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By Donald C. Barton

OF the four papers that comprise this Technical Publication, three are case histories of individual geophysical prospects, subsequently tested by drilling. The bibliography of Dr. Barton's published scientific paperst includes investigations in physiography and surface geological mapping, as well as his geophysical papers, and from this list it is to be observed that he early recognized the place of different types of geophysical prospecting methods in the search for geological structures of economic importance. Moreover, his viewpoint was not merely that the structures should be found, but that the geophysical data should be examined quantitatively to determine the geometry of the structures. In other words, that although these data are insufficient to deduce a unique form for the structure that caused the effects measured in the data, the engineering computations should be carried out to give as much of a definite configuration to the structure as the data permitted, in order that the testing of the structures could be conducted in the most economical manner and with the idea that the experience so gained could be later incorporated in the study of structures subsequently found. Dr. Barton continually emphasized the quantitative use of geophysical observations, whereas at the time that he began his specialization in geophysics it was considered sufficient to use observations only qualitatively. He, more than any one else, was responsible for the first volume on geophysical prospecting issued by the Institute in 1929, and his three articles in that volume stressed the quantitative use of geophysical prospecting. The fourth article in this present Technical Publication is a further contribution to this branch of geophysical interpretation, and is a supplement to the paper in the 1929 volume, "Calculations in the Interpretation of Observations with the Eötvös Torsion Balance." From the successful demonstration by Dr. Barton of the usefulness of quan-

Jan 1, 1946

By Franklin H. Wilson

COPPER base alloys containing various amounts of aluminum and silicon are of considerable commercial interest. In particular the alloy containing 7 pct aluminum and 2 pct silicon shows an attractive combination of high strength with excellent machinability. Since there is no evidence in the literature that this ternary system has been studied since the recognition by Smith1 and Anderson2 in 1939 of the kappa phase of the binary copper-silicon system, the determination of the equilibrium phase relationships in the copper corner of the ternary diagram has been undertaken to provide a fundamental basis for understanding the behavior of these alloys. Phase boundaries have been determined by the micrographic examination of quenched samples while points on the liquidus surface have been obtained by thermal analysis. The results, of sufficient precision to serve their major purpose of providing a guide for the control of the manufacture of alloys in the region covered, are presented in a series of both isothermal and vertical sections of the diagram. ALLOYS STUDIED For a rough survey of the copper corner of this ternary system the compositions listed in Table I (Series A) were employed. The results of examinations of these alloys indicated that the compositions listed in Table 2 (Series B) would further clarify regions of greater complexity. All alloys were prepared as 1200 g heats, the copper being melted under charcoal, and then first silicon and then aluminum were added. An [ ] excess of 0.05 pct silicon was allowed to cover deoxidation losses. Two small bars 5/8 by 1 ¼ by 1 ¼ in. were cast using Durville type casting equipment. Analyses were made on all alloys using material which was hot-rolled at 800 or 850°C and annealed 17 hr at 650°C. All analyses were found to be within 0.05 pct of the nominal composition. Since the precision of analysis is not much better than this, the points of both isothermal sections and vertical sections at fixed aluminum and silicon contents have been plotted at the compositions indicated by the nominal composition.

Jan 1, 1948

By R. L. Stegman, M. R. Achter

Nickel, fatigued in vacuum, shows intragranular crack initiation and growth at low temperatures. An increase in temperature initially prolongs fatigue life due to a more homogeneous distribution of slip. With a further temperature increase, the mode of failure undergoes a transitiotz to intergranular crack initiation with concurrent recrystallization which results in a shorter life. The transition temperature varies with bending strain and specimen purity. UNTIL recently, very little work has been done on the effect of temperature on the mechanism of fatigue and the resultant variation in fatigue life. Except for mild steel, where strain aging raises the strength at moderate temperature, fatigue lives had been shown to decrease with an increase in temperature. In their review article, Allen and Forrest' summarized the work of McCammon and Rosenberg and of Forrest and Mann on the fatigue of copper from -269" to 325°C. The fatigue life vs stress curves remained roughly parallel over this temperature range, the fatigue strength decreasing progressively with increasing temperature. When testing was done in vacuum, the present authors' found the results for nickel were different from those quoted above. Initially, the fatigue lives increased with temperature and then decreased as a grain boundary mode of failure was observed. The initial increase was attributed to a more homogeneous distribution of slip, a condition which was not as conducive to crack initiation as the bunching of slip lines observed at 20°C. Ronay, Reimann, and wood3 observed a similar change of slip line distribution in brass, tested in air, with rising temperature. Our previous observations were based on preliminary work with relatively few specimens, fatigued at comparatively low strains. To learn more about the mechanisms, the present investigation was undertaken for the purpose of studying systematically this effect over a wider range of strains and as a function of purity of the nickel. EXPERIMENTAL PROCEDURES The testing equipment, procedures, and specimen geometry have been described elsewhere.' An optical technique to measure bending strains was used as de-

