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By Ralph Nichols

THE mines are near the town of Gilmore, in the Texas mining district. This district was organized in 1880. The present producing mines are near the terminus of the Gilmore & Pittsburg railroad. This railroad connects with the main line of the Oregon Short Line at Armstead, Mont. The distance from Gilmore to Armstead is 70 miles. The town of Gilmore is near the head of the Lemhi river at an elevation of 7,000 ft., while the mines are from 400 to 1,300 ft. higher. The range of mountains upon which the mines are situated forms the water shed for the Little Lost river on the west and the, Lemhi river on the east. The winters are severe and the snow fall is heavy, but the mines ship right through the year. There is an abundance of timber suitable for all mining purposes in the immediate vicinity. Water is piped into the camp from a lake about 2.5 miles distant. This lake is about 1,400 ft. above the town of Gilmore. The water is exceptionally good for boiler and domestic purposes. The mining companies now producing are. the Pittsburg Idaho Co., Ltd. ; the Latest Out Mining & Smelting Co:, Ltd. ; and the Gilmore Mining Co., Ltd. Besides the above properties, there are a number .of prospects in different stages of development. The producing mines of the district are fissures in limestone, with a general northeast-southwest course .and a dip to the west of from 40° to 70°. These fissures are at about right angles to the bedding of the limestones. The veins are regular and the ore shoots strong, both laterally and in depth, so far as developed. The ore shoots have a rake or pitch to the south. The character of the formation is shown in Fig. 1, a section of the Latest Out mine.

Jan 11, 1913

By Thomas E. Garnar

Zirconium and hafnium are curious elements because they are almost always found together in nature. Zirconium was discovered by Klaproth in 1789 and isolated 35 years later by Berzelius. Because hafnium's chemical properties are so close to those of zirconium, it was not discovered until 1923 when Coster and Von-Heresey detected it using x-ray spectrographic analysis. These elements occur most commonly in nature as the mineral zircon (ZrSiO4) and less commonly as the oxide baddeleyite (ZrO2). They also are found as a variety of other silicates. Zircon was identified as a component in alluvial and beach sands in 1895, but it was not produced in any quantity until 20 years later. Zircon is always a coproduct from TiO2 mining and processing. During World War I it was produced as a coproduct of beach sand mining for titanium minerals just south of Jacksonville Beach, FL, and was patented as a refractory. It was not until the 1930s when Zircon Rutile, Ltd. began mining at Byron Bay on the east coast of Australia that zircon was first used as a foundry sand. Later in the 1940s, NL Industries, Humphreys Gold Corp., and E. I. du Pont de Nemours & Co., Inc. began production of zircon sands from fossil beaches in northeast and northcentral Florida. Baddeleyite first became available as a commercial product in 1916, but never in the quantity of zircon. Zircon holds a unique position as an industrial mineral because it is used for both its physical and chemical properties as well as an ore of zirconium and hafnium metals. Australia is the major zircon producer followed by South Africa and the US. Zircon is also produced in India, Sierra Leone, Sri Lanka, Malaysia, China, Thailand, and Brazil. Undeveloped heavy mineral beach sand reserves containing zircon are known to occur in Egypt, Malawi, Senegal, and Tanzania. Locations are shown in Fig. 1. Mineralogy Zirconium and hafnium are always present together in naturally occurring compounds. Most commonly they form as the silicate sometimes containing iron, calcium, sodium, manganese, and other elements. Less commonly they are found as oxides in combination with titanium, thorium, calcium, and iron. Zircon is the most common form. It is extremely resistant to weathering, therefore, often it is present in ancient beach sands and placer deposits. Although resistant to alteration from external sources, it is vulnerable to internal alteration as the result of thorium and uranium substituting for zirconium either in the zircon lattice or in solid solution. Alteration to the metamict state takes place as radioactive emanations from these elements disorder the crystal lattice, accompanied by hydration, reduction in specific gravity, and changes in color. The mineralogy of zircon and baddeleyite and variation of physical and chemical properties are shown in Table 1. The effects of zircon's internal alteration and darkened color can be corrected by heating to 1000°C for 30 min or so. A certain time-temperature relationship makes it possible for decolorization and reordering of the crystal lattice to take place when heating at higher temperatures for shorter periods or at lower temperatures for longer periods. After heating, x-ray diffraction patterns are sharper, the grains may be harder, and except for particles of malacon, the grains will be white or colorless in the absence of grain surface coatings. The color change is only temporary and the particles slowly darken with time. Zircon fluoresces light yellow in shortwave ultraviolet light. If exposed to ultraviolet light for extended periods of time, white (calcined) zircon turns purple. With time the induced color begins to fade and eventually disappears (e.g., calcined Florida zircon exposed to ultraviolet light for 24 hr still retains faint, but discernible, purple color after six months).

