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By R. S. Dean

JUST as the mineralogical name bauxite has come to include several minerals not known at the time the name was first applied, so the concept of bauxite as the one source of alumina must be enlarged during the war period to include the production of alumina from other, low-grade sources. Speaking in a narrow mineral logical sense, there is no such thing as bauxite, and similarly there is now no one source of alumina, and no one process for its extraction.

Jan 1, 1943

By J. R. Long, T. R. Graham, C. W. Matthews, R. S. Dean

IN a previous paper§ the authors reported on the mechanical properties of a 65 per cent copper, 10 per cent manganese, 25 per cent zinc alloy as compared with similarly processed cartridge brass. Additional investigations by these laboratories, on higher copper alloys, have demonstrated that at lower zinc concentrations even larger amounts of pure manganese may be added to copper-zinc alloys without exceeding the single-phase solid solution limits, and that similar increases in tensile strength, yield strength, and hardness may be obtained without excessive decreases in ductility. Several compositions in this range showed also a decided color change with increasing manganese. The normal "brassy" color was considerably lightened and reduced to a faint yellow cast at 15 per cent manganese. With higher manganese contents the alloys were essentially white and similar in appearance to the nickel-silver alloys. From this work it appeared that it would be desirable to determine more completely the properties of the wrought and annealed white alloys. Accordingly, a more detailed study was planned of an alloy having the composition 70 per cent copper, 20 per cent manganese, and 10 per cent zinc. This alloy remained single-phase throughout the working and annealing cycles of the preliminary tests and appeared to be about the strongest of the white single-phase alloys. The project included also an investigation of additional alloys, deviating from this composition by 5 per cent of each of the three components to evaluate the effects of variation in composition; also a study of the properties of the central alloy made with silicothermic manganese. MATERIAL PREPARATION Electrolytic manganese, wirebar copper, and electrolytic zinc were used for the preparation of the alloys. Representative analysis of the electrolytic manganese seldom exceeds 0.01 per cent iron, 0.02 per cent sulphur and 0.02 per cent lead, with no silicon or aluminum. A typical sample of the silicothermic manganese metal contained 2 per cent iron, 0.81 per cent silicon, 0.i6 per cent carbon, and 0.36 per cent aluminum. Melting and alloying were performed in a high-frequency furnace with magnesia crucibles. Melts were deoxidized with small aluminum additions and cast into 25-lb. slab ingots. Care was exercised in deoxidation to avoid excessive amounts of residual aluminum, which has been found to have significant effects on alloys in this system. All ingots were hot-rolled at 1200° to 1300°F. and then cold-rolled with intermediate anneal-

Jan 1, 1945

By Augustus Locke

MY conclusions apply to the engineer in California ore hunting; and, because the product has been overwhelmingly gold, that means gold-ore hunting. But, I wish to think of ore hunting, not as employment for engineers, but as engineering. I wish, moreover, to think of it as productive of ore in significant quantity. The small mine, even if good, means little. Only new districts, or large extensions of old districts can engage our attention here. The conclusions are summarized as follows: (1) The bright color of California mining history comes from the suddenness and intensity of its outburst of gold. Had the mining been averaged from the start, it would soon have become dimmed among greater industries. For fifty years, California has proceeded as an agricultural, timber and oil, but not a mining region. 1

