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By A. E. Harnsberger

I is obvious that details such as the physical and chemical properties and methods of heat-treating of the materials mentioned must be omitted in a paper on the subject of materials used in oil-refinery pumps1. Only sufficient identification is given to enable the reader to find additional information from already published data. Also, the subject covers many operating conditions, but only the most important services can be discussed here. To the oil refiner, the pumping equipment is of vital interest. Practically every refinery operation, from the charging of crude oil to a distillation unit to the shipping of refined products, involves some form of pumping machinery. Intermediate refining stages involve a great variety of pumping machinery to carry out successfully the aims of the refinery technologist. Temperatures at which oils are handled vary from — 50" F. to 900" F. Pressure may vary from subatmospheric to 2000 1b. per sq. inch. The selection of the proper materials involves a careful consideration of the conditions under which the particular pump must operate. The four most important considerations are temperature, pressure, corrosion, and abrasion or wear. Consideration of temperature may be divided into three parts: (1) extremely low temperatures of the order of —50" F.; (2) temperatures at atmospheric or slightly above; (3) temperatures from 200" to 900" F. Pressures fall into two groups: (1) pressures reached by ordinary trade pumps of the order of 200 lb. per sq. in., (2) extreme pressure conditions involving pressures as high as 2000 lb. Noncorrosive and corrosive oils can be treated differently. Under the latter falls corrosion in the presence of water, which will occur up to 250" F. The second type of corrosion occurs in high-temperature pumping equipment, with temperatures from 450" to 900" F., largely caused by sulfur compounds. There are also other corrosive conditions met with in refinery operations, particularly in the handling of acids, acid sludges and other specialized processes. These problems, although difficult to

Jan 1, 1935

By A. E. Harnsberger

I is obvious that details such as the physical and chemical properties and methods of heat-treating of the materials mentioned must be omitted in a paper on the subject of materials used in oil-refinery pumps1. Only sufficient identification is given to enable the reader to find additional information from already published data. Also, the subject covers many operating conditions, but only the most important services can be discussed here. To the oil refiner, the pumping equipment is of vital interest. Practically every refinery operation, from the charging of crude oil to a distillation unit to the shipping of refined products, involves some form of pumping machinery. Intermediate refining stages involve a great variety of pumping machinery to carry out successfully the aims of the refinery technologist. Temperatures at which oils are handled vary from — 50" F. to 900" F. Pressure may vary from subatmospheric to 2000 1b. per sq. inch. The selection of the proper materials involves a careful consideration of the conditions under which the particular pump must operate. The four most important considerations are temperature, pressure, corrosion, and abrasion or wear. Consideration of temperature may be divided into three parts: (1) extremely low temperatures of the order of —50" F.; (2) temperatures at atmospheric or slightly above; (3) temperatures from 200" to 900" F. Pressures fall into two groups: (1) pressures reached by ordinary trade pumps of the order of 200 lb. per sq. in., (2) extreme pressure conditions involving pressures as high as 2000 lb. Noncorrosive and corrosive oils can be treated differently. Under the latter falls corrosion in the presence of water, which will occur up to 250" F. The second type of corrosion occurs in high-temperature pumping equipment, with temperatures from 450" to 900" F., largely caused by sulfur compounds. There are also other corrosive conditions met with in refinery operations, particularly in the handling of acids, acid sludges and other specialized processes. These problems, although difficult to