Jan 1, 1983

By G. C. Rauch, T. H. Courtney, J. Wulff

The superconducting behavior of Nb-Ti alloys containing 40 and higher wt pct of Nb and variable oxygen content was studied as a function of thermomechanical processing. Critical current density (Jc) us applied transverse magnetic field (H) data were obtained for 0.010 in. diam wires at 4.2° Kin steady fields up to 120 kOe. The precipitate responsible for increase in Jc in each of the alloys studied was related to niobium and oxygen content. In alloys containing 40 to 60 wt pct Nb with less than about 1600 ppm of oxygen, w precipitation in the range 350° to 450°C appears to be responsible for the maximum value of Jc observed. In alloys of higher oxygen content (-2500 ppm), the oxygen-enriched a phase which precipitates in the temperature range 450° to 550°C is a more effective fluxoid pinner. Maximum Jc in low oxygen (350 ppm) 80 wt pct Nb alloys was achieved by 600°C aging heat treatments. Measurements of resistive critical field also reflect the changes in composition accompanying precipitation in these alloys. It is well known that the superconducting critical current density, Jc, of solid solution superconducting alloys can be increased by precipitation heat treatments.1-4 The precipitate, to serve as an effective superconzlucting fluxoid pinner and increase Jc, must be of proper size and spacing.' Its electronic properties must also be different from those of the matrix.6 As in age-hardenable systems, optimum temperature and time of aging are dictated by the composition and history of the particular solid-solution alloy under consideration. The alloy diagram of Ti-Nb7-9 shown in Fig. 1 is typical of ß-stabilized Ti alloys. Precipitation to achieve high Jc in Ti-Nb and Ti-Ta alloys is usually carried out in what is believed to be a two-phase a + ß region.1,2,4,10 Previous work on Ti-Nb4,11 and on other ß-stabilized systems such as Ti-V, Ti-Mo,12-14 has shown, however, that the first precipitate to appear is not necessarily (Y. Under specific conditions the meta-stable w phase is precipitated instead. A further complication arises in such alloys from the strong influence of contained oxygen on the phase stability and on the kinetics of precipitation.15,16 The superconducting critical current density of Nb-Ti alloy containing less than 36 wt pct Nb has been studied by Vetrano and Boom1 and Kramer and Rhodes.4 The most effective aging temperature was found to be about 425°C; fluxoid pinning was attributed to the precipita- tion of a by Vetrano and Boom and of w by Kramer and Rhodes. Although the latter workers used recrystal-lized material and the former cold-worked, studies carried out in our laboratory lead us to believe that the type of precipitate responsible for increased Jc is unaffected by prior cold-work.17 That other types of precipitates may also be effective, especially in higher oxygen-containing alloys, has been demonstrated by Reuter, et al.2 in this laboratory with the aid of electron microscopy. Reuter et al. found that at an aging temperature of 600°C, fee-TiO is precipitated, resulting in high values of Jc. Even higher values of Jc were observed after heat treatment at 500°C, but the precipitate could not be indexed as fee-TiO. Whether the precipitate was oxygen-rich w or a could not be clearly distinguished. The work nevertheless indicates that appreciable amounts of oxygen alter the nature of the phases precipitated at different temperatures, at least in alloys containing more than 36 wt pct Nb. Since such compositions are more readily worked into suitable wire than lesser niobium content alloys, it was decided to study the response to aging of the alloy compositions reported in the present paper with the hope of clarifying the effect of composition on the precipitation processes responsible for high values of Jc. I. EXPERIMENTAL Nb-Ti alloys containing 40, 50, 60, and 80 wt pct Nb were prepared by are-melting 35 g ingots of iodide crystal bar titanium and electron-beam melted niobium.

Jan 1, 1969

A. G. Cockbain—The paper by Burlingame, Bitsianes and Joseph is of great interest in extending the work done on high grade sinters, particularly that of Hessle, and the development and application to them of the technique of McBriar, Johnson, Andrews and Davies on ironstone sinters. In this laboratory the work of McBriar et al. has also been continued and extended to cover high grade sinters, and a sectioning technique similar to that used by McBriar et al. was attempted on sinter cakes made in the laboratory sinter unit, using magnetite concentrates (containing 64 pct Fe). In these experiments no attempt was made to flush out the products of combustion with nitrogen before cooling. It was considered that free air penetration would occur on only a limited scale with the size of sinter cake made (14 in. sq x 12 in. deep). Chemical analyses of the zones showed generally similar features of those described by Burlingame et al. and especially the FeO rich region at and just behind the flame front, i.e. zones of ignition and combustion. This seems to indicate that the nitrogen atmosphere does not materially affect the states of oxidation in the sinter cake or at least that special care is not required unless the sinter cake is small. Burlingame et al. consider that FeO present has some significant part to play in the mechanism of sintering. This view does not find favor with the author. The reduction of iron oxides in the presence of red hot coke is a well known phenomenon, whether conducted in an atmosphere of nitrogen or in a crucible in air, and in view of the presence of some carbon in the hot sinter, especially just at the ignition zone, cessation of the progress of the flame front will in no way affect the reduction of iron oxides near hot coke. Even in a nitrogen atmosphere some CO and CO, will be generated by reduction and by continual oxidation and reduction of CO as the transfer agent, the oxidation state of the iron oxides can be lowered quite rupidly so long as free carbon exists with enough heat. Knowing the composition of the gas at the flame front (obtainable by probes), it would be possible to calculate the static oxidation state of Fe2O3/Fe3O2 in equilibrium with it and hence obtain a check on the chemical analyses to see if in fact direct reduction of the Fe2O3/Fe2O1 to FeO has taken place. Have the authors attempted this? It appears to this writer that what is required is some means of reducing rapidly the heat content of the ignition zone and immediately behind, and at the same time insuring no oxidation by the air. In ironstone sinters the difficulty of oxidation state of the iron did not arise on account of the very large slag bulk. However, in high grade sinters knowledge of this, and also the mechanism whereby high oxidation states can be obtained in the final sinter, is of great interest. R. D. Burlingame (author's reply)—The question has been raised as to whether the high FeO content found in high-fuel sinters is due to actual reduction at the advancing flame front or due to unavoidable direct reduction during the quenching period. For such direct reduction to have taken place in the freshly-formed sinter, a considerable amount of solid carbon would have had to escape combustion and be available throughout the hot sinter zone during the quenching period. A simple stoichiometric calculation with the limited data available indicates that a zone of freshly-formed sinter over 2 in. wide must have averaged roughly 2 pct C to accomplish the amount of reduction found. Furthermore, the presence of this amount of carbon would indicate that the fuel in the charge had not burned over a narrow front but over a zone at least 2 in. thick. In contrast to such a condition, the data of the present investigation indicate that the combustion of fuel is confined mainly to a narrow front in which high temperatures and reducing conditions favor. the formation of excess ferrous iron.

