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By Tuncel M. Yegulalp, Malcolm T. Wane

In general, many problems relating to the exploitation of mineral deposits are probabilistic in nature. This derives from the fact that the geologic universe is inherently random. Probability theory and statistics have been found useful for forecasting the behavior of natural events that occur in the geologic universe. The objective of this paper is to illustrate the application of the theory of extremes to this fore-casting problem. For example, it is customary for design purposes to determine the rupture strength of geologic materials. The theory of extremes is exceedingly useful in describing that portion of the frequency distribution of rupture strength which contains the least strengths. Parameters describing the distribution of the least strengths are more important to the designer of mining excavations than parameters describing the total distribution. The basic principles of the theory of extremes will be detailed and illustrated. Any person required to work in the laboratory of nature is aware that uncertainty is a salient feature of all mining enterprises. A mining engineer required to plan the most efficient, practicable, profitable, and safe mine finds himself face to face with numerous ill-understood and often unquantifiable states of nature. Basic information necessary for adequate planning is often lacking or derived from incomplete tests on samples or experience of doubtful validity. The planning procedure usually takes the form of determining a feasible layout with the intent of determining an optimal layout when and if the necessary details and information become available. The crux of the entire procedure is the choosing of numbers to put into the operational and structural models which encompass the plan. Many times these numbers must be assigned qualitatively from past experiences and are called the "most probable ones." At other times, load records, performance records and material tests provide a basis for extrapolation. In any event, the numbers are chosen from a distribution or set of all numbers. Since each number in the distribution represents a possible state, the choice of any particular value is based upon a decision rule. To illustrate, consider the design of an underground structure or the design of a rock slope. The initial step is the formulation of the various possible structural actions which result from the geometry of the layout. For a given structural model various intensities of behavior are possible depending upon the load, deformation, and material characteristic spec-trums, respectively. Of particular interest to mining people is the failure behavior or condition, i.e., when there is a complete collapse of structural resistance by either structural instability or fracture. A necessary feature of the analysis is the "rupture strength" of the material. Information on the rupture strength is derived from testing either in situ or in the laboratory and the usual outcome is a variation in the test results. The methodology used to overcome this variation is to construct a frequency distribution of rupture strengths, and then determine a measure of central tendency and variability. The main idea involved is that the central tendency number will be used in the failure calculations and the measure of dispersion will be used to estimate the probability of failure. In particular if the distribution of rupture strength is normal, the mean rupture strength is the central tendency number and the standard deviation of the rupture strength is the measure of variability. Suppose the mean value of rupture strength is 1000 psi and the standard deviation is 200 psi. Insertion of 1000 psi into the failure calculation produces results that are unsafe, hence a common decision rule is to reduce the mean value by a "factor of ignorance" so that the failure calculation will produce a "safe result." If two is chosen as a factor of ignorance, this means the value inserted in the calculation is 500 psi or 2.5 times the standard deviation. The next step is to determine the percentage chance that failure will occur from a design created on this basis. Tables on the normal distribution function show that this percentage chance is 0.621% or approximately 7 times out of 1000. In practice, however, the situation is more complicated than represented by the foregoing illustration. The laboratory or field testing program usually constitutes a pathetically small sample of the geologic universe of interest and not enough testing is carried out to determine the exact form of the distribution of the test results. The normal, Cauchy and Student's T distributions are strikingly similar, and it becomes a matter of mathematical convenience to assume the normal law for phenomena which follow other laws.

