Search Documents

By W. J. Keep

Manganese is a nearly white metal, having about the same appearance when fractured as white cast-iron. Its specific gravity is about 8, while that of white cast-iron, reasonably free from impurities, is but a little above 7.5. As produced commercially, it is combined with iron, and with small percentages of silicon, phosphorus, and sulphur. It is generally produced in the blast-furnace. If the silicon is under 0.50 per cent., the product will be white. If the manganese is under 40 per cent., with the remainder mostly iron, and silicon not high enough to make the product gray, the alloy is called spiegeleisen, and the fracture will show flat reflecting surfaces, from which it takes its name. With manganese above 50 per cent., the iron alloy is called ferromanganese. As manganese increases beyond 50 per cent., the mass cracks in cooling, and when it approaches 98 per cent. the mass crumbles or falls in small pieces. When the percentage of manganese is high, the planes of the fracture are not so bright as when it is lower. The ferro-manganese which we have used in the experiments reported in this paper, contains Mn, 81.62; Si, 0.256 ; and combined carbon, 6.153 per cent. We have not been able to make test-bars from this, because the alloy cracks in small pieces in cooling. Manganese combines with iron in almost any proportion, but if an iron containing manganese is remelted, more or less of the manganese will escape by volatilization, and by oxidation with other elements present in the iron. If sulphur be present, some of the manganese will be likely to unite with it and escape, thus reducing the amount of both elements in the casting. Hence, in remelting irons, some of the sulphur which has entered from the fuel with which the iron is melted will very likely unite with some of the manganese in irons which make up the mixture and escape. Remelting, therefore,' reduces the percentage of manganese in cast-iron.

Jan 1, 1892

By G. Krauss, J. M. Thompson, H. Y. Kumagai

Boron-doped p-type and arsenic-doped n-type source materials were used to deposit thin silicon films on amorphous fused quartz substrates by cathodic sputtering in argon atmospheres. All as-sputtered films were found to have high electrical resistivities of about 104 ohm-cm, despite controlled variation of the substrate temperature from 50O to 400°C. The high resistivity of the n-type films persisted even after postdeposition heat treatments as high as 1000°C, while p-type films showed a sharp decrease in re-sistivity to values on the order of 1 ohm-cm or lower after heat treatments above 650°C. X-ray and electron diffraction, together with transmission electron microscopy of the p-type films, revealed that the improved electrical properties resulted from two distinct processes. A primary crystallization or recovery within the pains, which were approximately 200Å diam in the as-sputtered films, accompanied the initial sharp drop in resistivity at 650°C. Following this process, a secondary recrystallization or discontinuous grain growth was nucleated in films heated at 1000°C. The resulting significantly increased size of certain grains and the corresponding decrease in grain boundary area accompanied an additional decrease in resistivity after heat treatment at 1000°C. The properties of thin silicon films are of interest because of their possible application in device technology. Although evaporated silicon films on amorphous substrates1-3 and both sputtered and evaporated germanium films4-' have been studied in some detail, sputtered silicon films have not been widely investigated. It has been observed that evaporated silicon films deposited at substrate temperatures below approximately 600°C are amorphous.1,3,9,10 At substrate temperatures higher than this, the films are polycrys-talline, sometimes exhibiting a fiber texture with the fiber axis normal to the substrate surface.' Similar results have been obtained with germanium films, although in this case the substrate temperature for the amorphous to crystalline transformation is reported to be as low as 150OC.5 The mechanism of film deposition by cathodic sputtering differs markedly from that of thermal evaporation. It might be expected, therefore, that the properties of sputtered and evaporated silicon films would also differ. The purpose of our study was to determine the effects of deposition conditions and heat treatments on the electrical resistivity, structure, and composition of thin silicon films sputtered on fused quartz substrates. EXPERIMENTAL DETAILS Apparatus. A schematic diagram of the sputtering apparatus is shown in Fig. 1. The vacuum chamber was enclosed by an 18-in.-diam by 12-in.-high Pyrex bell jar mounted on a stainless-steel base plate. Access holes in the base plate were used to supply argon gas to the chamber, to allow for various electrical feedthroughs, and to provide mechanical motion to the shutter between the source material and substrate. The chamber was evacuated by a pumping system consisting of a 720 liter per sec oil diffusion pump backed by a 13 cu ft per min mechanical pump. Ultimate pressures of less than 1 x 10-6 torr could be achieved. The substrates were securely mounted on the stainless-steel substrate holder by quartz tabs held in place by stainless-steel screws. Temperatures of the substrate holder were measured by a thermocouple inserted within the holder. A quartz lamp was used to heat the holder and temperatures as high as 420°C could be maintained. Deposition Conditions and Procedure. The substrates used were polished fused quartz slides 116 by 1-12 by 3 in. and were outgassed at 200°C for 1 hr at a pressure less than 1 x 10-5 torr before film deposition. This was followed by a presputtering period of 2 hr during which the movable stainless-steel shutter was so positioned that deposition on the substrate was prevented. At a sputtering voltage of 5000 v dc and an argon pressure of 0.03 torr, the cathode cur-

