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By Stephan I. Zajac, Roger A. Blais, John B. Stubbins

THE iron deposits of central Labrador occur within a relatively small area, herein called the Knob Lake Iron Range, in which a northwest-trending series of low hills and ridges defines the height-of-land at the boundary between provinces of Quebec and Newfound-land. Approximately two-thirds of the deposits are in Quebec and the remainder in Labrador, with several deposits straddling the inter-provincial boundary. These deposits are being exploited in open-pit mines by the Iron Ore Company of Canada centered at Schefferville, Quebec. Since 1954 this company has produced more than 56 million tons of iron ore to become Canada's leading iron ore producer. With indicated reserves of more than 375 million tons of direct-shipping ore and large tonnages of iron formation amenable to beneficiation, this mining district is assured of a long life. This paper describes the Knob Lake iron ores and their geological settings and stresses the features that lead to a better understanding of their origin. The

Jan 1, 1961

By N. J. Grant, Masao Adachi

A number of Cu-SiO, and Cu-A1203 alloys of low oxide content, produced by internal oxidation of copper-silicon and copper-aluminum dilute solid solutions, were exposed at temperatures up to 1050°C for fairly long times to bring about partial or total re crystallization. The creep-rupture properties of these re crystallized alloys were compared to those in the as-extruded condition at 450° C. Some of the alloys were cold worked after re crystallization to note changes in creep-rupture properties, also at 450OC. SINCE the introduction of the SAP alloy in 1949,~ many studies have been carried out on similar oxide and intermetallic dispersion hardened alloys to determine properties and to establish the mechanisms involved in the strengthening process which led to stable, high-temperature behavior.'-' To date, it has been indicated that, however achieved, the structure should be composed of a continuous ductile metal matrix in which is dispersed a fine, submicron size, hard, insoluble second phase (or at least, essentially insoluble at temperatures very near the melting point), with a submicron or near submicron interparticle spacing. Stored energy, obtained by a high strain rate deformation process appears desirable, as an additional strengthening means beyond pure dispersion.=

Jan 1, 1961

By J. A. Boyle

In the Frick District of U, So Steel Corporation, we have had more than 37 years of experience in the use of multiple-fan ventilation systems, in our coal mines. In our Colonial field, with a long belt installation, we have mined 85 million tons of coal with the use of the multiple fan system of ventilation. In our Palmer field, with the use of the same arrangement, we have mined 90 million tons of coal--a total of 175 million tons without one accident attributable to improper mine ventilation. The same system, fundamentally, has been installed in our expanding Robena operations and at its present stage of development we are using eight fans to ventilate this area. To date we have mined 55 million tons of coal with very encouraging results and again without any accidents attributable to ventilation.

Jan 1, 1961

By James Westfield

Following is a brief resume of the Division's activities that have had a favorable effect on health, safety, and the reduction of injuries at coal mines: 1. The Federal Mine Safety Code for Bituminous Coal and Lignite Mines of the United States was issued originally by the Director of the Bureau of Mines on July 24, 1946, after consulting with management and labor representatives of the coal-mining industry. The code has been used by Federal coal-mine inspectors while inspecting bituminous-coal and lignite mines as a basis for determining the existence of unhealthful and unsafe conditions and practices in these mines. A revised code was issued by the Secretary of the Interior on October 8, 1953, after further consultations with representatives of management and mine workers and was incorporated by reference in the 1952 and subsequent bituminous-coal wage agreements. The agreement of May 29, 1946, between the Secretary of the Interior, acting as Coal Mines Administrator under authority of Executive Order 9728, and the United Mine Workers of America, covering bituminous-coal and lignite mines in Government possession, charged Federal coal-mine inspectors with the responsibility of making periodic investigations of the mines and reporting to the Coal Mines Administrator any violations of the Federal Mine Safety Code. Federal coal-mine inspectors also had temporary authority to close mines found to be imminently dangerous, but such authority under Executive Order 9728 was removed on June 30, 1947, when Government control of the mines was terminated.