Jan 1, 1969

P. L. Pratt (University of Birmingham, Birmingham, England)—The author has measured the hardening effect of isolated edge and screw dislocation boundaries in a remarkably elegant manner, and he proposes that the detailed structure of the boundary determines its effectiveness as a barrier to slip although "there are still unknown details of the distribution which may be extremely important." On p. 678 the author states "that for a good crystal (one having a yield of about 30 psi) a change in annealing temperature from 300" to 400 °C resulted in a negligible shift in the level of the stress-strain curve." Is this in agreement with the results of the earlier paper by Li, Washburn, and Parker8 in which such a change of temperature produced notable hardening in crystals with a yield of about 30 psi? Or were these earlier crystals, of the same nominal purity, less perfect than those used in this work? The experiment illustrated in Fig. 15, p. 681, shows that the boundary has sharpened after annealing at 400 °C, the temperature at which the hardening effect first becomes apparent. Did the author verify that no sharpening of the boundary occurred at, say, 300 °C where no hardening was found? This would seem to be an important check on the proposed mechanism, especially since zinc of this purity should polygonize at temperatures well below 400 °C within the annealing times used here. There seem to be at least two alternative explanations which could fit these facts: 1—The boundary may sharpen at 300 °C or even lower temperatures but be unable to contribute greatly to the hardening until jogged by thermal vacancies and other impurity atoms after 400 °C anneal. This mechan- ism, discussed in the earlier paper,' is believed to account for the thermal hardening observed by Blank'" in NaCl, as stated elsewhere: and by results from recent experiments which tend to confirm this view. 2—The dislocations in the diffuse boundary may be locked by impurity atoms at 300 °C and thus only sharpen the boundary at 400 °C with the aid of thermal vacancies. In this case it would be difficult to distinguish between the two sources of hardening (sharpening or jogging), using metal of this purity. Jack Washburn (author's reply)—The author wishes to thank Dr. Pratt for his discussion. In connection with his first comment, it should be pointed out that the temperature of testing in the present series of experiments was —196°C, whereas, in the earlier experiments he referred to,' it was 20°C. Therefore, the yield values should not be directly compared. It is likely that the crystals used in the present work were initially more perfect macroscopically than the large shear specimens used previously. The small size of the test section in the kink specimens made it possible to select regions of the large crystals, from which they were acid-cut, that were free of observable small angle boundaries. The sharpening of a microscopically diffuse boundary such as that in Fig. 15 begins in zinc of this purity well below 300°C. However, it is probably not justified to conclude that because a boundary looks sharp under the microscope it has attained the ideal structure. The author agrees with Dr. Pratt that jogging of dislocation lines is one of the structural features of a small angle boundary that should be important in determining its strengthening effect. More detailed information concerning the changes in boundary structure as a

Jan 1, 1956

By R. D. Hagni

The following is a case study illustrating the use of thin sections and polished sections of crude ore to predict metallurgical response. By examining polished sections of the metallurgical products, the textural and mineralogical reasons for unsatisfactory separation can be explained. An area of oxidized Negaunee Iron-Formation located south of Negaunee, Michigan, in the Marquette Iron Range, has been considered for roast reduction-magnetic separation. Preliminary metallurgical studies and subsequent pilot plant testing produced varied results. These results prompted this microscopic study which began with an examination of 126 thin sections and 82 polished sections prepared from 126

Jan 1, 1967

By G. St. J. Perrot, S. P. Kinney

Consumers of metallurgical coke are agreed that the quality of their fuel plays an important part in the performance of the furnace. Less unanimous agreement is evident when the properties of a desirable coke are discussed or when consideration is made of suitable testing methods by which the worth of a coke for metallurgical purposes may be determined quantitatively. Much has been written of the importance of combustibility as a factor in determining the performance of coke in the blast furnace and it is generally believed that cokes vary widely in this respect. The usual operating data of the furnace afford little evidence as to the combustibility of the fuel. As a part of a general investigation of the properties of metallurgical coke, the Bureau of Mines has explored the hearth combustion zone in a number of blast furnaces by means of water-cooled gas sampling tubes driven into the hearth through the tuyeres. The attempt has been made to determine the difference in combustibility of cokes varying widely in physical properties. Data have also been obtained in an experimental combustion furnace at the Bureau laboratories in Pittsburgh. This paper gives the results of experiments, made at eleven blast furnaces, in which the composition of the gases was determined at various points in the hearth in the plane of the tuyeres. Further work is in progress in which the zone above the tuyeres will be explored. Factors Affecting Coke Combustibility Brassertl has defined combustibility as the rate of progression of combustion, or, in other words, the speed at which the carbon molecules

Jan 1, 1923

By R. S. Bradley, B. K. Miller

The principal producing areas of fire clay in Missouri are: (I) the east central district, which includes Audrain, Callaway, Montgomery, Warren, and Boone Counties (Fig. I); (2) the St. Louis district, which includes St. Louis and St. Louis County; (3) the north central Ozark district, which includes Franklin, Gasconade, Osage, Maries, Phelps, and Crawford Counties. Most of the semiplastic‡ fire clay is found in Audrain, Callaway, Montgomery and St. Louis Counties, and in St. Louis. Flint fire clay is found in Callaway, Audrain, and Montgomery Counties and in most of the north centra! Ozark district. High-alumina diaspore clay is found only in the north central Ozark district, except a few deposits found in Montgomery County. This paper is concerned with the semi-plastic fire clay that occurs in the east central Missouri district near Mexico, Audrain County, Missouri, which is mined by the open-pit method as practiced by the A. P. Green Fire Brick Co. About one-fourth of the semiplastic fire clay in that district is mined in shaft mines, and three-fourths in open pits.