Jan 1, 1931

By Alexander R. Troiano, Taylor Lyman

Studies of the transformation of aus-tenite at constant subcritical temperatures have been numerous since the work of Davenport and Rain.' Considerable information has been obtained on low-alloy steels and on high-carbon alloys containing undissolved carbide or graphite at the austenitizing temperature. Little is known of the isothermal transformation of aus-tenite containing in solution large amounts of both carbon and a single alloying element. In this investigation four steels containing one per cent carbon and with chromium in the range 3 to 9 per cent have been examined with the view to establishing the fundamental character of the isothermal reactions when all carbon and chromium are initially in solution in austenite. Experimental Procedure Alloys The chemical compositions of the steels investigated are given in Table I. The 4 per cent Cr alloy is a commercial steel. The other steels were made by the Carpenter Steel Co. as 50-lb., induction-furnace heats and rolled to 5/8 -in. round bars. Bars were softened at 650' to 700°C. before the specimens were cut. Most of the lines on the transformation diagrams presented here have been placed on the basis of the microscopic examinatioll of partially reacted specimens, Thees specimens were approximately 1/2 by 1/4 by 1/8 in. ill size, specimens of the 9 per cent cr steel were held 10 to 12 hr, at 1200°to 1225°C. before quenching to the various subcritical temperatures. The other steels were held for 2 to 2 1/2 hr. at 12ooOC. before quenching. These treatments, carried out in an atmosphere of purified nitrogen, produced an austenite grain size larger than A.S.T.M. So. I, some grains being 1 to 2 mm. in diameter. There were a few undissolved carbide particles in some specimens of the 9 per cent Cr steel. It is believed, however, that any errors in the results due to incomplete solution of carbon and chromium in austenite are negligible; that is, austenite compositions may be considered as being those listed ill Table I. X-ray Methods Constituents were identified and mar-tensite axial ratios determined from Debye

Jan 1, 1945

Jan 1, 1895

By J. E. Flinn, E. R. Gilbert

Recently, Green reported some high-temperature, 0.60 to 0.89 T3, creep results on unalloyed tantalum. From his study he determined an activation energy of 114 kcal per mole for steady-state creep using the T, differential-temperature method25 for testing. He accounted for the difference between this value and 110 kcal per mole for self-diffusion by the temperature dependence of the elastic modulus, 4 kcal per mole. This reported activation energy is in apparent disagreement with that which can be determined from Green's isothermal data, which we have plotted as log creep rate vs 1/T in Fig. 15. From this figure, it appears that there are two activation energies of -185 kcal per mole at the higher temperatures and -75 kcal per mole at the lower temperatures. It is not obvious that the data can be fitted to a straight line corresponding to an activation energy of 114 kcal per mole. One is led to two possible conclusions regarding Green's study: there are two discrete processes controlling the creep rate from 0.60 to 0.89 Tm or the apparent activation energy is not discrete but continuously increases with increasing temperature. The former speculation would be in closer agreement with the high-temperature creep behavior of tungsten.28 The apparent disagreement between the activation energies determined by the AT and isothermal methods certainly suggests that further study on the high-temperature creep of tantalum is needed.

Jan 1, 1967

By C. F. de Mendonca, T. Kater, R. P. de Souza

Since 1976, Cia Vale do Rio Doce (CVRD) has carried out tests to develop a type of pellet made with an organic binder. Peridur is one binder that showed it could be used in industrial plants. Extensive tests were run in CVRD's pilot plant. The results are presented in this paper. The decision was made to carry out an industrial production of 50 ht (55,000 st) of pellets. The results are shown in this paper. No detrimental effects of the Peridur were observed in either the process or in product quality.

