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By Eckley B. Coxe

At the first meeting of the Institute, a paper was read by Mr. Rothwell, calling attention to the importance of at once considering the great waste of anthracite coal under the present system of mining and preparing that fuel for market, and a committee was appointed to examine and report upon the method now in use. About the time the committee were selected, a general resumption of work, after the long strike, took place in the coal regions, and the members of the committee have not in consequence had as much leisure to devote to the study of the question as its importance demands. In the present preliminary report we shall merely sketch out the . plan which we propose to pursue in our investigations, so that when our fellow-members are called upon to assist us in our work by furnishing statistics, etc., they may understand more clearly for what object our inquiries will be made. As one of the most practicable methods of obtaining the information requisite for an intelligent consideration of our subject, we propose to send, from time to time, to members and others interested in the mining of anthracite coal, printed sets of questions relating to points under consideration. We would here impress upon our fellow members the importance of filling up these papers as far as they can from their own knowledge. We would, of course, wish each question to be answered as fully as possible, but we do not expect every one to answer them all. One question well answered would be of more use to us than the whole paper filled up with answers, many of

Asarco's Sacaton unit, located near Casa Grande 45 miles southeast of Phoenix, Arizona, was brought into production in February 1974. Ore reserves are estimated at about 48 million tons at 0. 95% copper. Mineralization of the orebody comprises both sulfides and oxides, with minor amounts of gold and silver. Preproduction stripping of 40 million tons of overburden was accomplished in less than two years. Mining is done at the rate of 9,000 stpd ore with a waste-to-ore ratio of 4.6 to 1. 0. The mine is developed on 40 ft benches, and by 1979 underground block caving methods will be phased into the operation at a depth of 1900 ft. Ore is mined in the pit two shifts per day, seven days per week, and is hauled with 85 ton trucks to the primary crushing plant. Trucks dump their loads into a 165 st capacity pocket equipped with a chain curtain which controls the ore flow to the 6 ft 6 in. wide by 24 ft long (2. 0 m by 7.3 m) vibrating feeder grizzly. Grizzly bars are inclined at a 5º slope on the first half of the 0 feeder and 10 on the last half. Grizzly bars have 6 in. (13 mm) spacings which pass 60 to 70% of the mine-run ore. Grizzly oversize drops into a 48 in. by 60 in. (1. 22 m by 1.52 m) primary jaw crusher. Both the grizzly undersize and crusher discharge are collected on a 42 in. (1.07 m) conveyor belt operating 398 fpm (121 mpm) for transport to the 4,750 live st intermediate storage area ahead of the fine crushing plant. Capacity of the Sacaton primary crushing plant is a nominal 1150 stph (1043 mtph). It operates fourteen shifts per week with an effective crushing time of four hours per shift. An economical open-air design was used, but an enclosed operator control room is located on the upper level where the dump truck, feeder, and crusher can be observed. Oversize rocks are removed from the feeder or crusher by the 10-ton bridge crane. Direct operating costs for this well-designed primary crushing plant, including labor, power, supplies, and maintenance, are only 3.5 cents per short ton. An interesting feature of the Sacaton orebody is that the non-sulfide copper minerals, which are less prevalent than the sulfides, occur intimately with the sulfide minerals; for this reason, all ores as mined are treated in a flotation circuit using sulfidizing methods for oxide recovery.

Jan 1, 1978

By Frank A. Wilder

The most important process in a gypsum mill is calcining the crude mineral. There seems, however, to be little progress or change in calcining methods. This would not be surprising if the industry was not, in other ways, developing. The demand for gypsum in its various forms, however, is growing rapidly. The output has more than doubled in six years, while the value of gypsum products, through the introduction of higher priced. specialties like wall board, has nearly trebled in the same period. In other industries, under somewhat similar conditions, calcining in rotating cylinders, either by direct or indirect heat, has replaced the method that still prevails in gypsum mills. Efforts were made to use rotary calciners in manufacturing plaster of Paris in the early days of the industry in America; 25 years ago rotary calciners were in use in Germany. At that time there was great diversity of opinion in regard to their merit. In 1923, the output of calcined gypsum in the United States was 3,101,378 tons. About nine-tenths of this material was calcined in kettles, the remainder in rotary calciners. The ratio was about the same 10 years ago. During these 10 years, rotary calcining made relatively no gains, and there were no important changes in the construction of kettles. In their manipulation, the only change of consequence was in connection with the length of time that the gypsum is left in the kettle. For wall-plaster purposes, all producers who had not previously done so changed from second-settled to first-settled calcined gypsum, thereby reducing production costs and improving the plasticity and sand-carrying capacity of their plaster. Nevertheless, in the few mills in which they were installed, rotary calciners continue to operate, with possibly one or two exceptions, and to be highly successful. In these 10 years, the Cummer type of rotary calciner has disappeared. All rotaries now used are of the cement-mill type with a diameter of 6 or 7 ft. and length of 80 to 120 feet.