Jan 1, 1959

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By J. H. O’Dette

BLISTER formation on wrought aluminum products has been a matter of concern to aluminum fabricators for many years. The fact that blisters make their appearance during the final stages of fabrication means that much time and effort have been expended before it is evident that the material must be scrapped. This and the loss of production are ample reasons for embarking on a research program to find out more about blistering and possible methods of control. Many excellent papers on this subject have appeared in the technical literature in the last few years. In one of the more recent papers, Kostronl gives a fairly complete review of the problem of gas in aluminum and blistering in general. From the work of the various investigators, a general mechanism for the formation of blisters has evolved and may be summarized briefly as follows: Hydrogen gas is usually present in the cast ingot, in the atomic or ionic state, in excess of the solid solubility. At room temperature the gas atoms are relatively immobile, but at elevated temperatures they become mobile and diffuse to free surfaces where they associate to form molecules. If these free surfaces are discontinuities within the ingot then the associated gas molecules collect and build up considerable pressure until equilibrium is reached with the dissolved gas around the discontinuity. Since the solubility of the gas is proportional to the square root of the partial pressure it is evident that large pressures may be built up at the discontinuities. When the metal is rolled to sheet the pressure of the gas in these, discontinuities is sufficient to deform the surface of the sheet and form a blister, particularly when the strength of the material is reduced during the annealing. Although the mechanism of the formation of blisters was fairly well known, the actual impor- tance of the individual roles played by the gas and the discontinuities was not so well established that positive methods for control of blistering were at hand. It was the object of the investigation to learn more about the nature of the discontinuities giving rise to blistering and to develop methods of control. The investigation was carried out in three stages as follows: a) A study of the more commonly used methods of removing hydrogen from aluminum, such as fluxing and holding, and their effects on blistering. b) Location of the discontinuities giving rise to blistering. c) A study, by indirect methods, of the movement of gas in the metal and its effect on blistering, and the development of methods of blister control during fabrication. Removing Gas and Reducing Blistering by Fluxing or Holding-—The work of removing gas and reducing blistering by fluxing or holding was carried out on metal of Alcan 2s (1100) composition with an artificially high gas content. The high gas content was obtained by introducing water into the melt prior to casting; the water reacted with the aluminum forming A12O3 and hydrogen. The procedure was to raise the gas content by introducing water into an aluminum melt and using half the melt to cast one ingot immediately. The remaining metal was treated again with water to make up for the reduction in gas content during holding, while the first ingot was being cast, and then given a fluxing or holding treatment and cast into an ingot. Samples for gas determination were cast from the molten metal before and after the gassing operation; before, after, and during fluxing, and while casting. Samples were also cut from sections of the ingots. Gas determinations were made on these samples using the well known vacuum fusion technique. All ingots were hot rolled at 500°C to 0.250-in. slab which, in turn, was cold rolled to 0.040 in. sheet. The sheet was coiled and annealed for 2 hr at 500 °C and then cut into 5-in. squares which were inspected for