Jan 1, 1985

The Gooseberry Mine is located 38 krn (24 miles) by road east of Reno, 13 km (8 miles) south of Interstate 80. The mine was originally discovered in 1906 and remained in the control of the Martin family of Fresno, who worked the-property with Mexican ranch hands for 68 years. Westcoast took over the property in 1976 from Apco Oil Corporation. During the time the Martins operated the mine, a 305 m (1,000 ft) inclined shaft was sunk with drifts developed on eight levels exceeding a total of 3,000 m (9,000 ft) in length. It is interesting to note that for over one -half century all development ore was stockpiled. West- coast, the United States mining subsidiary of Home Oil Company Ltd., Calgary, Alberta, completed sinking another vertical shaft to the 396 m (1,300 ft) level. Development work between 122 m and 305 m (400 ft and 1,000 ft) levels has proved the existence of a fine ore body over 300 m (1,000 ft) long. The silver-gold ore grade is fairly consistent in the vertical section, but copper, lead and zinc may show slight increases with depth. Average width of the ore bearing portion of the vein is 2.5 m (8.3 ft). Stoping is by cut-and-fill method. Average silver values within the ore zone have increased from the 152 m (500 ft) level to the 305 m (1,000 ft) level, although the gold values do show some decrease. It is not possible for the geological staff to predict the depth of the ore. However, several years of ore reserves have been proved in the existing mining areas. Important ore minerals are argentite, native gold, and electrum. Trace amounts of galena, chalcopyrite, and sphalerite are associated with the precious metal mineralization. The vein is mainly composed of calcite and quartz. Mine-run underground ore is dumped from the hoisting skip into a coarse ore bin followed by a jaw crusher, an impact crusher, and a 600 mt (650 st) fine ore bin. The mill has a capacity of 317 mt per day (350 st per day). Two-stage grinding is done by a rod mill followed by cyclones with the underflow sent to a ball mill in closed circuit with the cyclones. Cyclone overflow after conditioning receives a primary float in four 1.7 cu m (30 cu ft) cells and a second stage of conditioning ahead of 24 0.8 cu m (30 cu ft) secondary flotation cells. No cleaning stages are used. Flotation tailings are cycloned for a sand-slime separation with the sands used as underground stope fill and the slime portion to tailing dam storage.

Jan 1, 1981

By C. W. Kovach, A. Moskowitz

Studies were undertaken to investigate the effects of manganese content on the machinability and other Properties of a free machining martensitic stainless steel (AISI Type 416). Machinability was found to be significantly improved in steels of high manganese content, and a direct relationship was obtained between machinability and steel Mn:S ratio. As the manganese content of the steel increases, the sulfide Phase present changes from CrS to (FeMn)Cr2S4 to (MnFeCr)S, and finally to MnS. The average sulfide inclusion hardness decreases through the same range of increasing manganese content. The mechanism for machinability improvement is discussed in terms of a soft ductile sulfide affecting deformation in the secondary shear zone. Type 416 containing relatively high manganese for improved machinability shows good general properties. The effects of increasing manganese content on mechanical properties, cold formability, and corrosion resistance are described. THE addition of sulfur is commonly used to improve the machinability of stainless steels. However, little attention has been paid in the past to the composition and characteristics of the sulfur-containing phase or phases present in these resulfurized steels. Recent information on the properties of sulfide phases, and their role in metal cutting, suggests that variations in these phases could have critical effects on machin-ability, as well as important effects on formability and other properties such as corrosion resistance. Manganese, chromium, and iron are strong sulfide forming elements present in stainless steels! of these, manganese has the greatest sulfide forming tendency and iron the least.1"1 The manganese content of resul-furized 13 pct Cr steels, often about 0.5 pct, can be insufficient or only barely sufficient to combine with the sulfur that is present; thus, the precise level of manganese can strongly influence the nature of the sulfide phase. Sulfide phases which may be present in stainless steels have been reported to include CrS, a spinel-type sulfide, chromium-rich manganese sul-fide, and manganese Sulfide.5,6 Detailed phase relationships for the Fel3Cr-Mn-S system have been reported by the present investigators,7 and a portion of this work will be referred to subsequently in this paper. Recent work by Kiessling6 and Chao et a1.8 has shown that sulfide phases can display wide variations in hardness, and may undergo considerable plastic deformation under isostatic loading.9-12 Early theories of metal cutting attributed the influence of sulfur to a lubricating effect. It is now apparent that the influence of the nonmetallic inclusions and their properties on crack initiation, deformation in the shear zones, and boundary films must also be considered in relation to the machining process. This paper presents the results of studies conducted to relate machinability to the various sulfide phases which occur in stainless steels. This work has led to the development of alloys with improved machinability, and has generated information on the effects of inclusions on metal cutting processes. Effects of sulfide inclusions and steel composition on other important metallurgical properties are also discussed. MATERIALS For drill machinability and inclusion studies, 10 lb laboratory heats were melted in an air induction furnace. These heats were made with sulfur contents be tween 0.10 and 0.50 pct and manganese contents be tween 0.05 and 3.0 pct. Residual elements were added to the heats in amounts typical for commercial steels. The typical compositional range covered by the heats is shown below: C Mn P S Si Ni Cr Mo Cu N 0.10 0.05 0.007 (M0 0.40 0.40 13.0 0.20 0.10 0.03 3.0 0750 The laboratory ingots were forged in the temperature range of 1800" to 2100°F to 3/4-in. sq bars, and all bars tempered to a hardness aim of 200 Bhn prior to testing. Because of differences in composition and tempering response, the tempered bars showed some variation in hardness (175 to 275 Bhn) as well as variations in delta ferrite content (0 to 50 pct). Composition, hardness, and delta ferrite content were considered in the analysis of the machinability data. Additional tests involving tool-life evaluation and determination of other properties were conducted on materials from commercially melted and processed 15-ton electric furnace heats. TESTS AND PROCEDURES Machinability of the laboratory heats was evaluated in a drill test. In this test, 1/4-in. diam holes, 0.4 in. deep, were drilled alternately in a test bar and in a standard bar for a total of four holes in each. This sequence was repeated three times using a freshly sharpened drill each time. The average time required to drill a hole in the test bar was compared to that for the standard bar. A drill machinability rating was assigned to the test bar relative to a rating of 100

