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By R. M. Brick, M. A. Williamson

CERTAIN features of the response of copper and brass to deformation and recrystallization remain obscure. The textures obtained on rolled sheet are listed by Schmid and Boas1 as: No adequate explanation has been advanced for the presence of the secondary deformation texture of copper and its absence in brass or for the origin of the cubic recrystallization texture of copper.2 A recent publication3 attempted to rationalize the above empirically described annealing texture of brass on the basis of retention of the (110) [112] rolling orientation plus twinning about the central octahedral poles of the usual secondary (110) [115] orientation. The difference in the textures of annealed copper as compared to 70-30 brass is also shown by the difference in the position of ears for drawn copper, at o° and 90°, as compared with drawn brasses, at 45°, for all compositions between 90-10 and 70-30.4 Data on individual crystals are as yet too few to permit of an analysis of these textures comparable to that of mild steel as made by Barrett and Levenson.5 EXPERITMENTAL METHODS The materials studied included copper specimens cut from the central, equiaxed crystal portion of a tough-pitch wirebar; brass made from this copper and high-purity (99.99 per cent) zinc including alloys of 7 per. cent, 15 per cent, 24 per cent, 29 per cent and 36 per cent Zn and large single crystals of 70-30 brass. Sections ¼ in. thick of the cast polycrystalline copper and brasses were reduced 40 per cent by rolling, recrystallized to a common grain size of 0.045 mm. and then rolled directly to foil 0.002 in. thick. Hardness readings employing both the Vickers and Rockwell machines were taken at intervals during the reduction. For comparison, similar specimens were cross-rolled-i.e., turned through 90 for each pass-and comparable hardness data were secured. Finally sections from the single crystals of brass were cut to obtain the following initial orientations; these sections were rolled, hardness data secured and a complete micrographic record of structural changes obtained:

Jan 1, 1941

By C. D. Hunter, J. B. Browning

During the year 1934, Kentucky oil and gas operators have partly overcome their past depression fears and in the oil industry, with possibly more abandonments of old oil producers than the completion of new oil wells, produced 4,814,904 bbl. of oil in 1934 against 4,501,511 bbl. in 1933. In the gas industry of eastern Kentucky, 115 gas wells were completed during 1934. This production is delivered through two 20-in., one 16-in., one 12-in., one 10-in., and two 8-in. pipe lines to supply both domestic and industrial markets in Cincinnati, Ohio; Louisville, Lexington, Frankfort, Winchester, Ashland, Covington and other Kentucky towns; Washington, D.C., and other eastern cities. The largest percentage of these gas wells and production are from the Devonian black shale area of Floyd, Pike, Knott, Martin and Magoffin counties, Kentucky. In this area the largest percentage of 1889 wells, developing 421,-215 acres, has been completed in the past 10 years, of which 55.3 per cent produce from the 400 to 550 ft. of Carbonaceous Devonian black shales. The successful results obtained from these Devonian shales are due to the physical effects of the 5000 to 6000 lb. of gelatinated nitroglycerin with which the entire 400 to 550 ft. of shale is shot. A very small number of the shale wells are natural producers and do not require shooting. Other than the Devonian shale gas production, the remaining 44.5 per cent of the gas in this field is encountered throughout the entire strati-graphic section above this horizon; namely, salt sands of Pennsylvanian age and Maxon, Big Lime and Weir of Mississippian Age. A very small percentage is encountered in the Corniferous Devonian lime and the Silurian Big 6 below the black shales. In western Kentucky, in the counties of Henderson, Webster, Hopkins, McLean, Christian, Muhlenburg, Ohio, Daviess, Hancock, Brecken-ridge, Hart, Barren and Warren, many gas wells have been completed, but, because of insufficient market, activity has been somewhat desultory. The area is served by the pipe lilies of the Kentucky Natural Gas Corporation, with headquarters at Owensboro. Their market is increasing and the gas is delivered to Owensboro, Henderson, Madisonville, and many

