Search Documents

Albin. B . R Billings. Mont . '28 Amnter . Nathan L 26 Broad St.. New York . N . Y . '28 Bache . Jules S 42 Broadway. New York. N . Y . '28 Borrett . C . P . 5338 Harper Ave .. Chicago. I11 '28 Baum . Frank G. . Cons . Hydro-Electric Engr Camel'. Shasta Co. . Cal. '23 Baylean, William S Russ Bldg .. San Francisco. Cal . '28 Bean, Louis H .. V.P.. Dwight P . Robinson & Co.. lnc 126 E . 46th St New York. N . Y . '28 Beatty . Roes J . 1106 First National Bank' Bldg .. Chicago . Ill . '28 Benwell . Oswald F . 110 Gilpin St .. Denver. 1310 . '28 Beymer. Albert 9.. V.P .. Keystone. National Bank Pittsburgh. Pa . '28

Jan 1, 1929

By V. Patarini, M. Salkind

BECAUSE of its high strength and stiffness coupled with low density, continuous boron filament is showing great promise as a potential reinforcement for both metals and nonmetals. Of primary consideration for structural applications is the fatigue behavior of boron fiber composites. Composite fatigue behavior is dependent upon three factors: 1) fiber fatigue behavior, 2) matrix fatigue behavior, and 3) the effect of the interface and fiber ends. The purpose of this note is to describe the behavior of boron filament in rotating beam fatigue. The filament, described by Talley' and Galasso, Salkind, Kuehl, and Patarini,' was made by the hydrogen reduction of boron trichloride on a hot tungsten filament. Testing was performed using a commercial rotating beam wire fatigue tester* described by Votta.~ One end of the test sample is held in a chuck in a synchronous motor. The sample is bent around in a "U" shape, and the other end inserted into a carbide bushing. The maximum strain occurs at the bottom of the "U" where the radius of curvature is a minimum. The strain is adjusted by adjusting the length of the specimen and the location of the bushing. Samples were rotated at 3600 rpm and an automatic shutoff device used to determine the number of cycles to failure. The measurements were accurate to the nearest 360 cycles. The fatigue behavior is summarized in Fig. 1 for fifty-one samples of 4.8 x 10"3 in. diam fibers and ten samples of 3.2 X 10"3 in. diam fiber. The two sample groups represent two different filament production runs and two different nominal size groups. Both groups exhibited nominal tensile strengths of 400,000 psi. No significant difference in the fatigue behavior of the two sample groups is apparent. The scatter in the data is not unexpected for a brittle filament which exhibits a tensile strength distribution with a standard deviation of 10 to 15 pct. Because the test procedure provides a known outer fiber strain in the sample, the maximum stress was calculated assuming a Young's modulus of 58 x 10' psi. This value was selected as being representative of several nominal fiber sizes.2 All of the samples which failed exhibited sudden, catastrophic fracture, and no permanent deformation. One sample was stopped after 1.66 x lo8 cycles at *200,000 psi. The fiber exhibited no apparent damage or deformation. It is apparent that the fatigue resistance of boron filament is quite good. It can therefore be speculated that the fatigue behavior of boron fiber composites would be controlled by the "weaker links", namely matrix fatigue resistance and interface behavior. In fact, preliminary investigations have revealed that this is true for boron-reinforced aluminum? It should be noted that the data presented herein may not necessarily reflect the tensile fatigue behavior of boron filament. It is well-known that boron filament has a radial residual stress pattern with the outer surface in ~om~ression.~ Because of this fact, tensile failure is normally nucleated in the interior of the filament.5 Since the data presented herein is for a rotating beam test in which only the outer surface of the fiber is stressed to the maximum value, it would be incorrect to assume that the failure mechanism and fatigue behavior would be the same if the fiber were tested in tensile fatigue. The fact that many of the data are well above the nominal 400,000 psi tensile strength would tend to support this argument. The authors would like to express their appreciation to the United Aircraft Research Laboratories for supporting this investigation and for permission to publish the results. A portion of this effort was supported by the Air Force Materials Laboratory under contract AF33(615)-2125.