Jan 1, 1968

By D. G. Hartley, P. C. Hayward, K. R. Weller, U. J. Sterns

The major copper loss at Mount Lyell is in the coarsest particles presented to flotation. An analysis of data collected from the five Primary and six secondary ball mill circuits showed that grinding was limited by low breakage rates in secondary mills, possibly due to oversize balk. For five months, the make-up ball size for one secondary mill was reduced from 50 to 30 mm (2 to 1.1 in.). Frequent steady-state tests indicated that overall average breakage rates could be increased by about 70% using smaller balk. A mathematical simulation of the whole circuit with increased breakage rates showed that the resultant finer grind was likely to improve copper recoveries by about 2%.

Jan 1, 1984

By C. R. Garr, A. R. Troiano

FLAKING or hair-line crack formation has been a major problem confronting the producer of large alloy steel forgings.' Today it is generally conceded that hydrogen in one or more forms in alloy steel sections is a requisite for flaking. Hence an obvious remedy is a thermal cycle that reduces the hydrogen content to some low level. In practice, this generally means holding the material at some subcritical temperature for a period of time depending on the size of the ingot or forging. Another method that will suffice in some cases is to cool large forgings slowly, i.e., bury in ashes. In practice, this hydrogen bake is sometimes accemplished inadvertently by a series

Jan 1, 1958

IN general in making such powders, all kinds of gravel, tuff, washed river silt, and similar earths whose grain is fine and lean by nature are good for this operation of casting, either by themselves or in mixture because they are disposed to receive the metals well on account of a certain dryness which they possess. Many kinds are also compounded by means of art. Of these, I shall proceed to tell of all those that experience [119] has taught me to recognize as good. But first I desire that we return to speak of the natural ones because they are real earths and can always be had wherever one may be, and in the necessary quantity. They please me greatly because they are easy to reduce on account of their disposition. A loam is made from these and mixed by beating with wool-cloth cut- tings, spent wash ashes, and horse dung. This is made into cakes and dried. These are then put to bake in a furnace or in some other way and, in fact, are baked very well. Then it is pounded and sifted with a fine sieve, or it is ground in a potter's color mill, or by hand on a porphyry with water, to the fineness that the craftsman desires, or as fine as he can make it. When it has been ground it is again drained free from water and dried out with fire. Then as much magistery of salt is taken as will moisten it. It is dried and pounded again and passed through a sieve. When it has been made as desired in this way it is moistened again before use with water, urine, or vinegar just enough so that it holds together when it is squeezed in the fist. Then, when it has been brought to this point, it is moulded as you will hear. Powders are also made of crushed brick, tripoli, vine ashes, tiles, and glazed drainpipes, or burned emery, calcined tin, straw, and of burned paper and horse dung as well as of young ram's-horn ashes and many other things. The goodness of all these depends on three things; namely, on receiving the metal well, on being so fine as to be almost impalpable, and on their being made .with a magistery that renders them hard and strong when they are dry. In addition to these powders I have used another when I needed it, and it has succeeded well every time I made it. To make this. I have taken I two parts of pumice and one of iron scale and ground them on the por-

Jan 1, 1942

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y, PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. BAND,': NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 2, 1915

By CHARLES F. RAND

PRESIDENT CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N.. Y. FIRST VICE-PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER. W. RAYMOND, NEW. YORK; N. Y. SECRETARY BRADLEY- STOUGHTON NEW YORK, N. Y.