Jan 1, 1961

By A. W. Ruff

In the last ten years large gains have been made in the field of blasting. These gains have been both in the theoretical and in the practical application of explosives. One of the most publicized changes in the practical application of commercial explosives is the now-prevalent use of ammonium nitrate and fuel oil. The new water-compatible mixture of ammonium nitrate and TNT should also have a large field of application. Most of the theoretical gains have been concerned with the actual rock breakage obtained with explosives. In the last ten years, large gains have been made in the field of blasting. These gains have been both in the theoretical and in the practical application of explosives. One of the most publicized changes in the practical application of commercial explosives is the now prevalent use of ammonium nitrate and fuel oil. The new water-compatible mixture of ammonium nitrate and TNT should also have a large field of application. Most of the theoretical gains have been concerned with the actual rock breakage obtained with explosives. EXPANDING-GAS-BUBBLE THEORY There has been an outstanding change in the conception of how an explosive produces rock failure. The early theory which explained rock breakage was correct for some of the first force-producing agents such as quicklime. When a drillhole was filled with quicklime and water added, the material expanded and steam was generated. The expanding material and the steam exerted a slowly increasing pressure on the sides of the drillhole. The force broke the rock by splitting. Because a great quantity of gas was produced by the deflagration of gunpowder, the same process of the gas pressure splitting the rock was assumed to take place. Even after 80 years of use, the rock-breaking action of all high explosives was thought to be caused entirely by the expanding gas bubble which tore and split the rock. Fig. 1 shows a vertical section through an exploding spherical charge of high explosive. It illustrates the early theory which attributed the entire breakage to the expanding gas bubble. The basic idea of this theory is that the breakage started at the explosive charge and progressed toward the free face. REFLECTED-WAVE THEORY me expanding-gas- bubble theory has gradually been replaced by the reflected-wave theory. The reflected-wave theory explains rock failure by explosives in the following manner: The enormously high gas pressure in the drillhole produces fracturing of the rock on the sides of the drillhole. The fracturing around a 1 1/2-in. diam drillhole is usually confined to an area with about a 6-in. diam. In the fractured area, the pressure of the gas is reduced until the force on the walls is no longer capable of fracturing the rock. Although the gas pressure does not continue to fracture the rock, the pressure imposes a high impact stress on the wall rock. In addition, a pressure or seismic pulse is produced in the rock. The pulse is probably entirely a compression pulse when originally produced in the rock. But, with distance, part of the energy of the compression pulse is transformed into a tension pulse which follows the compression pulse. The explosive charges and burdens used in conventional mine blasting are such that the tension pulse of the original wave is probably too small to be considered in a practical evaluation of the theory. The compression pulse is transmitted through the rock with no associated fracturing.

Jan 1, 1961

By R. W. Lewis

The Federal Bureau of Mines Boulder City Metallurgy Research Laboratory conducted experiments in order to develop a spectrochemical method for determining the concentrations of impurities In high-purity tungsten. This report presents a procedure, developed by these experiments, for determining 19 impurities in high-purity tungsten. Metal samples were thermally converted to the oxide, mixed with graphite, which was prepared and mixed with an internal-standard element, and excited in a d.c. arc. Sixteen of the impurity elements were determined with one set of conditions, using germanium as an internal standard. Lanthanum was used as an internal standard in the tests for boron and chromium. Molybdenum required the substitution of sodium chloride for the graphite and the use of copper electrodes. Data on the precision of the method are included in this report. The coefficients of variation vary considerably but average about 15 percent. Higher concentrations of impurities than those investigated may be determined with some modifications of the testing procedure, provided attention is given to the possibility of interelement interferences.

Jan 1, 1961

By W. M. Dressel

The objective of the research reported in this publication of the Federal Bureau of Mines was to devise a mineral dressing procedure that would concentrate zinc silicate minerals from certain deposits in southwestern Missouri. The best flotation results were obtained by batch laboratory flotation using sulfidizing agents and ethoxylated cocoamine. The flotation concentrate contained 70 percent of the zinc at a grade of 47.8 percent. Gravity concentration tests showed that 55 percent of the zinc could be recovered at a grade of 48.3 percent.