Jan 1, 1968

By J. W. Onuscheck

The oxygen-fuel oil burner lance is a very useful tool at the Monessen B.O.F. It increases the overall flexibility of the operation. An additional 15,000 to 20,000 ingot tons can be produced at a given hot metal supply. It helps overcome sporadic drops in hot metal thermal values and/or supply. It results in increased yield, in particular, on high carbon heats where much yield was lost on reblow triggered slag reactions. The burner has also been adopted as a standard tool to aid burning in new vessel linings. Overall, steelmaking performance has improved with the use of standard preheat practice. Scrap charges up to 50 percent have been used routinely in times of extreme hot metal shortages, but the performance is weak in some categories. Development of a single step oxy-oil process is in progress. In this process, scrap and hot metal are charged as in the normal B.O.F. practice, but fuel oil is fired with the refining oxygen.

Jan 1, 1972

By J. H. Polhems, R. B. Brackin, D. B. Grove

THE heavy media separation process plays an outstanding role in the concentration of 4000 tons of zinc ore per day at the Mascot mill of the American Zinc Co. of Tennessee. Of the total tonnage, 72 pct is treated in the heavy media separation plant to reject 56 pct of the ore as a coarse tailing, which has a ready market. Concentrates from this separation are beneficiated further by jigging and flotation. Approximately 25 pct of the total zinc concentrate production is made in the jig mill. Jig tailings are ground and pumped to the flotation circuit where the balance of the production is made. Fig. 1 shows a generalized flowsheet of the mill. The Mascot ore is a lead-free, honey-colored sphalerite in dolomitic limestone, with lesser amounts of chert and some pyrite. A mineralogical analysis is given in Table I. After 10 years of successful operation with galena medium and treatment of nearly 10,000,000 tons of ore, a decision to convert to ferrosilicon was made early in 1948 because of the increasing price of galena and consequent high operating costs. The conversion was made on Nov. 6, 1948, and the results obtained since that time have shown remarkable improvement over those made with galena. The Table I. Mineralogical Analysis of Mill Feed, Pct Calcium carbonate 49.5 Magnesium carbonate 35.2 Iron oxide and aluminum oxide 1.5 Zinc sulphide 4.5 Insoluble 9.3 100.0 Table II. Comparative Data, Galena and Ferrosilicon Ferro- Diner-Gelenaa siliconb ence Operating costs per ton milled, ct. 21.21 9.12 12.09 Medium consumption per ton milled, lb 0.80c 0.15 0.65 Reagent consumption per ton milled, lb 0.45 0.02 0.43 Tailing assay, pct Zn 0.310 0.297 0.013 Concentrate. oct Zn 12.08 10.33 1.75 Heavy medla ieparatlon recovery. pct 89.38 90.22 0.84 Mill feed rate, tons per hr 153 166 13 Heavy mesa separation feed rate. tons per hr 100 10 0 Tons milled per heavy media separation man shift 350 620 270 Mill feed to coarse tailings, pct 51.0 56.7 5.7 Lost mill time, pct 5.6 5.0 0.6 Power consumption, kw-hr per ton 2.06 1.92 0.14 a 1947. " First 6 months of 1950. c Net consumption after deducting credit for reclaimed waste galena. Consumption of new galena was 1.320 lb per ton milled. For entire life of galena operation, a credit of 40 pct of the value of the new galena added was realized from the sale of waste galena. comparisons given in this report cover the first 6 months of 1950 as representing the ferrosilicon operation, and the year 1947 as representing the galena operation. This was the last full year in which galena was used exclusively and is representative of the best work done during the 10 years of operation with this medium. After only 2 years' operating experience, with ferrosilicon and treatment of 1,807,585 tons many advantages have been revealed and are summarized in Table 11. Development Prior to the introduction of the heavy media process, all the mill feed was crushed through 5/8 in. and treated by jigging. A finished tailing assaying 0.66 pct Zn was made on rougher bull jigs, and cleaner jig tailings were ground for treatment by flotation. The first test work on the sink-and-float method of mineral beneficiation was carried out at Mascot in 1935, using a 3-ft cone and galena medium for batch tests. The following year a 6-ft cone was installed for pilot-plant work. This unit became a part of the mill circuit on March 1, 1936, and handled a gradually increasing tonnage in the next 2 years as the process developed to the point where it could treat all the + 3/8-in. material in the mill feed. Coarse jigging was then discontinued on March 1, 1939, and all coarse tailings have been made by the heavy media separation plant since that time. Feed Preparation: The original feed preparation plant consisted of a drag washer followed by two 4x10-ft Allis-Chalmers washing screens. A surge bin and two additional 5x12-ft AC washing screens were added in 1943. Use of primary and secondary washing screens was found essential to provide the cleanest possible feed for the cone and thereby avoid excessive contamination of the galena medium. Improved washing was obtained by replacing the drag washer with a 7x20-ft Allis-Chalmers scrubber, shown in Fig. 2, which has been in service since May 1944. Throughout the life of the galena operation, delivery of extremely muddy ore to the mill overloaded the medium cleaning system, and it frequently was necessary to cut off the feed and clean the medium for several hours until its normal viscosity had been re-established. The cleaning circuit