Jan 1, 1958

By F. E. Bash

CONSTANTAN is an alloy of copper and nickel that is extensively used, under a number of trade names, as a resistance wire with a low temperature coefficient of resistance, and one of the elements of base-metal thermocouples, iron usually being the other thermoelement, although for low-temperature work copper is also used. Before the war, constantan was imported, in common with many other technical necessities. Since it required considerable time to receive the constantan after it was ordered, fairly large stocks were kept on hand; but after the beginning of the war no more was imported acid the stocks of foreign material were exhausted about the same time that the steel and munition manufacturers began to need great quantities of it for thermocouples for the heat treatment of steel. To meet this demand, the International Nickel Co. began manufacturing constantan that met all the requirements of the users of resistance wire but did not give the same electromotive force against iron as the German material and consequently could not be used with instruments calibrated for a definite e.m.f.-temperature relation. It so happened that all the constantan made had an e.m.f. lower than that necessary to meet the specifications of the Leeds & Northrup Co. for whom this investigation was carried out. If some had been higher and some lower, good wire could have been obtained by a, process of selection, but as it was no wire at all could be procured. To remedy this situation, a thorough investigation was started with the close cooperation of the International Nickel Co. and the Electrical Alloys Co. The specifications to which the constantan had to conform were that it should give an e.m.f. of 47.40 millivolts. against pure iron at 1500° F. (816° C.) with the cold-junction temperature at 0° F., or a proportional e.m.f. at temperatures near 1500° F. The method of checking a wire was as follows: It was first welded to a piece of iron wire; Armco iron was found to be satisfactory but iron with greater than 0.1 per cent. carbon would give a lower e.m.f. against the same piece of constantan than pure

Jan 9, 1919

WE must begin by defining what we mean by the Copperbelt. This term is generally used to denote that region of Northern Rhodesia in which the copper mines of that territory are situated. The first published use of the term Copperbelt we have been able to trace dates back to 1905. The African World of December of that year contained an article entitled "The Great Northern Copper Belts of Rhodesia." The next reference we have traced is in 1909 in an article in the Transactions of the Geo- logical Society of South Africa. It began to be used generally in the late twenties and by 1929 was in common use to denote the region which today contains the existing large copper mines of Northern Rhodesia. The first of three accompanying maps is a very simple outline map of Africa showing where Rhodesia is within Africa, and where the Copperbelt is within Rhodesia. The second is a larger scale map of the Copperbelt itself. It will be seen that within the present Copperbelt there are six producing mines. Two of these are new and four are relatively established, having started operations between the two world wars. The Copperbelt also includes a town- ship called Ndola, which is not a mining town, but a railhead on the main line. This town has developed primarily as a result of the mining industry in the neighborhood. It describes itself as the Gateway to the Copperbelt and is shortly to become a refining center.

Jan 5, 1957

By R. E. Hook, R. L. McGaughey, A. M. Adair

The initial yielding characteristics of a vacuum-melted iron have been measured as a function of thertnal history after slow cooling or quenching from a 700°C recrystallizntion anneal. A thermal history favoring the segregation of interstitials to grairz boundaries results in a material having high values of upper and lower yield stress and long, irregutar Luders' plateaus, wheueas specimens treated to minimize grain boundary segregation have significantly lower values of these yielding characteristics. The struc- ture of typical grain boundary areas as revealed by electron transmission microscopy is consistent with these findings. The grain boundaries in iron are considered to be principally responsible for the release of dislocations during macroscopic yielding and it is suggested that strong locking results when a substantial amount of grain boundary segregution is present; it follows that weak locking results from a more random distribution of interstitials to grown in dislocations. RECENT years have seen an increased emphasis placed on a more quantitative study of the influence of grain boundaries on the yield behavior of bcc metals. The earlier picturk of dislocation pileups at grain boundaries building up a sufficient stress concentration to unlock dislocations in neighboring grains1

Jan 1, 1967

By L. G. Huntley

I. HISTORY OF OIL DEVELOPMENT IN MEXICO THE occurrence of oil or "tar" in Mexico was mentioned as early as the seventeenth century by Friar Sagahun, who gives the Indian name "chapopote," by which these asphalt seepages are still called. This asphalt was apparently used, as it has been used by primitive people in many parts of the world, in religious ceremonies and for medicinal purposes. Travellers also report that the ruins in Yucatan and the pyramids in southern Mexico show traces of the use of "chapopote" as a building cement.1 DeGolyer says that the first attempt to exploit oil or gas in Mexico in a commercial way is shown by the records of the Memoria de Fomento of 1865, when permission was granted to a Senor Ildefonso Lopez to exploit the deposits of petroliferous substances in the San Jose de Ias Rusias area in the State of Tamaulipas. Other concessions follow, and probably refer to surface seepages which occur in that district. This was several years after the discovery of oil in Pennsylvania. In 1868, a well 125 ft. deep was drilled by a company organized in Mexico City, in what is now known as the Furbero district, and a little oil was refined there. In 1873, residents of Tampico denounced seepages along the Tamesi River, and asphalt was mined near Tempoal in the Canton of Tantoyuca. No drilling was attempted. But between 1880 and 1883 several shallow wells were drilled for oil in Mexico, two of them being near the present Potrero de Llano field west of Tuxpam. The wells were drilled by a Boston company with Canadian rigs, and are said too have reached a depth of about 400 ft., while one is reported to have flowed. Several other abortive attempts were made to drill for oil between 1885 and the beginning of the present century, about which time the Mexican, Petroleum & Liquid Fuel Co., Ltd., in which Cecil Rhodes was interested drilled 24 wells unsuccessfully, several of them as deep as 1,500 ft., in the State -

