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By Harry C. Gatos, Frank J. Bachner

It was shown through high-pressure experiments that tin loss by volatilizatim is necessary for the degrada-tion of the superconducting transition temperature of Nb,Sn associated with high-temperature annealing. Crystallochemical analysis of the degraded Nb3Sn showed that it constitutes a new phase with ordered niobium-site vacancies, created by the migration of niobium atoms to vaccnt tin sites. This new phase was found to form when 4 pct Nb-site vacancies were present. It has a transition temperature of 6'K and a lattice parameter of 5.283A. A similar degradation effect was observed in Nb,Al. Its superconducting transition temperature dropped from 16.5" to 8" K following a high-temperature annealing. The superconducting temperature degradation in these 0-tungsten structure compounds is attributed to the disruption of the interchain d bonding by the periodic interruption of the niobium atom chains. By annealing the degraded Nb, Sn at 1000 C in nitrogen its normal superconducting behavior is restored most likely due to the incorporation of nitrogen atoms causing the elimination of the ordered vacancies. HANAK et al.' have observed low superconducting transition-temperature values (T, - 9"K) in some NbsSn samples deposited from the vapor phase. They attributed such low T, values to disorder in the 0-tung-sten structure. Much lower T values (down to 5.6"K) were reported by Reed et al.zC for NbsSn samples annealed at high temperatures. These authors also attributed this degradation effect to disorder (random occupation of the A and B sites by niobium and tin) but pointed out that such disorder could be brought about (by high-temperature treatment) only in samples containing niobium in excess of the stoichiometric composition NbsSn. Both groups reported that the normal superconductivity behavior could be rever-sibly restored by appropriate heat treatment. Courtney et al., also found that degradation in NbsSn requires excess niobium brought about by the loss of tin during the treatment. However, these investigators proposed that the degradation is due to niobium-site vacancies resulting from the migration of the niobium atoms to the vacated tin atom sites. They did not consider the reversibility of the effect. The present study attempts to establish the nature of the above degradation phenomenon. EXPERIMENTAL PROCEDURES All compounds prepared for this investigation were made from the powders or filings of the elements which were intimately mixed, cold-pressed into a cylindrical pellet at approximately 50,000 lb per sq in., and then submitted to the desired heat treatment. The samples annealed under high pressure were placed in a MgO sample container which was mounted in a pyrophyllite tetrahedron designed for a tetra-hedral-anvil press. Details of the experimental arrangement are given elsewhere. This setup allowed heating at 1800°C or above under pressures in excess of 30kbars for 3 hr. The samples annealed in a vacuum were prepared in a high-temperature vacuum furnace which could reach temperatures up to 2400°C under a pressure of 2 x lo-' Torr. For annealing in a reactive atmosphere, a quartz tube was placed in a clamshell furnace and the desired gas ambient passed through the tube. Lattice parameters were determined using a Debye-Scherer 114.6-mm camera. Cohen's method, programmed for the IBM 7094 computer, was used to calculate the lattice parameter from the measured d spacings. X-ray integrated intensity measurements were made on several samples. These samples were ground to -400 mesh and the powder mixed with a solution of collodion in amyl acetate. The mixture was poured into a depression milled in a bakelite disc. When the mixture dried, the surface of the disc was ground flat leaving a diffraction surface defined by the face of the disc. The disc was mounted in a Philips rotating specimen holder which allowed the rotation of the sample in the plane of the diffraction surface and the integrated intensity measured using a scintillation counter and a pulse-height analysis sys-tem. The superconducting transition temperatures were determined by means of self-inductance techniques.' EXPERIMENTAL RESULTS AND DISCUSSION The Role of Tin Loss in the Degradation of Super-conductivity. The loss of tin during high-temperature annealing can be effectively suppressed by annealing under high hydrostatic pressures. Accordingly, a series of experiments were performed under pressures of approximately 30kbars. This pressure was the minimum under which high-temperature experiments could be safely performed in the particular pressure apparatus employed. Experiments were also designed to test high-pressure effects on the superconductivity behavior of NbJSn. The results of the high-pressure annealing experi-ments are summarized in Table I. All samples were prepared as described earlier. They were reacted and homogenized at 1000°C for 24 hr under argon at-

Jan 1, 1967

By Robert S. Williams

On several occasions, when 60-40 brass is first obtained in the beta condition by quenching at about 825" C. and is then reheated, the writers have noticed that reerystallization will take place in the form of twin crystals at the grain boundaries of the original beta crystals. It was, therefore, thought that interesting results would be obtained if this twinning process was studied further, especially as to the temperature at which it first occurs. The material used in the investigation was a bar of extruded muntz metal, 1/2 in. in diameter, and of the following composition: Copper, 60.21 per cent.; zinc, 39.73 per cent.; lead, trace; iron, trace; tin, nil. Specimens 1 in. in length were sawed from this bar and a hole was drilled into the side of each specimen until it reached the center, and the tip of a platinum-platinum rhodium thermocouple was inserted. A small Hoskins' resistance-type electric furnace was used for heating the specimens. The specimens were first heated at 840' C. for 2 hr. and then quenched ' in cold water, in order to get the material entirely in the beta state. In every case, in the reheating process, the furnace was brought to the desired temperature before the specimen was introduced. The time occupied in preheating was from 20 to 30 min. By sawing back 1/4 in. on each side of the hole, two parts were obtained from each specimen and duplicate observations were possible. The specimens were held at the reheating temperatures for periods of 15 min., 30 min., 1, 2, and 4 hr. All specimens were etched with a freshly prepared mixture of equal volumes of concentrated NH4IOH and H2O2.