Jan 2, 1914

By Donald Ingvoldstad, Harold E. Lee

AT Bunker Hill the original charge storage and preparation system was installed in 1917 to accommodate lead-silver gravity mill products. Only minor tonnages of wet fines such as vanner and flotation concentrates were received. Charge flux and diluent requirements were .provided by an ample supply of siderite middlings and coarse lime-rock. While oversize material was crushed through ¼in., the use of roll crushers in series resulted in a more or less granular, free-running charge of adequate porosity. Under such conditions, receipts could be proportioned directly from receiving bins, and suitable blending was obtained by passing the resultant layered composite through a small Stedman disintegrator. This elementary system served well for production and smelting of an extremely lead-rich sinter, in the low column blast furnace. Here sinter physical quality is less critical, and appreciable quantities of raw flux and oxidized ore may be charged directly to the blast furnace without seriously impairing furnace capacity. Prior to 1938 the relative proportions of zinc receipts were low and extraneous flux requirements at a minimum. However, subsequent war-inflated zinc demands brought marked increase in fine concentrate and slimy zinc leach residue receipts and an abrupt introduction to smelting a more refractory zinciferous charge. The higher temperature demands of the more refractory zinciferous charge required a higher smelting column and the higher column, in turn, rendered the blast furnace less receptive to improperly prepared feed. Inadequate presinter processing facilities prevented the production of acceptable sinter, and blast furnace production declined to 50 pct of former capacity. In view of a prevailing contention among lead metallurgists as to the deleterious action of high zinc slag on blast furnace capacity, it was natural to overstress this factor and to concentrate on possible changes in furnace design. Another interpretation was that primary correction should be sought through expanded sintering facilities. This divergence of opinion, together with the extreme material shortages of the 1940's, delayed corrective

Jan 1, 1957

INTRODUCTION This chapter summarizes characteristics of porphyry copper deposits within the Cordilleran orogen east of the Coast Range plutonic complex of the Yukon and British Columbia and south to the Columbia River plateau and the Idaho batholith. Porphyry copper deposits in this area reflect a geologic environment different from that found for mineralized intrusions elsewhere in the Cordilleran orogen, both to the south in the United States and Mexico and to the west in Alaska. A section on the Tertiary Cascade porphyry copper province is included herein. The Cascade province is considered separately because its deposits display a unique mineralogy and age of mineralization. That portion of the Cordilleran orogen described in this chapter is shown in Fig. 32, with the Cascades shown in Fig. 39 (see p. 114). The regional geology of this area has been described by Monger, et al. (1972), Hollister (1974), Wolfhard and Ney (1974), Field, et al. (1974), and Stacey (1974). Each offer slightly differing views on the post-Mississippian evolution of the geology in this porphyry copper province. The descriptive geology in this chapter has benefited from many discussions with J. E. Armstrong and J. W. H. Monger. Two separate petrologic models have been used popularly to categorize porphyry copper deposits in this area, a diorite and a quartz monzonite model. The diorite model, which involves a mineralized quartz-free pluton, has also been called the alkalic type (CZM Special Volume 15, 1976, and Soregaroli, 1975) and the syenite suite (Sutherland Brown, et al., 1971). The quartz monzonite model has also been named the calcalkalic type (CZM Special Volume 15, 1976) and includes mineralized quartz-bearing plutons compositionally ranging from quartz diorite to granite, with the igneous phase closest to ore in time and space commonly being quartz monzonite.

Jan 1, 1978

By C. E. Sims, C. A. Zapffe

AN investigation of the behavior of inclusions in steel several years ago1 led to the conclusion that some of the commonly occurring inclusions in steel have appreciable solubilities, particularly in liquid steel. In the belief that further study and clarification of this matter was warranted, a laboratory study of oxides in liquid steel was started. These oxides are generally the result of deoxidation treatment, and the basis of an understanding of their behavior must be, therefore, the behavior of the deoxidizer in liquid iron. The Fe-Si-O system was selected for the first study, and the apparatus used and experiments conducted are described herein. APPARATUS The apparatus is shown in Fig. I and the system is shown by diagram in Fig. 2. Furnace Atmosphere Commercial hydrogen (1) passes through an orifice (2) into a manometric system that measures the tankside pressure (3) and the back pressure (4) in the system. A water trap (5) guards against excess tankside pressure. A by-pass with stopcocks (6 and 7) is provided, so that the hydrogen can be routed directly from the tank to the furnace if desired. When stopcock 7 is closed and stopcock 6 is open, the gas proceeds through the conditioning train, of which the first unit is a furnace (8) that contains platinized asbestos at 350°C. The temperature is measured by a thermocouple and potentiometer (9) and is controlled by a slidewire resistance (10). In [ ] this furnace free oxygen is converted to water vapor. The exiting gas passes over a water bath (11) kept slightly below boiling temperature by an auxiliary heating unit (12). This unit also heats a surrounding copper coil (13) containing water, and the heated water rises through a collar (14)