Jan 1, 1925

By J. O. Mack, J. B. Russell

IN recent years, solders containing 20 per cent tin with no bismuth or cadmium have been developed by a few companies, and personnel have been properly instructed in their use. In addition, since the tin shortage, a number of solders containing less than 10 per cent Sn, and some with no tin, are being used in special applications; however, a solder of this type has yet to be developed that is satisfactory for general use. [ ] The purpose of this investigation was to develop an alloy containing a maximum of 15 per cent tin, with no cadmium or bismuth, having solder properties equivalent to or better than those of substitute solders now specified containing i8 to 20 per cent tin (Table I), or even approaching the properties of the standard 40 to 60 tin-lead solder. The wartime restriction of bismuth and cadmium, elements that have beneficial effects on fluidity, solidification range and strength, makes it increasingly difficult to develop a general-purpose solder containing a maximum of 15 per cent tin. In the course of this investigation, 11 elements were used in various combinations with the basic 15-85 tin-lead alloy. These elements were antimony, silver, copper, indium, thallium, lithium, calcium, barium, potassium, sodium and arsenic. In all, 116 low-tin solders were investigated, with the idea of developing a solder that will give satisfactory working properties, specifically in regard to "wetting" of copper, brass and iron, solidification range, capillarity and shear strength of a soldered joint. The relative importance of these various properties plays an important role in the search for substitute solders, since it is almost impossible to retain all of the desired qualities of a high-tin solder and still make drastic changes in the alloy composition. Because of the expected uses of a general-purpose solder, it is necessary that it have properties, especially in regard to wettability, that will enable it to be used on the metals in common use. BASIC CONSIDERATIONS The maximum liquidus temperature of a solder is determined by the particular application involved and the temperature that can be obtained by the source of heat.

Jan 1, 1944

By J. C. Bokros

At temperatures above 950°F, zirconium which has been strained a critical amount will experience critical recrystalli-zation. The large grain size thus formed can result in a reduction in the fatigue life by a factor of 2 to a factor of 9 at both high and low temperatures. The critical strains for zirconium vary from 15 pct at 900°F to about 2 pct at 1125°F, while those for zircaloy III vary from 15 pct at 1050°F to 5 pct at 1200°F. Zircaloy II ,experiences no critical recrystallization up to 1200°F. ZIRCONIUM has become increasingly important for nuclear applications and is being employed in reactors at temperatures where recrystallization can occur. Recent work' on the fatigue properties of zirconium has shown that coarse-grained structures developed in zirconium during recrystallization have much lower fatigue lives than fine-grained material. The development of these large grain sizes under such conditions is well known to be the result of critical recrystallization.2-4 Briefly, critical recrystallization occurs when a metal is strained a critical amount and annealed in the recrystallization range. The critical strain is defined as that minimum strain necessary to promote nucleation in the time unit and temperature considered. The maximum grain size occurs at the critical strain, since at this strain the fewest stable nuclei per unit volume grow into new grains. Recrystallization is not evident below this; strain since the nucleation rate is vanishingly lolw, and metal strained more than the critical amount has a higher nucleation rate per unit volume which results in a finer grained structure. This paper describes the critical recrystallization observed in reactor-grade zirconium, zircaloy 11, and zircaloy I11 as a function of annealing temperature and temperature of strain. EXPERIMENTAL The zirconium used was hafnium-free, double arc-melted sponge obtained from the Bureau of Mines. The ingots were forged and hot reduced to 0.08 to 0.10-in. sheet and subsequently cold reduced to 0.035-in. sheet with intermediate and final anneals at 1200 OF for 15 min. The zircaloy II and zircaloy III used were 0.035-in. sheets in the annealed condition. Compositions of these materials as tested are given in Table I. To determine the critical strain at a given temperature, tensile specimens having a0.065-in. taper in a 2-in. gage length were machined from the sheets parallel to the rolling direction. The specimens were polished, etched, and examined metallographically to ensure that all of them were strain-free, initially. Tukon indentations were made every half millimeter along the gage length of each specimen. These served as fiducial marks enabling the plastic strain to be measured with a microscope and micrometer stage. The specimens were pulled to failure at a rate of 0.002 in. per min in an Instron tensile-testing machine. Three temperatures were used for straining: room temperature, 500 ºF, and 900 ºF. The 500º and 900 ºF tests were run in an argon atmosphere. Since the rate of work hardening changes with temperature, a different critical strain was obtained for each temperature of strain. Specimens, prepared in the manner described, were annealed in vacuunl at various temperatures ranging from 900" to 1200 F for up to 1000 hr, after which they were examined metallographically. The critical strain and the recrystallized grain size as a function of strain were determined for each specimen. Results for the same temperature and time indicated that the critical strain measured was reproducible to within 5 pct of each other. RESULTS AND DISCUSSION Since increasing the time of anneal increases the probability of the nucleation of a new grain, the critical strain decreases with time at a decreasing