Jan 1, 1935

By F. Keller, R. H. Brown

BECAUSE of the extensive use of Alclad 24s alloy sheet in aircraft construction, there is much interest in the metallurgical changes caused by heat-treatment of this product.1,2 One of these changes is the result of the diffusion of soluble elements from the core into the coating during treatment. This paper deals with the thermal treatments that may influence diffusion and with the practical effects of diffusion on the serviceability of the product. As is well known, Alclad 24s-T sheet has a core of high-strength alloy combined with surface layers of relatively pure aluminum. The microstructure of a cross section of this product is shown by Fig. I. hot only does the relatively high-purity coating have a high resistance to corrosion, and hence serves as a mechanical barrier between the core metal and the corroding environment, but in addition this coating I exerts electrochemical protection over areas where the core may be exposed, such as cut edges. In addition, the coating affords electrochemical protection to projecting heads of *417S-T, 17S-T and 24S-T rivets, or attached members made from these alloys. Under some conditions of heat-treatment, however, diffusion of copper into the coating will alter the electrochemical relationship between the coating and the core to the extent that only partial protection will be obtained under some corrosive conditions. The reason for the electrochemical protection lies in the fact that the coating layers of pure aluminum are anodic to the alloy core. The addition of copper to aluminum produces alloys in which the potential is lower than that of the pure metal. Moreover, as the amount of copper in solid solution in z4S alloy is increased, the potential of the alloy becomes more cathodic. When heat-treated at 920°F. and quenched in cold water, 24s-T is about 0.16 volt cathodic to pure aluminum. However, copper will diffuse from the core into the coating, and if it reaches the surface the potential will be altered in a cathodic direction. Thus the potential dif-erence between the core and coating may be less than 0.16 volt, depending upon the thickness of the coating, and the time and temperature of heat-treatment. Of the methods available for determining the extent of diffusion of copper from the core into the coating of Alclad 24S-T, two are generally used; namely, the metallographic and the solution potential method.3 METALLOGRAPHIC METHODS Metallographic methods will reveal the progress of diffusion of copper into the coating. For instance, the diffusion zone in the coating intermediate between the coating surface and the core is shown in Fig. I. This photomicrograph is of a polished and etched cross section of 0.040-in. Alclad 24S-T sheet. Diffusion proceeds into the coating more rapidly along the grain boundaries than through the body of the grains. consequently, the diffusion zone is not of uniform width

Jan 1, 1944

By F. P. Dewey

Bone-ash cupels have been used from time immemorial to absorb litharge, and accompanying oxides, in assaying. Doubtless, also, from the earliest days cupels have been most unjustly blamed for much poor assaying. It has long been known that the precious metals go with the litharge into the cupel. This occasions a loss of precious metals and reduces the results of the assay. There have been many investigations of cupels and the most diverse views have been expressed, the extremes being the statements of Lodge1 that every cupel has some effect upon the loss in assaying telluride ores and of the Campredons2 that coarse and fine and hard and soft cupels all give the same loss of silver when cupelling the same weights. The truth lies between these statements and much nearer the latter. In a vast majority of cases the influence of the cupel is not dominant and is outweighed by other conditions, particularly the temperature of the cupelling bead. At the Spokane meeting of the Institute I presented a paper on the Assay and Valuation of Gold Bullion,3 which recorded the results of many hundreds of assays made in the Mint service under everyday commercial conditions, which of necessity differ from scientific conditions. In following this matter up, for the purpose of increasing the accuracy of our commercial methods of bullion assays, the question of the absorption of gold by the cupel was found to be a most important one and was taken up for investigation. In a lesser degree, the silver absorption is important and interesting, but at resent it appears to be far more complicated and, while many figures showing silver absorption may be found through this paper, much further investigation is required to put the subject upon a satisfactory basis.

Jan 1, 1918

By Fred A. Krafft

The time allotted to this paper will permit only the sketching of general principles and practice as generally employed in the industry to maintain and preserve the physical well-being of the miner and his family. Let it be emphasized on behalf of the industry that coal opera- . tors, individually and collectively, have given primary consideration to the appointment of a mine or community physician who is charged with the responsibility of caring for the sick and injured. However, it too frequently happens that with the selection or appointment of the camp doctor many operators wash their hands of further responsibility toward the health and the working efficiency of their employees. The coal industry is so organized in most of the coal-producing areas that not only is the health of the individual miner an important production problem but the collective health of the entire mining community is a fundamental operating problem. This is particularly demonstrated when epidemics of communicable diseases attack entire communities, with resultant loss of life and production and general community distress. The problem and responsibility of maintaining high health standards among miners and their families should be given as much consideration as safety, economical production and efficient distribution are given in the successful operation of coal mines. Company Policy In the inauguration or administration of a medical program for a large mining operation or for an individual mine, the first question to be solved is what the company policy is to be with respect to the following factors pertinent to a medical program: 1. On what basis will the company and the employees finance the program ? 2. Should a contract doctor or a full-time doctor on salary be employed ? 3. What measure of service is to be rendered the employee and his family in return for his monthly contribution to the medical program?