Jan 1, 1935

THERE is probably no phase of basic open-hearth steelmaking that is more of an art and less of a science than mold and pouring practice. It varies widely from plant to plant; consequently it is obviously impossible to set down in detail in this chapter the many ramifications of practice that are now used. The discussion that follows therefore attempts only to give an outline of the more common methods, with examples sufficient to indicate some of the variations in procedure, and to emphasize a few of the many underlying problems that face the open-hearth operator at the pouring platform. MOLD DESIGN Ingot molds are hollow castings of considerable wall thickness. Despite this, non-uniformity in wall thickness should be strictly avoided to prevent the setting up of unnecessary stresses. Molds are cast in various forms, sizes, and shapes depending on the type of steel, and on whether the ingot is to be withdrawn from the mold or the mold from the ingot. The selection of ingot-mold material, which is usually cupola or blast-furnace iron containing approximately 3.5 per cent carbon, 1 per cent silicon, 0.9 per cent manganese, 0.2 per cent phosphorus, and 0.07 per cent sulphur, is governed by numerous considerations that affect mold life. (1) Factors in addition to wall thickness that should be given primary consideration at the foundry are casting skin, shrinkage stresses, and casting temperature. Factors in Mold Design. In use, mold thickness is of greatest importance, for it must be heavy enough to freeze the molten metal rising in the mold and to reduce the temperature of the steel below that of the melting point of cast iron to prevent the inner surface of the mold from melting, which would result in the welding of the ingot to the mold. The skin of an ingot, which solidities immediately upon contact with the relatively cold walls of the mold, must soon become thick enough to contract on the fluid mass and pull away slightly from the sides of the mold. The separation of the ingot from the mold depends entirely on the heat taken up by the mold from the steel.

Jan 1, 1944

By R. S. Archer

In the microscopic examination of aircraft-engine parts made of heat-treated alloy steels, the writer has been forcibly impressed by the failure of the usual etching processes to disclose any but gross defects in heat treatment. It seemed particularly desirable to bring out the grain size of the steel, which is indicated in the ordinary etching processes chiefly by the change in orientation of structure from grain to grain. After various attempts, a fairly successful method has been found, which is here presented in the hope that it may be of use to those who have occasion to examine these steels in the hcat-treated condition. The specimens worked with have been mostly chrome-nickel steels heat treated (that is, hardened and tempered) to a Brinell hardness of around 300. A few experiments with other specimens will be referred to later. Briefly, the method employed consists in etching the steel about 10 min. in a fresh solution of picric acid in ethyl alcohol, and then rubbing off the smudge of carbonaceous matter on moist broadcloth. Different samples of almost identical analysis, heat treatment, and physical properties (including resistance to impact) respond quite differently to this treatment. In some, the grain boundaries are developed quite readily, while in others, especially in those whose grain is unusually fine or in which the final hardening heat has not quite obliterated the previous crystallization, the results are more obscure. The exact time of etching to secure the best results also differs for various samples, and the greatest success is usually attained by a process of "tinkering." Such a process is illustrated in a series of micrographs, the first six of which were taken at a magnification of 300 diameters. The properties of the steel are as follows: Carbon, per cent............... 0.42 Brinell hardness.............. 293 Nickel, per cent................ 1.35 Yield point, pounds per square Chromium, per cent............. 0.90 inch........................ 131,000 Copper, per cent................ 0.025 Maximum strength, pounds per Manganese, per cent............ 0.74 square inch................. 144,500 Phosphorus, per cent............ 0.024 Elongation in 1 in., per cent... 28 Sulfur, per cent................ 0.036 Lod impact, foot-pounds...... 51 Reduction of area, per cent...... 57.3

Jan 1, 1920

By Edmund Shaw

In the year just past there were produced in the United States about 170,000,000 tons of sand and gravel. Much of this was pit-run material used for gravelling roads and as railroad ballast on lines that did not carry heavy traffic. But more than half of it was marketed as washed and sized, or graded, material. The methods used for preparing sand and gravel for the market have long been used in ore dressing and, as in ore dressing, depend on differences in the specific gravity of two substances or in the size or weight of particles. But many changes in the design and operation of plants and machines have been necessary. In ore dressing, the concentrate is only a small part of the feed; in sand and gravel washing, it is much the larger part of the feed. In addition, such close work as is needed when concentrating a metallic ore is not needed when washing gravel; the ability to put through a large tonnage is more important, and sizing, which is only a preliminary process in ore dressing, is an end to be attained. Rock crushers are found in most sand and gravel plants and they are used to break up the larger pieces from the deposit (known as boulders and cobbles) which are removed by a scalping screen. The crusher discharge is usually sent back to the scalping screen, the perforations in this screen setting the maximum size of the finished product. Washing Washing is to prepare sand and gravel so that they may be used as aggregates in concrete and wall plaster and in various processes in which impurities would harm the product. At one end of the scale of washed materials may stand ordinary concrete sand, which in some states may contain as much as 3 per cent, of clay and still be used in highway concrete construction. At the other end will stand the silica sand used for making plate glass, which must be washed so clean that the impurities that can be removed by washing do not exceed a few hundredths of a per cent. The methods and machinery that would produce one of these