Jan 1, 1961

Jan 1, 1913

By G. K. Manning, W. E. Few

WORK on the effect of vacuum heat treatment of 0.040 in. diam sintered and wrought molybdenum wires has been sponsored by the Office of Naval Research at Battelle for the past several years. An electrical resistance furnace' capable of maintaining a vacuum of less than 0.1 micron of mercury at temperatures as high as 4000 °F was used for heat treating the wires. Early in the work, it was found that the introduction of a few microns pressure of oxygen into the furnace resulted in a rapid increase in the oxygen content of the wire specimens and the appearance of a discrete oxide phase. Subsequent elimination of the oxygen atmosphere caused the disappearance of the oxide phase. This was used to determine the solid solubility of oxygen in molybdenum over the temperature range of 2000" to 3000°F.2 It was observed that, with the disappearance of the oxide phase, the wires regained some ductility. Single-phased wires possessed from 5 to as much as 40 pct elongation in 2 in. Later, attention became centered on determining the cause of this wide range in ductility. Wires containing less than 0.002 pct C, less than 0.0007 pct 0, less than 0.0005 pct N, and less than 0.00003 pct H exhibited the erratic ductility noted above. These percentages represent approximately the limit of accuracy of presently available methods of analysis and thus it became apparent that chemical analysis would be of little help in the study. A number of possible explanations for the wide range in ductility were suggested during the course of the work. It was first suspected that variations in the grain size of the recrystallized wire specimens might be responsible. Wire from several lots of material was available. One of these lots tended to develop very large grains when recrystallized, the others all developed an ASTM grain size of 3 to 4 when heated above 2700°F. No correlation between grain size and ductility could be found. It was thought that back diffusion of oil from the diffusion pump might cause contamination of the wire, principally with carbon, but when wires were treated without cooling the cold trap in the pumping system,

Jan 1, 1956

Jan 1, 1914

By M. C. Flemings, R. Mehrabian

In a recent series of papers,1-3 it was shown that a variety of apparently different types of macrosegrega-tion result from the same basic mechanism, the inter-dendritic flow of solute rich liquid to feed solidification and thermal contractions. The important parameter governing sign and extent of segregation was shown to be (v.?T)/ where v is interdendritic flow velocity, ?T is temperature gradient, and E is rate of temperature change. It was proposed in one of the previous papers that the "negative cone of segregation" often found at the base of large ingots results from the large value of (v. VT)/E expected to pertain there. The reason why this parameter is expected to be large in that location is the high flow velocity to be expected there, as discussed earlier,' and as shown schematically in Fig. 1. In this note, two experiments are summarized which are intended as laboratory simulations of the inter-dendritic flow behavior sketched in Fig. 1 and, therefore, of the "negative cone of segregation". Experimental procedures employed are as described in the the earlier work.3 Alloy cast was nominally Al-4.5 pct Cu. Fig. 2 shows one of these ingots, a "prism" ingot, 6 cm high by 12 cm wide by 10 cm long, unidirectionally solidified from a water cooled base. In this ingot, in-terdendritic flow velocity increases near the upper portion of the ingot because of the gradually decreasing ingot cross-section. Calculations were presented earlier of the negative segregation to be expected in this type of ingot,' and results presented in Figs. 2 and 3 agree closely with those of earlier calculations. A more direct (although less easily calculable) simulation of the "negative cone of segregation" is the