Jan 1, 1936

By Fred A. Krafft

The time allotted to this paper will permit only the sketching of general principles and practice as generally employed in the industry to maintain and preserve the physical well-being of the miner and his family. Let it be emphasized on behalf of the industry that coal opera- . tors, individually and collectively, have given primary consideration to the appointment of a mine or community physician who is charged with the responsibility of caring for the sick and injured. However, it too frequently happens that with the selection or appointment of the camp doctor many operators wash their hands of further responsibility toward the health and the working efficiency of their employees. The coal industry is so organized in most of the coal-producing areas that not only is the health of the individual miner an important production problem but the collective health of the entire mining community is a fundamental operating problem. This is particularly demonstrated when epidemics of communicable diseases attack entire communities, with resultant loss of life and production and general community distress. The problem and responsibility of maintaining high health standards among miners and their families should be given as much consideration as safety, economical production and efficient distribution are given in the successful operation of coal mines. Company Policy In the inauguration or administration of a medical program for a large mining operation or for an individual mine, the first question to be solved is what the company policy is to be with respect to the following factors pertinent to a medical program: 1. On what basis will the company and the employees finance the program ? 2. Should a contract doctor or a full-time doctor on salary be employed ? 3. What measure of service is to be rendered the employee and his family in return for his monthly contribution to the medical program?

Jan 1, 1936

By C. D. Young

IN an effort to employ cast steel of a stronger structure than that found in the annealed steel castings, the possibilities of heat treatment which will increase the strength without materially decreasing the ductility may be resorted to. The following abstracted report (which is a brief outline of what has already been clone by the Pennsylvania Railroad Co. at its shops and Test Laboratories at Altoona, Pa.) is of material interest, as it indicates what may be done with steel castings when properly treated, thereby permitting in railway service greater strength of cast steel parts without any increase in weight or space. The question of the heat treatment of alloy steel castings is not taken up in this paper. The obscurity formerly surrounding the heat treatment of steel has been for the most part removed by the development of our knowledge of the critical points of steel, pyrometers, furnace construction, and the testing of the finished product. The operations of the heat treatment proper will be taken up under the heads of (1) heating for quenching; (2) quenching; (3) drawing. (1) Heating for Quenching.-Heating for quenching is best conducted slowly, especially in the case of castings of variable thickness. Cracks may occur either in heating or in cooling, clue to different temperatures at different points of the casting. The castings should be thoroughly soaked at the maximum temperature (generally 1,500° to 1,600° F.), 1 hr. being sufficient for sections 1 ft. in thickness. The minimum temperature which will produce the desired hardening effect will, in all cases, be found to be the most satisfactory, as the grain coarsens when the critical range is exceeded to too great an extent. All temperatures should be governed by a checked pyrometer with the hot junction to the heated object, and with several couples in a large furnace to insure a uniform temperature.

Jan 2, 1914

By T. S. Spicer, C. C. Wright

A CHARACTERISTIC property of bituminous coal is that upon being heated the coal becomes plastic, evolves volatile gases, and finally solidifies into coke This fundamental characteristic is of utmost importance and is utilized in the production of the high-temperature coke upon which the steel industry is so dependent, but from the standpoint of operation in the domestic underfeed stoker this coking tendency seriously interferes with efficient combustion When the coke formed has too strong a structure, certain difficulties result, such as low rate of burning, slow response to heat demand, and, in extreme cases, extinction of fire The plastic mass prevents uniform distribution of air through the fuel bed and, With strongly coking coals, large dense pieces of coke are produced which have much less reacting surface thin was possessed by the original coal In both ignition and combustion of solid fuels, the extent of the reacting surface is an accelerating factor Poor combustion permits a surplus of fuel to accumulate in the furnace because the rate of feed and the rate of combustion are not in equilibrium, and this produces an unbalanced condition detrimental to continued) automatic service In order to burn strongly coking coals satisfactorily in a conventional stoker during the three requisite types of operation continuous, intermittent and hold-fire, frequent attention is necessary Domestic stokers are defined by the industry as residential stoker heaters that burn 60 lb of coal or less per hour With a few exceptions, these units employ the underfeed principle of combustion in which both air and coal move in the same direction up and through the fuel-bed Domestic combustion equipment has difficulty in meeting the problems presented by the several variations in ash and volatile matter, in ash-clinkering tendencies, in coking properties, and in the particle size of bituminous coals The work of Bituminous Coal Research Inc at Battelle Memorial Institute has shown that, of these, coking characteristics and the clinkering tendencies have the greatest effect upon the operation of the conventional clinkering type of stoker Typical coke formations in a clinkering type of underfeed domestic stoker are illustrated in Fig. I, which shows (A) the ideal fuel bed obtained with a noncoking or free-burning coal, (B) the type of fuel bed formed -with, a coal that produces a weal coke, and (C) the type of fuel bed obtained with a strongly coking coal C is characteristic of the fuel bed developed when the average Pennsylvania bituminous coal is ,burned in an underfeed stoker of conventional type It is apparent from these pictures that the formation of coke trees will seriously interfere with the efficient automatic combustion of Pennsylvania bituminous coals