Jan 1, 1942

By W. E. Quist, R. Taggart, D. H. Polonis, C. J. van der Wekken

An intermediate compound that has been identified as Niab is observed to form as a decomposition product from supersaturaled Ni-Nb solid solutions during aging at temperatures between approximately 300" and 500°C. On the basis of data from electron microscopy and selected-area diffraction, the structure of this compound has been determined as fct with a = b - 3a0 and c = a, wlzere a,, is the lattice parameter of the parent solid solution. The compound consists of close-packed layers with triangular ordering, where the niobiutrl atoms are separated by two nickel atoms ([long- close?-packed directions. A nine layer stacking sequence is required to describe the proposed structure. STUDIES of the Ni-Nb binary system have been limited primarily to phase diagram determinations,'-4 investigations of high-temperature equilibrium phases,5"1 and the determination of the influence of deformation on the structure of the equilibrium compound.8 The nickel-rich portion of the binary system is reported to be of the simple eutectic type in which the maximum solubility of 12.7 at. pct Nb occurs at 1282"c.' The two-phase field below the eutectic temperature is bounded by the a fcc solid solution and an orthorhombic Ni3Nb compound. No metastable phases have been reported in previous investigations. In transformation studies of certain nickel-base commercial alloys that contain niobium, two ordered metastable compounds containing niobium have been shown to precipitate from the solid solution, both of which have been identified as y' and have the composition NisNb or Ni,Nb. One compound has been reported to have the bct DOz2 type Al3Ti structure" and the other the cubic LI2 type Cu3Au structure.9,11 In the present work on Ni-Nb binary alloys a metastable y' compound has not been detected after conventional quenching and aging treatments. An anomalous behavior was noted in electrical resistivity measurements. in alloys containing between 7 to 12 at. pct Nb when aging treatments were performed below 500°C after fast quenching from 1250°C. Transmission electron microscopy has shown that this behavior is caused by the formation of a low-temperature precipitate of unreported structure type and composition. EXPERIMENTAL METHODS Several Ni-Nb alloys, containing up to 11.5 at. pct Nb. were prepared by either levitation melting and casting in copper molds or by induction melting in alumina crucibles; both techniques employed purified helium gas as a protective atmosphere. The purity of the nickel and niobium used to make the alloys was 99.98 wt pct Ni and 99.9 wt pct Nb. The composition and homogeneity of the alloys were checked by weight measurements and by electron microprobe analysis. The induction-melted alloys were homogenized for 100 hr at 1100°C. The resistivity specimens were prepared from rods swaged to 2.5 mm and the electron microscopy specimens were cut from sheet that was rolled to 0.4 mm and thinned using a modified Bollmann technique." The elevated-temperature solution treatments were carried out in a purified helium atmosphere followed by direct quenching into a 10 pct NaCl solution at 23°C. Additional protection against oxidation of the samples during solution treatment was accomplished by using tantalum foil as a "getter" in the furnace. The specimens were aged at various temperatures in salt baths controlled to +2oC. A Leeds and Northrup K5 potentiometer was used to make electrical resistivity measurements on specimens immersed in liquid nitrogen. Electron microscopy and diffraction studies were carried out with JEM-7 and Philips EM-200 microscopes operating at 100 kv. RESULTS AND DISCUSSION Ni-Nb alloys containing between 7 and 11.5 at. pct Nb that have been solution-treated in the range 1220" to 1280°C and quenched to 23°C undergo a precipitation reaction when aged in the temperature range 300" to 500°C. Precipitation was detected by selected-area electron diffraction after aging a specimen for as little as 30 sec at 350°C) whereas the reaction was well-advanced after aging for 150 hr at 475°C. Electrical resistivity measurements were used to monitor the progress of the precipitation reaction. In the present experiments the nucleation process for precipitation required a high solution temperature and a rapid quench into brine. The presence of aluminum, iron? and carbon in amounts totaling less than 1 wt pct was found by electron diffraction to completely suppress the formation of the low-temperature precipitate that has been detected in the binary alloy. Electron diffraction techniques were used to determine the structure of the precipitates that formed during the decomposition of the Ni-Nb supersaturated solid solutions. Figs. l(a) through l(d) show electron diffraction patterns oriented to the [loo], [110], [lll], and [I031 zone axes of the matrix. Areas of reciprocal space between these sections were investigated by slowly varying the orientations of the crystal under study; this procedure revealed no reflections other than those depicted in Fig. 1. The presence of super-lattice reflections at points coincident with the matrix reflections was confirmed by the examination of an almost completely transformed structure. On the basis of the accumulated diffraction data, the reciprocal lat-