Jan 1, 1970

By Robert J. McKay, F. P. Huston, WILLIAM G. HUMPTON

THE manufacture of nickel-clad steel plate and the fabrication of articles from it has progressed far enough to permit a general description of the working methods used. The manufacture of sheets made up of layers of nickel and steel is not new as a sheet of this character was patented in Germany in 1893. Present development differs mainly in the size and finish of the product. The earlier light-gage highly finished products have been limited in their application due to their similarity, in certain respects, to electro-plated and highly finished alloy sheets. The new product is a relatively heavy plate 1/4 or 3/s in. thick and heavier, with one side coated with nickel, the weight of nickel being of the order of 10 per cent of the whole. The finish is that of hot-rolled steel plate.

Jan 1, 1931

By Zay Jeffries

IT is well known that many properties of a given metal vary with the size of grain or cell. For most industrial purposes, where high ultimate strength and high elastic limit are desired, the manufacturer tries to produce a. fine-grained structure. For some purposes, for example in transformer iron, a coarse-grained structure is desirable. The terms fine-grained and coarse-grained are used only in a relative sense. For example, a fine-grained cast copper might have grains 100 times larger than coarse-grained high-speed steel. Similarly, a fine-grained steel rail might have grains or cells 100 times larger than coarse-grained wire, which was made of steel from the same heat. In some metals, the change in grain size is more appreciable than the changes in any of the properties determined by the tensile test. Furthermore, in metals which have been annealed or subjected to high temperatures, grain size may prove to be a better indication of the life of the metal in use than the tensile test. One of the authors was able to supplant the tensile test with grain-size determinations in the control of. metal for a specific use, the latter determination being more indicative of. the life of the metal part than the tensile test. A grain-size determination with a tensile test is, of course, more valuable than either singly. At present there is a decided dearth of data on actual grain-size determinations in metals, and consequently a corresponding lack of ability to interpret the determinations after they are made. It would be desirable to have correlation made between grain size and properties of metals, comparing thousands of determinations. In this way, grain-size determinations might be interpreted in much the same manner that tensile tests are now.