Jan 1, 1924

By J. D. Cannon

SLAGS studied in this investigation were from 0.25 to 0.35 pct plain carbon steels and were melted in a 3-ton acid-lined Lectromelt furnace with a 2500-kva transformer. The melting process employs a short, violent boil, which is partially blocked, and the desired carbon content is adjusted by pig iron or iron ore, depending on the preliminary carbon. A relatively small volume of slag is used in refinement. Bottom is here defined as that portion of the furnace that comes in contact with the molten metal, or all the surface below the slag line. Bottom trouble-i.e., holes in the bottom lining-is very seldom experienced at our plant. We have been watching the bottom lining over a period of some boo heats in the hope of having holes large enough to supply data for this report, but none occurred during that period. The bottom is eroded uniformly, occasionally with slightly deeper depressions around the taphole.

Jan 1, 1947

By Henry Howe

THE data which are collected in Table 1 show that the ferrite of low-carbon steel and of electrolytic iron, like the network of hypo- and hyper-eutectoid carbon steel, inherits, either absolutely or relatively, the, grain size of the mother austenite from which it is born in cooling through the transformation range. This evidence is so abundant and concordant as to cast doubt on Prof. Jeffries' 1 hypothesis of what might be called reversed inheritance, by which he explains Mr. Ruder's observation2 that the grains of a "slug of pressed pure electrolytic iron powder"were coarser, perhaps 12,000,000µ2, after a 3-hr. exposure to 1000° C. than after a 3-hr. exposure to 1250-1300°, when they were about 35,000µs. His explanation implies a natural tendency of coarser austenite grains to yield finer ferrite ones than spring from finer austenite grains, so that the inheritance is reversed. What seems to me a simpler explanation is that the enormous grains which followed the 1000° heating were not inherited from the mother austenite, but were formed by the process of natal coarsening, by means of which Stead and Carpenter developed grains of this same order of magnitude in this same kind of material, on heating to 950° or to 1000°, the temperature used by Mr. Ruder, provided the exposure was not unduly prolonged, and it does not seem to have been in Mr. Ruder's case. That their coarsening was natal and not through inheritance is shown first by the fact that their grain coarseness was out of all proportion to their relatively low temperatures and short periods, and hence was very far in excess of the grain size which the mother austenite must have had, and second and more cogently by the fact that the shape of these coarsened grains was evidently determined by the temperature distribution which existed during and immediately after the Ar3 transformation, that during the passage from the gamma to the non-gamma state.

Jan 9, 1917

By C. S. Allen

WITH increased coal production and mechanization of coal mines many transportation problems arise. The main objective is to bring the coal to the tipple or dump it as quickly as possible. Larger and faster haulage locomotives or two locomotives connected in tandem have been adopted to solve the problem. Motor equipment, gears and control systems of locomotives to be placed on these hauls are carefully studied to meet these requirements, by an analysis of motor characteristic curves with the corresponding tractive effort curves, in order to determine the correct load for maximum efficiency and to determine the approximate schedule. Control equipment is usually considered to be the controller and resistance. Sometimes accelerating curves are calculated in order to obtain smooth starting in the least possible time without slipping the wheels. Train control is very important, but why limit this to acceleration? Deceleration or retardation of the locomotive is a part of the train control and should be given as much consideration as the control for acceleration. TYPES OF BRAKING Common braking systems for mine locomotives utilize screw-type mechanical brakes, dynamic braking and the air brake. For gathering and haulage locomotives, the screw-type mechanical brake is regarded as standard. A brake of this kind cannot be applied without much effort and lapse of time. Motormen, like other people, follow the path of least resistance, and therefore have their brakes ready for instant application-which means that the shoes are virtually dragging. Even then, a motorman bucks and plugs the motors to gain time and avoid as much physical effort as possible. "Bucking of motors" consists in turning the reverse cylinder of the controller to parallel position corresponding to the opposite direction of travel while the locomotive is in motion, without applying power from an external source. When this occurs, both motors tend to act as series generators, because the armatures are revolving and there is residual magnetism in the field circuit. Owing to slight differences in motor manufacture, one of these will generate a slightly higher potential and will overcome the generated voltage of the second and tend to drive it as a motor in the reverse direction. This action retards the locomotive but is very severe on the segments of the reverse cylinder and on the motor commutators. "Plugging motors" is the application of power to the motors corresponding to the opposite direction of travel. In order to "plug" the motors it is necessary first to "buck" them (which reverses the connections to the motors) and then to apply