Jan 1, 1967

By M. Gensamer

ONLY recently has it been realized that preferred orientations are common in hot-rolled steels. In a recent paper, N. P. Goss1 stated that hot-rolled mild steel exhibits a texture different from that charac-teristic of cold-rolled steel. No complete study of these hot-rolling textures has been reported using the pole-figure method of Wever. The material used in the work reported in this paper was the same material used by Gensamer and Mehl2 in a recent study of preferred orientations in cold-rolled steel, to which reference may be made for the composition and thermal history of the steel. Automobile-body sheet bar, 4 in. thick was hot-rolled at two temperatures, 780° and 910° C. (1436° and 1669° F.). (These temperatures refer to the tempera-ture of the furnace in which the steel was heated.) After each pass the steel was returned to the furnace and held there long enough to return to temperature. Although no accurate method was used to measure the temperature after each pass, it was estimated by color that only a slight drop in temperature occurred. In order to determine the effect of any preferred orientation that might have persisted through the normalizing treatment, one specimen at each temperature was rolled in the same direction as the original working direction and the other at right angles to it. The total reduction in each case was 85 per cent, the specimens having been reduced from 0.250 to 0.0375 in. in five passes. Final cooling was in air. Pinhole reflection photograms were taken of all four specimens, with the rolling direction vertical and the X-ray beam at an angle of 7° with the transverse direction (the transverse direction is defined as that direction in the rolling plane perpendicular to the rolling direction). These photograms, taken with a Me target at 35 kv., are reproduced in Figs. 1, 2, 3 and 4. They show that a more pronounced texture was developed by the low-temperature rolling (780° C.), and that of the two

Jan 1, 1936

By Russell A. Carter

Although significant phosphate mining activity has occurred in four western states-Idaho, Montana, Utah, and Wyoming-southeastern Idaho contains the largest, most easily mineable reserves, and mining has focused there. More than half of the western phosphate field's economic reserves are within a 32 x 96-km (20 x 60-mile) rectangle bounded by Montpelier, Idaho, on the south, Soda Springs on the west, and Grays Lake on the east. A large amount of this land lies within the boundaries of the Caribou National Forest.