Jan 1, 1926

J. M. HARTMAN, Philadelphia, Pa.: Mr. Fackenthal can remember some queer things that occurred at Durham, Pa., Aug. 3, 1876, while he was superintendent. The furnace was working stiff, i.e., blast-pressure 10 to 11 pounds, which was high pressure for those days. With this pressure there was some circulation through the stock. At 9 p.m., flushed cinder. After flushing, air was thrown off' for a moment to " bot up "; the keeper turned the lever and threw on air just as the scaffold dropped, which eased up the pressure to 4¼ pounds. The air-receiver is twice as large at Durham as at other places. The air from this receiver, added to the two seven-foot blowers, gave an extra large volume, which, rushing into the furnace, fired the finely-divided carbon, causing an explosion that threw part of the stock in the furnace out into the open air, threw up the bell-and-hopper with the tunnel-head plates, and gave off' a large volume of carbondust. The bell-and-hopper going up first, the stock followed, and, striking the bell-and-hopper, was deflected in a shower over the cast-house roof, breaking the slates. Sitting at the corner of the engine-house at the time, the stock pelted me, when I ran around the corner to get rid of it. Remembering there were two men at the furnace-top, I shut down the engines, and, running to the top, found them sitting in the hoist-house enjoying the fire-works. The explanation of this explosion is simple. There is in the blast-furnace a bed of fuel extending up, say, 16 to 18 feet above the tuyeres; in this bed of fuel some stray pieces of limestone are found, and a few pieces of unreduced ore; but, generally speaking, it is all fuel. On this bed of fuel is the zone of fusion. In this zone the descending stock is liquefied, except the fuel; the iron, melting, drops out of the ore, and the gangue unites with lime, forming cinder. The iron falls in the form of shot, and, with the cinder, trickles

Jan 1, 1899

By Robert H. Richards

THE Institute of Mining Engineers has shown so much interest in the educational problem of profitably combining theory and practice, that it seems especially appropriate to lay before its members the methods and aims of the mining laboratory of which I have charge, and in which one form of combination of hand with head work is now being tried. If anything may be contributed toward the solution of this problem by the discussion which follows, my purpose mill be attained. Whether it was wise or not to establish a mining school so far from the principal mining centres, does not now enter into the question. Given, a mining school already begun, how shall it be made most efficient in developing engineers who are trained to think for themselves as well as versed in the works of others ? This is the question with which we have had to deal. In considering the bearing of this laboratory work upon the students' preparation, it will be convenient to take it up under five different heads: 1. The methods and aims of the laboratory. 2. The advantage to students of having a part, at least, of their practical work in the curriculum of their school. 3. The advantage to be derived by mine; and works. 4. Degree of accuracy which may be attained in working ores on a small scale. 5. Reslts of work in the laboratory. 1. The Methods and Aims of the Laboratory.—During the May meeting of 1873, held in Boston, I had the privilege of reading before you a paper stating the plan; and aims of this laboratory. Since that time me have been constantly following out those plans, and are more than ever convineed that me are working in the right direction. We do not feel that the time we have spent has been in any sense thrown away. Perhaps the aims of the laboratory can be most clearly shown by illustration. Many young engineers have school thinking that they know everything. They go to the works, and expect to teach the superintendent something and the men a good deal, regardless of the fact that it is this spirit that has prejudiced workmen against schoolmen. They are often more trouble than they