Jan 9, 1915

By I. Tamura, J. O. Brittain, T. Mura

Plain carbon steel in the cold worked or marten-sitic conditions has an internal friction peak at about 250 oC at a frequency of I cps. The influence of substitutional alloying elements on this peak was examined experimentally. The alloys were vacuum melted Co-, Cr-, Mo-, Ni-, and Si-iron (about 3 pct alloying elements), and carburized Si-iron. The internal friction of the alloys in the temperature range 30o to 500 OC was determined by means of a torsion pendulum. The 250 oC peak of the cold-worked alloys was lower in height than that observed in plain C-iron and steel. Carburized Si-iron in the quenched condition had a peak which occurred at a slightly lower temperature than in quenched plain C-steel, but the height of the peak was substantially greater than that found for the same alloy in the cold-worked condition. The activation energy of this peak for martensitic Si-steel was about 35 kcal per mol. ANNEALED a iron has two internal friction peaks due to nitrogen and carbon at 20o and 40o C respectively, at a frequency of 1 cps. If a iron is cold worked, these diffusion peaks become smaller and a new peak appears at about 250o C. The activation energy for the 250o C peak is in the range of 32 to 44 kcal per mol and has an average value of 38 kcal per mo1. It has been experimentally verified that both interstitial solute atoms and dislocations are necessary for the 250o C peak. 3 Wert has also shown that an incubation period precedes the appearance of the 250 C peak.4 With regard to quenched martensitic steel, Ke et al.596 observed two peaks at around 130o and 250o C. They conjectured that the 250o C peak in martensite was due to the same mechanism as the 250°C peak in cold worked a iron, and the 130°C peak was due to the nature of tempered martensite. They did not report the activation energy for these peaks. Chernikova7 found only one peak at about 200° C in tempered martensite. In a previous paperS we reported an activation energy of approximately 40 kcal per mol for the 250° C peak in plain carbon martensitic steels. Ichiyama8 found the activation energy to be about 36 kcal per mol for the 250° C internal friction peak in steels in the martensitic condition. The present authors proposed a theory for the 250°C peak for cold worked and quenched iron and steel.= The theory for the peak is based upon the addition of a strain-energy term to the free energy for the formation of a carbide precipitate due to the presence of a disclocation. The model employed for the relaxation process consists of the growth and solution of a carbide precipitate of critical size as a consequence of an oscillating dislocation. In this report, the influence of substitutional alloy ing elements on the 250° C peak is examined and the experimental results are discussed in terms of our theory for the peak. Most of the experimental work on the alloy steels was confined to the Fe-Si-C alloys.

Jan 1, 1962

By R. E. Miner, J. K. Jackson, D. F. Gibbons

Internal-friction measurements were made during isothermal aging treatments of 18 pct Ni maraging-steel wires between 420° and 612°C. A sharp initial drop in the internal-friction level was interpreted in terms of a rapid dislocation recovery reaction. The rate of the recovery was found to be independent of temperature. Truncation of the recovery reaction was apparent in those systems that exhibited the rapid age-hardening characteristics of the maraging steels. It is proposed that this initial hardening response is the result of a low activation energy preprecipitation reaction involving molybdenum. A gradual rise in the internal-friction level at longer aging times was associated with the precipitation of a molybdenum-containing precipitate. CONSIDERABLE research effort has recently been devoted to the mechanisms responsible for the high strength and toughness of 18 pct Ni maraging steels. These bcc martensitic alloys are found to harden during aging at temperatures between 400° and 600°C. The aging response is very rapid with more than half the total hardness increase occurring within the first few minutes of aging, Fig. 1. Precipitate particles have been observed in the later stages of aging by a number of investigators.'-' While the identity of the precipitates remains the subject of some controversy, one or more of the intermetallic compounds, Ni3Mo, Ni3Ti, and Fe2Mo, are almost certainly involved. Heterogeneous nucleation of precipitates at dislocations has been noted8 and cobalt is believed to enhance the formation of fine, homogeneously distributed particles by lowering the solubility of the alloying elements in the martensitic matrix.3,7 Transmission electron microscopy studies of the initial hardening behavior have not been fruitful. Strengthening mechanisms based on atomic ordering have not been generally supported by X-ray and neutron-diffraction experiments.9 In the present investigation, the aging reaction was studied using isothermal-aging internal-friction measurements. The marked sensitivity of internal friction to short-range diffusion and precipitation processes has provided a convenient tool for the elucidation of the strengthening mechanisms operative in the maraging steels. EXPERIMENTAL PROCEDURE An upright torsion pendulum was used to measure the internal friction of several maraging steels during isothermal aging. The pendulum was placed in an atmosphere of helium at a pressure slightly less than atmospheric. To permit measurement of internal friction during the first minutes of aging, the specimens were rapidly heated by passing a current through them in a manner similar to that described by Ang and Wert.10 Thermal gradients in the specimen were largely eliminated by using specially designed specimen grips11 which produced temperature variations of less than 1 pct over 90 pct of the specimen length and less than 3 pct over the entire length at aging temperatures up to 620°C. A proportioning strip-chart program controller was employed to maintain constant specimen temperature during treatments of up to 36 hr duration. A number of vacuum-melted laboratory heats having compositions near that of a typical commercial 18Ni-7Co-5Mo-0.4Ti alloy were investigated. The amount of cobalt was varied from 0 to 7 wt pct in five of the heats. Either molybdenum or titanium was omitted in the remaining two heats. The alloy desig-