Jan 1, 1942

By Herbert J. French

Herbert 1. French (Member 1934), vice president of the International Nickel Co. Inc., assistant vice president of the International Nickel Co. of Canada Ltd., and AIME Howe Memorial Lecturer for 1956, died in Rochester, Minn. on Aug. 17, 1955, after a long illness. Before his death, Mr. French had laid the foundation of research on which the Howe Memorial Lecture (p. 770) was based. His associates at Inco, 0. 0. Miller and J. W. Sands, were able to complete the project, present the lecture, and prepare it for publication, following Mr. French's general outline. Born in New York on May 27, 1893, he graduated from the School of Mines, Columbia University, with a degree in metallurgical engineering in 1915. Mr. French gained his early engineering experience with the American Smelting and Refining Co., serving as a chemist and as-sayer at the company's Murray, Utah, installations. He later returned east and became a metallurgical engineer for the General Vehicle Co., Long Island City, IT. Y., a subsidiary of the General Electric Co. In 1917 Mr. French was appointed civilian inspector of materials for the U.S. Army Signal Corps, and continued this work when it was later absorbed into the Bureau of Aircraft Production. Subsequently he was appointed district inspector in Philadelphia for the Pittsburgh (Ordnance Metallurgical) office, later transferring to Pittsburgh. After World War I Mr. French became an assistant physicist on the metallurgical staff, U. S. Bureau of Standards, Washington, D. C. During his years with the Bureau, he was successively associate physicist, metallurgist, senior metallurgist, and assistant chief, division of metallurgy. In 1929 Mr. French joined International Nickel as a metallurgist at the company's Bay-onne, N. J., research laboratory. Transferring to the development and research division, New York, in 1931, he took charge of alloy steel and iron development, becoming assistant manager of this division in 1943. Mr. French's appointment as an Inco vice president came in March 1947. Previously, he was appointed assistant vice president of the International Nickel Co. of Canada Ltd. in January 1947. Mr. French served the War Production Board during World War II as senior technical consultant in charge of the metallurgical and specifications section of the iron and steel branch. When this section of the WPB was organized into the steel division, he was appointed chief of the metallurgical branch. From March 1944 to September 1945 Mr. French served as assistant director. Herbert French was well known not only for his prolific contribution to the metallurgical literature, for which he received numerous awards, but also for his prolonged service to the profession through its technical societies. He was a past president of ASM, and was the Campbell Memorial Lecturer for that group in 1933. Mr. French was honored by the American Society for Steel Treating in 1931 when he was awarded the Henry Marion Howe Medal. A series of lectures he gave in 1941 before the Fourth Western Metal Congress in Los Angeles was later published in book form under the title Alloy Constructional Steels.