Jan 1, 1952

By D. M. McFarland

A FEW years ago a novel electric detonator known as the split-second or millisecond delay electric blasting cap was introduced for use in quarry blasting. Regular electric blasting caps fired in series may be depended upon to fire within a millisecond or so from the first to the last in a series. Regular delay electric blasting caps are provided that fire one period after the other period in intervals of 1/2 to possibly 1 1/2 sec. Most split-second or millisecond delays are designed to fire one period after the other period in possibly 25 to 50 millisecond intervals. The ear is not capable of detecting time intervals of this magnitude. The primary thought at the time millisecond de- lays were introduced was to investigate the results on rock breakage by firing a line of holes in a quarry face.so that charges in adjacent holes would not be detonated simultaneously. This could not be accomplished satisfactorily with regular delays. The time interval between successive periods of $5 to 1 sec was sufficient to permit considerable movement of the burden. If the burden of one hole was reduced to a great extent by the firing of an adjacent hole, the firing of the hole with the reduced burden would likely reveal this lack of confinement by a terrific report and wild throw of rock.

Jan 1, 1950

By S. G. Valentine

BLAST-FURNACE blowing engines are broadly of two main types: either steam- or gas-driven reciprocating engines, or turbine-driven rotary engines. Some results of experience with a furnace blown by an engine of the latter type may be of sufficient general interest to relate. The first engine of this type was installed at Oxford Furnace, New Jersey, before the writer's connection with this plant, in March, 1910. This furnace uses chiefly New Jersey magnetites and had been in blast seven months on its old engines when the turbo blower was started. It was 80 ft. high by 17 ft. 6 in. bosh and 11 ft. hearth diameter. It is of interest to see from the records what happened when the turbo engine was put to work. But of course, as the old blowing equipment was rather antiquated, consisting of two I. P. Morris engines with air cylinders 72 by 72 in., in good running order, however, it is evident that the comparison between their work and that of the turbo blower cannot be interpreted as being between machines that were respectively of equal excellence as representatives of their types. Still the results were gratifying and -interesting. The records show that, with the old engines blowing 13,630 cu. ft: of air per minute, measured by piston displacement, the furnace was working up about 480 tons of stock per 24 hr. and producing an average of 132 tons per day and a maximum of 166 tons. The rotary blowing engine installed was a General Electric Co. machine, the driving end being a Curtis steam turbine and the air end a six-stage rotary compressor, all running at about 1,500 to 1,600 rev. per minute, and having a capacity of 25,000 cu. ft. of air per minute up to 25 lb. pressure, and equipped with an automatic constant-volume variable-speed governor. After running this blower, for a period equal to that covered above by the old engines, at an average rate of 15,000 cu. ft. of air per minute, the furnace worked up an average of about 592 tons of material and produced an average of 170 tons per day. Thus, on an apparent increase of 10 per cent. in the air volume there was an increase of about 23.5 per cent. in the materials worked up and of about 28.8 per cent. in the product. For the first calendar month's operation of the turbo blower, on an average of 15,040 cu. ft of air per minute, there is