Jan 1, 1967

By Frank H. Reed, P. W. Henline, Harold W. Jackman

A SUMMARY of the consumption of coal in 1945 shows that the coke industry accounted for 17 pct of the total coal used. No substitute for coke and the blast furnace in the reduction of iron ore has gained sufficient prominence so far to be given serious consideration. However, while the same slot-type ovens are being built and used now as were in use a few years ago, the problem of obtaining suitable coking coals, both high- and low-volatile, has forced many operators to revamp coal-blending facilities. Until the beginning of World War II, high-temperature coke plants were able to secure the required high-volatile and low-volatile coals from two or three seams and from three or four mines. Thus, many of our coke oven plants were able to operate with storage bins for two coals only. The variance in raw materials was not great, and uniformity of blend was a relatively simple problem. Since the beginning of World War II, many and important changes have taken place. Demand for all coals increased greatly. Production, though kept as near maximum capacity as possible, could not meet the demands for coal generally, and particularly for the various kinds of coal which have proved to be satisfactory for specialized uses; coals were allocated as nearly as possible in the order of greatest need; storage piling was reduced to the minimum necessary to keep plants in operation; uniformity of quality could not be maintained, and with this last, uniformity of composition of blends for coking could not be maintained. Whereas before the war producers of metallurgical coke could fill their needs from three or four mines, by the end of the war it was not unusual to find shipments to a single coke oven plant coming from as many as 30 different mines, in a single month. Since many of the mines producing both high- and low-volatile coal for high-grade metallurgical coke are rapidly nearing depletion, the problem of seeking new sources and of blending a number of coals in each plant for the production of high-temperature coke is facing practically every producer in the United States at the present time, and is one which will probably continue for many years to come. Midwestern by-product coke ovens in the Chicago and St. Louis areas use annually from 12 to 15 million tons of bituminous coals which are transported 500 to 700 miles from the Appalachian coal fields of Pennsylvania, West Virginia, and eastern Kentucky. Approximately two-thirds of this coal is high-volatile bituminous. The critical transportation problem confronting the nation in 1943, and the growing scarcity of the best Appalachian coking coals, prompted the Illinois Geological Survey to propose a research program in which would be studied the coking properties of blends of low-sulphur, high-volatile Illinois coal with the high- and low-volatile coals from the eastern fields. Such blends containing Illinois coal, if substituted for the all-eastern blends normally coked,

Jan 1, 1948

By W. F. Hosford

W. F. Hosford, (Massachusetts Institute of Technology) —evelopment of methods for predicting the plastic anisotropy of textured metals is an important step toward the improvement of properties by texture control. The engineering value of the present analysis is indicated by the good agreement between prediction and experimental findings. The purpose of this discussion, however, is to point out the weakness of the assumptions on which the analysis is based. The authors state that "the relative width and thickness strains are believed to depend only on the slip direction" and accordingly they disregard the orientation of the active slip plane. where E,, cW, and et are the tensile, width, and thickness strains, A,, A,, and At are the angles between the tensile axis x, the width direction w, and the thickness direction t, respectively; and G,, GW, and 4 are the angles between the slip-plane normal and x, w, and t, respectively. Therefore, the ratio of width to thickness strains resulting from slip on a single system would be These relations hold regardless of whether the slip plane is a crystallographic plane of the {110}, (1121, or (123) type or whether noncrystallographic slip occurs. If noncrystallographic slip occurs, it might be reasonable to assume that the effective slip plane is the most highly stressed plane containing the slip direction. In this case the slip direction, S.D., the slip plane normal, S.P.N., and the tensile axis, x, are coplanar (Fig. 19) and the angles are related by following expressions: where 9 is the angle between t and the projection of the slip direction in the w-t plane (igs. 1 and 2). The normal strains, Eq. [9], become

Jan 1, 1963

By J. J. Sense

This paper deals with the Asarco method for the determination of equipment availability. It is apparent that no single availability equation will provide all of the information necessary for the complete record of equipment availability. In the Asarco system, three separate availability records are carried on major equipment. The first is mechanical availability, the second is operational availability, and the third is a historical record of equipment use. The derivation of the three items and the definitions of the time elements used in the various availability equations are presented and discussed. The Mission unit of American Smelting and Refining Co. is located in Pima County, Ariz., approximately twenty miles southwest of Tucson. The unit consists of an open pit copper mine and concentrator. The concentrate is shipped by rail to company smelters at Hayden, Ariz., or El Paso, Tex. Mine stripping began at Mission in the fall of 1959, and construction of the 15,000 tpd concentrator was started in the spring of 1960. The first ore was treated in midsummer of 1961 and full ore production was reached in August 1961. At that time over 46 million tons of material had been moved from the pit. Current production (ore and waste) averages over 100,000 tpd. Total production to date (ore and waste) is over 120 million tons. Major equipment currently in operation at the Mission pit is as follows: 3 P & H 1800 Electric Shovels - 9 cu yd dippers 1 P & H 1900 Electric Shovel - 9 cu yd dipper 2 B.E. 190-B Electric Shovels - 9 cu yd dippers 35 Euclid LLD Trucks - 60-ton capacity 6 KW-Dart 55-T Trucks - 55-ton capacity 1 KW-Dart D-2550 Truck - 65-ton capacity 1 LeTourneau Westinghouse 65 Haulpak - 65-ton capacity 3 Euclid S-18 Scrapers - 274011 capacity 4 Caterpillar D-8 Dozers 4 LeTourneau Westinghouse Tournadozers 1 Michigan 280 Dozer 2 Caterpillar Model 12 Motor Graders