Jan 1, 1957

By S. Floreen

Seven iron alloys ranging from 5 to 12 pct Ni and 5 to 14 pct Cr were studied. All alloys transformed to bcc massive martensites. Tempering increased the strengths , probably because of relief of residual stresses generated by the martensite transformation. The major strengthening mechanism appeared to be solid-solution hardening by nickel and chromium. Studies of the work-hardening behaviw, of the effects of prior austenite grain size, and of the effects of changing strain rate and test temperature gaue results very similar to iron or low-alloy steels. Increasing nickel contents markedly improved the toughness at subzero temperatures. Studies of the flow properties did not, however, indicate the reason for the beneficial effect of nickel on toughness. The marine atmosphere corrosion resistance of the alloys was improved primarily by chromium additions, but increasing nickel contents were also beneficial at low levels of chromium. J\ number of maraging and PH stainless steels are strengthened by precipitation hardening in a low-carbon Fe-Ni-Cr martensite matrix. To some extent the resultant properties of these steels must depend upon the properties of this matrix. The present study therefore was conducted to evaluate the transformation characteristics and mechanical properties of a series of Fe-Ni-Cr martensitic ternary alloys. A limited evaluation of the corrosion resistance of the alloys in marine atmosphere was also made. ALLOY PREPARATION Seven 100-lb air induction melts were prepared using electrolytic iron, nickel, and chromium metal additions. The initial Fe-Ni charge also contained 0.05 wt pct graphite to produce a carbon boil during melt down. After melting of the base charge, the heats were refined with 0.1 wt pct additions of manganese, silicon, aluminum and titanium and poured into cast-iron molds. The ingots were homogenized at 1250°C and uni-directionally hot-rolled to 2-in. plate. They were then homogenized another hour at 1250°C, and unidirection-ally hot-rolled to %-in. plate at a finishing temperature of approximately 1050°C. The compositions of the heats are given in Table I. Two additional heats were prepared as 40-lb vacuum-induction melts using electrolytic iron, nickel, and chromium metals, and commercially pure molybdenum chips. A carbon boil, and 0.1 wt pct additions of aluminum and titanium were again employed, but manganese and silicon were not added. The heats were converted to %-in. plate using the procedure described above. The compositions of these heats are included in Table I.

Jan 1, 1967

By C. D. Woodward

THE subject of electric signals for the despatching off mining cages through shafts has received cousiderable attention recently from various mining companies. The Anaconda Copper Mining Co. has found it necessary to develop a system that is reliable, safe and simple in operation, and easy to repair. The movement of all mine cages or skips is under the direction of a station tender, who rides on the cages when men or supplies are being lowered or raised. When ore is hoisted, he is stationed at a skip pocket for loading and despatching the skips. For the station tender's use, two signal systems are installed in each hoisting compartment, and he is the only employee authorized to use them. One system is known as the "AC" or Station bells, as it is operated from the 110-volt, 60-cycle, power service; the other system, called the "DC" or shafts bells, takes its energy from closed-circuit primary batteries. As a supplement to the two main signals, a buzzer system is installed. The general arrangement is similar to "the main signal, except that there is a mine buzzer at each station. When a signal switch connected into the buzzer system is pulled down, all buzzers are operated, thus notifying the station tender that he is wanted at some particular level. Placed on the station posts, and within easy reach of the men on the cages, are the signal pull switches for the main signals. The station, or "AC," pull switches are furnished with a short rope as shown in Fig. 1, while the shaft, or "DC," pull switches are equipped with ropes that extend down the shaft past the next station. To avoid all confusion in the use of the three signal systems, a standard arrangement has been adopted in all mines for the location of the pull switches. Fig. 2 illustrates the position of the pull switch at the various mine stations for the main signal systems, but it does not show the buzzer pull switch; this is fixed to the roof timbers about 25 ft. back from the shaft. If the skip pockets are a considerable distance below the station, a pull switch for each main shaft compartment is connected to the "AC" system and placed at this point. However, if the distance is short, a light cord is attached to the station pull switches and dropped down to the skip pocket.