Jan 2, 1914

By O. D. Gonzalez, R. A. Oriani

The migration of hydrogen and of deuterium dissolved in a iron and in nickel induced by an applied electrical potential has been measured over a range of temperature. In all cases the intevstitial solute migrates to the cathode. The deduced charges of transport are positive, independent of or slightly dependent on temperature, and markedly larger for the beavier mass. These results are interpreted as showing predominating momenlum transfer between electron holes and the acticated complex of the elementary diffusion act. THE migration of components of a metallic system under the action of an applied electrical potential is called electromigration or electratransport. This phenomenon has been known since 1861 and is becoming of increasing interest to metal scientists because of the opportunity it offers to explore the connections between mass transport and electron transport. Until recently, reliable data have been very scarce because of the difficulties inherent in the measurements. In addition, theoretical understanding has been either nonexistent or rudimentary and at present this situation is only moderately improved. Whereas the prevalent notion had been (and is still widely held) that electromigration directly reflects the state of ionization of a component in its equilibrium state in the metal, it is now becoming clear that the major, if not the sole, factor is the momentum transfer between the charge carriers, themselves in motion because of the applied field, and the metallic components in their activated state. It becomes important therefore to obtain reliable data over a range of temperature on electrornigration in systems where only one component moves, that is, either in pure metals (vacancy motion) or in interstitial solid solutions. Our choice of systems was dictated by our measurements' of the Soret effect in solid solutions of hydrogen and deuterium in iron and nickel. Indeed, the main reason for making measurements on electromigration at all is that we suspected a mechanistic connection between thermal diffusion and electromigration. In our former paper' we proposed that what is common to both phenomena is the momentum transfer between the charge carriers in the metal and the atom as it jumps from one equilibrium position to another. In Soret diffusion, however, there is in addition the dissipation of the energy of the jumping atom via pho-nons. We have since found that similar ideas for this interconnection have been developed by Fiks.2 In the present paper we will discuss in more detail our understanding of the mechanism of electromigration itself, but we turn first to a presentation of the experiments and results. EXPERIMENTS AND RESULTS Let us consider a metallic system in which only one component, m , can diffuse at the temperature in question, and to which are applied simultaneously an electrical potential gradient, grad cp, and a chemical potential gradient, grad p,. One may write3 for the material flux Jm and the electronic charge flux Je by applying the condition, grad = 0, to Eq. [I] and evaluating grad(um/T) for the isothermal case and for activity coefficient independent of composition over the relevant composition range. ere, c is the concentration and D the diffusivity of the mobile component. The experimental technique that we have used to measure Z* for the isotopes of hydrogen individually dissolved in each of two transition metals has been developed from a method used by Wagner and Heller.4 (A somewhat similar method was also used by Herold.5) A wire or thin rod of the metal under study connects two volumes of gaseous hydrogen at identical pressures; hence grad um = 0. A direct current is made to pass through the specimen, serving to maintain the specimen at the desired temperature and also to produce the electromigration of the hydrogen dissolved in the metal in equilibrium with the gaseous hydrogen. Under these conditions, the flux of hydrogen from one volume to the other is given, from Eq. [I] for grad( um/T) =0by

Jan 1, 1968

By Paul Billingsley

THE development of the North Lily ground, which lies in the East Tintic district, Utah,. about half a mile northwest of the famous Tintic Standard mine, was undertaken by the International Smelting Co. on purely geological reasoning. The geologic theory on which this work was based resulted from several years' intensive study of the East Tintic district by the geological department of the International Smelt-ing Co., who were, during this period, indebted to many for valuable suggestions that were adopted and became part, of the gradually maturing concept. For example, E. J. Raddatz, president of the Tintic Standard Mining Co., first called attention to the significance of rhyolite alteration; J. W. Wade, assistant manager, contributed greatly to our knowledge of the great Tintic Standard orebodies; and so on all along. the line. In short, the ultimate theory embodies the aggregate experience and thought of all those most familiar with the area in question. The problem in brief was this: is the Tintic Standard deposit an isolated occurrence of ore, or are other ore deposits to be found in the vicinity? If the latter is the case, where can these others be looked for? The difficulty of the problem lay in the fact that most of the area is covered by rhyolite; beneath which lies the limestone in which the orebodies occur; so that the available evidence as to the structure of the formations, and, their mineralization; is of the slightest. The sav-ing features of the case, by means of which it proved possible to solve the problem, are three in number first, the rhyolite is pre-mineral and hence has been exposed to alteration by the mineralizing agencies; second, certain persistent dikes and fissures are con-tinuous through the rhyolite into the limestone below; and third, the extensive underground workings of the Tintic Standard gave a good basis for study of the sub-rhyolite structure and the occurrence of ore. The rhyolite overlies the Tintic Standard orebodies, and over them shows a large patch of brownish altera-tion. This patch proves to be due to chloritization and sericitization, which has spread out from certain zones of dikes, pebble-dikes and fissures. The dikes are com-posed of a light fine-grained rock which has been altered to an aggregate of quartz, alunite, and magnetite. They can be traced southwest to a common center in Big Hill, the entire mass of which is composed of the same material. The pebble-dikes, which consist of a mass of rounded pebbles, mainly quartzite, in a matrix ranging from the same quartz-alunite-magnetite rock as above to almost pure vein quartz, are closely asso-ciated with these light dikes, but in general extend farther northeast. They thus represent a specialized phase of the intrusive action of which Big Hill is the center. The brown chloritized rhyolite, then, is an alteration product due, in all. probability, to emana-tions closely associated with this phase. Since it coin-cides geographically with the Tintic Standard area of highly altered limestone, with its many great ore-bodies, it has been concluded, that it is the expression in the rhyolite of activities which have also altered and mineralized' the underlying limestone.