Jan 12, 1915

By L. A. Price

With increased stripping ratios and with dwindling ore content, the mining fraternity is increasingly turning to larger and larger equipment for profitable open pit operations. The availability of higher horsepower prime movers and increased-capacity electric transmissions using either wheel-mounted or axle-mounted traction motors makes a reality of single-axle, rear dump trucks having 150 to 250 ton capacity. The size of electric loading shovels is inherently geared to the size of haulage equipment. To work effectively with this new generation of trucks, the Harnischfeger Corporation has introduced its P&H Model 2800 with a capacity of 20 to 25 cu yd and a working weight of nearly 1,500,000 lb. The Model 2800, depicted in Figure 1 loading a 200 ton truck, has many new electric and mechanical features designed to give excellent production and low cost operation. Chief among the new features is the ELECTROTORQUE control system. Electrotorque is a completely static, solid state electronic system supplying controlled power both to the armatures and to the fields of the d-c shovel drive motors. It eliminates many major electrical rotating machines and their attendant maintenance. The system was developed jointly by ASEA of Sweden and Harnischfeger Corp.

Jan 1, 1970

By B. H. Bergstrom, C. L. Stevenson

In any process wherein materials must be pelletized, a crucial period exists during the interval between the manufacture of the green pellets and their subsequent heat treatment. The pellets must possess sufficient strength and plasticity to withstand conveying and sizing. Also, they must be neither excessively brittle nor excessively plastic when placed in a bed on a traveling grate for heat treatment. An acceptable pellet, in the event sufficient forces are applied to cause its fracture, will merely split into two or three large fragments which would not drastically alter the permeability of the pellet bed. However, when brittle pellets are broken, they shatter so that the resultant fine particles either decrease the perimeability of the bed or become entrained in the gas stream and thereby cause dust problems. On the other hand, excessively plastic pellets may not break at all but may merely flatten. This would seriously hamper bed permeability. In the past, pellet evaluation has usually been left to the creative and artistic talents of the balling operators. A multitude of techniques have evolved, of which the most common is the simple compression test. For this test a hand-operated device loads single pellets to fracture, but reliability is strictly operator- dependent. Probably the next most common test is the drop test, which is conducted according to several different procedures. This is an important quantitative test for estimating the amount of handling a pellet will withstand. There are many other tests, such as pinching a pellet between the thumb and index finger, but none are capable of producing reproducible results.

Jan 4, 1962

By K. E. Merklin, F. D. DeVaney

In the past most of the research in pelletizing has as its aim the production of a physically strong pellet. Now that this problem is solved, more attention is being paid to uniformity in grade and chemical composition. Consideration has been given in recent years to a study of additives which will make pellets partially or fully fluxed. Blast furnace tests show fluxed pellets to have advantages over both fluxed sinter and acid pellets. Lower slag volumes are used more frequently in the blast furnace and the uniformity of the charge, both physically and chemically, is becoming increasingly important. A considerable improvement can be secured by having all of the flux uniformly distributed through the pellets in a calcined state. A fluxed pellet, therefore, should be a superior product. The use of an ore burden that contains an appropriate quantity of fluxing materials is not new to the blast furnace industry. For years the Minette ores of France and Germany, the Clinton ores of the Birmingham, Ala., areas, as well as others, which are low in iron but contain calcium carbonate in sufficient quantities to give them self-fluxing properties, have proven economical. The adaption of the sintering process to the preparation of ore burdens provided a means for artifically associating the fluxstone with the iron ore prior to charging to the blast furnace. In 1944 Torpl discussed the effects of using lime in sinter made in Sweden on the sinter's metallurgical performance in a blast furnace. Hessle2 reported in 1945 on the advantages of using lime in sinter to increase the sintering plants' capacity and reduce fuel requirements. Robinson3 discussed the use of lime in Swedish sintering practice at the 1950 Blast Furnace, Coke Oven, and Raw Materials meeting. One of the suggested advantages was the combining of lime with silica to prevent the formation of a fayalite slag, which is difficult to reduce in the blast furnace. Nilson4 at the same meeting commented briefly on experimental work that had just started in the U. S. on the use of lime in sinter. The literature tends to indicate that most of this early work was directed towards improvement in sinter physical quality, and the fact that the feed to the blast furnace was partially fluxed was incidental. It was not long, however, before blast furnace advantages were being claimed. The matter was forcibly called to the attention of North American operators by reports of remarkable production records established by the Russians using fluxed sinter. The leading step was taken on this continent by the Steel Company of Canada in 1957; McMahon5 reported on the marked improvement in performance of an 18-ft blast furnace using fluxed sinter at its Hamilton works. Other North American operators quickly followed theStelco lead.