Jan 1, 1970

By Rizo-Pairón Alfonso, A. M. Gaudin

PREVIOUS studies of activation in flotation have directed attention to the action of the activator on the mineral to be floated rather than to the relationship of the activator to the collector The latter phase of the problem, however, seems to have definite scientific, if not also practical, interest In the investigation reported in this paper, experiments were carried out, largely with quartz as subject, barium as activator, and oleate as collector The results obtained indicate that a I I ratio of collector ion to activator ion gives optimum results, and that a 2 I ratio almost fails to achieve activation and flotation Yet, a 2 I ratio would have been expected on stoichiometric grounds, had the coating been a normal salt of the activator ion with the collector ion, since barium is a divalent cation and oleate a monovalent anion To interpret and rationalize the observations, considerations of the crystal chemistry of quartz are helpful The point of view to which these considerations lead may be of general applicability to systems involving suspensions of solids in liquids, they confirm that an adsorbed coating is inescapable APPARATUS AND SUPPLIES The experimental work consisted in barium-ion abstraction tests, hydrogen-ion and hydroxyl-ion abstraction tests, flotation tests, and determinations of the surface of the crushed quartz The flotation machine was built according to the design of D W McGlashan It consists of a drill press in which the bit has been replaced by a stainless-steel impellor surrounding a stainless-steel stator, as in the Fagergren laboratory machine The air intake is controlled by a valve, and the cell consists of a beaker The quartz was obtained from vein quartz stored in large chunks It was first crushed to 20 mesh, then sized on a 28-mesh screen The 20 to 28-mesh size alone was retained for use This size was freed of coarse iron by passage through a Ball-Norton magnetic separator, bleached with boiling hydrochloric acid to remove residual abraded iron, washed with distilled water until the washings were thoroughly free of ferrous, ferric, and excess hydrogen ion, and stored in covered Pyrex beakers under water until used The barium was used as barium chloride, Baker's analyzed C P The oleate was used as sodium oleate It was prepared from sodium hydroxide, Baker's analyzed C P , and oleic acid purified by R R de Arellano3 in the laboratories at the Massachusetts Institute of Technology The purification procedure was elaborated from the recent researches of Brown and Shinowara 2 It consisted in (I) saponification of olive oil with potassium

Jan 1, 1942

By Alfonso Rizo-Patrón, A. M. Gaudin

PREVIOUS studies of activation in flotation have directed attention to the action of the activator on the mineral to be floated rather than to the relationship of the activator to the collector. The latter phase of the problem, however, seems to have definite scientific, if not also practical, interest. In the investigation reported in this paper, experiments were carried out, largely with quartz as subject, barium as activator, and oleate as collector. The results obtained indicate that a I : I ratio of collector ion to activator ion gives optimum results, and that a 2:I ratio almost fails to achieve activation and flotation. Yet, a 2:I ratio would have been expected on stoichiometric grounds, had the coating been a normal salt of the activator ion with the collector ion, since barium is a divalent cation and oleate a monovalent anion. To interpret and rationalize the observations, considerations of the crystal chemistry of quartz are helpful. The point of view to which these considerations lead may be of general applicability to systems involving suspensions of solids in liquids; they confirm that an adsorbed coating is inescapable. APPARATUS AND SUPPLIES The experimental work consisted in barium-ion abstraction tests, hydrogen-ion and hydroxyl-ion abstraction tests, flotation tests, and determinations of the surface of the crushed quartz. The flotation machine was built according to the design of D. W. McGlashan.* It consists of a drill press in which the bit has been replaced by a stainless-steel impellor surrounding a stainless-steel stator, as in the Fagergren laboratory machine. The air intake is controlled by a valve, and the cell consists of a beaker. The quartz was obtained from vein quartz stored in large chunks. It was first crushed to 20 mesh, then sized on a 28-mesh screen. The 20 to 28-mesh size alone was retained for use. This size was freed of coarse iron by passage through a Ball Norton magnetic separator, bleached with boiling hydrochloric acid to remove residual abraded iron, washed with distilled water until the washings were thoroughly free of ferrous, ferric, and excess hydrogen ion, and stored in covered Pyrex beakers under water until used. The barium was used as barium chloride, Baker's analyzed C. P. The oleate was used as sodium oleate. It was prepared from sodium hydroxide, Baker's analyzed C. P., and oleic acid purified by R. R. de Arellano3 in the laboratories at the Massachusetts Institute of Technology. The purification procedure was elaborated from the recent researches of Brown and Shinowara.2 It consisted in: (I) saponification of olive oil with potassium