Jan 1, 1964

By Earl C. Henry

Magnetic iron ore was mined in Essex County, N. Y., during the American Revolution; Benedict Arnold is said to have mined ore near Port Henry to secure iron for chains and spikes for the Lake Champlain fleet. Details regarding the operations prior to 1804 are not easily obtained but work on a commercial scale appears to have been started about 1838. The Witherbee, Sherman & Co. was established in 1849. The property of the district is held in fee almost entirely by the mining companies. The Mineville iron-ore district, as well as the entire Adirondack region, belongs to the pre-Cambrian complex. The readily identified rocks consist of gabbro, anorthosite, syenite, and granite, and are classed as igneous, eruptive, and intrusive. In addition, there is a great variety of gneisses, rocks with a variable mineral composition but all more or less distinctly foliated. The Grenville series are the oldest rocks in the district; this series consists of graphitic white limestones, graphitic sandstones, and quartzites and gneisses with or without graphite. The orebodies occur in the gneissic rocks and are comformable to the structure of the rocks. The typical occurrence of the ore in this district is in lenticular bodies with a parallel pitch to the southwest; this structure is best exemplified in the New Bed mine. The Harmony and Old Bed orebodies are faulted by two sets of diabase dikes, one set having a southwest strike and the other set an east-west strike. The ores occurring in the acid gneissic rocks are non-titaniferous. The ores occurring in the gabbros and anorthosites are high in titanium; these deposits are irregular, have no structural relation with one another, and are unquestionably of igneous origin. The origin of the gneissic rocks and the ores therein contained is not settled; both the sedimentary theory of ore concentration and the igneous theory of magmatic segregation have been advanced. The iron mineral in all the orebodies is crystalline magnetite; some very perfect and large specimens have been obtained. The gangue is

Jan 1, 1925

By T. K. Perkins, L. R. Kern

A study of fluid mechanics, rupture of brittle materials and the theory of elastic deformation of rocks shows that, for a given formation, crack width is essentially controlled by fluid pressure drop in the fracture. Operating conditions which cause high pressure drop along the crack (such as high injection rate and viscous fluids) will result in relatively wide cracks. Conversely, operating conditions which cause low pressure drop (low injection rates and thin fluids) will result in relatively narrow cracks. Charts and equations have been derived which permit the estimation of fracture widths for a variety of flow conditions and for both horizontal and vertical fractures. INTRODUCTION There has been considerable speculation concerning the geometry of hydraulically created fractures in the earth's crust. One of the questions of practical importance is the width of fractures under dynamic conditions, i.e., while the fracture is being created and extended. Such width information could be used, for instance, to help estimate the area of a fracture generated under various conditions. Also, there has been a recent trend toward the use of large propping partiles.13, 15 Therefore is is desirable to know what factors can be varied in order to assure entry of the large particles into the fracture. There has been some work on fracture widths reported in the literature. In particular, there have been several Russian publications dealing with this sub-jeCt.1.31,3 These papers have dealt principally with the elastic theory and the application of this theory to hydraulic fractures. These studies have not led to an engineering method for estimating fracture widths under dynamic conditions. A recent paper3 has reviewed and summarized the Russian concepts. An earlier paper- from our laboratories also discussed the application of the elastic theory to hydraulic fractures. This first approach, based largely on photoelastic studies, has proved to be too simplified to accurately describe the fracturing process. However, these early thoughts have served as a guide during the development of more exact concepts. We would like to present in this paper our current concepts regarding fracture widths and some estimates of hydraulic fracture widths for several conditions. We believe that it is now possible to predict with fair accuracy the factors influencing fracture widths. Furthermore, the method of prediction has been reduced to a simple and convenient graphical or numerical calculation. CRACKS IN A BRITTLE, ELASTIC MATERIAL Many investigators2, 4, 30 have shown that competent rocks behave elastically over some range of stresses. Of course, if the tensile stress imposed upon a rock exceeds some limiting value, then the rock will fail in tension. In similar manner, there are some limiting shear stresses that can be imposed upon rocks. Hubbert and Willis11 have discussed the shear conditions which will lead to failure. Under moderate stress conditions (such as those likely to be encountered when hydraulically fracturing) and when stresses are rapidly applied, relatively, most rocks will fail in a brittle manner. Hence, for this discussion of hydraulic fractures in the earth's crust, we assume the rocks behave as brittle, elastic materials. Let us develop the discussion in the following way. (The following thoughts are applicable only to brittle materials.) 1. First we consider a brittle, elastic system. An energy balance will show the minimum pressure necessary to fracture rock, and from this pressure we calculate the minimum crack width resulting from extension of a hydraulic fracture. 2. Then we will show that, under ordinary fracturing conditions, fracture widths are appreciably greater than the minimum widths of extending fractures. In fact, we will find that crack width is controlled by fluid pressure drop in the fracture. 3. We will discuss pressure drops in fractures and resulting crack widths for various operating conditions and both vertical and horizontal fractures. 4. Finally, we will discuss the significance of these concepts, their relationship to fracturing pressures, etc. First, consider minimum fracture extension pressures. We can shed some light on this question by considering the theory proposed by Griffith7, 8 Yo explain the rupture of brittle, elastic materials. Griffith recognized that solid materials exhibit a surface energy8 (similar to surface tension in a liquid). The fundamental concept of the Griffith theory is that, when cracks spread without the application of external work (in the interior of an elastic medium which is stressed