Jan 1, 1961

By Robert K. Koch

The reactions of alumina and alumina monohydrate with wet hydrogen fluoride gas were studied by the Federal Bureau of Mines to determine the feasibility of producing commercial-grade aluminum fluoride from offgases generated by pyrohydrolysis of siliceous fluorspars. The test results showed than an aluminum fluoride reactor operating at maximum efficiency could retain 96 percent of the fluorine contained in off-gases generated by pyrohydrolysis of siliceous fluorspar. The requirements are a reactor temperature of 200° C. and a reactor entrance gas containing 5 mole-percent hydrogen fluoride. Partial pressure equilibrium constants were determined for the reaction of alumina monohydrate and wet hydrogen fluoride gas from 200° to 350° C. and for the reaction of alumina and wet hydrogen fluoride gas from 350° to 700° C. Both reactions are reversible, and they proceed in directions that are dependent upon the temperature and the relative HF:H2O concentration. Logarithms of the equilibrium constants were used to plot the reaction isobars; these can be used to calculate the theoretical maximum efficiency of a reactor processing wet hydrogen fluoride gas between 200° and 700° C. The theoretical maximum efficiency decreases with increasing temperature.

Jan 1, 1961

By D. Bienstock

In connection with air-pollution studies, the Bureau of Mines is cooperating with the U.S. Public Health Service in investigating the use of solids for removing sulfur dioxide in concentrations of less than 0.5 percent from combustion and waste gases. Removal of sulfur dioxide at flue-gas tempera¬tures would no longer result in the cooling of scrubbed gas, which is inherent to liquid scrubbing processes used exclusively in industry today. Results are reported of extensive investigation, using metallic oxides as absorbents, adsorbents, and oxidation catalysts at 130° and 330° C. (temperatures at which flue gas may be treated in powerplant practice). The most active absorbents tested were the oxides of manganese, cobalt, copper, and alkalized alumina; 23 to 33 grams of sulfur dioxidn were removed by 100 grams of absorbent at 130° C., while scrubbing more than 90 percent of the sulfur dioxide from a simulated flue gas, and 19 to 61 grams of sulfur dioxide were removed at 330° C. A more detailed study is reported on absorption and regeneration, using manganese oxides and alkalized alumina. Adsorption of sulfur dioxide on activated carbons and molecular sieves at elevated temperatures is considerably less efficient than removal by absorption--a maximum of 7 to 8 grams of sulfur dioxide could be removed with 100 grams of adsorbent at 130° C. A potash-promoted vanadium pentoxide is effective in converting sulfur dioxide to trioxide; complete conversion in a simulated flue gas containing 0.35 percent sulfur dioxide was obtained at 365° C. Pilot-plant and cost studies are being made by the Bureau to determine the economic feasibility of removing on an industrial scale the sulfur dioxide present in gases in low concentrations.

Jan 1, 1961

By C. E. Westley, R. R. Beebe

Recent works by Plaksh et al.,1,2 Glembotsky,3 and others have renewed interest in the effects of oxidation on the surface activity of the sulfides. Since considerable supporting data are available on galena-potassium ethyl xanthate, this system is being studied at South Dakota School of Mines and Technology by contact angle measurement, using the technique of McGlashan and McLeod.4 The contact-angle method is well adapted to investigation of the influence of small amounts of oxygen on the establishment of a stable contact angle on galena in potassium ethyl xanthate solution. Samples of massive galena containing less than 0.001 pct Cu, 0.001 pct Ag, and 0.01 pct Zn are mounted in castable plastic and ground and polished manually in a glove box containing the desired proportions of oxygen and purified nitrogen. Oxygen and nitrogen contents of the test atmosphere are determined with an Orsatt analyzer. In this way a reproducible surface is created in contact with whatever oxygen concentration is desired. Water and all reagents are prepared and stored in the test atmosphere. An absorbent is used to control carbon dioxide that might be present. Final polishing is done with levigated alumina on a glass plate. The prepared sample is placed in the test solution and transferred to the contact angle apparatus in a sealed box, and the test is conducted while both sample and solution are maintained under a slight positive pressure of the test atmosphere. Table I gives the results of contact angle measurements made at various 02-Nz concentrations.5 Each value of contact angle is the average of at least six individual measurements made with different bubbles at different locations on the sample surface. A period of 20 to 25 min has been found by preliminary tests to be sufficient to permit develop- ment of maximum angle, and all measurements are made after at least this much time has elapsed. Exposure of prepared samples to pure water under the test atmosphere before exposure to the xanthate results in a small but measureable and consistent reduction in contact angle. This is particularly true in the oxygen-deficient atmospheres; for example, at 2.2 pct O2 such water contact reduces the average angle about 8" from that obtained by immediate testing in xanthate. The general trend of increasing contact angle with increasing oxygen concentration corresponds to the results of Plaksin et a12 The absence of diminish-ment of contact angle at very high oxygen concentration has been attributed to the high concentration of xanthate per unit of galena surface: At oxygen concentrations below 1 pct (the limit of accuracy of the Orsatt analyzer), no contact angle is obtained. Furthermore, no contact angle is obtained at any oxygen concentration in the absence of xanthate. This result seems to be in disagreement with those cited by Plaksin.1 Further work on the interaction of galena and potassium ethyl xanthate or a similar collector as influenced by oxygen is contemplated. The true nature of the interrelation is as yet unknown. For example, it is not known whether the governing oxygen reaction is with the mineral, with the reagent, or with both.