Jan 4, 1927

By R. H. Oliver

The purposes, types, preparation, and testing of flocculants are discussed. A flocculation compendium is included, indicating choice of flocculant for a given set of conditions. An economic evaluation of the process is presented. Solid-liquid separation is a major expense in most mineral processing flowsheets today. Proper use of flocculation can often lower the overall cost of a solid-liquid separation by reducing the size of sedimentation or filtration equipment. PURPOSE OF FLOCCULATION When is use of a flocculant justified in terms of overall process economy? 1) when it results in process improvement, such as producing a clear liquor for electrolysis, precipitation, ion exchange, or solvent extraction; 2) when it results in satisfying requirements of pollution abatement ordinances; 3) when it results in increased recovery of values that would otherwise be lost; or 4) when it results in considerable savings in capital expenditure due to use of smaller equipment. When can the use of a flocculant adversely effect overall process economy? 1) when it results in increased filter cake moisture, 2) when it results in decreased filtration rates, 3) when it results in considerable bulking of sedimentation underflow, 4) when it contaminates either the supernatant or sludge, or 5) when the cost of using the flocculant is greater than the savings due to its use. First step in consideration of flocculants for a given application is establishment of desired goals in terms of increased clarity of effluent, increased recovery of solids, or decreased size of equipment. The most economical solution to a solid-liquid separation problem is that combination of equipment and flocculant costs which meets the established goals at the lowest total annual expenditure. This economic decision can be made only after technical data has been obtained as outlined in next four sections. TYPES OF FLOCCULATION Flocculation is a process wherein individual particles are united into more or less tightly bound agglomerates or flocs, thereby increasing effective particle size of solids suspended in a liquid. Degree of flocculation of a suspension of finely divided solids in a liquid is controlled by a combination of probability of collision between particles and probability of adhesion after the collision has occurred.' Probability of collision can be increased commercially through use of a paddle-type flocculator, combination flocculator, and clarifier or flocculating-type feedwell. Probability of adhesion usually can be increased by addition of a reagent known as a flocculant. Reagents act as flocculants through one or a combination of three possible mechanisms. The first is electrolytic neutralization of inter molecular repulsive force due to Zeta potential. This neutralization enables Van der Waal's cohesive force to hold the particles together after they collide.' The second is the precipitation, within a definite pH range, of voluminous metallic hydroxide flocs which entrap fine particles. This process is known as coagulation.14 Third is the bridging of two or more particles by either natural or synthetic long-chain, high-molecular-weight organic polymers. This bridging is accomplished by adsorption of two particles at different sites on the same molecule or by bonding of two molecules, each adsorbed to a different particle. Considerable effort has been expended in explaining the action of these polyelec-trolytes and detailed accounts are available in the literature. CHOICE OF FLOCCULANTS It is impossible, at the present time, to specify the optimum type or amount of flocculant for a given application from a knowledge of the material to be treated. The standard procedure is to choose reagents or combination of reagents most likely to be effective on the slurry; then test them.' The accompanying Flocculation Compendium (Table I) contains details of all currently available reagents sold as flocculants and it should be used when selecting the group of reagents for tests. This selection can be based on information listed in columns 4 and 5. Column 4 presents industries in which each floc-

Jan 1, 1961

By G. A. Koenig, Moritz Stockder

Locality and Geological Occurrence. The Alpine region of Southwest Colorado, comprising the San Juan and Uncompaghre Mountains, is composed of a deeply eroded sheet of acid eruptive rocks, overlying in part gneissic sehists, and in part limestones and sandstones, including portions of the Silurian, Devonian, and Carboniferous systems. The section is clearly and beautifully exposed along the Uncompaghre River from its headwaters to its exit from the mountains. The river's course from the town of Ouray towards the Los Pinos agency is due north, and four miles from Ouray, in this direction, the Uncompaghre receives from the east the Red Cafion Creek. Following up the narrow caftan we find the section through white.. sandstone in strata dipping to the north and west, and belonging either to the lower or middle Devonian system. Presently the steep cafion-liko character of the ravine gives place to more gentle slopes, and we have entered crystalline rock-porphyry. The contact is well marked, for the sandstone, to a depth of from six to ten feet, resembles quartzite, i. e., is semifused. Ascending still higher, a small