Jan 1, 1978

By Floyd C. Kelly

There is an ever-increasing demand for furnaces with controlled atmosphere, due to the large quantities of steel being used in the automotive industry, such as the high-chromium stainless irons, the 18 Cr, 8 Ni stainless iron and low-carbon steel sheets. The difficulties involved in the annealing of such materials, if they are to be kept absolutely free from oxidation, are many. It is possible to bright-anneal these steels in small laboratory hydrogen furnaces, using specially purified hydrogen and taking some additional precautions. In the first place, the insulation, usually of alumina or magnesia, holds small amounts of water vapor, which it is almost impossible to remove completely. Secondly, there is always condensataion of water vapor in the cooling chambers of such furnaces, and with the continuous circulation of the hydrogen gas in the furnace, the water vapor is carried from the cooling chamber back into the heating chamber. This water vapor oxidizes the charge. Lastly, the supply of moisture is made sure by the diffusion of small amounts of air from the atmosphere into the furnace against the pressure of the hydrogen. The oxygen combines with the hydrogen and forms more water. Under such conditions there is little gained by using specially purified gas, because it becomes contaminated after reaching the furnace. Low-carbon Steel If a sheet of low-carbon steel is annealed in such a furnace at 750" C. and allowed to cool with the furnace, an adequate flow of purified hydrogen being maintained all of the time, the steel will come out with a very thin coating of blue oxide. If a similar sheet is annealed at the same temperature and quickly pushed into the cooling chamber, it will come out nearly bright, or perhaps with only the edges slightly discolored. It is difficult to get a piece of steel through a furnace of this type with an absolutely bright surface. This is due to the fact that there are always traces of oxygen or water vapor in the furnace. When the steel is allowed to cool with the furnace, it reaches a critical temperature where the affinity of iron for oxygen is greater than that of hydrogen for oxygen, and the steel comes out discolored. If the steel is pushed from the hot zone

Jan 1, 1931

By John M. Sharp

John M. Sharp, Jr. (Assistant Professor of Geology, University of Missouri, Columbia, Mo.)-Geothermal gradient and surface temperature data anomalies are potentially useful tools in mineral exploration, These data, however, may reflect a number of geologic and hydrologic processes as well as the thermophysical properties of the geologic materials. The author presents a relatively simple model which may be of value in mineral exploration. The lack of consideration of other processes, however, limits its usefulness. For instance, because of erosion or sediment deposition over geologic time the land surface must be considered a moving boundary in such a model. Evaluation of this effect coupled with annual surface temperature and thermal conductivity variations can result in temperature profiles such as shown in [Figs. 4 to 7]. These effects and others, such as ground-water movement," must be considered and filtered from the data before proper interpretation is possible. Another assumption which should have been discussed is, why were the observed mean surface temperatures not used for extrapolation of the gradients in [Figs. 4, 6, and 7?] Conductive heat transport responds to the actual boundary (land surface) temperature, not to theoretical temperatures in the absence of perturbations. Benfield presents a theoretical model for calculating perturbations in the geothermal gradient for erosion and sedimentation. The temperature (T) at any time (t) and any depth below the surface (x) is given by [ ] where T is the mean surface temperature, G, the geothermal gradient, v, the rate of erosion (or sedimentation),[ ], the long-term rate of change of T0, and k is the thermal diffusivity of the rock. Using the author's values and a rate of erosion of 1.54 cm per yr for a period of 10,000 yr, a thermal profile as shown in [Fig. 10] will be generated. A thermal diffusivity of 0.0164 sq cm per sec was used, corresponding to a thermal conductivity of 0.0082 cal per cm per sec per C. In [Fig. 11], a sediment deposition rate of 3.0 cm per yr for a period of 1000 yr was used to generate the subsurface temperature profile. A surface temperature of 24.3°C was used, as specified in [Fig. 9, 7], was set equal to zero for both cases. Superposition on the generated profiles in [Figs. 10 and 11] of the annual surface temperature variation perturbation (which may be calculated in a number of ways) will yield profiles similar to those in [Figs. 4 and 7]. Similar profiles can also be produced by regional ground-water flow. Models like the author's can be of value in mineral exploration. Other processes, however, which affect surface temperatures and gradients must first be considered, calculated, and filtered from the data if anything but the crudest qualitative interpretation is to be made. Robert C. Edmiston (Author's reply)-Professor Sharp has raised three objections to my interpretation of the subsurface temperature data I collected at Silver Bell. These are: 1) No correction was made for erosion or sedimentation,

Jan 1, 1977

By D. F. Coolbaugh

Successful mine exploration requires sound planning and modern exploration techniques, but it also requires perseverance and the right timing. The La Caridad mineral area has been known for over 70 years, but as with many mines, it was not "discovered" until viewed under new economic conditions and exploration philosophies. Present exploration of the La Caridad area began in 1964 and was carried out under a joint Mexican Government-United Nations Project. Detailed exploration was begun by Asarco Mexicana S.A. in late 1968. The geology of the La Caridad deposits conforms, generally, to the "porphyry copper" deposits of Arizona. However, breccias and pegmatites play a very important part in the emplacement of mineralization.