Jan 1, 1941

By F. G. Miller, T. D. Mueller, L. B. Davidson

A mathematical model of reservoir behavior during one cycle of the intermittent steam injection process is presented in this paper. A cycle of the process is considered to be composed of three stages: injection, condensation and production. The model concentrates on behavior during the production stage. The influence of several parameters on production improvement is described, using the results obtained with a numerical equivalent of the model. Reservoir system parameters considered are thickness, reservoir thermal conductivity, oil viscosity, solution gas-oil ratio and the change in oil effective permeability with temperature. Operating parameters investigated are heat injection rate, steam temperature and cumulative injection time. In the face of considerable uncertainty, the model appears to give a fair prediction of the behavior observed during an actual test. This makes the model a useful means of selecting projects. It is shown that the model may also be utilized to select an optimum set of operating conditions for a particular project. Results of this study show the extent to which production improvement depends on each of the parameters investigated and give an indication of the range of system conditions within which the process would be effective. INTRODUCTION In recent years the intermittent steam injection or steam soak process of oil recovery has become a popular method of improving recovery in reservoirs bearing high-viscosity hydrocarbons. Production improvement due to the process results from heating the reservoir near the wellbore. The process is applied on an individual well basis and is executed in a series of cycles, each consisting of three stages: injection, condensation (the soaking period) and production. During the injection stage, high-pressure steam is injected into the reservoir surrounding the well-bore. This study assumes that injection is carried out over the entire vertical section of the reservoir rock that can be exposed to fluid injection. The condition of steam entering the reservoir is considered to fall within the following limits: (1) steam pressures less than 1,000 psig, (2) steam temperatures between 300 and 700F and (3) steam quality less than 90 percent. The last restriction is due to equipment limitations. Normally, injection re maintained for less than 3 weeks. After termination of injection, the condensation stage begins. The well is shut in for several days, supposedly to make certain that the injected steam condenses. This condensation would insure the retention of injected heat. The production stage is initiated when the well is opened again. Reservoir response during this stage determines the effectiveness of the process (response is defined as the oil production rates, the water production rates and the wellbore temperatures observed during the entire production stage). The immediate response of the reservoir is sometimes quite good. Sets of case histories by Longl and by Owens and Suter2 give some typical figures for response. Duration of the production stage is equal to the time needed for the oil production rate to decline to some predetermined value. This usually requires 4 to 6 months. Termination of the production stage coincides with the start of the next cycle. The process is continued, cycle by cycle, until it becomes unprofitable to continue. One simple model2 and two more sophisticated models3,4 of the process have been presented. These are based on fundamentally different assumptions than those used in this investigation. Although the three models might be modified to fit the assumptions used in this study, it is felt that greater rigor would result by developing a

The object of crushing and grinding for leaching is obviously to permit contact of the solvent and mineral and subsequent removal of pregnant solution in a reasonable time. Heap leaching is the leaching of ores that have been mined and transported to prepared, relatively impervious pads for leaching by sprinkling or ponding, and percolation of the lixiviate through the ore. Dump leaching is the leaching of dumps or low-grade ore or overburden without the use of prepared pads under them. Run-of-mine material, e. g., low -grade ore from open pit stripping operations, may be leached without crushing, and a fairly high recovery made by heap leaching. An alternate method for better grade gold/silver ores is to crush to 9 to 13 mm (318 to112 in. ) size for pad heap leaching, as used by Smoky Valley Mining Company at Round Mountain, Nevada, on gold ore, and to 38 rnrn (1 -1 12 in.), which will be done by Candelaria Partners, at Candelaria, Nevada, on silver ore. Heap leaching of copper probably began at Rio Tinto, Spain, about the year 1752. This was done by the leaching of weathering piles of ore in the open air followed by iron cementation of the liquor that drained off the heaps. Its application to the low -grade southwestern United States copper ores was overlooked for many years, and low- grade ores from Sacramento Hill at Bisbee, Arizona, were the first to be heap leached in 1923. Site preparation used a half century ago is the same today. "The need for some form of waterproofing of the pad was evident. Before leaching ore was piled, the site was cleared of cactus and brush. After clearing a gentle sloping area, it was then covered with a blanket of rolled and tamped clay or slime tailing. When heaps are built, a layer of coarse fragments may be put down first to assist drainage. A second method of leaching without grinding, usually for higher grade ores, is by vat or tank leaching of material crushed to 9 to 13 mm (318 to 112 in.) size. Such a plant is considerably more expensive than a heap leaching installation but much less costly than grinding for agitation leaching, and a recovery higher than that obtained by heap leaching is to be expected. Vat leaching has been widely used by the copper industry on higher grade copper ores but has been used in only a few small operations on that size gold or silver ores. However, such a plant should be considered for a modest tonnage of a few million tons, 3 to 7 g per mt (0.10 to 0.20 oz per st), of Carlin-type leachable ores crushed to 9 mm (318 in.).

Jan 1, 1981

By J. B. Macelwane

GEOPHYSICS differs from geology and physics in many respects. In the first place, geophysics is a complex science embracing the fields of seismology, geomagnetism, geoelectricity, geodesy, meteorology, volcanology, physical oceanography, physical hydrology, tectonophysics and exploration geophysics. Geology is also a complex science and so extensive in its various fields that no one can master them all, and no part of geology deals in any sense with several of these fields of geophysics. In the second place, geophysics makes use of methods and instruments that are derived primarily from the science of physics. Geology, on the other hand, has methods of its own and it draws its borrowed techniques and its instrumental equipment not only from physics but also and perhaps primarily from chemistry and biology. The difference, therefore, between the geophysicist and the geologist lies partly in the phenomena that are observed, partly in the methods and instruments with which each carries on his exploration; but partly also, and perhaps principally, in the habitual attitude of mind and in the background of specialized training with which each approaches the problems presented by this planet of ours. The geologist as such, therefore, is no geophysicist. On the other hand, the physicist is not a geophysicist either. Isolation of each problem in a closed laboratory system under complete control is fundamental to the methods of the physicist. The geophysicist must apply physical instruments and physicomathematical reasoning to the study of physical quantities in their undisturbed natural environment. What, then, is a geophysicist? In the sense that he is a trained expert in all of the geophysical sciences, I do not believe that such a person ever existed. It would be beyond the possibilities of a single lifetime. I think there is confusion in our ideas and in our use of terms. We are not all thinking of the same thing when we say geophysics or geophysicist; yet we seem to talk as though we were. It is as absurd to say that the whole of geophysics belongs to geology because the field of a particular type of geophysicist-the exploration geophysicist -calls for some knowledge of geology as it would be to say that the whole of biology belongs to geology because a particular type of biologist-the paleontologistneeds some knowledge of geology. DEVELOPMENT OF A GEOPHYSICIST Since it is impossible to become an expert in all the fields of geophysics, and since students entering college seldom know the field they will choose as a career, what would we suggest as the best general preparation for work in geophysics, whether as a meteorologist, an oceanographer, a seismologist, a geodesist, a geomagneticist, a volcanologist, a tectonophysicist, a hydrologist, or an exploration geophysicist? We may distinguish five phases in the development of a geophysicist: (I) his mathematical and scientific studies in high school; (2) the general mathematical and scientific