Jan 1, 1963

By C. Schlumberger, M. Schlumberger

In order to explore electrically a terrain composed of a succession of horizontal beds, a current of known intensity i is caused to flow between two grounds A and B, and the resultant drop of potential , caused by the resistance of the earth, is measured between two given points in the soil, M and N. In practice it is convenient to choose the two points M and N so that they lie on the line AB and their midpoint coincides with the middle 0, of that line, although this is not imperative. When the lengths L and I of the two lines AB and MN are varied, equations are obtained which may be solved for the resistivity p of the subsoil at various depths. Recall briefly that the formula 4 x l gives the average resistivity, in the horizontal direction, of a layer of earth which extends to a depth1 about equal to L/4. This elementary concept is adequate for numerous practical applications. Nevertheless, it must be said that, in many cases, a rigorous mathematical analysis may be made, provided it is always a question of homogeneous, superposed horizontal beds. The authors expect to publish, later on, appropriate methods of calculation for some specific cases.

Jan 1, 1932

By ERIIL SCHROEDTER

THE death, on May 6, 1908, of Dr. Hermann Wedding, Privy Mining Councilor of the Kingdom of Prussia, and Professor of the Metallurgy of Iron and Steel at the Royal Mining Academy of Berlin, was a loss keenly felt by the whole metallurgical world. Not alone in his native land, but also in foreign countries did he enjoy an esteem of which the title of honorary membership in the American Institute of Mining Engineers, the United States Association of Charcoal Iron-Workers, and the (British) Iron and Steel Institute bears eloquent testimony. Hermann Wedding was born March 9, 1834, in Berlin. At the suggestion of Dr. C. J. B. Karsten, the veteran father of Prussian metallurgy and author of the first German text-book of the metallurgy of iron, lie turned his attention, after gradu¬ating from the gymnasium, to mining and metallurgy. In 1853, he began a practical course at the Malapane iron-works, in Upper Silesia. Subsequently, he studied at the Berlin Mining Academy, and received from the University in 1859 the degree of Doctor of Philosophy. A journey which be made to England, somewhat later, led to his undertaking a German translation, with revision and additions, of John Percy's classic treatise on the metallurgy of iron and steel, the publication of which, in successive installments, stretched through many years. In 1863, lie published, as a thesis in connection with his "Assessor's examination," an essay, entitled The Results of the Bessemer Process for the Production of Steel, and Its Prospects for the Rhenish and Westphalian Iron and Steel Industry, which revealed such ability and knowledge as to secure for him a call to the chair of metallurgy in the Berlin Mining Academy.

Jun 1, 1909

By C. K. Leith

AT the outset I would like to make it clear that I do not enter this discussion in a controversial spirit, but in an attempt to contribute something helpful to an understanding of a difficult problem. I have too high regard for the sterling quality of the work of the men who have studied this subject in detail to offer anything in the way of essential contradiction to their statements of fact. Difference of opinion arises from differing valuation of the possible alternative hypothesis which these facts suggest. Some degree of recrystallization in limestone contact zones has been recognized by many investigators. Earlier investigators, for the most part, assigned an important, if not the most important, role to recrystallization in development of these zones. With the growing recognition, of introduction of ores and gangue materials into the contact zone from igneous rocks through the medium of primary magmatic solutions, there has been a tendency to ascribe to this process most, if not all, of the chemical and mineralogical characteristics of the contact zone. This has involved a correspondingly diminished emphasis on recrystallization of substances already there as a factor in the process, and in some cases even the complete elimination of this hypothesis. From detailed study of a few contacts, casual observation of others, and a general familiarity with the literature, some of us have been led in recent years to raise the question whether the pendulum has not swung too far away from recrystallization toward direct introduction from igneous sources, and to argue for more recognition of the part played by recrystallization.1 The inevitable sequence has been that those of us who have taken this view have been charged, at least by inference, with emphasizing recrys-tallization to, the total exclusion of the alternative process. Scientists, like other men, like to classify and pigeon-hole views under simple and definite designations, leaving out qualifications which would tend to make the classification more difficult to state. This has made the problem seem more definite and simple, but has tended to obscure the fact that the disagreement is primarily not one relating to essential facts, but one of