Jan 1, 1972

Carlisle: Jim Knapp, has been the good friend of hundreds-maybe thousands-of mining men in these western states in the last 40 or 50 years. Jim is going to talk about many of the mining camps of Nevada, where he has done plenty in the mining field during the last 50 years. Jim, for a starter, how did you happen to go to Nevada? Knapp: In the summer of 1902, two years after the discovery at Tonopah, the professor of mining at Stanford sent out myself and another student by the name of Joe Miller to make a report on the camp. We left San Francisco at 8 p.m., got to Reno the next morning, then took the train to Sodaville, arriving about 4:30 in the afternoon. The first man I met when I arrived at the Tonopah station was Tasker Oddie, a gentleman who later became the Govenor of the State and then a United States Senator. Before we got away from the stage station I also met S. H. Brady, the first mining engineer to put out his shingle in Tonopah. He afterwards became general manager of the West End Mining Co.

Jan 3, 1965

By Terkel Rosenqvist

J. Chipman (Massachusetts Institute of Technology, Cambridge, Mass.)—The fact that the experimental work has been applied to copper rather than iron and that the paper is presented to the Iron and Steel Division, I regard as rather significant. It shows the unity of metallurgy and the fallacy of trying to cut it up by metals. This result for the solubility of sulphur in molten copper correlates with Professor Schuhmann's finding that the published data on the other side of the copper-sulphur miscibility gap are also in error. I should like to ask the author to say a little bit more about the sulphur capacity of the slag. T. Rosenqvist (author's reply)-—I hope that Dr. Chipman will find the derivation of the expression for sulphur capacity more clearly explained in the printed version of the paper than in the oral discussion at the meeting. I feel that this quantity, which actually is the ratio of two activities, can be measured more easily than the individual activities. Even if the ratio CaO/CaS is chosen as the standard state, the expression can be used for any slag, even for slags completely free of lime, and it represents a way to put the desulphurizing power of all slag constituents into one bag. Some doubt has been expressed as to whether oxygen ions really exist in calcium oxide and in molten slags. From a thermodynamic view point that question is of minor importance. The term oxygen ion activity, or any activity for that matter, is defined rigorously by the equation: activity = exp p/RT, where p is the change in free energy connected with the transfer of one mol of ions from the standard state into the slag. Whatever happens to the ion in the slag is of no concern to the thermodynamicist. Regardless of whether the ion is "free" in the slag or not, or whether it is present in a very small amount, its activity can always be expressed, and for a thermo- dynamic calculation that is all we need. However, ionic activities will only be of some real value if they are simple functions of the slag composition, or can be measured easily. Concerning the real nature of the oxygen in the slag, my feeling is that the oxygen atom has a rather multiplex nature depending on how strongly it is tied by covalent forces or polarized by the other atoms or ions present. The oxides of iron, cobalt, and nickel differ from calcium oxide and blast furnace slags as to the amount of free electrons that can give rise to electronic conductivity. In slags we know that the conductivity is mostly ionic. The fact that reversible emf's can be obtained with oxygen electrodes in certain salt melts, indicates a significant amount of oxygen ions in these melts. But extended work, e.g. polaragraphic studies and measurements of transference number; are needed to obtain quantitative information about the real structure of the slags. D. E. Babcock (Republic Steel Corp., Youngstown, Ohio)—-With reference to the ion, it might be well to remember Dr. Moses Gomberg. All of his life he had no use for the ionization theory and he contributed greatly to the field of chemistry on the assumption there was no such thing as ions. I do not think we have to worry about whether the oxygen is ionic or not. I think one thing specifically should be brought to your attention and this I think is one of the important contributions of Dr. Rosenqvist. He pointed out what we know as oxygen potentials or what is described as oxygen potentials. I have used this concept for a long period of time and I want to state that if this concept is properly applied, it vitiates much of what we have in the literature, or makes our usual ideas regarding oxidation seem primitive. That one thing is more valuable than almost all the rest of the discussion as a fundamental basis on which to build a reasonable in-