Jan 1, 1941

By U. C. Tainton

THE world-wide continuation of low prices for zinc in 1934 has militated against any striking changes in the position of the metal. The price of zinc in London at the end of the year, about £11 5/8 per long ton, or 2.5c per pound at the existing rate of exchange, is more than 25 per cent below the average price for last year. In these circumstances probably the most significant event of the year was the putting into operation of the new electrolytic plant of the Giesches company at Magdeburg, Germany. This plant is designed to have an initial capacity of 20,000 long tons per year, and it is planned to increase this to 40,000 tons annually. This development is significant not only as indicating a continued swing of zinc metallurgy towards electrolytic methods, but also because it will make Germany virtually independent of foreign sources of zinc. This will mean that the zinc tonnage normally exported to Germany from Belgium and Poland will. become available for other markets, and it is feared may lead to lower prices unless the production of Bel-

Jan 1, 1935

By Arthur Taggart

FLOTATION of ores is a practical utilization of the energy that resides in the surfaces of solids and liquids. The best known manifestation of this energy is called surface tension; an equally important, though less apparent, phenomenon is adsorption. This paper reviews some of the recent investigations of these phenomena, and gives the results of certain experiments performed by the authors. Surface tension is a manifestation of energy having its seat at the bounding surface between the adjacent phases of a multiphase system. Thus, at the interface between a liquid and a gas, or between two immiscible liquids, or between a solid and a gas or a liquid, there are forces capable of doing work, their magnitude depending on the nature of the adjacent phases and the extent of the bounding area. These surface forces are inappreciable when the ratio of surface to volume of the adjacent phases is small, but they become powerful when this ratio becomes large, as it does when one of the phases is highly dispersed. Froth flotation, which consists in buoying solids heavier than water to the surface of water by means of gas bubbles, utilizes the force of surface tension to attach the solid particles to the gas bubbles and again to maintain the floating mass of bubbles as a more or less persistent froth at the surface of a pulp for a sufficiently long time to allow its removal. It follows from the second law of thermodynamics that the potential energy of a system in equilibrium is a minimum. Therefore a multiphase system, tending toward equilibrium, will arrange itself in such a way that the total energy of the interfaces will be the least possible. This end can be accomplished in two ways: by a change in shape that will reduce the interfacial area; by a change in the nature of the surface layer in

Jan 8, 1922

By Frank C. Greene

Missouri has had one of the best years in history in the development of gas, the 49 completed gas wells having an average of nearly 1,000,000 cu. ft. initial open flow. Altogether 101 wells were drilled in the western part of the state, from Andrew County on the north to Vernon County on the south. Of these 49 were gas wells (including four old wells drilled deeper) with an initial open flow of 48,850,295 cu. ft., eight were oil wells (including one old well drilled deeper) with an initial capacity of 125 bbl. per day and 44 were dry holes (including five old wells drilled deeper). All the oil wells were in previously discovered pools in Jackson and Cass Counties. The outstanding discovery was a "shoestring" of a sand that is termed the Bartlesville, trending northwest and southeast across townships 48 and 49 N., R. 32 W., in central Jackson County. The sand is believed to be a narrow channel or bar, probably not over 800 ft. wide, lying at a higher horizon than the Bluejacket or true Bartlesville sand. A total of 32 wells with 47,453,080 cu. ft. initial open flow has been completed along the 6 miles of the shoestring. The largest individual well had an open flow of 4,500,000 cu. ft. The depth of these wells ranges from 350 to 635 ft., depending on surface elevation. The rock pressure ranges from 145 to 169 pounds. The Missouri Valley Gas and Oil Co. and Panhandle Eastern Pipe Line Co. have laid pipe lines into the area and most of the wells are now connected. In other parts of Jackson County and in other counties of the state there was very little activity during 1937. Of the 101 completions, 88 were in Jackson County. Cass County had five oil wells and three dry holes, Bates County one dry hole and Vernon County two dry holes. In the northern counties, Andrew and Clinton were represented by one dry hole each. At the end of 1937 drilling and leasing operations were very active and wildcatting promises to feature the coming year.