Jan 2, 1922

By Walter Herd

FOR the past eight years No. 2 mine of the Cumberland Railway & Coal Co., Springhill, Nova Scotia-a subsidiary of the Dominion Coal Co., Ltd.-has had an unenviable reputation for bumps. As the workings extended in certain directions under a greater cover, these bumps increased in severity and it became apparent that some change in the system of extraction was necessary if the mine was to continue to operate. In September, 1924, following several fatalities resulting from bumps, the Mines Department of Nova Scotia requested from the U. S.. Bureau of Mines the services of George S. Rice, Chief Mining Engineer of the Bureau, to report on the conditions then prevalent in No. 2 mine, Springhill. This request was promptly and courteously granted. Mr. Rice made a full investigation and a comprehensive and helpful report, which is embodied in the 1924 Annual Report of the Department of Public Works and Mines, Nova Scotia. Prior to 1925, the room and pillar method wasp employed and in January of that year (there being a cessation of work from March to August due to labor troubles) longwall retreating on the west side, on a limited scale, and in a small section on the east side of the mine was started. The major portion of the east side was not operated on this system till August, 1926, as there was developed a considerable area ready for pillar extraction between an arbitrary boundary and a point up to which bumps of any consequence had not been experienced. In the interval development work for longwall retreating below the 5900-ft. level was vigorously pushed. This longwall retreating system was suggested by Mr. Rice as a possible remedy and was heartily endorsed by the company officials. This paper describes the conditions and happenings subsequent to Mr. Rice's report and more especially the results with the longwall retreating system of mining under the peculiar circumstances pertaining to mining No. 2 Seam, Springhill, at depth, and records the conclusions which experience with several severe bumps under this mode of extraction would suggest. Except where necessary to make the paper intelligible as an entity any duplication of Mr. Rice's report will be avoided.

Jan 1, 1929

By Henry Louis

The object of the present paper is to call attention briefly to a novel method of analyzing the action of the ordinary gravity stamp, which has not only thrown much light upon the exact motion of the stamp-head, but promises also to be of value in determining the efficiency of a new mill before setting it to its work of crushing, and in this respect should be of service to constructors of mining machinery as well as to mining engineers. The method was devised by Mr. D. B. Morison, and developed in connection with his experiments on the comparative crushing-effects of his patent high-speed stamp and the ordinary cam-stamp, which were carried out at the works of Messrs. L. Richardson & Sons, Engineers, Hartlepool, and on which he read a paper at Newcastle in 1897.* Mr. Morison's experiments were of a very exhaustive nature; and having been consulted by him during his investigations, I had frequent opportunities of examining the methods employed and the results obtained. Experiments were first made with an apparatus resembling the indicntor of a steam-engine, inasniuch as the drum revolved alternately backwards and forwards, thus producing a closed diagram. This form was not found satisfactory, and it was therefore altered so as to cause the drum to revolve continuously in one direction, thus giving a continuous or open diagram. The arrangement is shown in plan in Fig. 1; a collar, A, surrounds the stamp-stem loosely and works between the guides B, B, which constrain it to move in a vertical line only. Immediately above it and below it, a couple of collars are clamped to the stamp-stem, so that the latter, while free to revolve,