Jan 1, 1881

By Lewis Blanchard Brown

It is my purpose in the following paper to describe the south-central part of Siberia, with special reference to its geology and the mineral deposits. This region is known politically as the Achinsk and Marinsk districts of the Tomsk Government. It is situated among the Altai mountains, in. ]at. 50° to 55O n and long. 87O to 93O E., not far from the northern frontier of Mongolia, and is divided as follows: Mining Districts.—(1) The Tomsk mining district, including the political districts of Altai (belonging to the private crown lands of the Russian Emperor) and Marinsk; (2) the AchinskMinusinsk mining district, including the political districts of Achinsk and Minusinsk; and (3) the North Yenisei mining district, situated in the northern part of the Yenisei political district of the Yenisei Government. Fig. 1 is a map of the Tomsk mining provinces, showing the useful mineral-deposits, excepting those of gold, and giving the routes of the railroads and post-roads connecting the various districts. Political Divisions.—The Tomsk Government is sub-divided into seven " oojesdy " or districts, as follows: Barnaul; Biisk; Kuznetsk; Kainsk; Kolyvan; Marinsk; Narim; and the Altai district (private land, as above). The Yenisei Government is sub-divided into five "oojesdy" or districts, as follows : Erasnojarsk ; Kansk; Yenisei; Achinsk; Minusinsk. Concerning the geology of the region, in addition to the record of my own observations, references will be made to the works of earlier writers. These have been consulted for the purpose of comparison, as regards the districts which I have actually traversed, and for the purpose of completing my account of such portions as I have not been able to visit.

Jan 1, 1904

By C. H. Samans, G. F. Tisinai, J. K. Stanley

The addition of nitrogen (0.10 to 0.20 pct) to Fe-Cr-Ni alloys of simulated commercial purity results in a real displacement of the u phase boundaries to higher chromium contents. The effect is small for the (Y + s)? boundary, but is pronounced for the (y + a +s)/(y + a) boundary. Although there is an indication of an exceptionally large shift of the n boundaries to higher chromium contents, especially in steels with nitrogen over 0.2 pct, the major portion of this apparent shift results from the fact that carbide and nitride precipitation cause "chromium impoverishment" of the matrices. The effect of combined additions of nitrogen and silicon to the Fe-Cr-Ni phase diagram is demonstrated also. Nitrogen can nullify the effect of about 1 pct Si in shifting the (y + o)/? phase boundary to lower values of chromium at all nickel levels from 8 to 20 pct. NItrogen can nullify this U-forming effect of about 2 pct Si at the 8 pct Ni level, but not at the 20 pct Ni level. The alloys studied were in both the cast and the wrought conditions. There are indications that the u phase forms more slowly in the cast alloys than in the wrought alloys if both are in the completely austenitic state. The presence of 6 ferrite in the cast alloys accelerates the formation of U. Cold working increases the rate of o formation in both cast and wrought alloys. THE major improvement in Fe-Cr-Ni austenitic alloys in recent years has been in the addition or removal of minor alloying elements to facilitate better control of corrosion resistance, sensitization, and heat resistance. One shortcoming of the austenitic Fe-Cr-Ni alloys, which never has been completely circumvented, is their propensity toward u formation. In the AISI-type 310 (25 pct Cr-20 pct Ni) and type 309 (25 pct Cr-12 pct Ni) steels, sufficient amounts of u phase can form, if service or treatment is in a suitable temperature range, to cause severe embrittlement. Also, there is a growing conviction that this phase may be contributory to some unexpected decreases in the corrosion resistance of certain of the 18 pct Cr-8 pct Ni-type steels. The present paper discusses the effect of nitrogen additions on the location of the (r+u)/d and the (y+a+u)/(y+a) phase boundaries in the ternary Fe-Cr-Ni system, for cast and wrought alloys of simulated commercial purity, and in similar alloys containing up to about 2.5 pct Si. The objective is to define compositional limits for alloys which will not be susceptible to u formation when used near 1200°F (650°C). An excellent review of the early studies of the u phase in the Fe-Cr-Ni system has been compiled by Foley.1 Rees, Burns, and Cook2 have determined a high purity phase diagram for the ternary system, whereas Nicholson, Samans, and Shortsleeve3 are- stricted themselves to a portion of the simulated commercial-purity phase diagram. Both groups of investigators show almost an identical position for the commercially significant (y+u)/y phase boundary. Further comparison of the work of the two groups indicates that, below the 8 pct Ni level, the commercial alloys have a decidedly greater propensity toward u formation than the high purity alloys. The two groups of workers agreed that both the AISI-type 310 (25 pct Cr-20 pct Ni) and the type 309 (25 pct Cr-12 pct Ni) steels are well within the (y+~) region and that the 18 pct Cr-8 pct Ni-type alloys straddle the U-forming phase boundaries. Nicholson et al.3 showed, in addition, that these boundaries shift toward lower chromium contents if greater than nominal amounts of silicon or molybdenum are added. The effect of nitrogen on the location of the s phase boundaries in the Fe-Cr-Ni system has not been known with any certainty. In 1942, an approach to this problem was made by Krainer and Leoville-Nowak,' but at that time they apparently were unaware of the slow rate of s formation in strain-free samples and aged their samples for insufficient times, e.g., 100 hr at 650°C (1200°F) and 800°C (1470°F). For this reason, it would be expected that their (y+ u) /y boundary would be shifted toward lower chromium contents (restricted ?-field) when equilibrium conditions were approximated more closely. Procedure for Studying the Alloys The alloys used were prepared in the following way: Heats of 200 lb each were melted in an induction furnace. A 5 lb portion of each heat was poured into a ladle containing an aluminum slug for de-