Jan 1, 1938

By C. Max Bauer

THE most important development in the petroleum industry in Montana, during 1924, was the bringing in of the Hepp well on May 12, by the Midwest Refining Co. This followed three years of active prospecting and drilling in the state by this company. The well is located 35 miles west of Billings, in Stillwater County, and makes a high-grade paraffin oil from the Dakota sand at a. depth of 3825 ft. After flowing for several months at the rate of 150 bbl. per day, the well has been shut in for lack of storage, awaiting further development in the field. TABLE 1. Production Cat Creek and Kevin-Sunburst Fields Month Kevin-Sunburst Pipe- Estimated Cat Creek Pipeline Estimated line Runs Fuel Oil Used Runs Fuel Used January 3,214 0 133,400 140 February 3,250 0 134,248 490 March 11,989 595 163,129 910 April 116,897 1,155 125,918 980 May 179,726 2,310 152,179 770 June 126,131 2,697 122,270 910 July 132,173 2,170 118,034 770 August 202,001 2,695 142,313 1,120 September 187,201 2,135 110,012 350 October 162,589 1,995 121,683 350 November 130,392 2,520 139,900 350 December 107,465 1,780 124,169 0 Total 1,363,028 20,052 1,581,255 .7,140 There are two producing oilfields in the state-the Cat Creek and the Kevin-Sunburst, which produced a total of 2,971,475 bbl. in 1924. The only other field of proved value is Soap Creek, which contains a heavy black oil and is shut in for lack of marketing facilities. Gas is produced for local use at Havre, Chinook, and Baker, and a carbon-black plant is located at Baker.

Jan 3, 1925

By J. W. Pugh, J. D. Nisbet

F. B. Foley—The use of data published by Wever and Jellinghaus in 1931 to fix boundaries of the sigma phase in the Fe-Cr system, in the face of the author's own references to the suggestions of Bradley and Goldschmidt, Aborn and Bain, and Hougardy that the phase is much more extensive, and the very much more accurate work, which weighs heavily in favor of these suggestions, of Cook and Jones, published in 1943 and evidently disregarded by the authors, makes their derived ternary diagram, especially fig. 15 for 400°C, quite inaccurate on the Fe-Cr side and affects the extent of phase boundaries in the most controversial and important part of this ternary system. In commercial Fe-Ni-Cr alloys the occurrence of sigma has been observed time and time again at lower chromium contents than that of the 24 pct Cr, 16 pct Ni, 60 pct Fe alloy which is the lowest permitted by fig. 15 of practically carbonless metal. Newel1 reports sigma in 27 pct Cr-Fe even with some carbon present to be one of the greatest detriments to its extensive application, whereas Pugh and Nisbet set a low limit of 36 pct Cr for sigma in the binary Fe-Cr system. J. J. Heger—The diagrams presented by the authors do not agree with observations made on commercial Fe-Cr and Fe-Cr-Ni alloys, nor do they agree with two recent investigations made on the Fe-Cr and the Fe-Cr-Fe systems. I refer first to the investigation made by Cook and Jones1' on the sigma region of the Fe-Cr system. On the basis of their results which were published in 1943, Cook and Jones established new boundary limits for the sigma and the alpha plus sigma regions. These new limits have been accepted and are incorporated in the Fe-Cr diagram that appears in the 1948 edition of the Metals Handbook. This diagram is shown here as fig. 34. As will be noted, the boundary limits of the alpha plus sigma region in this diagram extend to much lower chromium contents than do those in the diagram presented by the authors in fig. 2. These new limits indicate that sigma phase should form in an Fe-Cr alloy containing 26 pct Cr, and experience with commercial alloys confirms this finding. Indeed, recent studies on a commercial Fe-Cr alloy containing 17 pct Cr have shown sigma phase to be stable in this alloy at 550°C. I recognize that the authors' work did not include studies on the sigma region; however, I believe this is a serious omission because sigma phase may profoundly affect the physical properties of these alloys and should be evaluated in any investigation which attempts to relate physical properties to the equilibrium diagram. The second investigation to which I refer is that made on the Fe-Cr-Ni system by Rees, Burns, and Cook,'' who used pure alloys and employed heating 17 W. P. Rees, B. D. Burns, and A. 3. Cook: Journal Iron and Steel Institute. (July 1949) 162, Part 3. p. 325. times that extend to 200 days. These investigators published their results in July 1949 and from these results constructed isothermal sections at 800" and 650°C. The isothermal section at 650°C is shown here as fig. 35. This diagram indicates sigma phase should form in a pure 18 pct Cr-8 pct Ni alloy. Although sigma phase has not been observed after 10,000 hr at 1200°F in commercial 18-8 alloys containing carbon and nitrogen, it has been observed under the same conditions in 18-8 alloys modified with titanium and columbium, both of which serve to reduce the effect of carbon and nitrogen. This section and the one at 800°C suggest that the constant iron sections which are presented by the authors, should be considerably altered, if they are to represent an accurate picture of the system. A few of the suggested alterations are as follows: In fig. 9, the section at 50 pct Fe, the gamma plus sigma region should be widened, not narrowed at 800" and 650°C. In fig. 10, the section at 60 pct Fe, the gamma plus sigma region should be widened at 800° and 650°C. In fig. 11, the section at 70 pct Fe, an alpha plus sigma, an alpha plus gamma plus sigma, and a gamma plus sigma region should be added. In fig. 12, the section at 80 pct Fe, the alpha plus gamma region should be widened at 800°C. In fig. 13, the section at 90 pct Fe, the alpha plus gamma region should be widened at 650° and 800°C. Undoubtedly, the chief reason for the discrepancies between the authors' data and those of Rees, Burns, and Cook is that the authors did not employ long enough heating times to allow for transformation. In this connection, I wish to warn that transformations in these alloys, particularly transformations at temperatures below 800°C, are extremely sluggish and may require a year or more to approach completion. Therefore, unless extremely long heating times are employed or steps are taken to accelerate these transformations by such means as mechanical working, the results will not yield an accurate picture of the alloy system. Certainly, an accurate picture is needed for the development of better high-temperature materials. E. J. Dulis-The purpose of this work is not clear. If an improvement of the ternary equilibrium diagram of the Fe-Cr-Ni system was wanted, it seems logical that testing techniques superior to those previously used would be a prime requirement. To approach equilibrium in this system, long holding times are needed; a fact established long ago but apparently ignored by the present authors, who used the continuous heating and cooling tests in equilibrium studies. A publication on the same system by Bradley and Goldschmidt6 was criticized by Monypenny in a