Jan 1, 1899

By D. Cox, M. J. Duggin, L. Zwell

The carbides of approximate composition and Mn have been studied using X-ray diffraction techniques. Those carbides of the type (Fe,Aln)zC ave isostructural with cementite. The cell pararmeters a and c have minimum values at approximately 10 at. pd substitution of manganese for iron; no satisfactory explanation has yet been found for this phenomenon. The carbide fFeMn4)C has a monoclinic unit cell whose dimensions are close to those of ,11,15Cz A neu-troip-dij~ractiot~ study of (F'eAlrz4)C~ reveals that, like MnsCZ, it is isostructural with Pd5Bz. The iron and manganese atoms occupy the palladium atom sites, while the carbon atoms were found to have the same atomic coordinates as the hovon atoms. A neutrorr-diffraction study of indicates that the carbon-atom positions are very close to those occupied in (Fez.,ll/lr~,.3)C. In both carbides studied, tlre iron and manganese atomzs were found to be essentially randomly distributed, although, in the case of (Fe,.811fn1.2)C, it is possible that there may be a slight preference of manganese atoms for- the general (d) positions and a corresponding slight preference of iron atoms for the special (c) positions. It has been found that a complete range of solid solution exists between Fe3C and Mn3C at 1050°C,I although Mn3C becomes unstable when the temperature is reduced to 95O0C,' and can only be retained by rapid quenching. It is also known that a complete range of solid solution exists from Fe5Cz to M~SC~,~ although the stability range of carbides of the type (Fe,Mn)sCz as a function of the relative proportions of iron and manganese is not known. X-ray examinations of Oh-man's carbide3 and Spiegeleisenkristall,~ which have the approximate compositions (Fe3.67Mnl.33)C2 and (Fe3-,Mn,)C, where x lies between 0.4 and 1, respectively, have been made. The following carbides have also been studied: ] The lattice parameters determined during these investigations are listed in Table I. It is seen that carbides of the type (Fe,Mn)sCz have a monoclinic unit cell while carbides of the type (Fe,Mn)3C have an orthorhombic unit cell. It is evident that the variation of lattice parameters with manganese content is not linear for carbides of the type (Fe,Mn)3C. The coordinates of the atoms in (Fe2.7Mno.3)C have recently been determined by single-crystal analysis., The fractional atomic coordinates have been shown by Fasiska and jeffrey to be in good agreement withj those deduced from an earlier analysis of Fe3C by Lipson and etch.' However, it was impossible to determine whether iron and manganese atoms occupied ordered positions because of the small difference between the atomic scattering factors of iron and manganese. The atomic positions in Mn5Cz (Refs. 8 and 9) and Fe5C2 (Refs. 7 and 8) have been obtained only by comparisons made with the isostructural compounds P~SB~.' Since X-ray diffraction techniques were used in these investigations, accurate positioning of the carbon atoms, which have a low atomic scattering factor, was difficult. No attempt has been made to determine the atomic positions in the other carbides previously studied. It was felt that an investigation of the lattice parameters of a number of intermediate carbides of the types (Fe,Mn)sCZ and (Fe,Mn)& would be of interest. It seemed likely that a neutron-diffract ion study of such carbides would indicate whether ordering occurred between the iron and manganese atoms because of the large difference between the neutron-scattering cross sections of iron and manganese. It also seemed probable that such an investigation would provide a determination of the atomic coordinates of the carbon atoms. I) EXPERIMENTAL DETAILS Specimens, each weighing approximately 20 g, were carefully prepared according to the following proportions: The components were 500-mesh powders of 99.995 pct purity iron and spectroscopically pure carbon and a 200-mesh powder of 99.995 pct purity manganese. The component powders were intimately mixed by prolonged shaking, then each specimen was inserted into a spot-welded cylindrical container of tantalum foil, whose end was closed but not sealed. Each specimen in its envelope was then sintered at 1050° C for 24 hr in a thin-walled evacuated quartz capsule, such a time having been previously found sufficient for equilibrium to be attained.' Each specimen was then quenched in order to attempt to retain the high-temperature phase, as the literature indicates that transformations may occur on cooling. Debye-Scherrer X-ray photographs were taken of each specimen using a 114.6-mm-diam camera, Fig. 1, patterns 2 to 6. The exposure time was 6 hr using filtered iron radiation at a tube voltage of 40 kv and a tube current of 12 ma.

Jan 1, 1967

By B. T. Brady

Rock mechanics, like all engineering disciplines, must have a theoretical foundation. The subject of this chapter is the formulation of analytical methods that may aid in the rational design and determination of the stability of engineering structures in competent brittle rock materials. By an engineering structure in rock, we mean any (1) excavated sub- surface opening, (2) open surface structure, or (3) system of openings in rock that is virtually self-supporting-that is, not requiring artificial systems to carry structural stresses. One factor necessary for designing or evaluating a structure's stability is knowledge of the material's mechanical properties, such as stress-strain behavior and fracturing characteristics. The composition of most structural materials such as metals and concrete is uniform and reproducible to the degree that their mechanical properties in service are nearly the same as those measured in the laboratory. Consequently, a rational design can be made on the basis of published mechanical property values. The same equivalence does not exist for rock materials for two reasons: (1) the composition of even the most common rock types is highly variable, and (2) the problem of the size effect is present. Mechanical property tests not conducted at a scale that includes these effects in normal proportion will not be representive of the in-situ rock mass. Of course, the alternative is to perform the test in-situ. Comparatively few mechanical property tests have been performed in-situ because of the physical limitations of test equipment and the prohibitive cost. The current procedure is to design a structure based on small-scale laboratory measurements, with a safety factor usually determined by the experience of the design engineer. While this procedure is somewhat unsatisfactory, laboratory measurements can and do provide a useful basis for the initial design.