Jan 1, 1970

Jan 1, 1930

By John M. Hartman

THE high temperature of the blast of modern furnaces renders it desirable that the pipe conveying the blast into the furnace crucible shall transmit and radiate as little heat as possible. To accomplish this, the pipe shown in the accompanying sketch was devised and patented. It consists of a slide-valve, leg-pipe, and belly-pipe, which are held together and to the tuyere by a system of levers and links. The slide-valve is superior to the old throttle-valve. The leg-pipe is formed of two thicknesses of wrought-iron pipe, with a space of half an inch filled in with clay and brick. The belly-pipe is made in the same way as the leg-pipe, and terminates in a globe face to suit the tuyere. The quarter turn is made extra thick, of cast iron, and the cap on the end is lined with clay also. The catches, A, B, C, are merely for convenience in putting the pipe together. The joints D and E are globe faces, and allow the pipe to adjust itself to any angle. The eye-piece is made of violet glass, which cuts off the glare from the bright coals in the furnace and allows a close examination of the interior, so that any water dropping or vapor can be detected. The glass does not become coated with dirt, like mica. Since good running of furnaces is shown by a bright tuyere, it is necessary to have a good eve-piece to examine then. To detach the pipe, a man lifts the weights, the side rods are then slipped off the bell crank under the quarter turn, the link under the belly-pipe is unhooked, and the pipe carried away. The same process is reversed to put the pipe together. The nozzle is changed by taking off the cap, G, drawing the nozzle through the belly-pipe, and inserting another. In this way the change can be made quickly, without taking down the pipe. On the old tuyere pipe bolts with brass nuts were used, which burned up and gave trouble. In other cases key-bolts were used, making it difficult to adjust the pipe. Bolts make too rigid a joint, and there is no provision for movement from contraction or expansion. As the temperature of the blast increases there is more expansion, and where rigid joints are

Jan 1, 1879

By L. Luini, E. Lee

An exploratory survey of the heat treatment response of commercial titanium alloys (Ti-150A, RC-130B, and MST 3AI-5Cr al-loys) shows a wide range of possible hardness and microstructural characteristics. The hardening is primarily dependent on the solid state transformation of the phase. An age hardening reaction which apparently is associated with ß decomposition and precipitation has been shown. Brittleness and notch sensitivity appear to be characteristic of age hardening to high hardness. Ductility, tensile strengths, and elongations are given. A NUMBER of commercially produced titanium-base alloys have been made available by the titanium metals industry. These alloys were developed to combine the light weight of titanium with increased strength through alloy additions. Usually the properties of these alloys are reported for material in the hot rolled and annealed condition. Since the production of commercial titanium has preceded the investigation of titanium-base alloy systems, the potential of these alloys is not well known. Although heat treatability has been indicated for these alloys, data on the response to heat treatment are quite limited. The heat treatability of titanium is based on the allotropic transformation of the high temperature, body-centered cubic ß structure to the low temperature, hexagonal close-packed a structure at approximately 1625 °F. This transformation in the pure metal is of little practical significance in heat treatment since the high temperature phase is not amenable to controlled transformation. Alloy additions serve to alter the transformation kinetics and permit control of the transformation by heat treatment variables. The effects of different alloys on the allotropic transformation in titanium classify them in two general categories,1 a stabilizing and ß stabilizing elements. The a stabilizers, represented by aluminum and oxygen, raise the temperature limits of the low temperature phase and introduce a two-phase a + ß temperature range. The ß stabilizers, represented by molybdenum and columbium, lower the equilibrium temperature of ß and give rise to an extended temperature range where both a and ß phases are stable. Another type of ß stabilizer, represented by iron, chromium, and manganese, introduces a eutectoid reaction. Some commercial titanium alloys belong to complex multiple element systems. Based upon the phase diagrams of the binary systems, the general effect of commercial compositions is to vary the stability of the high temperature phase and significantly alter its transformation characteristics. Therefore it is expected that the characteristics of alloyed titanium can be altered by heat treatment. The present investigation was undertaken to survey the variations in hardness, microstructure, and mechanical properties as affected by heat treatment variables. Commercial Alloys lnvestigated The commercially available titanium-base alloys selected for this investigation and obtained as 3/4 in. diameter hot rolled and annealed bars are listed in Table I. The producer did not determine the chemical composition of the Ti-150A heats X1052 and L685. The early heats of Ti-150A, prefixed with the letter X, were melted with tungsten-tipped electrodes and cast in approximately 500 lb ingots 12 in. in diameter. The heats prefixed with the letter L were melted under a revised melting practice yielding approximately 1300 lb ingots 16 in. in diameter. The final annealing treatment was at 1200" to 1250°F for 1 hr. The MST-3A1-5Cr alloy was melted in an induction furnace and cast in 7 in. diameter ingots. This practice produces high carbon material and some variation in the amount of carbides was found in different sections of the same bar. The RC-130B alloy was melted with a carbon arc. This alloy showed approximately 2 pct carbides. No large segregation effects were observed.