Jan 1, 1951

By G. Nabi, W-K. Lu

Cylindrical specimens of natural dense hematite were reduced to magnetite at atmospheric pressure in H2-H2O mixtures of known composition over the temperature range 1084° to 1284°K. The rate of reduction was measured by the rate of movement of the interface between hematite and magnetite. The diffusion of gases through the gaseous boundary layer, the magnetite layer, and the interfacial chemical reaction were all considered in the interpretation of experimental data. The mass transfer coefficient through the boundary layer was calculated using accepted correlations. Values of the chemical reaction rate constant and the diffusivity of hydrogen in the magnetite phase were determined. THE present investigation is concerned with the reduction kinetics of natural hematite to magnetite by H2-H2O mixtures in the temperature range 1084" to 1284°K at atmospheric pressure. This reaction is the first step in the series of topochemical reactions in the process of reducing hematite to iron. Kinetic information of the simple steps such as hematite-magnetite transformation is necessary in order to have a better understanding of the complex processes of hematite reduction in iron-making. It also has direct industrial significance because magnetic roasting is one of the most important methods in benefication of lean ore.&apos; Although many technical papers have been published on the process of magnetic roasting and iron oxide reduction, very little information is available in the literature concerning the fundamental nature of hematite reduction to magnetite by reducing gases. Hansen et al.2 reduced the dense synthetic pellets of high-purity oxide in CO-CO2 mixtures and determined the reaction rate by weight-loss method. They were able to interpret most of their results by applying the interfacial area control theory developed by Mckewan.3 In contrast, Wilhelm and St. Pierre,4 who studied reduction of hematite to magnetite in H2-H2O mixtures by weight-loss method, stressed that the resistance of the porous magnetite layer to the diffusion of gases cannot be neglected in consideration of the overall reaction rate. In the present study the contributions of interfacial chemical reaction, diffusion of gases through the magnetite phase, and the gaseous boundary layer to the overall reaction rate will be considered. APPARATUS AND PROCEDURE Hematite Specimens Preparation. Natural hematite ore from Vermillon range of Northern Minnesota was selected for the present investigation because of its high purity and thermal stability. Chemical analysis of five samples gave the following average values: 67.52 pct total iron (96.62 pct Fe2O3, 0.28 pct FeO, 0.03 pct metallic iron), 2.53 pct SiO2, <0.07 pct MgO, 0.03 pct CaO, 0.05 pct combined mixture, 0.07 pct loss on ignition, and 0.34 pct other. Cylindrical specimens of 0.93 cm in diam and 2.7 cm in length were drilled from slabs of ore with a water-cooled diamond core drill. These specimens were heated to 1000°C and furnace-cooled. Specimens with silica pockets developed large cracks. The uncracked specimens were heated a second time, and their surfaces were carefully examined with a microscope. Those with hairline cracks or surface inhomoaenitv-- were rejected. Preparation of H2-H2O Mixtures. H2-H2O mixtures were prepared by the combustion of H2-O2, mixtures in a pyrex glass chamber in the presence of a catalyst. Alumina pellets coated with palladium, supplied by Englehard Industries, were used as the catalyst. Purified grades of hydrogen and oxygen were used which were repurified by usual techniques. Hydrogen before entering the combustion chamber was passed through an activated alumina H2O absorption bulb, with copper turning at the top. The cover of this bulb was not made pressure-tight so that any pressure development in the hydrogen line would cause the cover to blow off and also the copper turnings would act as a flame arrester in the case of a flashback from the combustion flame. Oxygen flow rates were measured with a bubble flow meter after purification with 1 pct accuracy. Hydrogen flow rates were measured by "precision wet test meter" and the amount of unburnt hydrogen was accurately measured by a bubble flow meter, after condensing water vapor in the gaseous stream. The Pyrex glass bulb contained concentric Vycor glass tubes as shown in Fig. 1. Oxygen was prevented from diffusing into the hydrogen line by threading platinum wire through pores at the combustion end of gas inlet tube. The glass bulb was heated with a Kanthal heating wire pasted in asbestos paper. The surface temperature of the bulb was measured with a thermocouple and adjusted to remain at approximately 350°C. The gaseous reaction chamber also served as a preheater for gases to avoid thermal segregation. The following sequence of operation was adopted. 1) Nitrogen was passed through the outer concentric tube to purge the catalyst bulb of oxygen. 2) Hydrogen was introduced through the inner tube until a steady flow was obtained. 3) Oxygen was then introduced into the nitrogen stream passing through the outer tube. 4) When combustion had commenced and a flame was visible over the platinum wire, the N2 was turned off.