Jan 1, 1952

By Alan U. Seybolt

In examination of some cold-rolled copper and cupronickel that contained a little columbium, it was discovered that these alloys were unusually resistant to annealing. This effect was suficiently pronounced to warrant some investigation of the annealing characteristics of such compositions. Experimental Procedure The alloys were made from cathode copper, electrolytic nickel, and a special copper-columbium hardener alloy furnished by the Electro Metallurgical Corporation. This hardener alloy contained 10 per cent columbium, with tantalum, aluminum and iron as major impurities. The melting was carried out in a clay-graphite crucible in a high-frequency induction furnace! under a charcoal or electrode carbon cover. No deoxidizing additions were made. The 7-lb. copper heats were poured into a steel mold, hot-rolled to 1/4-in. thickness, and annealed for 56 hr. at 760°C.; the cupronickels were annealed I hr. at 815°C. The material was then cold-rolled to a 50 per cent reduction in thickness and annealing tests were carried out on this 1/8-in. hard-rolled strip. A little silver was added to copper-columbium alloys 402 and 403 to find out

Jan 1, 1942

By Alan U. Seybolt

In examination of some cold-rolled copper and cupronickel that contained a little columbium, it was discovered that these alloys were unusually resistant to annealing. This effect was suficiently pronounced to warrant some investigation of the annealing characteristics of such compositions. Experimental Procedure The alloys were made from cathode copper, electrolytic nickel, and a special copper-columbium hardener alloy furnished by the Electro Metallurgical Corporation. This hardener alloy contained 10 per cent columbium, with tantalum, aluminum and iron as major impurities. The melting was carried out in a clay-graphite crucible in a high-frequency induction furnace! under a charcoal or electrode carbon cover. No deoxidizing additions were made. The 7-lb. copper heats were poured into a steel mold, hot-rolled to 1/4-in. thickness, and annealed for 56 hr. at 760°C.; the cupronickels were annealed I hr. at 815°C. The material was then cold-rolled to a 50 per cent reduction in thickness and annealing tests were carried out on this 1/8-in. hard-rolled strip. A little silver was added to copper-columbium alloys 402 and 403 to find out

Jan 1, 1942

By Paul L. Hunter

Nearly 2000 people are employed at Kennecott's Chino Mines Division, which recently completed its 50th year as a leading copper producer. Chino operates an open pit mine at Santa Rita, N.M., and a reduction plant, including mill, power plant, and smelter, at Hurley, N.M. The property mines 66,000 tons of copper ore and materials per day. There have been safety and industrial health programs at Chino for a number of years, but in 1955 these procedures were reorganized on a more active basis. The following discussion evaluates the progress made during the 1955-1958 period.

Jan 6, 1960

By J. C. Bayles

THE most unsatisfactory occurrences in the experience of a manufacturer are those from which he suffers damage and learns nothing useful. That there are such incidents, and that they occur with annoying frequency, is unfortunately true. An accident which can be understood and explained always carries some consolation with it. However bad the copnsequencee, one finds comfort in reflecting that they might have been worse, and that the knowledge of how to avert a more disastrous calamity from the same cause is worth what it cost. But when an accident occurs, which remains unexplained after anxious days of investigation and sleepless nights of reflection, and which is as liable to occur twice or twenty times, as once, very little satisfaction of any kind can be extracted from it by the most philosophical victim. Three such incidents have come under my notice in one establishment. Fortunately none of them were attended with very serious consequences, as no one was hurt, and the damage to property was slight; but in each instance, loss of life and great destruction were escaped by so narrow a margin as to make them extremely disquieting. I have recorded them in the hope, that from the experience of others maybe gained what my own careful investigations have failed to reach-—satisfactory explanations. The first of these curious occurrences was the bunting of a 16-inch pipe carrying air under a compression of about 1 pound. The pipe was made of light galvanized iron with soldered seams. Into it a rotary fan-blower delivered air, and from it smaller pipes were carried to the furnaces. The blower was run continuously. Neither the main pipe nor its branches had any connection with the gas conduits. Both air- and gas-pipes delivered into the furnaces; but although the gas was under much higher compression than the air, there appeared to be no good reason why, having free escape in case of leakage, it should ever make its way back into the air-pipe. One warm afternoon in June the main air-pipe exploded with great vio-