Jan 1, 1942

By Gerald Edmunds

In a paper1 before this Institute in 1940, the writer reported that the surface orientation texture of zinc and cadmium differed from the texture existing within the casting, in that basal planes were parallel to the surface. He was unable to rationalize the , origin of this surface texture. It is conceivable that the surface orientation texture is influenced by the atomic force fields, which are different at the surface and within the body of metal. It was considered that a radical changc in the surface against which the metal is cast might alter the surface texture. In trial of this, zinc has been cast against a surface of molten lead, but the same result has been obtained—i.e., (001) parallel, ± 2oo, to the surface—as was obtained when it was cast against air, Transite or iron.' Into the bottom of an open cast-iron tray, 7 by 14 in. by 2 in. deep, preheated to about 275°C., about 1/4 in. of lead, then 1/2 in. of zinc was poured, and the whole was covered with an electric heater to enforce freezing from the bottom upward. After a lapse of time sufficient for the zinc but not the lead to solidify, the zinc slab was raised free of the molten lead. The bottom surface of the zinc casting was coated with a thin layer of lead. A specimen of the slab 136 in. square was metallographically polished to flatten it and remove the slight film of lead, and the orientation was determined by the method used before,' with the result stated above. Some determinations have also been made on other metals, as follows: Surface orientation determinations were made on the 3/8-in. diameter grip section of two 1/4-in. diameter aluminum-alloy die-cast tensile bars and on a 1/8 by 1/2-in. flat aluminum-alloy die-cast tensile bar. None of these three aluminum die castings exhibited any preferred orientation at the surface. A brass die casting (nominal composition: 60 Cu, 37.75 Zn, 1.00 Sn, 1.00 Pb, 0.10 Al, 0.15 Si) furnished by C. S. Smith was also examined. The surface showed a random orientation of alpha and beta. Summary A zinc casting solidified against a molten lead surface was found to have the same surface orientation texture, (001) parallel to the surface, as other zinc and cadmium castings. Aluminum and alpha-beta brass die castings were found to have random grain orientation textures at the surface. Acknowledgment The X-ray determinations were conducted by M. L. Fuller.

Jan 1, 1945

By Eugene C. Robertson

INTRODUCTION A direct proportionality between the observed displacement of a fault and its thickness of breccia and gouge has been proposed recently (Robertson, in press). To validate this finding, an explanation of the mechanics of continuous breccia formation is needed and is offered in this paper. A summary of evidence for the finding will show why an explanation is needed. The correlation between fault displacement [d] and accompanying breccia- plus-gouge thickness [t] seems to be linear and reasonably well established over 6 orders of magnitude, with a range in [d] from 1 mm to 1 km, on a trend of [d/t]= 100, shown in Figure 1. Most of the points are for faults observed underground in mines. The [d] – [t] relation is limited to normal and reverse faults, that have a flat to steep dip and a displacement less than 5 km. It is not applied to large strike-slip and low-angle overthrust faults, whose displacements and breccia thicknesses are widely variable and uncertain. Undisplaced jointed rock is not included in the thickness measurement. A complete description of sources and analysis of the data is given in Robertson (in press). One would intuitively expect that continued movement on a fault would grind up the previously formed breccia and gouge and not produce any more, but the evidence (Fig. 1) indicates otherwise. A physical model to explain continuous formation of gouge and breccia from the wall rocks can be obtained from laboratory experiments on friction.