Jan 1, 1969

By A. E. Nehrenberg

THE mechanism by which austenite forms in steels has received a great deal of attention in the literature in past years.&apos;-&apos;* Our present knowledge concerning this mechanism has been recently summarized quite concisely by Bain and Vilella,1 while a few years ago the literature was carefully reviewed by Roberts and Mehl.² The consensus is that any ferrite-carbide interface is a potential site for the nucleation of austenite during heating above the Acl temperature, and that the new austenite generally grows freely to produce approximately equiaxed grains, whether the carbides are initially present in the lamellar or the spheroidal form. In the case of eutectoid steels, growth of the new grains of austenite continues until contact is established with other grains. Then growth stops and an initial austenite grain size is established which does not change until the heating is continued to some high temperature at which grain coarsening begins. In the case of pearlitic steels which are not of eutectoid composition, the proeutectoid ferrite or carbide may interfere with the growth of the austenite if the temperature is not above that designated the A63 or the Acm, respectively. Although a large amount of work has been done to establish the mechanism of austenite formation in steels, it became clear to the present author while he was studying the transformation characteristics of a new 0.25 C Mn-Si-Ni-Mo hypoeutectoid steel" that the manner in which austenite grows in steels depends upon some factor, or factors, not previously considered. This was indicated by the fact that when this steel in the spheroidized condition was heated above the Ae1 temperature the new austenite which was formed did not envelop the carbides and grow in an equiaxed manner as described by Bain³ or spheroidized steels. Instead, in this steel, the austenite was observed to grow much more readily in certain directions than in others with the result that at temperatures within the Ac1-Ac³ ransformation range the austenite grains were acicular in shape. The excess ferrite was also found to be acicular with the distribution of these phases being such that a lamellar pattern was developed. This unusual directional growth of austenite in this new steel initially in the spheroidized condition is illustrated by fig. 1. A search of the literature revealed that this type of growth was not necessarily peculiar to this steel for similar microstructures had been observed by other investigators.4-8 However, the full significance of these microstructures does not appear to have been appreciated, and no work has been done to determine the conditions responsible for this directional growth of austenite or to arrive at an understanding of it. It was for this purpose that the work described in the present paper was carried out. Material: During the course of this investigation a total of 15 steels was studied. They consisted of hypoeutectoid, eutectoid and hypereutectoid carbon steels, and hypoeutectoid and hypereutectoid alloy steels, all of which were obtained in the annealed condition from commercial warehouse stock. As received, the carbon and alloy hypereutectoid steels had microstructures which consisted of spheroidal carbides in ferrite, whereas the eutectoid steel and the hypoeutectoid steels were pearlitic. The grades of steel represented were 1050, 1080, 10110, 3310, 4140, 4340, 4615, 6145, 8620, 9260, 9442,

Jan 1, 1951

By A. Springer

Chemists, physicists and others, whose occupations necessitate the use of fine scales, have heretofore regretted their inability to obtain any which would remain uniformly accurate. The difference between the theoretical and the actual results obtained in the ordinary balance (provided the pivot-distances are exact) is mainly due to the frictional resistance between the knifeedges and their bearings. This frictional resistance, although reduced to a minimum in the finest scales when new, constantly increases, thereby decreasing the sensitiveness proportionately. When examined under the microscope, neither the surface of the knife-edge nor that of&apos; its hearings ever appears perfectly smooth. Soft kunife-edges are easily blunted, whereas hard ones are brittle and liable to crumble under the effects of over-load or shock. Prof. Frederick A. Roeder for many years attempted to discover some means by ,which the knife-edge could be replaced with some device free from the above-mentioned objections. His experiments convinced him that a torsion-joint was best suited for that purpose. After he had communicated his conclusion to me, we jointly developed the system to its present form. A torsion-wire had been used for the centre of rotation, prior to Prof. Roeder&apos;s invention, but it was found impossible to replace the terminal knife-edges with torsion-joints.

Jan 1, 1884

By G. N. Maniar

G. W. Healy (union Carbide Metals Co.)-The author&apos;s paper is a useful contribution to the store of maps of chemical activities of oxides in multi-component slag systems. It is also a good example of the utility of the Gibbs-Schuhmann technique for calculating activities in a system where that of one of the components has been measured. This paper Koh and Caugherty. This plot is reproduced by alor in X-ray Metallography. Because of this nonlinearity, preparation cf suitable standards and/or correction for absorption and enhancement are essential in microanalysis. However, our objection is not the conclusion that Dr. Aaronson has arrived at nor the technique he has used; but only to the foot-note credited to V. Macres. The level of chromium that he was concerned with (less than 3 pet) is so low that the deviation of uncorrected Cr-curve will be negligible. Besides Dr. Aaronson has used chromium intensity from martensite and set it equal the bulk chromium content of the alloy. Using this chromium-intensity as a reference, he has calculated the amount of chromium in the ferrite. This amounts to the same as using an internal standard. Since the chromium content in austenite and ferrite are almost the same, enhancement due to iron in both will be the same and therefore does not need to be corrected. together with the author&apos;s recently published one1 on the CaO-FeO-Fezo3 system will be most helpful to others learning to apply Schuhmann&apos;s method, which merits a far wider application than it has received to date and should greatly aid our understanding of equilibria between metal and oxide phases. As shown by okcen" its use may even be extended to sections of systems with any number of oxides. I have some questions as to the selection of equilibrium constants made by Dr. Turkdogan. He has chosen one for the formation of Fe2O3 from FeO and oxygen which gives Fea3 activities 50 pct higher

Jan 1, 1963

By A. M. Radigan, W. G. Prast

Various industrial minerals that are traded internationally receive support from governments, enabling these materials to be more competitive. The role of government in encouraging nonmetallics exports ranges from the ownership of an integrated mining company to partial or selective government ownership, to the sponsorship of exporter organizations. In certain cases, regional governments have a direct stake in the industrial minerals industry. This paper assesses the commercial impact of these involvements.