Jan 1, 1879

By John Chipman, K. C. McCutcheon

To a very large extent the quality of a mild steel ingot is determined by the manner in which it is poured into the ingot mold and its behavior during the first few minutes after it has been poured. The formation of the solid rim of metal around the periphery of the mold, the effervescent action of the liquid steel within this solidified rim and the upward or downward movement of the metal level are indications of what is going on beneath the surface of the liquid metal, especially at the interface at which solidification occurs. Observation of this "rimming action" enables an experienced observer to predict the thickness of the sound skin of the ingot and the location and extent of cavities or "blowholes" caused by entrapment of gases. The control of rimming action at the hands of a skillful steel pourer is a vital part of the control of quality in mild steel sheet, and the behavior of the liquid steel during the rimming period is a useful criterion of the melting and refining practices employed in the open hearth. The behavior of rimming steel during solidification depends primarily upon the evolution of gases from the molten metal and it is therefore a problem of considerable interest to determine the nature and amount of the gases evolved. A number of attempts to determine either the amount or the analysis of the evolved gases have been reported. Klinger,1 in 1925, analyzed the gases extracted from rimming, semikilled and killed steel ingots and found that the chief constituent of the rimming gas was carbon monoxide. The relatively large amounts of nitrogen reported in his first few samples may have been due to incomplete removal of air from the gas-collecting mechanism. McKune2 reported similar studies of rimming ingots from which surprisingly large proportions of nitrogen and hydrogen were evolved. Ameen and Willners3 determined both the amount and composition of gases extracted from unkilled ingots with the aid of diminished pressure. . Their ingots weighed only 80 kg. (176 lb.) and apparently were solid within two or three minutes, so that their

Jan 1, 1938

By John A. Church

When, in 1879,I examined the mines of the Tombstone Mill and Mining Company, at Tombstone, Arizona, I found a bed of tailings containing 12,000 tons, which had a value of 9 to 12 ounces of silver per ton and some gold. The ore had been amalgamated in pans, in which each charge had been ground for four hours, having been pre viously stamped through rough-punched screens, which gave a pro duct varying from 1-100th to 1-20th of an inch, according to the state of wear of the screen. It was certain that a large proportion of the tailings must be in fine slimes, and the question of recovering their value was difficult. Even now the concentration of slimes is . an unwelcome task, and at that day very little was known about it. Nevertheless, after considering the results of a test by repanning the tailings, I advised the company to concentrate and smelt, although they had to face the difficulty of making a smelting-product from slimes containing only 3 per cent. of lead. Limestone was abundant enough, but no iron suitable for flux was to be had for hundreds of miles. One of the company's claims con tained an argeutiferous manganese-ore, which gave but poor results by amalgamation. This was one reason for recommending smelt ing ; for if manganese would play the part of a precipitant, as iron does, the company could smelt by combining two of its silver ores, without other flux than the small amount of lime that might be needed. At that time no smelter had ventured to trust manga nese as a precipitant, though large quantities of this ore containing silver were bought and used by custom-smelters, who looked upon the manganese solely as a basic flux for silica. I believe that no other furnace has been obliged to trust this metal, and that the man ganese practice of Tombstone remains unique among the records of smelting lead-ores in the shaft-furnace. The bright side of the problem was given by the fact that the mines were shallow and that the enterprise would at least begin with oxidized ores. The tailings contained about 85 per cent. of silica,

Jan 1, 1895

By John T. Crawford

Much has been written of late regarding the flotation of coal as a means of reclaiming the valuable portion of the fines encountered in nearly all methods of coal preparation. Whether the process be wet or dry, whether the dust be sent through the entire process or removed prior to the cleaning by some such method as screening or aspiration, one of the final products consists of a considerable proportion of — 48-mesh material. The percentage of this —48-mesh material depends upon the mining method, transportation, storage, and method of preparation. The tonnage of this dust material ranges from 1 to 10 per cent of the total output of the cleaning plants. Four methods of disposal are available for this coal: 1. Disposal with the refuse from the plant. 2. Addition, after being reclaimed from the wash water, or dust collectors, without cleaning to the larger sizes. 3. Separate disposal as a pulverized fuel. 4. Cleaning so that addition to the larger sizes benefits the product as a whole. It is also true that flotation in one form or another is the only known way to effectively clean this material. While some processes do a reasonable cleaning job down to and including +l00 mesh, by far the greater majority stop at or short of the + 48-mesh size. Much of the literature on coal flotation passes by the fred pulp density and size by merely stating that the feed varies from 20 to 30 per cent solids and that the size range is from — 1/4 in. or — 1/8 in. to 0. Small wonder then that some operators with entirely different conditions, and not knowing the machine capacity, throw up their hands in despair when flotation is mentioned. Too much parallel is drawn between flotation methods as applied to ores and as applied to coal, to the detriment of the latter. In the flotation of metalliferous ores the feed pulp density ranges from 20 to 30 per cent solids, depending upon the amount of mineral to be floated and upon the size analysis. Thus where 2 to 5 per cent of the