Jan 6, 1914

By C. K. Leith

At the outset I would like to make it clear that I do not enter this discussion in a controversial spirit, but in an attempt to contribute something helpful to an understanding of a difficult problem. I have too high regard for the- sterling quality of the work of the men who have studied this subject in detail to offer anything in the way of essential contradiction to their statements of fact. Difference of opinion arises from differing valuation of the possible alternative hypothesis which these facts suggest. Some degree of recrystallization in limestone contact zones has been recognized by many investigators. Earlier investigators, for the most part, assigned an important, if not the most important, ro1e to recrystallization in development of these zones. With the growing recognition of introduction of ores and gangue materials into the contact zone from igneous rocks through the medium of primary magmatic solutions, there has been a tendency to ascribe to this process most, if not all, of the chemical and mineralogical characteristics of the contact zonc. This has involved a correspondingly diminished emphasis on recrystallization of substances already there as a factor in the process, and in some cases even the complete elimination of this hypothesis. From detailed study of a few contacts, casual observation of others, and a general familiarity with the literature, some of us have been led in recent years to raisc the question whether the pendulum has not swung too far away from recrystallization toward direct introduction from igneous sources, and to argue for more recognition of the part played by recrysta11ization.l The inevitable sequence has been that those of us who have .taken this view have been charged, at least by inference, with emphasizing recrystallization to the total exclusion of the alternative process. Scientists, like other men, like to classify and pigeon-hole views under simple and definite designations, leaving out qualifications which would tend to make the classification more difficult to state. This has made the problem seem more definite and simple, but has tended to obscure the fact that the disagreement is primarily not one relating to essential facts, but one of

Jan 1, 1915

By Donald H. McLaughlin

THE activity and enthusiasm of pioneers still prevail among workers in applied geophysics1.- Within the year, new devices have .been tried out, instruments and technique have been improved and the methods of application to commercial problems have been increased in many ingenious ways. There is still great need for more skillful interpretation of results in terms of geology, but oil the whole geophysical prospecting is making encouraging progress toward finding its proper place and function in engineering and geological practice. Spectacular successes continue to be reported, particularly .from the Gulf Coast, where the race for salt domes has not slackened, and encouraging results have been giined elsewhere in the mapping of structures in the search for oil. In the mining field, however, it can hardly be claimed that the same measure of success has been obtained, for brilliant efforts worthy of wide recognition have been overshadowed to some eatent by the unfortunate outcome of surveys undertaken unwisely without recognition of the limitations of the work. Consequently, hopes were aroused that could not be fulfilled, and it must be admitted in an impartial survey that there are a few regions, chiefly in the far north, where the standing of geophysical prospecting is somewhat doubtful and where the course of public opinion regarding it shows a certain similarity to the history of the market during the past few months. Reliable work, however, is steadily going 011 and it can confidently be expected that the methods will eventually be regarded in many regions as an essential part of the technique of securing geologic data needed for intelligent exploration.