Jan 1, 1955

The Institute conducts jointly with the American Society of Civil Engineers, American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them of certain properties. United Engineering Trustees, Inc. When Mr. Carnegie made. his gift ?for the erection of a suitable home? for the engineering societies,

Jan 1, 1942

By Fred W. Stiefel

THIS paper covers the operation and maintenance of Diesel locomotives underground on a portion of the Delaware River Aqueduct.[t] This part of the tunnel is 15 miles long, with shafts 14 ft. in diameter spaced about 5 miles apart. These shafts (2, 2a and 3) are 825 ft., 1551 and 840 ft. deep, respectively. The grade of the tunnel is almost level, except for the 12,100 ft. north of shaft 2, which has a grade of 2.31 per cent. The tunnel is circular, 17 to 19 ft. in diameter. It lies at a depth of 400 ft. below sea level, with a maximum over-burden of 2400 feet. The tunnel driving was carried on in six headings, using 15 storage-battery locomotives, each of 13 gross tons and having a maximum speed of 8 miles per hour. The longest haul was 3 miles, which proved to be the maximum distance for which storage-battery locomotives could be employed economically for the amount of material to be moved. One locomotive was used for switching cars at each heading, one for switching cars at the bottom of each shaft and one on the main-line haul from the heading to the shaft. The maximum amount of material hoisted in one shaft from two headings when 104 ft. of tunnel was driven in 24 hr. was 1000 cu. yd., or about 2000 tons of rock in place. The total quantity excavated was 750,000 cu. yd. (1,500,000 tons of rock). The tunnel-lining operations using concrete presented a problem of hauling a maximum distance of 5 miles in the tunnel. The concrete-placing equipment had a capacity of about 2000 cu. yd., or 4000 tons in 24 hours. Experience had shown that storage-battery equipment could not handle this quantity of material within the time required at the distance of 5 miles. Trolley-locomotive haulage was considered dangerous and expensive, and would cause interference because transmission equipment would be required. Therefore the performance of Diesel locomotives of 160 hp., with a speed of 18 miles per hour, in comparison with that of other types of locomotives, was studied. CHOICE OF LOCOMOTIVES In deciding upon the type of locomotive to be used for the 5-mile haul, four alternatives were considered, as follows: I. To purchase additional storage-battery locomotives with the necessary batteries over the 6 locomotives and 12 batteries available. 2. To convert the existing battery locomotives to the trolley type. 3. To purchase new trolley locomotives. 4. To purchase Diesel locomotives. PROPOSITION No. I The 90-hp. storage-battery locomotives available (each weighing about 12 tons), when hauling a load of 64 tons, with a drawbar pull of about 1900 lb. on a level track, developed a speed of 8 miles per hour and could make five round trips in 8 hr. with a

Jan 1, 1942

(Members are urged to send in for this. column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at the Institute headquarters during the period Sept. 10, 1916 to Oct. 10, 1916. Arthur K. Adams, Chanaral, Chile. C. F. Moore, Salt Lake City, Utah. Hiram W. Belnap, Washington, D. C. L. D. Moore, Providence, R. I. E. A. Bridgman, Seattle, Wash. George A. Morrison, Chicago, Ill. D. W. Buckly, Wallace, Idaho. Pablo Ortega, Havana, Cuba. G. L. Carlisle, Jr., New York, N. Y. L. W. Paige, New York, N. Y. Ernest H. A. Cohen, Johannesburg, So. Africa. Charles Petzel, New York N. Y. A. Faison Dixon, Camp Rio de Oro, Venezuela. C. A. Pierce, Patagonia, Arizona. Charles E. Dutton, Goldfield, Nev. W. E. Pomeroy, El Paso, Texas. D.-F. Hewitt, Washington, D. C. George S. Rice, Washington, D. C. . James E. Howard, Washington, D. C. G. J. Schofield, Seattle, Wash. A. 0. Ihlseng, Joplin, Mo. Warren D. Thompson, New York, N. Y. I. Ishikawa, Niagara Falls, N. Y. M. M. Valerius, Tulsa; Okla. Montrose L. Lee, New York, N. Y. G. B. Waterhouse, Buffalo, N. Y. V. H. McNutt, Billings, Mont. Joel H. Watkins Washington, D. C. Benjamin L. Miller, So. Bethlehem, Pa. H. P. Wherry, Chicago, Ill. Arthur K. Adams has left for Chile, where he will act as geologist for the Andes Copper Co., a subsidiary of the Anaconda copper company.