Jan 1, 1936

By David B. Reger

Oil and gas and their derivatives continue to be stable products in West Virginia. In the midst of the cataclysmic happenings of 1930 to 1934, which have swept away banks and practically destroyed many other enterprises of presumably nonspeculative character, the possession of a royalty or working interest in a few old oil or gas wells has prevented disaster in literally thousands of homes. These old wells yield their daily quotas of basic commodities, which the public must have. Fortunately, the facilities of disposal in the Appalachian Province are so ample and well managed that the owner of such equities may be reasonably certain that his proportionate share of existing markets will be afforded him without much effort on his part. In most cases these investments are free from encumbrance or hypothecation, therefore the main uncertainty is the date of ultimate exhaustion at the source. Generally, this is known to be fairly remote. The net result has been that individual owners part with such investments only as a last resort. In sharp contrast to the action of the small owner of wells or royalties who has prudently refrained from jeopardizing his rather certain income by drilling new wells that may be failures, or of which the product may not be needed for the moment, has been the plight of various promotional enterprises in natural gas. Many of these ventures have been operated by amateurish remote control and practically all have been overloaded from the start with bonds and debentures, which could only be satisfied in a rising and expanding market; and with operating costs that have been exceedingly high because of widely scattered producing units and large overheads. Many of these promotions are now in receivership or bankruptcy and in various instances the original units have been recaptured by former owners and have again become profitable by reason of personal operation and elimination of all forms of overhead expense. New Development In 1934, the State issued 524 permits for drilling. According to the trade journals, 553 wells were completed, with 184 oil wells, 274 gas wells and 95 dry holes (Table 3).

Jan 1, 1935

By L. D. Jaffe, John H. Hollomon

THE hardenability concept has become widely used during the last few years for the choice and substitution of steels. Before the work of Grossmann,1 the systems for predicting hardenability from chemical composition could be used only over a narrow range of composition. Grossmann introduced a comprehensive system, which has been effective in calculating the hardenability of most types of moderate or low-alloy steels. However, occasions .often arise that require the calculation of the hardenability of high-alloy steels from their chemical compositions. Experimental determinations of the hardenabilities of such steels indicate that the Grossmann system predicts much greater hardenabilities than are realized. The fact that cases do arise in which the Grossmann method does not, apply indicates that the fundamental hypothesis of the system may not be generally applicable. It seems advisable to re-examine not only Grossmann's system but also the concept of hardenability itself. HARDENABILITY If steel parts are to possess a martensitic structure after quenching, they must first be austenitized and then cooled through the pearlite and bainite transformation ranges sufficiently rapidly to avoid the formation of pearlite, bainite, and proeutectoid products.* If, on cooling, these transformations are avoided, the resulting structure can consist only of martensite (and retained austenite). The hardenability of a steel is measured in terms of the severity of the cooling conditions necessary to avoid the pearlite and bainite transformations. The less rapid is the cooling necessary to prevent the formation of bainite and pearlite, the higher is the hardenability. The pearlite and bainite reactions appear to be differently affected by the alloying elements. Not only is this indicated by the published isothermal transformation data, but recent work by Zener2 affords a rational interpretation of the differing effects of the alloying elements. Manganese,3 for example, appears to decrease the rates of the pearlite and bainite transformations by equal percentages, while molybdenum4,5 is approximately 10,000 times more effective in retarding the pearlite than in retarding the bainite transformation, on the basis of isothermal measurements. In some steels, the formation of bainite restricts the formation of martensite while