Jan 1, 1982

By G. H. Ashley

THE Pittsburgh coal bed stands today: as probably the largest contributor of wealth of any single mineral deposit in the world. If it is not, what other deposit is? To the present it has contributed more than 2,530,000,000 tons of high-grade coal from Pennsylvania alone, worth nearly $4,000,000,000. Since 1910 it has added more than $2,500,000,000 to the value of Pennsylvania's mineral output. There is estimated to be about three times as much coal still in this bed as has been mined. To realize the full value of this wonderful bed it must be remembered that the figures given are for one State only. To them should be added the figures for the same bed from West Virginia, Ohio and Maryland. Furthermore, as known by man, this great deposit is only a fraction of its original whole. Outliers in Somerset County, Pa., indicate that its original extent in Pennsylvania in an east and west direction was more than two times its present extent. Add to that the northward extension as indicated by outliers in northern Allegheny, Armstrong and Indiana counties,, and it seems safe to say that its original extent was not less than three times the area at present underlain by it. And as the subjacent beds of the Allegheny group are found still further eastward and northward, it is at least a possibility that it originally covered an area many times its present area.

Jan 10, 1926

By Carolyn Barnes

The Offshore Technology Conference, the world's largest technical conference and exhibition on the development of offshore resources and protection of the ocean environment, is sponsored annually in Houston, Texas, by 12 international engineering and scientific societies. This year's OTC, the seventh, will be held May 5-8 at the Astrodomain, and will be the largest in its history. The technical program for the first meeting in 1969 consisted of 100 papers, an exhibit display of 380 booths, and an attendance of 4300. This year. 280 technical papers are to be presented, and more than 2800 exhibit booths, representing some 1200 companies and nine countries, will be on display for an anticipated audience of 40,000.

Jan 4, 1975

By G. Sachs, E. J. Riping

All ferrous alloys can be made brittle by straining at sufficiently low temperatures. However, the changes in mechanical properties for different ferrous materials with decreasing testing temperature do not appear to follow any universal law. In particular, complex effects of testing temperature have been observed if cold worked steels were subjected to tensile tests at low temperatures. EFFECTS OF PRESTRAINING AT A TEMPERATURE ABOVE THE TESTING TEMPERATURE ON THE FRACTURE CHARACTERISTICS‡ A considerable amount of data has been presented by a number of investigators on the fracture characteristics of various cold worked steels.' These data usually relate to a two-step procedure first used by Davidenkov,² consisting of stretching by tension to a certain strain or " prestraining" at room temperature and then completing the tensile test, or "testing" at the temperature of liquid air. On the basis of data of this type made available to date, ferrous alloys can be classified into two groups with respect to their fracture characteristics observed on testing at a low temperature after prestraining at room temperature. Very complex phenomena have been observed for all annealed steels. On the other hand, some observations indicate that steels in certain other conditions represent a fundamentally simpler relation. In considering the effect of prestraining at one temperature on the properties obtained at some lower temperature, it should be expected that any cold work reduces the ductility retained in proportion to the magnitude of the cold work. However, the test data presented to date indicate that only heat treated (quenched and tempered) steels appear to conform to this expectation, according to the very limited test data in Fig 1, presented by McAdam, Geil and Mebs. This series of tests, Fig 1, shows that the retained ductility became smaller the larger the prestrain. However, this decrease is less than the amount of prestrain or, in other words, less than the decrease in ductility at the prestraining temperature. These effects of prestraining are fundamentally identical with those observed by Bridgman3 when a steel was prestrained (in tension) under hydrostatic pressure and then subjected to a regular tension test. It appears, therefore, that the basic effect of prestraining under conditions which yield a higher ductility than the (subsequent) testing procedure, consists of gradually increasing the total ductility of the metal from the initial low value of testing to the higher value of prestraining. On the other hand, all annealed steels, if cold worked by tension at room temperature and then tested at a lower temperature, provided that some ductility is retained, showed a far more complex behavior than that discussed above. This relationship is exemplified by Fig 2, for three pearlitic steels.4,5 These particular steels were selected because of the various shapes of their ductility-prestrain curves. All three steels, and any other investigated so far, suffered a rapid decrease in retained (and consequently also in total) ductility when subjected to small pre-strains. Then, after exceeding a certain prestrain it was generally observed that the ductility recovered.* This rather complex behavior of annealed steels may be tentatively correlated with the presence of stretcher strains at small restrains. Heat treated steels do not exhibit stretcher strains. This fact might possibly explain their simpler prestrain-retained ductility relationship. The destructive effect of these stretcher strains may possibly be associated with the presence of triaxiality, which may occur in any highly non-uniform stress and strain state (and which is retained as residual stress after unloading). Even a small degree of triaxiality may then cause a reduction in ductility, or even embrittlement at a sufficiently low testing temperature. The discussion presented above deals with the effects of cold working at a high temperature on the fracturing