Jan 1, 1955

By Eckley B. Coxe

THE plummet lamp, to which I called the attention of the Institute, at the Bethlehem meeting, in August, 1871, with the improvement of the compensating ring, suggested by Mr. Heller, having come into general use for mine surveying in this country, and my attention having been called to the fact that it could not be employed in mines in which there was danger of meeting with fire-damp, I have so modified it that it can be used in all cases with safety. Mining engineers, who are in active practice in those districts where fire-damp is met with in the mines (and I am sorry to say it is becoming much more common in the anthracite regions), know how dangerous their work is when they are called upon to survey such mines, particularly when they are obliged to run lines in those parts of a mine which have been unworked, since by opening of doors, brattice, etc., to get the sights, they are liable to disarrange the currents of air, and cause any fire-damp that may have accumulated in the old workings to find its way into the levels, etc., where the party is at work. It is, therefore, very dangerous to leave an open light (such as the original form of plummet lamp) in an old breast or gangway, even when the safety lamp has shown that no fire-damp is present, for the opening of the doors, etc., may drive the fire-damp to the light, and thus endanger the lives of the engineers. The improved form of plummet lamp, now shown to you, can be used either with or without the safety apparatus. Upon the top of the plumb-bob portion of the old lamp a screw is cut, upon which a ring A is screwed. (See Plate II.) On the external cylindrical part of this ring two small conical holes are drilled, 180° apart. The compensating ring, by which the plumb-bob part of the lamp is suspended, passes over the ring A, and is fastened to it by two small screws having conical points, which fit into the conical holes in the ring A. The safety apparatus resembles, to a certain extent, that of the Mueseler lamp. It consists of a ring B and plate C, which are united by four rods. The plate C has a cylindrical hole in the middle, and four apertures distributed radially around it. In the central cylindrical hole is fitted a conical brass chimney, which projects below the plate C, and is fastened to the latter, being kept ver-

Jan 1, 1875

[ ]

Jan 1, 1938

By C. A. Heiland

The new geophone described herein was developed by Charles H. Hull, instrumentmaker of the Colorado School of Mines, and the writer. The first geophone was invented during the war for the purpose of detecting enemy sapping or underground mining operations and for locating enemy artillery. It is based on the principle of the seismograph—a heavy lead mass suspended by one or two diaphragms, which are clamped to an air-tight case. When the ground vibrates during the transmission of sound waves, the case moves with it while the so-called steady mass remains practically motionless. Attached to the top of the casing is a hose leading to an earpiece shaped like a stethoscope. When the mass and the diaphragm move up and down in the case, the air is compressed and rarified in the inside; thus the vibration is communicated as sound wave to the human ear. The geophone combines a surprising simplicity of construction with an extreme sensitivity. Other listening instruments were developed during the war, adaptations of the telephone and the microphone—that is, instruments operating through the medium of electricity—of which the so-called seismicrophone, an adaptation of the carbon-granule microphone receiver, probably has found the greatest application, but such instruments apparently have not proved as useful as the simple geophone despite obvious advantages arising from the use of electricity. The carbon receivers were more subject to extraneous noises and to what is called "frying," and they did not offer the advantage possessed by the geophone; namely, the simultaneous use of two receivers, which makes it possible to determine the location of the source of sound. During the war, the U. S. Bureau of Mines made a study of the geophone and of the propagation of sound waves through rock. These studies have been continued, as the earlier results proved the possibility of using the geophone in various non-military ways, principally in mining, and the results of these studies have been published.'