Jan 1, 1961

By LeRoy Kienitz

There may be someone here who is not required to run his equipment at its maximum capacity. There may be some fortunate enough to have more crushers than needed, wider conveyor belts than required, and other mill equipment equally oversize. If so, then this paper will have no interest for him; but if most of you are in the situation we in the aggregate producing industry are in, then you probably wish to crowd your mill equipment to its limit. When you do this you must watch for block-up and overloads of all sorts. You need more eyes than you have to guard the critical points. The human eyes that now do nothing much, but watch should be freed for more productive work.

Jan 1, 1961

By A. R. Troiano, E. A. Steigerwald, F. W. Schaller

The initiation of localized cracking in hydrogenated high strength steel was dependent on the developmeni of a critical hydrogen conceniration and relatively insensitive to the magnitude of the applied stress. The stress was believed to influence the deluyed failure process by providing the means for grouping the hydrogen. On the basis of an assumed distribution law the observed changes in the lower critical stress as a function of notch acuity, yield strength, and temperature were predictable over a significant range of these variables. THE phenomenological characteristics of delayed failure in high-strength steel have been comprehensively investigated and the behavior has been attributed to the strong embrittling action of hydrogen.1-3 Delayed failure or, as it is also termed, static fatigue, is the most sensitive means of detecting hydrogen embrittlement since it allows the maximum time for hydrogen diffusion during a test.3 The nature of delayed failure cail be aptly described by four parameters which are schematically depicted in Fig. 1. The upper critical stress corresponds to the rupture stress in a conventional notch tensile test. The lower critical stress or static fatigue limit is the stress below which no delayed failure will occur. The incubation period is the time required for the formation of the first crack and the fourth parameter is the failure time. An increase in hydrogen content, notch acuity, or strength level of the material increases the susceptibility for delayed failure by decreasing the lower critical stress, the incubation period, and the time to failure.lY3 A decrease in test temperature prolongs the incubation period in accordance with the lower diffusion rate of hydrogen, and also de-

Jan 1, 1961

By W. R. Huff

This report describes the development and operation by the Bureau of Mines of a pilot plant designed for using high-volatile A bituminous coal-in-water suspensions as a source of preheated coal and superheated steam in the pressure gasification of coal with oxygen. Figure 1 on page 2 is a block diagram of the integrated gasification process, in which a total of 70 tons of coal was fed from slurry and gasified. The present work included (1) development of equipment and methods both for mixing pulverized coal and water to produce slurry and for pumping and metering the slurry at gasification pressure; (2) development of equipment for heating the flowing slurry and, because slurry that can be pumped produces more steam than is necessary as a gasification reactant, developing equipment for removing and metering the excess steam; and (3) demonstration of the process under actual gasifier operating conditions, at a coal rate of about 800 pounds per hour and gasification pressures in the range 100 to 300 pounds per square inch gage. By using the forced-convection principle, a flow of slurry made from a caking, high-volatile A bituminous coal can be continuously heated to 600° F. in a coil-type heater. The flow rate and concentration of the slurry and the temperature gradient along the length of the heating coil must be closely controlled. In a radiant-type heater, involuntary reductions in flow rate, even momentary, can lead to coking and plugging of the heater coil.