Jan 1, 1984

Flaubert, as we know, laid stress on the selection of the right word, le mot juste, the precise epithet, the word that belongs to the thing. A sentence, or even a paragraph, may be spoiled. by the use of a word that is not proper, that does not fit or is foreign to the meaning intended. An Australian mining expert is reported to have said: You have a property of considerable value, and what I saw warrants s good development of very rich cubicular galena, with gossan intermixed. &apos;Cubicular&apos; means &apos;belonging to a small bedroom&apos;, a &apos;cubicle&apos; being a sleeping compartment. He meant &apos;cubic&apos;, of course. This is a malapropism, and reminds me of the lady from Chicago that, on her return from Europe, said how much she had enjoyed the rural parts of France, because, among other things, it was "so delightful to hear the French pheasants singing the mayonnaise to the tune of the Los Angelus". It is impossible to amalgamate coal-tar thoroughly with the pulp in the agitating-tank. In metallurgy, &apos;amalgamate&apos; refers to the combination of mercury with one or both of the precious metals, forming an amalgam, which is an alloy of mercury with another metal. It differs from other alloys, such as brass or bronze, in being made without the aid of heat, inasmuch as mercury is molten at the ordinary temperature. The word comes to us from the Greek through Old French and means &apos;something soft&apos;. It is a mistake to use technical terms, having a specific meaning, for purposes that are foreign to that meaning. The writer of the quotation is not discussing any combination of metals; he is dealing with the physical process of mixing and is using &apos;amal-

Jan 1, 1931

By S. V. Krusiewski, J. W. Gabelman

Regional metallogenic zones and areas of equal paragenetic range have been interpreted from a compiled metallogenic map. of Mexico. Mineralization gradients of the pattern subsequently identified extend inland from coastal zones of high-temperature mineralization, and join in a central longitudinal zone of relatively low-temperature mineralization, apparently leaving no zonal room for lowest temperature deposits. The striking regional zoning pattern can be correlated with regional deformation gradients of similar position and orientation. The gradients represent at least three major orogenic cycles in two structural belts. Paleozoic structural belts existed along each coast with deformation gradients diminishing inland toward a narrow, central peninsular craton. The Mesozoic-Tertiary Mexican (Cordilleran) belt covered the entire country with a gradient oriented toward the Gulf of Mexico. Most ore deposits in this belt are of Tertiary age, although Tertiary mineralization gradients seem to have "inherited" the pattern left by Paleozoic tectonic gradients. Mineralization gradients can be used to identify the regions most favorable for the occurrence of selected metals. A metallogenic province is characterized by particular proportions of various metals, and the relative proportions can vary from province to province; but within any province the same intensity of mineralization would produce similar deposits in different places. Declining intensity of minetalization produces different kinds and sizes of deposits in zones that are concentrically arranged around sites of strongest rock alteration. On a regional basis, districts of similar average intensity of mineralization occur in zones that generally parallel some tectonic grain with the result that tectonic deformation has been designated a principal cause of mineralization. Variations in the type and intensity of deformation would determine the type as well as size of metal deposits. Mexico is especially favorable for such a study be- cause of its great abundance and variety of epi-genetic mineral deposits in various lithologic, structural and tectonic environments. The concept is also useful in recognizing portions of Mexico favorable for the occurrence of specific metals. METALLOTECTONIC ZONING IN MEXICO Theory: In studies of individual districts and groups of districts throughout North and South America, areal zoning of metal deposits generally seemed to respond to the paragenetic sequence of iron, gold, copper, zinc, lead, silver, antimony and arsenic, gold and fluorite. However, the definition of district zones is greatly obscured by contemporaneous or rhythmic deposition of metals, especially in the middle of the paragenetic range, and by the common superimposi-tions of different generations of metals. Zones could usually be distinguished only for groups of metals, such as early precious metals, base-metal sulfides, sulfosalts and late precious metals. The best defined zoning in a district is normally the spatial separation of the greatest volumes of altered and metallized rocks.&apos; Exceptions are districts representing the high- and low-temperature extremes of the mineralization range where the former creates a matrix for the latter. In most districts the total quantity of alteration products is greatly in excess of, and appears to be roughly proportional to, the total quantity of metallization products. Subsequent to the bicomponent nature of each district, the most important mineralogical feature is the great excess of one to several metals or minerals which results in a district identifiable as one of predominantly gold, copper, lead-zinc, fluorite, etc., although a great variety of other elements may be present. The para-genetic range for the abundant elements in any district is only a portion of the entire possible range for all the elements representing the complete process throughout the region. Early during investigations of this type, it became apparent that the consistent bicomponent character of districts allows two methods for studying epi-genetic mineralization patterns. One is to identify and plot altered rock "pipes,"* which are easily recognizable in the landscape by their anomalous

Jan 1, 1969