By J. D. Alexander, W. L. Martin, J. N. Dew

This paper presents data obtained using a flood-pot technique to determine the fuel available and the corresponding theoretical air requirements for in situ combustion of crude oils. Since the technique is relatively quick and easy, it is a practical and convenient tool for evaluating reservoirs as fireflood prospects. It is also a research tool which facilitates systematic study of the variables affecting fuel availability and corresponding air requirements. The understanding of these variables is of prime importance to those concerned with the technical and economic development of in situ combustion as an oil-recovery process. The experimental results show conclusively that the fuel available for in situ combustion is not a constant but, rather, varies with crude-oil characteristics, porous-medium type, oil saturation, air flux and time-temperature relationships. Thus, the fuel availability for specified field applications should be determined using actual reservoir crude and core material and the process conditions expected during in situ combustion in the reservoir. INTRODUCTION In situ combustion is a thermal process for recovering crude oil from reservoirs. The thermal energy released during the combustion of a small amount of the oil in place aids in the displacement of the remaining oil. Numerous articles have been published describing the in situ combustion process giving detailed results of laboratory and field experiments.10 In order to engineer an in situ combustion project, a number of important factors must be considered and determined. These factors include: (1) the amount of fuel consumed per unit of reservoir volume swept by the combustion zone, (2) the composition of the fuel consumed, (3) the amount of air required to consume this fuel, (4) the portion of the reservoir swept by the combustion zone, (5) the appropriate air-injection rates and pressures, (6) the amount of oil that will be recovered, (7) the rate of oil production and (8) the operating costs. Nelson and McNiell1 recently have described a procedure which utilizes laboratory combustion-tube data as a basis for the calculation of some of these design factors. Various authors have attempted to describe the in situ combustion process mathematically, and considerable progress has been made. Analytical solutions to the problem of heat transfer from a moving combustion front have been obtained for linear and radial systems."-' All of the published results involve the assumptions that: (1) fuel concentration is constant throughout the reservoir, or that fuel concentration is inversely proportional to the velocity of the front for a given rate of oxygen consumption; and (2) the fuel reacts instantaneously with injected oxygen, while liberating a constant amount of heat per unit weight of fuel at all temperatures. It seems both desirable and reasonable to test the validity of these assumptions experimentally. This paper presents laboratory data which were obtained by means of a "fire flood-pot" method for determining fuel availability and composition, and the corresponding theoretical air requirements for in situ combustion of crude oils under variable conditions. The mechanics of the method are similar to a conventional tube-run experiment.' The important differences involve the size of the reservoir model used and the method for providing the experimental environment. The new method subjects conventionally-sized core samples or unconsolidated sands to a programmed environmental sequence similar to that experienced by a similar volume of rock during the approach and passage of a combustion front in a long tube or in an oil reservoir undergoing in situ combustion. Restored-state samples can also be used. The small samples and relatively simple techniques involved allow an experiment to be set up, run and calculated in about three 8-hour days. This is a considerable improvement over long-combustion-tube techniques which can require several days to run and several more work days to set up and calculate. All the runs presented were run at 40-psig injection pressure. Pressure was not considered as a variable for these experiments, since we previously had found that it had only a small effect on fuel availability up to 600 psig.APPARATUS AND MATERIALS APPARATUS The fire flood-pot apparatus consists of a consolidated

By Chas. F. Jackson

IN these days the headlines and spotlight have been focused largely upon the new processes developed and new plants erected to meet the multiplied demands for mineral products required for prosecution of the war. By comparison, the less spectacular achievements of the miner, who is meeting the demand for raw material without which these processes and plants would be useless, have received little attention. Attendance at the mining meetings here reported was small, averaging about 35 to 40, but interest was as keen as ever, and evidenced to your reporter that the miner is no less on the job than is the metallurgist. It is evident that the mine operators are not neglecting any improved methods and practices in their struggle to produce more in the face of diminishing labor supply.

Jan 1, 1943