Jan 1, 1942

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By S. P. Kinney, G. St. J. Perrot

Consumers of metallurgical coke are agreed that the quality of their fuel plays an important part in the performance of the furnace. Less unanimous agreement is evident when the properties of a desirable coke are discussed or when consideration is made of suitable testing methods by which the worth of a coke for metallurgical purposes may be determined quantitatively. Much has been written of the importance of combustibility as a factor in determining the performance of coke in the blast furnace and it is generally believed that cokes vary widely in this respect. The usual operating data of the furnace afford little evidence as to the combustibility of the fuel. As a part of a general investigation of the properties of metallurgical coke, the Bureau of Mines has explored the hearth combustion zone in a number of blast furnaces by means of water-cooled gas sampling tubes driven into the hearth through the tuyeres. The attempt has been made to determine the difference in combustibility of cokes varying widely in physical properties. Data have also been obtained in an experimental combustion furnace at the Bureau laboratories in Pittsburgh. This paper gives the results of experiments, made at eleven blast furnaces, in which the composition of the gases was determined at various points in the hearth in the plane of the tuyeres. Further work is in progress in which the zone above the tuyeres will be explored. Factors Affecting Coke Combustibility Brassertl has defined combustibility as the rate of progression of combustion, or, in other words, the speed at which the carbon molecules

Jan 1, 1923

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By Noel Stearn

WHEN the Age of Machinery was suddenly thrust upon civilization about the beginning of the 19th century, an unprecedented demand for mineral resources sprang up. This demand brought about the rapid development of the known ore deposits and the discovery of such other deposits as could be encountered by energetic and canny prospectors. Thus in the countries now reasonably accessible nearly all orebodies have been located except those which are totally concealed even from the eyes and "senses" of experienced and expert prospectors. The high rate of exhaustion of known ore deposits and the necessity of looking farther and farther ahead for raw materials as a matter of insurance on the stupendous capital outlays involved in mining, development, and conversion operations, have resulted in exceptional activity in three different fields of effort. The first is purely geographic. Prospectors are now penetrating the few hitherto inaccessible regions in the hope of stumbling upon exposed ore deposits or locating visible indications of their presence. The second is chemical. Industrial chemists and metallurgists are seeking to facilitate the exploitation of lower grade ores or to find methods of recovering valuable metals from common substances. In the third field of effort lie the activities of the economic geologist and the mining engineer, who endeavor to locate concealed ore deposits which would remain hidden from the prospector no matter how expert or conscientious he might be. Obviously the task which such a man must face is both exacting and indefinite, and the tools which he has heretofore been permitted to bring to it are, for the most part, abstract-a knowledge of certain fundamental principles and processes involved in the origin, occurrence, structure, and distribution of deposits of natural resources and of the rocks which form the environments of those deposits; and a process. of reasoning by analogy supplemented by the use of the diamond drill, or such artificial exposure as -the test pit, trench, shaft, or tunnel.

Jan 1, 1928

By P. Lees, N. Parkinson, K. Hartley, D. M. Donaldson

The reprocessing of advanced fuels such as carbides, oxides, and cermets, containing up to 30pct pu has been studied. Dissolution of uranium carbides in nitric acid produces appreciable quantities of mellitic acid which has undesirable effects in subsequent stages of the process. Mixed oxides containing up to about 40 pct Pu in solid solution with UO, are soluble in nitric acid and a leaching type process in nitric acid for a stainless steel/UO,. PuO, fuel containing 30 pct Pu appears to be feasible. It offers considerable economic advantages THE reprocessing of the U-Cr alloy core of the Dounreay Fast Reactor was described by Buck and others at the Second Geneva conference.' This paper described the flowsheet and plant for processing a relatively simple fuel of good dissolution charac- over total dissolution routes. A new oxidation-sub -limation process is described for metallic fuels containing up to 12 pct Mo. New data is presented on the solvent extraction of uranium and plutonium nitrates into tributyl phosphate -odorless kerosene and of the influence of radiolytically produced acid phosphates on this part of the process. It is concluded that there are no insuperable difficulties which will prevent the satisfactory reprocessing of high burn-up plutonium fuels by a solvent extraction route. teristics and of low-plutonium content after irradiation. However, it has been clear for some time that more satisfactory operation of the reactor can be obtained by the use of a core with better irradiation performance than U-Cr alloy and a U-Mo alloy will be used for the next charge. Recent modifications to the core mean that it is now possible to carry out irradiations of fuel element subassemblies similar to those which might be used in a fast power reactor and trials with plutonium-bearing fuel elements will be made in the relatively near future. These changes have meant that a considerable amount of reprocessing development work has had to be carried out for