Jan 1, 1946

By John T. Crawford

Much has been written of late regarding the flotation of coal as a means of reclaiming the valuable portion of the fines encountered in nearly all methods of coal preparation. Whether the process be wet or dry, whether the dust be sent through the entire process or removed prior to the cleaning by some such method as screening or aspiration, one of the final products consists of a considerable proportion of — 48-mesh material. The percentage of this —48-mesh material depends upon the mining method, transportation, storage, and method of preparation. The tonnage of this dust material ranges from 1 to 10 per cent of the total output of the cleaning plants. Four methods of disposal are available for this coal: 1. Disposal with the refuse from the plant. 2. Addition, after being reclaimed from the wash water, or dust collectors, without cleaning to the larger sizes. 3. Separate disposal as a pulverized fuel. 4. Cleaning so that addition to the larger sizes benefits the product as a whole. It is also true that flotation in one form or another is the only known way to effectively clean this material. While some processes do a reasonable cleaning job down to and including +l00 mesh, by far the greater majority stop at or short of the + 48-mesh size. Much of the literature on coal flotation passes by the fred pulp density and size by merely stating that the feed varies from 20 to 30 per cent solids and that the size range is from — 1/4 in. or — 1/8 in. to 0. Small wonder then that some operators with entirely different conditions, and not knowing the machine capacity, throw up their hands in despair when flotation is mentioned. Too much parallel is drawn between flotation methods as applied to ores and as applied to coal, to the detriment of the latter. In the flotation of metalliferous ores the feed pulp density ranges from 20 to 30 per cent solids, depending upon the amount of mineral to be floated and upon the size analysis. Thus where 2 to 5 per cent of the

Jan 1, 1936

By J. E. Sandor, P. F. Schmidt

A general review of the present knowledge of the semiconductor/oxide interface is given, with emphasis on silicon and germanium. The electrical properties of clean surfaces and the changes that occur upon oxidation are described. A brief disczcssion of the methods and mechanisms of oxidation of silicon is given, and the interaction between the semiconductor substrate and the oxide phase is considered. Physical properties of the oxide film, charge storage effects due to the dielectric, and some device applications of oxide films on semiconductors are discussed. THIS paper will be heavily preoccupied with the elemental semiconductors germanium and silicon. Undoubtedly some injustice is done thereby to other semiconductor-oxide systems, but it is not readily possible to cover all aspects of so vast a field in the present review. In considering the semiconductor/oxide interface, we may start out by discussing briefly an idealized clean semiconductor surface, and may then follow the changes brought about by oxidation, as the oxide is allowed to grow progressively thicker. The references given are not a complete list, but are to be taken as guides to the literature. Tamml suggested in 1933, based upon the study of a one-dimensional asymmetrical potential model, that localized surface states may appear at the surface of a crystalline lattice; it was pointed out by Fowler that these states should occur in pairs. shockley3 examined the origin of such surface states on the basis of a more general one-dimensional model and found that surface states may appear in the forbidden region between the highest filled and the lowest vacant band. This happens when the two bands overlap, as, for instance, the "s" and ('p" bands of the diamond structure. In a three-dimensional model these levels would produce a surface band which is half-filled for diamond, and the number of surface states should be approximately equal to the number of surface atoms. This picture of the surface has been refined by more recent theoretical work, like Handler's4 and Koutecky and Tomasek's~ without introducing essential modifications. When these concepts were applied to semiconduc-

Jan 1, 1965

By W. D. Robertson

A considerable quantity of experimental data is available on the effect of time, temperature, work-hardening and composition on the mechanical properties and corrosion resistance of aluminum alloys. There is, however, little unity of purpose or generality in most of the studies and, because the number of variables is large, the results often are not applicable to the problems that arise in practice. Furthermore, the customary expression of the effect of different variables as separate curves or as three-dimensional diagrams with time, temperature and the dependent variables as coordinates, renders the task of selecting the optimum time and temperature of precipitation treatment, with respect to their simultaneous but unequal etfect on the various properties, exceedingly difficult. The introduction of precipitation treatments to raise the yield strength of 24s-type alloys has created a need for a method of correlating and summarizing the effect of time and temperature on the mechanical properties and susceptibility to inter-crystalline corrosion. Correlation is particularly desirable because the choice of time and temperature is of necessity a compromise to achieve the best possible combination of properties, and the optimum conditions cannot he accurately specified unless the data are in a form in which the alternatives can be readily compared. Therefore, the work described here was undertaken to find a common relationship that would be capable of expressing the effect of precipitation time and temperature on the various properties and by means of which the relative effects could be correlated and their interpretation facilitated. Review of Previous Work In connection with an investigation of the interrelation of age-hardening and creep performance of nickel-silicon-copper alloys, Jenkins and Bucknalll demonstrated that the time required to attain maximum hardness and tensile strength could be expressed by a relationship of the form: t = K • io"^ (i) where t is the time in hours and T the temperature of aging, expressed in degrees absolute, and m and K are constants. They also pointed out that this expression is analogous to that which describes the change of the diffusion coefficient D with temperature; namely, D = Ae-~/m (2) Later, Cohen used this relationship in studies of the mechanism of age-hardening of a silver.rich copper alloyZ and of duralumin.3