Jan 1, 1950

By Gordon H. Geiger, John M. Svoboda

One mechanism of metal penetration into mold aggregates by cast steels is vapor state mass transport. In order to further understand and quantify this mechanism, the steady-state diffusion of metallic vapors was studied at 1250" to 1600°C in controlled oxygen pressure atmospheres by measuring the weight loss from a metal bath whose vapors were allowed to diffuse through a porous aggregate compact held at constant temperature. Mass transport rates substantially greater than those predicted from the assumption that the vaporizing species was the elemental metal vapor were observed. Vaporization rates were found to increase with an increase in the oxygen partial pressure in the gas atmosphere with maximum vaporization occurring at oxygen partial pressures just below those in equilibrium with a liquid oxide layer at the given temperature. When the liquid oxide layer was present, no vaporization was observed. Metal carbonyls were ruled out as the vapor species involved because of their thermodynamic properties. The species with the enhanced volatility were deduced to be gaseous metal-oxygen molecules, probably the polynuclear oxides (FeO)2 and (Mn0)2. Diffusion followed the ordinary diffusion mode, and Knudsen diffusion is not important in normal foundry molds. The interdiffusivities of the metallic vapors and the mold atmosphere, through the porous aggregates, were measured. The effective interdif-fusivity of the vapor species and mold atmosphere through the aggregate may be expressed as follows: Deff,12 - — where E is the void fraction of the aggregate and 7 is the "tortuosity factor". Aggregate material had no effect on diffusion rates, and the only relevant parameter was the void fraction. Values for 7 ranged from 3 to 6 for normal foundry aggregates with 4 being considered a good representative value. An area of interest in high-temperature metallurgical processes which has received little attention in the past is the diffusion of metal vapor species in porous aggregates. Research into the metal penetration phenomenon' in foundry molds has shown that a major penetration mechanism is the vapor transport of metallic species into the porous foundry sand molds, followed by condensation of metallic films on the sand grains. Considerable study of the vaporization of metallic species has been reported in the literature, and the vapor transport properties of many metallic species have been determined.2'3 Many instances have been observed where the vaporization behavior could only be explained by the existence of a metallic species with a vapor pressure greater than the elemental metallic species. These species were identified or, in some cases, presumed to be carbonyls,4,5 hydroxides,6-9 or vaporous oxides.10-16 The diffusion of gases through porous aggregates has received considerable attention in the literature pertaining to catalysis, although primarily at low temperature, and more recently in the literature concerned with ore reduction.17-22 The following experiments were devised and carried out in order to determine the nature of the metallic species involved in the metal penetration phenomenon, and the effective diffusivities involved. EXPERIMENTAL APPROACH Steady-state diffusion was selected for experimental convenience. The experimental systems used, shown in Figs. 1 and 2, consisted of a porous aggregate specimen contained in an impermeable alumina tube held above, and just separate from a metal bath. The entire system was held at constant temperature and pressure in a furnace with a controlled oxygen partial pressure atmosphere. After a brief period of nonsteady state behavior, a steady flux of metal vapor through the porous aggregate will develop due to the concentration gradient of metallic vapor in the gas phase. The flux of metallic vapor from pressure may be neglected because there is no pressure gradient. There is no flux from convection because there is no net flow of gas within the metal-aggregate system, and thermal diffusion is negligible compared to the flux from ordinary diffusion. If the material being studied is allowed to vaporize until steady-state behavior is attained, the experimental results may be analyzed using Fick's First Law.

Jan 1, 1970