Jan 1, 1961

By Abdul-Fattah K. Kaddou, P. C. Rosenthal

THE authors have studied the problem of temper brittleness in steel1 employing an internal friction method. The specimens are in the form of wire, 14 B and S gage (0.064 in diam), 6 in. long. It was very desirable to have an apparatus to test the wire specimens for temper brittleness without making standard notched-bar Izod or Charpy impact tests. Such a device would have two favorable advantages: the first is that no standard impact specimen would be necessary, thus saving time and labor; the second is that there would be a direct correlation with internal friction results, thus eliminating the size factor if standard impact specimens had to be used. A search was made without result to find a commercial apparatus for this purpose. The literature was surveyed to investigate if such a test had been utilized. No such work has been reported in the literature; however, zapffe2 has described an apparatus used for testing for hydrogen embrittlement in

Jan 1, 1961

By Arden D. Fugate

The Federal Bureau of Mines conducted extensive studies on solid-state defluorination (laboratory scale) and tests on molten defluorination (intermediate scale) of siliceous fluorspars. The studies were made to develop a pyrohydrolytic process for liberating fluorine from offgrade fluorspars. Test results showed that more than 90 percent of the fluorine can be evolved by solid-state defluorination at 1,300° C., and more than 97 percent can be liberated by molten-state defluorination at 1,420° C. Solid-state defluorination conditions were established by conducting tests on mixtures of ceramic-grade fluorspars and high-purity silica flour. Pelletized mixtures were defluorinated under varying conditions of time, temperature, and relative concentrations of silica, calcium fluoride, and water. The effects of adding various amounts and combinations of aluminum oxide and iron oxide on defluorination were also studied. Investigations of solid-state defluorination indicates that the following two reactions are involved: 2CaF2 + 3SiO2 = 2CaSiO3 + SiF4, and CaF2 + Sio2 + H20 = CaSiO3 + 2HF, The second reaction is dominant, although significant defluorination can be achieved by the first reaction.

Jan 1, 1961

By P. L. Allsman

A method of analyzing blasting action indicates that major cost savings are possible by revising practice and bringing the classical blasting formulas up to date; difficult problems such as taconite and throw-breakup can be attacked by engineering Denonation pressure — the peak pressure developed by the explosive reaction; "shatter blasting." Average detonation pressure — the average pressure over the time the reaction continues; "heave blasting." Radial presswe — the stress in a radially expanding sphere about the detonation. Corresponds to the diminishing peak pressure. Lateral stress - the stress in a circumferential direction, induced by outward movement of the rock away from the detonation. Limiting stress or Slim— the rock property at which failure will occur in the case at hand; may be tensile or compressive strength, or combinations. Recent developments in explosives technology, following the advent of nuclear explosions, have led to a rather complete understanding of their action. A survey was made for the purpose of uncovering any knowledge which might be applicable in the mining and quarrying industries, the principal users of explosives. Although no revolutionary techniques have become apparent, much basic data pertaining to blasting — fortunately not classified — have been developed by recent research, from which a good general understanding of the process can be derived. It is hoped this explanation of the scientific principles governing explosive action, together with a proposed analysis of blasting practice, will further the development of mining engineering. NATURE OF THE REACTION: The phenomenon of explosion, termed detonation, is in reality a rather complex chemical reaction, and as such is completely explainable by physical and chemical laws. Detonation is characterized by high temperature and pressure, extreme rapidity — often being complete within one microsecond — and most importantly by formation of a shock pulse which accompanies the reaction zone. As with any chemical reaction, there is a critical value of temperature and pressure below which detonation can not occur; this is termed the "critical point". Whereas an explosive substance will decompose slowly at ordinary temperature, with the formation of gases which readily dissipate; at elevated temperature the reaction is considerably speeded. If pressure is suddenly applied at some point in an explosive medium, adiabatic compression results, and the temperature is locally raised. When the temperature becomes high enough the decomposition will be so rapid that the gaseous products do not have time to dissipate, but contribute to a further build-up of pressure. This, in turn, furthers adiabatic temperature rise over a widening area, and with any heat generated by an exothermic reaction, causes a rapid increase in temperature. Both temperature and pressure are spontaneously built up in this manner until the critical point is reached, resulting in detonation. The values of pressure and temperature necessary to create detonation are established by the unusual nature of the process. If temperature alone is raised above the critical point, without sufficient increase in pressure, deflagration or "low-order detonation" occurs. In the true, or "high-order detonation", the shock pulse resulting from the violent decomposition becomes an integral part of the reaction, and itself aids in increasing the detonation