Jan 1, 1891

The elite group of companies below represent the mining sector of Fortune magazine's June Directory listing the 500 U.S. industries that chalked up the largest dollar sales volume in 1966. The companies are listed according to their 1966 sales rank, which is given along with their 1965 rank for comparative purposes. All of the firms except two-Freeport Sulphur and Texas Gulf Sulphur-were in the Fortune Directory last year, and both these exceptions have been counted among the top 500 in former years. The one mining name that is missing from last year's list-Consolidation Coal-has actually jumped from number 217 to 4 by virtue of its merger with Continental Oil. As can be seen from the Industry Medians, the mining industry as a whole boosted its sales 17.8%, in 1966, making it the seventh largest gainer among the 22 industrial classifications covered in the Directory. By comparison, 1965 mining sales increased 10.2%, a gain which was surpassed by 13 other industries. In two other comparative tables, mining leads the field, topping the entire list in return on sales and in assets per employee.

Jan 8, 1967

By James Ruddy

THE medical program of the Climax Molybdenum Co. is under the supervision of the department of industrial medicine of the University of Colorado, of which James J. Waring, professor of medicine at the University Medical School, is director. Dr. Waring is consultant and direct supervisor of both the hospital and industrial medical department at Climax. At Climax the program is in charge of the medical director and the associate physician, Dr. Galen M. Hover. The hospital at Climax is completely equipped with all that is necessary for the practice of scientific medicine and surgery. Only graduate registered nurses with experience in industrial medicine are employed. Being only a few hundred yards from the portal of the mine. acci-

Jan 1, 1946

By E. W. Parker

Anthracite, as sent to market, comes under three general terms of description: characteristics, source and size. Anthracite is generally classified as white ash, red ash, or Lykens Valley. The white ash coals are sometimes further described as "hard" or "free-burning." Lehigh white ash would come under the former description and Shamokin white ash under the latter. As a rule, it may be said that the nearer the origin of the coal to the western extremity of the anthracite region, the softer and more free-burning it is. Indeed, for many years the coal from Trevorton, at the western tip of the Middle Western field, was classified as "semianthracite" in the shipment reports. Lykens Valley coal is always a red ash coal, with a higher volatile content than the general run of anthracite, and consequently free-burning. The name does not exclusively indicate the neighborhood in which the coal is dug, but rather refers to the beds from which it is obtained. These beds lie, not above the Pottsville conglomerate, as is the rule, but encased in it. The extreme eastern limit of the Lykens Valley beds would seem to be about Tremont, in Schuylkill County, and the Natalie mine, near Mount Carmel. There are, of course, traces of these beds farther to the east, but they do not seem to be workable. There are as many as six of the Lykens Valley measures found in the conglomerate at some points, but to a large extent they are unworkable. Whether this coal is obtained in the Lykens Valley proper, where the beds were first identified, or from the Shamokin Valley, it is always Lykens Valley coal, and it has long been considered a premium coal, especially desirable for domestic use, particularly when a quick, hot kitchen fire is desired. Coals are, of course, frequently marketed under special names—Jeddo, Scranton, Kingston, Old Company Lehigh, Famous Reading, Lacka-wanna, etc.—which, of course, have the trade significance which their producers and vendors have built up. General Description of the Various Coals, with Name of Seam and Producing District This is partly covered in the paragraphs above. Lykens Valley coal is produced from one or another of the six Lykens Valley beds lying within