Jan 1, 1963

By B. K. Miller, R. S. Bradley

The principal producing areas of fire clay in Missouri are: (I) the east central district, which includes Audrain, Callaway, Montgomery, Warren, and Boone Counties (Fig. I); (2) the St. Louis district, which includes St. Louis and St. Louis County; (3) the north central Ozark district, which includes Franklin, Gasconade, Osage, Maries, Phelps, and Crawford Counties. Most of the semiplastic‡ fire clay is found in Audrain, Callaway, Montgomery and St. Louis Counties, and in St. Louis. Flint fire clay is found in Callaway, Audrain, and Montgomery Counties and in most of the north centra! Ozark district. High-alumina diaspore clay is found only in the north central Ozark district, except a few deposits found in Montgomery County. This paper is concerned with the semi-plastic fire clay that occurs in the east central Missouri district near Mexico, Audrain County, Missouri, which is mined by the open-pit method as practiced by the A. P. Green Fire Brick Co. About one-fourth of the semiplastic fire clay in that district is mined in shaft mines, and three-fourths in open pits.

Jan 1, 1942

Jan 1, 1884

By L. A. Roe

Magnetic separation occupies an attractive position in the field of ore beneficiation. It is a simple yet effective method, used for some 150 years and steadily growing more important. This type of beneficiation orginated in 1792, when William Fullarton was issued a British patent covering the separation of iron ore by magnetic attraction. What is magnetism, and why are some materials capable of being magnetized and others not? The study involves many unknowns, and even a partial answer to these questions would be a dissertation in solid state physics and perhaps other fields of science. But the last two decades have revealed basic facts as to why certain materials are magnetic and what happens to them when they are magnetized.

Jan 12, 1958

By Hugh M. Roberts, R. D. Longyear

Introduction ............................ 27 GEnERal Geology........................... 29 The ORebodY in Western Falco~ridgI TownsRip........... 31 Quartzite-Graywacke Formation................... 33 Greenstone............................ 33 Norite ............................. 33 Metamorphism.......................... 35 The Orebody........................... 36 Mineralogy ........................... 37 Grade of Ore........................... 42 Genesis oF tEe Ores . :....................... 43 Summary of Various Hypotheses.................. 44 Magmatic Segregation by Crystallization of Sulphides........ 44 Gravitational Segregation of Molten Sulphides at the Base of the Magma 45 Intrusion of Molten Sulphides after the Consolidation of 'he Nurite.. 45 Deposition by Hydrothermal Solutions.............. 46 Magmatic Segregation by Extraction from Crystallizing Norite... SO The Relationship between the Exploration and Theories of Origin .... 50 Volume Relations of Norite and Sulphides............... 62 Intimate Association of Norite and Sulphides............. 53 Granitic Material........................ 54 Uniform Content........................ 54 Sulphides in Walls......................... 54 Absence of Typical Hydrothermal Minerals.............. 55 SUmmaRY................................ 56 Introduction During 1916 and 1917. the E. J. Longyear Co. of Minneapolis. Minn., carried out a campaign of exploration for nickel-copper ore in the Sudbury District of Ontario. The work was initiated by W. E. Smith. a resident of Sudbury. who called the attention of W. J. Mead. Chief Geologist

Jan 1, 1918

By George K. Burgess, Robert A. Hadfield

1. Introduction.—The methods of production of sound steel ingots have been described in several papers read recently before this Institute. It was thought by Director Stratton, of the U. S. Bureau of Standards, and ourselves to be of sufficient interest and importance, as a further contribution to this subject, to compare the properties of rails rolled in one mill according to American practice, from several types of ingot of substantially the same chemical composition but cast by several processes; and to compare in considerable detail the properties of an ingot manufactured by the Hadfield special-feeding process and one of the usual type for rolling into rails. We are greatly indebted to F. W. Wood, President of the Maryland Steel CO., who made this investigation possible by kindly placing his rail mill at our disposal; and he and his associates at Sparrows Point did everything possible to make the experiment a success, including the execution of several of the tests and analyses. 2. Classification and Manufacture of Ingots.—Of the ingots used in this investigation, eight were made in Sheffield and furnished by Sir Robert Hadfield, and one was made and furnished by an American steel company,l as a comparison ingot, and was supposed to represent the usual type of ingot from which rails are made. The characteristics of the ingots are given in Table I. Ingots 1, 2, 3, and 4 were cast large end up and fed by the Hadfield method in the usual manner with charcoal and blast continued until the molten steel has set on the top of the head, say varying from 20 to 40 min. To ingots 1, 2, and 4 was added 0.1 per cent. aluminum, and to the nickel-chrome ingot, No. 3, 0.125 per cent. For sake of comparison, there were also included two ingots, Nos. 8 and 9, cast with the small end up and fed by