Jan 1, 1946

By W. D. Robertson

A considerable quantity of experimental data is available on the effect of time, temperature, work-hardening and composition on the mechanical properties and corrosion resistance of aluminum alloys. There is, however, little unity of purpose or generality in most of the studies and, because the number of variables is large, the results often are not applicable to the problems that arise in practice. Furthermore, the customary expression of the effect of different variables as separate curves or as three-dimensional diagrams with time, temperature and the dependent variables as coordinates, renders the task of selecting the optimum time and temperature of precipitation treatment, with respect to their simultaneous but unequal etfect on the various properties, exceedingly difficult. The introduction of precipitation treatments to raise the yield strength of 24s-type alloys has created a need for a method of correlating and summarizing the effect of time and temperature on the mechanical properties and susceptibility to inter-crystalline corrosion. Correlation is particularly desirable because the choice of time and temperature is of necessity a compromise to achieve the best possible combination of properties, and the optimum conditions cannot he accurately specified unless the data are in a form in which the alternatives can be readily compared. Therefore, the work described here was undertaken to find a common relationship that would be capable of expressing the effect of precipitation time and temperature on the various properties and by means of which the relative effects could be correlated and their interpretation facilitated. Review of Previous Work In connection with an investigation of the interrelation of age-hardening and creep performance of nickel-silicon-copper alloys, Jenkins and Bucknalll demonstrated that the time required to attain maximum hardness and tensile strength could be expressed by a relationship of the form: t = K • io"^ (i) where t is the time in hours and T the temperature of aging, expressed in degrees absolute, and m and K are constants. They also pointed out that this expression is analogous to that which describes the change of the diffusion coefficient D with temperature; namely, D = Ae-~/m (2) Later, Cohen used this relationship in studies of the mechanism of age-hardening of a silver.rich copper alloyZ and of duralumin.3

Jan 1, 1946

DURING the past year the Committee on Coal and Coke has been collecting data concerning various points in the bituminous industry about which a large amount of misinformation circulates through the press and, in some cases, through the coal trade papers. The data presented have been compiled by various members, from the most authentic sources available, and where possible cover the period 1913-1924. They will enable comparisons to be made within the industry, and of this and other industries, and will explain some of the differences between conditions existing now and in the prewar period. CAPACITY AND OVER-DEVELOPMENT The capacity of bituminous mines is frequently stated at figures ranging between 800,000,000 to 1,400,000,000 tons per year. Table 1 shows statistics for the industry, mainly from U. S. Geological Survey sources but partly from U. S. Coal Commission reports. Column 3 gives the mine capacity with equipment and labor as of given date, as estimated from the data published by the U. S. Geological Survey. This is calculated for each State by obtaining the total man days worked as. reported by the operators (multiplying average men employed by total days worked at each mine) and dividing this figure into the total production, getting the production per man day; this figure times number of men employed times 308 (a theoretical full working year) equals estimated- full-time capacity. Two major objections are made to this method-one that the total number of men employed is used, instead of the number actually working, and the other that the number of days used only deducts Sundays and five holidays. The first objection is answered by the fact that the same number of men is used in estimating capacity as is used in actual production, and while this number is always from 12 to 20 per cent. more than are actually working, this condition exists at all times, although it is worse at times of maximum output. Few coal men will agree with the conclusion that the use of 308 days is correct, as it is practically impossible to keep any mine working full time at the same

Jan 2, 1926

By Harry T. Davis, Jasper L. Stuckley

The object of this paper is to record and interpret field and laboratory observations made by the writers during five years of study of the barite deposits of North Carolina. Deposits of barite are known to occur in three localities in North Carolina (Fig. 1) two of which—the Hot Springs and Kings Mountain —contain material of economic value. The Hot Springs area begins near Bluff, some 6 miles south of Hot Springs, and continues northeast by Stackhouse; a total length of 7 miles. The Kings Mountain deposits lie along a belt that extends from the north end of Crowders Mountain in a southwestward direction, along the east side of this and Kings Mountain, to Kings Creek, South Carolina. The third locality is 3½ miles southeast of Hillsboro, Orange County, a short distance west of the highway leading from Hillsboro to Chapel Hill. It is not known when barite was first discovered in North Carolina, but production from the Hot Springs area began some 50 years ago. The state has never produced large quantities of barite—usually there have been less than three producers—and definite figures are not available, but reasonably reliable estimates indicate a total production of 300,000 tons. From 1901 through 1920 barite mining was on a seemingly prosperous basis and a large tonnage was shipped from the Hot Springs and Kings Mountain areas. With the depression of 1920 the industry began to decline and production practically ceased in 1926. Geology of the Barite Areas In the Hot Springs area barite is found in the Max Patch granite of Archean age and the Snowbird formation of Cambrian age. The Max Patch granite is of two varieties, one gray to whitish and the other red. The gray granite is coarse, at times porphyritic, and composed of quartz, orthoclase and plagioclase feldspar, with a little biotite and muscovite. The red granite is also coarse and differs from the other only in having conspicuous pink and red feldspar. Both varieties have been much metamorphosed and weathered in places, so that they contain secondary