Jan 1, 1930

By Albert Sauveur

(Cleveland Meeting, October, 1912.) ALTHOUGH many metallurgists know that some pearlitic special steels can be made troostitic, martensitic, and even austenitic, without quenching, and, therefore, without exposing them to the dangers of the quenching-bath, the practical significance of such possibility does not seem to have received the attention it deserves. Let us recall briefly the mechanism of the transformation alluded to. In Fig. 1 (after Guillet) is shown the constitutional diagram of nickel-steel that; is, of alloys of iron, carbon, and nickel. Any steel the composition of which falls within the area LPO is pearlitic after slow cooling; any steel the composition of which is represented by a point within the area MLO is martensitic, and any steel within the area MNO is austenitic. Starting with pearlitic steel, then by increasing the carbon-content or the nickel-content, or both, the metal becomes martensitic and eventually austenitic; that is, its composition crosses first the boundary-line LO and then the line M0-and it remains martensitic or austenitic after slow (air) cooling.1 We have inn this way imparted to the metal without quenching it the properties of hardened carbon-steel. In other words, the steel is now self-hardening. Nickel cannot be introduced into solid steel, but by the well-known process of case-hardening it * Professor of Metallurgy and Metalllography in Harvard University. + Assistant in Metallurgy and Metallography in Harvard University. 1 The boundaries between the various zones are not, as a matter of fact, as sharp as indicated in the diagram, because pearlite is not transformed abruptly and in its entirety into martensite when a certain critical composition is attained, nor is martensite suddenly and completely converted into austenite. Greater refinement in the construction of the diagram would undoubtedly result in the introduction of troosto-pearlitic, troostitic, and troosto-martensitic zones between the pearlitic and martensitic areas and-of a martenso-austenitic zone between the martensitic and austenitic areas. Fur the purpose of this note, however, the existence of these transition-conditions may be ignored.

Nov 1, 1912

By G. F. Huff, G. R. Bailey, J. H. Richards

An improved bomb-sampling technique for obtaining samples for oxygen analysis from liquid steel is described. Analyses of samples taken from open-hearth furnaces by the improved method show sufficient agreement with laboratory data to indicate the accuracy of the method is better than that of other existing sampling methods. THE bomb-sampling method of determining the oxygen content of a liquid-steel bath was studied by obtaining and analyzing more than 200 samples from normal open-hearth heats. Of these samples, about 60 were obtained with a bomb of conventional design;' the remainder were taken with a somewhat modified bomb designed to give greater protection against slag contamination. In the new device, the contacting faces of the cast-iron mold halves are machined so that they fit closely; the opening at the top of the bomb is covered with a thin steel cap; and the top of the bomb is further covered with a wood block held in place by heavy steel wire. After the bomb has passed through the slag layer and has entered the steel bath, the wire melts and the wood block floats to the surface. Thereafter, the steel melts through the thin cap and flows into the bomb cavity where it is deoxidized with aluminum wire. An assembled bomb, ready for sampling, is shown in Fig. 1. To standardize sampling procedure, the samples were usually taken through the center door and at the bottom of the furnace; that is, the bomb was on the bottom when the metal cap melted. After each addition to the furnace, at least 20 min elapsed before a sample was taken. The oxygen contents of all the samples were determined by using the vacuum-fusion method, two or more specimens from each sample being analyzed. The specimens were cubes of metal cut from a region in the interior of the bomb sample, as shown in Fig. 2. Drillings for carbon analysis were obtained immediately above the oxygen-analysis region. Reproducibility of Results In determining the reproducibility of the results obtained with the modified bomb, the following four factors were studied: 1—variation in the oxygen concentration of duplicate specimens taken from a single sample; 2—variation in the oxygen concentration of duplicate samples taken in quick succession: 3—effect of the amount of aluminum wire

Jan 1, 1953

By J. Dehais, W. A. Wallace

The pressures of urbanization are forcing producers of construction minerals either to transport their product greater distances or find new mineral sources. In areas with significant urban development near the coastal zone, offshore resources may prove to be an economically attractive alternative source. This paper addresses the economic viability of offshore mining of fine mineral aggregate. It proposes a model using a mathematical programming formulation based upon past research on both the onshore construction aggregate industry and the coal industry. The model is then used to assess offshore mining economics in the greater New York metropolitan area. Results show that in this region total consumer cost would be reduced by offshore mining of fine aggregate. In addition, increasing economies of scale could be realized by progressively larger mining operations. The distribution of these savings is also discussed.

Jan 1, 1982

Jan 1, 1896