Jan 1, 1961

[Admissions: Aurel E. Smith, Chairman Edmond F. Egan Lawrence S. Fennell John S. Fuller Howard J. Ritts, Jr. Gene E. Roark Kenneth W. Robbins Ben M. Gottlieb Advertising: Bernard F. Klein, Chairman Henry N. Lyle R. E. Howard H. M. Krause, Jr. Mrs. Evelyn R. Robertson]

Jan 1, 1961

By Malcolm Heyburn

Airborne and ground magnetic surveys were made over and in the vicinity of the Sanford Hill ore body at Tahawus, Essex County, New York. These geophysical surveys served to: l. delineate, lithologic and structural features associated with the ore bodies; 2. indicate a major extension of the Sanford Hill ore body; and 3. guide a drilling program to prove this extension. The titaniferous magnetite ore body at Sanford Hill is associated with gabbro occurring in anorthosite. The contrast in the magnetic susceptibilities of these rock types, reflected in the magnetic measurements, allows geologic-mapping showing rock types and inferred structural features. The anomalous magnetic high of the airborne magnetometer survey indicated a southern extension of the Sanford Hill ore body. Diamond drilling, guided by the airborne and specifically the ground magnetic results, substantiated this interpreted ore extension to be of major magnitude.

Jan 1, 1961

By M. Kaufman, A. E. Palty

THE mechanical properties of an alloy under given test conditions are in the main determined by the grain size and the phases present, their distribution and temperature-time dependence. Alloys intended for use at elevated temperatures, especially multiphase alloys depending upon precipitation reactions for strengthening, are particularly susceptible to changes in the phases present. Unfortunately, for modern superalloys, very little published information exists which relates the mechanical properties to the basic structural variables. The present work is an effort to do this for an alloy widely used in aircraft gas turbines and related applications, Udimet 500.* The mechanical properties inves- two heats is within the normal specifications for the alloy. However, the elements which most strongly influence the phase reactions, C, Ti, Al, and Mo, are comparable in the two heats. There was no intentional addition of boron, but normal pickup is about 0.002 pct. The vacuum-melted material was received in the form of centerless ground wrought bar stock % in. diam. PHASE STUDIES A) Methods—Two methods were used to determine the phases present: X-ray diffraction measurements on electrolytically digested residues, and microscopic examination. No single commonly used electrolyte will reveal all the phases that may be present; therefore, two complementary acids were selected: HCl and H3PO4. The necessity for this will be shown below in the results. The acid concentrations used were 10 pct HC1 in alcohol and 10 pct H3 PO4 in water. The current density was maintained below 0.1 amp per sq in. Residues were rinsed and separated by centrifuga-tion. X-ray diffraction patterns were obtained in a 114 mm Debye-Scherrer type camera using cobalt radiation. A temperature of 2250°F was selected to obtain as complete solutioning of phases as possible without encountering incipient melting. Specimens were

Jan 1, 1961

The preeipitation of dissolved lead from a strong brine by metallic iron is a chemically controlled, first order reaction. The precipitation rate is sensitive to changes in chloride concentration and temperature. The precipitation of dissolved silver is a diffusion controlled, first order reaction. The precipitation rate is insensitive to changes in chloride concentration and temperature.INTRODUCTIONLead and silver sulphates can be extracted from electrolytic zinc plant tailings, or residues, by leaching with strong brine solutions, the lead and silver going into solution as complex chlorides. One of the methods which can then be used to recover the dissolved lead and silver is to precipitate them with metallic iron. The deposition reactions which take place are of the type Pb++ Fe - Fe++ Pb............ (a)To fit such a method of precipitation successfully into a practical flowsheet it is necessary to have some knowledge of the kinetics of the various reactions, Le. to know how the precipitation rates vary with temperature, brine and metal concentrations, and so on. Reaction rates are also needed to design suitable precipitation vessels. However, when examining the possibility of using a brine leaching process to extract the lead and silver from the residue produced at the Risdon plant of the Electrolytic Zinc Co. of Australasia, it was found that, although the use of metallic iron to recover lead and silver from the pregnant brine had been reported by Ralston (1924) and by TrumbulI, Hardiek and Lawford (1948), very little was known about the precipitation reactions. Consequently a laboratory investigation was undertaken, and this paper covers those aspects considered to be...

Jan 1, 1961