Jan 1, 1935

By Harry T. Davis, Jasper L. Stuckley

The object of this paper is to record and interpret field and laboratory observations made by the writers during five years of study of the barite deposits of North Carolina. Deposits of barite are known to occur in three localities in North Carolina (Fig. 1) two of which—the Hot Springs and Kings Mountain —contain material of economic value. The Hot Springs area begins near Bluff, some 6 miles south of Hot Springs, and continues northeast by Stackhouse; a total length of 7 miles. The Kings Mountain deposits lie along a belt that extends from the north end of Crowders Mountain in a southwestward direction, along the east side of this and Kings Mountain, to Kings Creek, South Carolina. The third locality is 3½ miles southeast of Hillsboro, Orange County, a short distance west of the highway leading from Hillsboro to Chapel Hill. It is not known when barite was first discovered in North Carolina, but production from the Hot Springs area began some 50 years ago. The state has never produced large quantities of barite—usually there have been less than three producers—and definite figures are not available, but reasonably reliable estimates indicate a total production of 300,000 tons. From 1901 through 1920 barite mining was on a seemingly prosperous basis and a large tonnage was shipped from the Hot Springs and Kings Mountain areas. With the depression of 1920 the industry began to decline and production practically ceased in 1926. Geology of the Barite Areas In the Hot Springs area barite is found in the Max Patch granite of Archean age and the Snowbird formation of Cambrian age. The Max Patch granite is of two varieties, one gray to whitish and the other red. The gray granite is coarse, at times porphyritic, and composed of quartz, orthoclase and plagioclase feldspar, with a little biotite and muscovite. The red granite is also coarse and differs from the other only in having conspicuous pink and red feldspar. Both varieties have been much metamorphosed and weathered in places, so that they contain secondary

Jan 1, 1935

By J. W. Halley, T. S. Washburn

Rimming steels derive their name from their action during solidification in the molds. As a result of incomplete deoxidation, gas is evolved during freezing, and the metal has a characteristic rolling action. The metal rises along the mold walls and descends in the center of the ingot. This action keeps the top of the ingot open and the advancing rim of solid metal can be seen. The rim grows until the rolling action is insufficient to prevent the top of the ingot from freezing or until the action is stopped by capping the ingot with a heavy plate. The violence of the reaction and its characteristics, such as growth or drop in the molds, are determined by the composition, the furnace practice, and the deoxidation in the ladle and in the molds. Though rimming steels represent a large proportion of the amount of plain carbon steel made, they have received comparatively little attention in the technical literature. The manufacture of rimming steels has been described by Hibbard,1,2 Fleming,3 Pierce4 and Jackson.5 The reactions occurring during rimming have been considered from the theoretical point of view by Chipman and Samarin.? The structure of rimmed-steel ingots has been discussed by Nead and one of the present authors6 Meyer: in studying segregation, investigated the distribution of carbon, sulphur and phosphorus in rimmed-steel ingots by analyzing the rim and core of blooms. In their studies of segregation, the Joint Committee of the Iron and Steel Institute and the British Iron and Steel Federation9 studied distribution in one billet and one ingot of rimmed steel. A detailed study of the distribution throughout the ingot has not been published. The present investigation was undertaken to determine accurately the distribution of carbon, manganese and sulphur in normal rimmed ingots and the general distribution of other common elements present. The study included some work on the effect of pouring conditions and furnace practice on the distribution, though there is still much to be done in this direction. The structure of a rimmed ingot that has been split by dynamiting and a schematic diagram of the zones in the ingot are illustrated in Fig. 1.

Jan 1, 1938