Jan 1, 1930

By G. R. Heckman, H. J. Murphy, C. T. Sims

An incestigation has been made of the effects of heat treatment and alloy composition on the long-time stress-rupture properties and structural stability of the similar nickel-base alloys Udimet-500, Lrdimet-520, and Udimet-700. Rupture test data are presented at stresses ranging from 4 to 50 ksi at temperatures from 1450° to 1900°F for times up to 14,000 hr. Ductility response is emphasized. Optical and electron tnicroscopy were complemented by X-ray diffraction analyses of extracted phases to relate microstructural stability to the observed rupture properties. Particular attention is paid to Udimet-520 since structural characteristics of this alloy appear to vary somewhat from its sister alloys. Both cast and wrought performance of Lrdimet-500 are discussed. The computerized PHACOMP calculational technique, based on electron-vacuncy theory, is discussed and related to structural stability where appropriate. Electron microscopy and microprobe techniques were used to conduct evaluation of the oxidation characteristics of Udimet-500 exposed in air for 16,100 hr. The steady advance in strength and reliability of nickel-base superalloys continues to be one of the high points of modern metallurgy. The stress capability of these materials has increased steadily, allowing higher and higher operating temperatures in the highly sophisticated aircraft and industrial gas turbines now on the market. The attendant increase in efficiency, of course, means greatly improved power output. Gas turbines for industrial and marine use have long been designed with these objectives paramount the usual design requirements in terms of time of service being 100,000 hr. High-efficiency, long-life aircraft such as the supersonic transport require superalloy engine materials with high-strength and long-time structural stability. Thus, materials studied for and operating experience from industrial gas turbines provide a good reservoir from which technology of high value to the SST program can be drawn. This study is one such case. Three prominent nickel-base super alloys—Udimet 500, Udimet 520, and Udimet 700 were extensively evaluated for industrial gas turbine bucket use. Particular attention was directed toward structural stability as a requisite property. Within the present context, structural stability is defined as freedom from the propensity to form strength-robbing or embrittling phases such as u,p,x,or Laves, and the ability to maintain useful rupture strength and ductility throughout design life. MATERIALS The three alloys, cast Udimet 500 (U-500C), Udimet 520, and Udimet 700, were chosen for detailed evaluation based on preliminary studies which indicated that U-500C and U-520 possessed comparable rupture strength capabilities, and that U -700 had a greater strength capability but somewhat poorer ductility than wrought U-500. The nominal compositions of the three alloys, along with the compositions of the heats investigated, are presented in Table I. PROCEDURE Dimensionally rejected U-520 buckets from Special Metals Corp. heat 63370 were heat-treated using the four cycles delineated in Table 11. Cycle A was investigated to determine the effects of a shortened 1700°F primary age. Cycle B was considered a "standard" treatment. Cycle C investigated a higher solution temperature in combination with a shortened primary age, while cycle D assessed the effect of the higher solution temperature alone. These heat treatments were designed to produce optimum combinations of rupture strength and ductility through maximum y' development, the development of a y' grain boundary cushion, promotion of MC carbide degeneration reactions, and agglomeration of resultant M23CB. Since one of the premises of the evaluation of U-520 was that rupture strength would be equivalent to U-500, forged U-500 buckets from Special Metals Corp. heat 62916 were heat-treated with cycles A, B, and C to provide comparison. The heat-treated structures of U-520 and U-500 are illustrated in the 8700 times electron micrographs of Fig. l. The U-700 tested was all from 3-in.-diam hot-rolled and centerless-ground rod from Special Metals Corp. heat 2-1426. Two heat-treatment cycles were employed, E and F of Table 11. Cycle E is a standard four-step, triple-age treatment intended to provide an optimum match of strength and ductility through well-developed matrix and grain boundary y', as recommended by U-700 vendors. Treatment F is a shortened , single-age cycle which could provide a significant processing cost reduction should adequate strength and ductility be maintained. Following heat treatment, rupture specimens of U-500 and U-520 were machined from the buckets and tested. Standard rupture bars of U -700 were machined from the heat-treated rod and rupture-tested. Failed and withdrawn rupture bars were prepared and examined by optical and electron microscopy. Select specimens were electrolytically digested, and the residues analyzed for carbide and topologically close-packed phases using CrKa or CoKo radiation. Of the six different U-500C heats evaluated, five were cast by Misco Precision Casting Co. and one was cast by Haynes Stellite Co. Cast-to-size rupture bars

Jan 1, 1968