Jan 1, 1915

By Gealy W. Wallwork

INTRODUCTION The administrative processes of coal mines are becoming increasingly complex. As society evolves into a more complicated structure with greater emphasis on individuality, government regulations reach deeply into every activity in an effort to force individuals into a standardized mold. These contradictory pressures add an extra burden to the administration of a mining operation. Recent years have brought a substantial change in the skills needed by mine supervisors and managers. As a result, a better understanding of the administrative functions is necessary. The mine superintendent has the overall responsibility for the mine; for effective operation he must be sufficiently knowledgeable to oversee all the complex functions that make up the mine. This chapter does not cover all the administrative requirements because of the variation in mine operation and in company policies and organizational structure. It does attempt to identify the administrative functions that would be required at a large mine with a preparation plant. It is assumed that the mine operation is decentralized with very little duplication of functions at the organizational levels above the mine. Thus each function is assumed to be relatively complete at the mine and under the general supervision of the mine superintendent. EMPLOYMENT PROCEDURES Throughout the mining industry, in deep or surface mining, in union or nonunion companies, the success or failure of an organization is directly related to the caliber of employees who make up the organization. A company is nothing more than a group of people working together with

Jan 1, 1981

By Samuel M. Cassidy, John A. Garcia

IN some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. As far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haul- age and air. On completion of the panel the two entries are sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1937

By G. R. Fitterer

NonmEtallic inclusions in steel have received much attention by metallurgists during the past few years. Many investigators have been emphatic in stating their belief that these impurities are the chief causes of steel failures, while others think that their effects are negligible. One of the main reasons that definite information on the effects of these impurities is lacking is that no reliable method has been developed for the exact determination of the amounts of these different impurities in steel. Some valuable new information has been brought out by a reliable method for nonmetallic inclusions which has been developed at the Pittsburgh Experiment Station of the U. S. Bureau of Mines, in cooperation with the Carnegie Institute of Technology and the Metallurgical Advisory Board. This procedure satisfactorily extracts some of the more common inclusions from steels, thus enabling the investigator to correlate steel failures with inclusion content. Although the data given herein are the first to be published on the subject of the electrolytic extraction method, the interest in the subject is evidenced by the fact that it is already being used by some 20 to 30 steel companies for their various purposes. Some of the comments received from these laboratories indicate that the method is highly satisfactory: the unfavorable comments, when traced to their sources, have been found to be based on some small mistake made in either installation or operation. The chief discrepancy seems to have occurred in attempts to apply the method to the extraction of inclusions from alloy steels. The procedure can be used only for the plain carbon steels and for such low alloy steels as those containing the usual amount of copper (0.2 to 0.3 per cent). Steels containing the carbide-forming alloys such as chromium, tungsten, etc., present far too many difficulties for the accurate determination of inclusions. Luckily, the iron and manganese carbides do not offer any difficulties and no contamination of the oxide-sulfide residue results, It is highly probable that some modification of the following

Jan 1, 1931

By M. F. Smith

BELOW the nose of the bainitic C curves in isothermal transformation diagrams, the rate of the austenite-to-bainite transformation usually decreases with decreasing temperature. However, in some steels and iron-carbon alloys, there is a noticeable acceleration in the initial reaction rate at temperatures just above Ms. Such speeding-up of the bainitic transformation would be understandable at temperatures just below Ms because of the catalytic effect of the martensite formed,' but the reversal in isothermal kinetics just above Ms seems quite anomalous. This behavior was observed by Howard and Cohen' in a 1.35 pct C steel and, on the basis of metallo-graphic examination, it was attributed to the formation of a thin plate-like product not belonging in the bainitic sequence. More recently, schaaber2 found two-stage reactions occurring in the vicinity of Ms in a number of steels, and suggested that the first stage might be the isothermal formation of marten-site, preceding the isothermal formation of bainite in the second stage. A decrease in the bainitic incu-

Jan 1, 1960

PRESIDENT WILLIAM KELLY, District 5 IRON MOUNTAIN, MICh PAST PRESIDENTS E P MATHEWSON, District 0 NEW YORK, N Y ARTHUR S DWIGHT, District 0 NEW YORK, N Y FIRST VICE-PRESIDENT J V W REYNDERS, NEW YORK, N Y TREASURER CHARLES F RAND, NEW YORK, N Y

Jan 1, 1923