Jan 10, 1916

By Thos. W. Gibson

The object of taxation is the raising of a revenue. Unless a tax accomplishes this, it is a failure. The right to take for public purposes a part of the moneys obtained from the carrying on of private enterprises is an attribute possessed only by a lawful government, and may indeed be called the supreme attribute of government. In free, democratic communities this power must of necessity rest upon the consent of the governed. Power implies obligation, hence it is obviously the duty of a government, in framing a system of taxation, to provide one which, while effective in producing a revenue, is also just and impartial. • It will be conceded that mines and mining property ought to bear a fair share of the public expenditure. The question is, upon what basis taxation should proceed. Two separate taxing principles are usually contended for: Taxation should be proportionate to the benefits received by the person or property taxed; taxation should be based on ability to pay. A third is sometimes added, taxation should have reference to the extent and value of the natural resources enjoyed. As applied to mining taxation, it is pointed out by those who support the fist mentioned basis that, mines being usually situated in rocky and hence sparsely peopled regions, mining companies are frequently obliged to construct roads, railways, telegraph and telephone lines, schools, water and sewerage systems, and many other amenities and conveniencea of civilization the cost of which in regions better suited for agriculture, and consequently more thickly populated, has either been defrayed locally, or can be spread over a sufficiently large taxable group of people to materially lighten the financial burden on the mine. The mining company, it is argued, having made these outlays, should receive credit for them and be relieved of taxation to a corresponding extent. There may be some force in this contention, but the situation is capable of relief without attempting to place taxation upon so unworkable a basis as the value of benefits received. Who is to be the judge of these benefits, and how are they to be valued? The very existence of a mining company and its ability to carry on business in peace and security depeind on the prevalence of law and order, which is a result of good government. The state provides protection against violence, and courts of law for

Jan 1, 1920

By J. H. Swisher

An experimental study has been made of the possible mechanisms for foam stability in the system CaO-SiO2-Cr2O3, where Cr2O3is the foaming agent. The degree of lowering of surface tension by Cr2O3 was determined at 1600 "C for high -silica melts. Measurements were also made of foam stability under standardized conditions. The results of the two sets of measurements then were correlated by applying the Gibbs and Marangoni theories of film elasticity. It was demonstrated that the Marangoni elasticity effect is probably the largest single contributor to foam stability, although the high uiscosity of' silicate melts makes some contribution in controlling the rate of drainage of liquid from bubble lamellae. ThE tendency of metallurgical slags to foam has frequently been observed during steel-refining operations. In the open-hearth furnace,this tendency is considered undesirable because it slows down the rate of heat transfer from the burners to the molten-metal bath. On the other hand, it is sometimes desirable to have a "foamy" slag in the basic oxygen converter.' A more effective blanket over the steel bath is made by a "foamy" slag, and loss in yield of metal due to splashing is minimized. In addition, a flush slag can be removed more easily in this condition. Since slag-foaming problems in the field have been attacked largely on an empirical basis, it appeared desirable to obtain a better basic understanding of the mechanism of foam stability. The experimental work was directed almost entirely toward the behavior of Cr2O3 as the foaming agent in CaO-SiO,-Cr2O3 melts. In the first stage of the investigation, the degree of lowering of surface tension by Cr2O3 was determined at 1600°C. The second stage consisted of measuring foam stabilities under standardized conditions. The two sets of experimental results then were correlated by applying various theories of foam stability. For convenience in interpreting the surface-tension and foam-stability results reported here, a portion of the CaO-SiO2-Cr2O3 phase diagram2 is reproduced in Fig. 1. EXPERIMENTAL 1) Surface-Tension Measurements. Very little information is available in the literature on the lowering of surface tension of slags by foaming agents. Kozakevitch 3 mentioned that the addition of 1.5 pct Cr2O3 lowered the surface tension of FeO slightly. In another system, some data on the lowering of surface tension of foaming slags by P2O5 were reported by Cooper and Kitchener.4 The technique used for the surface-tension measurements was the maximum bubble-pressure method,' using a single tube immersed to various depths in the melt. This method has been used extensively in high-temperature systems, such as in liquid metals, slags, and glasses.6,7 It has the advantage that the contact angle between the liquid and the tube material need not be known. The equation used for calculating surface-tension values from maximum bubble-pressure measurements is the Schroedinger equatioq5 which can be written as follows:

Jan 1, 1964

By J. M. Kane

IN all probability the mining and metallurgical industry as a whole can demonstrate a larger economic return from installation of dust-control equipment than any other major industrial group. This fact has partially accounted for the marked increase of dust-control installations made during the past decade. While the primary objectives for installation of dust-collecting systems are improved working and operating conditions for men and equipment, the fact that an economic return can be anticipated on salvageable materials is an added advantage which shows in partial or complete equipment write-off. The conditions apply to most phases of the mining, milling, and smelting industry, both non-metallic and metallic.

Jan 1, 1953

By R. G. Davies, R. H. Richman

Several techniques, X-ray diffraction, transmission electron microscopy, conventional, metallography, and mechanical property measurements are combined to investigate decomposition in the suPersaturated solid solution Fe-27 at. pct Be. The following sequence of structures for aging temperatures below 400°C is established: massive short-range order, pseudo-FeBe (L2o) order, Fe3Be (DU3) order, sinusoidal modulation of composition, general or continuous precipitation, and discontinuous or cellular precipitation. In addition to this sequence itself, several features of the individual stages are noteworthy; for example, when coherent modulations occur, their development is parallel to (100) everywhere in the specimen apparently without incubation, and both the wavelength and the composition amplitude of the modulations increase with aging time. Two types of discontinuous reaction are observed, depending upon the aging temperature. At low temperatures (<550°C) the boundary-nucleated variety of discontinuous precipitate predominates; but at higher temperatures (>600°C) the crystallographic variety occurs instead. Hardness and flow-stress measurements clearly reflect the quoted structure sequence. Some qualitative aspects of the structure changes and of the relationship between mechanical properties and structure are discussed. BERYLLIUM in solid solution markedly strengthens iron.&apos;" A recent study demonstrated that not only were supersaturated single crystals of Fe-27 at. pct Be very strong, but they deformed primarily by mechanical twinning.3 Such behavior, coupled with the decrease in solid solubility of beryllium in a Fe from about 33 at. pct at 1165°C to about 10 at. pct at 500°C4 as shown in Fig. 1, leads naturally to questions about property changes with aging in this system. In 1929 roll,1 and later Seljesater and Rogers,5 reported that useful increases in strength could be obtained by aging quenched Fe-Be alloys, but it was not until quite recently that any of the details of precipitation in these alloys were studied. Richman6 observed that both an Fe3Be superlattice (with a DO3 crystal structure the same as Fe3A1, illustrated in Fig. 2) and a modulated structure preceded the appearance of a discrete second phase in the 20 at. pct Be composition. Here, a modulated structure refers to a periodic composition fluctuation within one crystal, while its lattice remains coherent. Subsequent work on a Fe-Be alloys by Heubner7 and von Heimendahl and Heubner8 confirmed the existence of the modulated structure, although only an FeBe (L20) ordered structure was detected (also shown in Fig. 2). Both Rich-man and Heubner corroborated the large increases in hardness during aging reported earlier, but other mechanical properties were not examined. Since modulated systems are encountered relatively infrequently, the influence of coherent modulation upon mechanical properties is not well-known. With the accumulation of information about age-hardening systems, it has become clear that many precipitation reactions cannot always be described by the concept of heterogeneous nucleation at some lattice discontinuity followed by diffusional growth. Rather, complex sequences involving prior "preparation" of the matrix are quite common; that is, a transition structure occurs in the parent phase, instead of in some "nucleus" form. Delineation of such subtle sequences appears to be a worthwhile step toward the understanding of solid-state precipitation. Since not many structural progressions of comparable nature have been reported, the objectives of the present survey are to identify and elucidate the various

Jan 1, 1967