Jan 1, 1970

By W. P. Sykes

Seven years ago, Dr. S. L. Hoytl presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. Steps in Preparation While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows : 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

By W. P. Sykes

Seven years ago, Dr. S. L. Hoytl presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. Steps in Preparation While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows : 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

By W. P. Sykes

SEVEN years ago, Dr. S. L. Hoyt1 presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. STEPS IN PREPARATION While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows: 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

By George Smith

IN discussing present-day business and industrial troubles we easily drop into the habit of clinical diagnosis. Talk of this kind, with its emphasis on suspicious symptoms and abnormal tendencies, makes us all morbid. As an English essayist has put it, we may thus induce a melancholy, temper that simply in-vites the ministrations of social and political quacks. It is far better-because nearer the truth-for us to recognize that our condition is in no sense diseased, that our body politic, social and economic, is suffering merely from growing pains; that America is not de-cadent-indeed, that any lapses from staid normality are traceable to the, excesses of youth. Our chief .trouble, then, is only that our industrial state is still young; it may be that we have been growing too fast. The growth in the industrial development of our country from pioneer days to the present time has been marvelous. Too many of us, however, take all this as a matter of course-we credit this record of American progress to our American genius alone. Too often we overlook the fundamental relationship between resources and progress-that man is aided and even guided by Nature. The fact is, social advance, indus-trial progress, national prosperity all have their ma-terial basis in natural resources. In furnishing the needed mineral raw materials to the great manufac-turing industries of the United States there has been no halt, but rather a general acceleration. No other phase of American activity can show-equal advance. As the decades have passed, the winning of mineral wealth has progressed from the role of a stimulus for western exploration to that of the foundation for nation-wide business. In 1890 the Sherman law was passed; since then the population of the United States has about doubled. Since then, too, thevalue of the annual product of the mines of this country has increased better than eight-fold-from 650 millions to 51/ billions of dollars. Since then the four largest branches of the mineral industry, which supply the iron and copper, the bituminous coal and petroleum-the bone and sinew and the energy of all other American industries-have increased their annual output nearly ten-fold as to value and six-fold as to quantity. Such a growth in the volume of mineral output must be taken as a true measure of the ex-ceptional service rendered by the mines of the United States. Not only is this a much larger country than it was 38 years ago, but its growing mineral industry has met demands that have been out of all proportion to the growth of the population.

Jan 8, 1928

By J. L. Gillson

IN a brief summary of the many occurrences of fluorspar in our western states, it is not possible to go into detail in regard to the geology, mining and milling methods, and reserves about individual deposits. Rather a broad review is made of the occurrences and an analysis of how the western deposits may fit into our future domestic economy is presented. GENERAL STATEMENT ON FLUORSPAR SITUATION Fluorspar has been used for years as a flux in the manufacture of basic open-hearth steel, in foundry cupolas for melting pig iron, in the manufacture of opalescent glass and in the preparation of hydrofluoric acid. In 1880 the annual production of fluorspar in the United States was around 4000 tons per year. By 1900 it was up to 21,656 tons and between 1902 and 1908 it averaged about 40,000 tons annually. Prices were then so low, by present standards, that it seems impossible to believe now that mining could have been performed profitably at the price levels then prevailing. In 1890 fluorspar sold at the mines for $6.70 per ton, in I901 for $5.81, in 1916 for $5.92. When the United States entered World War I, fluorspar production and price skyrocketed; the production reached 263,817 tons in 1918, with prices above $20.00 per ton, and prices were even higher in 1919 and 1920. After 1920, the domestic production fell from the 1918 level to about 125,000 tons annually and the average price dropped back to about $I8.00 per ton. By 1935 the average price had fallen to $15.00, but in 194o with a rising demand the average price of all grades had gone back up to $20.31. Today it is 75 per cent higher than in 1940 and presumably the price of acid grade at least would be even higher if it were not for price ceilings. The first subsequent year that the domestic production exceeded that of 1918 was 1941, and the 1944 production is expected to exceed 400,000 tons, 'or over one and a half times that of 1918. In five-year periods, average production and imports were as are shown in Table I. [ ] Many people concerned with the consumption of fluorspar believe that the postwar period ahead will show a repetition of price trends of the last such period. They believe that imports will be- again an important factor in the available supply and the price will fall back gradually toward the prewar level. The following basic factors are pertinent in analyzing this conclusion:

Jan 1, 1945