a multiplying factor, the value of which depends on the amount of the element present and the degree of effectiveness of the particular element. (The value of the factor for a given carbon content varies with the grain size.) When the factors for all elements present in a steel have been determined from charts, they are multiplied, and the resultant product is the D, of the steel. The validity of Grossmann's scheme of multiplying factors has been confirmed in a number of other investigations.3 -6 It can be appreciated that a certain desired level of hardenability can be obtained by adding chromium, molybdenum, nickel and vanadium to a base composition containing carbon, manganese, silicon and the usual impurities. Many of the ranges of hardenability used commercially can be obtained by any of the foregoing alloying elements used singly in the base composition. The same hardenability levels also can be obtained through use of any of a great number of multiple element combinations of these alloying elements. In this report a method will be presented for determining what one combination is the most efficient (based on hardenability and cost of added alloy) for a given level of hardenability. It should not be assumed from the emphasis given to hardenability, that hardenability is the only criterion for the selection of an alloy composition. Such properties as the hot-working characteristics, machinability, carburizing characteristics, amount of distortion during quenching and the retention of austenite may be considerations of importance in many applications. However, hardenability is one of the most important properties of an alloy steel and one that must be considered in almost all cases involving heat-treatment by quenching. Therefore, a method for determining the lowest-cost alloy combination should be of considerable value. DETERMINATION OF MOST EFFICIENT COMBINATIONS For comparing the alloying elements on standards of cost and hardenability, it

Jan 1, 1945

By A. D. Bryant

APPROXIMATELY 2 1/2 million tons of silica sand and ground silica with a value of $7.25 million is produced annually from the Ottawa, Illinois, district. These silica products come from the well known St. Peter sandstone formation which covers part of the Mississippi Basin extending from St. Paul on the north to the central part of Arkansas on the south and from Muncie, Ind., on the east to Kansas City on the west. Practically the whole state of Illinois is underlain by this formation except where removed by erosion. Sand produced from the St. Peter sandstone in the Ottawa district is noted for its purity, uniformity, and quality. In addition to various screened grades for industry about 10 pct of the total production of the Ottawa district is ground into silica flour for use in glass, abrasives, enamel, porcelain, tile, for foundry and filter sand, and other uses.

Jan 3, 1953

By S. N. Sharma, William Davis

Because of diminishing energy resources and rising energy costs, every industry is forced to carefully examine its pattern of energy consumption. The copper industry is no exception; current smelting practice begs for technological innovations that would improve the efficiency of its energy utilization. The thermochemical simplicity of copper metal production, as shown in Fig. 1, is deceptive. Designed from the same basic principles, there are four major commercial processes either in use or under construction; and others, such as the Mitsubishi process, are being developed.

Jan 5, 1977

By Taylor Lyman, E. P. Klier

The structures formed when austenite is quenched to subcritical temperatures and allowed to transform isothermally have been the subject of intensive study since the work of Davcnport and Bain.' Isothermal transformation diagrams summarizing the results of many of these studies have become widely familiar to metallurgists. Of particular interest to metallographers are the dark-etchingl acicular products of transformation formed by isothermal reaction below the temperature of maximum velocity of the austenite to pearlite reaction. These products, the bainite structures, can he formed in a wide variety of steels. However, the constitution of bainite is not well understood and divergent views have been expressed as to its mode of formation. In this investigation a combination of dilatometric, microscopic and X-ray methods has been brought to bear upon the problem in the hope of some elucidation of the bainite reaction as it occurs in hypo-eutectoid steels. Mechanism OF Bainite Formation Davenport and Bainl considered the mechanism of bainite formation to consist of two steps—an allotropic transformation followed by precipitation of carbide. The separation in time of the two processes was considered to be very slight in the upper temperature range and very marked at temperatures just above the martensite range. This concept has been restated by Vilella, Guellich and Bain2 in the form of a definition of the acicular mode of transformation as: The successive, abrupt formation of flat plates of supersaturated ferrite along certain crystallographic planes of the austenite grains; this supersaturated ferrite begins at once to reject carbide palticles, (not lamellae), at a rate depending upon temperature In effect, this is the acicular mode of transformation, even though the temperature be such as to limit the actual life of the quasi-martensite to millionths of a second. The investigation of isothermal decomposition of austenite in certain alloy steels (notably those containing chromium or molybdenum) has revealed that there may be a range of temperatures between the pearlite and bainite reactions in which the austenite decomposes at a relatively low rate.3-6 Further, it is characteristic that in the second region of fast reaction the decomposition of the austenite is incomplete by one reaction but goes to completion by a second reaction. These observations led Wever7 to a description of the bainite reaction as follows: I. The reaction takes place by initial precipi. tation of a martensitic intermediate structure. 2. In the upper temperature range this structure readily decomposes into ferrite and cementite. In the lower range carbon separates in an unknown form. 3. In the upper temperature range the precipitated carbide nucleates the precipitation

Jan 1, 1944