Jan 1, 1932

By J. Leja, J. H. Schulman

FROTH flotation is usually effected by the addition of a collector agent and a frothing agent to an aqueous suspension of suitably comminuted mineral ores. The action of collectors is to adsorb onto the surfaces of minerals to be separated, sensitizing them to bubble adherence. The action of frothers has, in the past, been accepted as that of froth formation only, brought about by a lowering of the air/water interfacial tension. Substances capable of producing froth are classed1a,b according to their relative capacities for production of froth-volume and froth stability in the simple frother-water system. The purpose of this paper is to show that the surface active agents acting as frothers become effective only when there is a suitable degree of molecular interaction taking place between collector molecules and frother molecules at the air/water and solid/ water interfaces. Further, the discussion will demonstrate that the actual mechanism of adherence of an air bubble to a suitably collector-coated particle is due to the molecular interaction collector-frother. This leads to the formation of a continuous interfacial film of associated molecules, anchored to the mineral by polar groups of the collector, and enveloping the whole bubble. The tenacity of adhesion mineral-to-bubble results from the strength and the visco-elasticity of this mixed film.

Jan 2, 1954

By James F. Kemp

(San Francisco Meeting, September, 1915) THE iron ores of southeastern Cuba present a subject of exceptional geological interest. Their relations to the inclosing rocks are varied and in some cases unusual. The problem of their geological origin is not a simple one and for this reason has occasioned some divergence of views among previous observers. Profiting, however, by. these earlier studies and by more detailed field and laboratory observations as well as by the experience of added years of mining, much more satisfactory descriptions and interpretations can now be prepared. PREVIOUS WORK In 1884, interest in the southeastern coast of Cuba became active among the consumers of iron ore along the Atlantic seaboard of the United States. Active development was undertaken by the Juragua Iron Co., Ltd., a corporation affiliated with the Bethlehem Steel Co., and the Pennsylvania Steel Co. The property of the Juragua company, which is situated about 15 miles east of Santiago, was studied in June and July, 1884, by Dr. James P. Kimball, at the tine Professor of Economic Geology in Lehigh University and one of the best known of American mining geologists. Dr. Kimball published on his return two papers, the first important descriptions which we have of the local geology.1 It is

Jan 9, 1915

By S. H. Ward

Since the advent of the first airborne electromagnetic system, it has been evident that such systems were inherently limited to shallow depths of exploration of the orderof 100 to 200 feet. Hence in 1948 the author and his associates commenced a study of the feasibility of applying natural audio frequency magnetic fields to investigation of the electrical properties of the subsurface in order to provide a system capable of overcoming this limitation. This research culminated, in the summer of 1958, in the development of a new airborne prospecting device — AFMAG. This device has detected surface massive sulphide bodies while flown at heights as great as 3000 feet. Hence, by inference, it is deduced that it could find similar sulphide bodies if they were buried 2500 feet below surface and the aircraft flown at 500 feet. Thus a considerable improvement over conventional airborne electro-magnetic systems is obtainable with AFMAG. Airborne exploration in mountainous terrain involving deep valley fill now becomes possible. Examples are presented of the results of actual airborne AFMAG test surveys over known deposits of massive sulphide mineralization. Interpretation of the data is discussed with particular reference to the knowledge of size, dip, depth, depth extent, and conductivity of causative bodies as deduced from the flight records. The possibility of mapping major geologic structures, for both mining and oil exploration purposes, is discussed with the aid of examples of airborne AFMAG data. INTRODUCTION Electrical prospecting with natural audio frequency electromagnetic waves as a source has, within the last three years, become a practical reality. Both airborne and ground survey instruments under the trademark "AFMAG" (for audio frequency magnetics) have been used successfully in the search for conductive mineral deposits. It is the object of this paper to discuss the principles of airborne AFMAG and to illustrate its application by means of examples obtained over known geological situations. WHY AFMAG? In view of the large number of good airborne electromagnetic systems available for purchase or contract surveying, one may well ask, "Why another new system?". Primarily the answer lies in the fact that AFMAG does not suffer from the very limited depth of exploration available with, and inherent in, any conventional airborne electromagnetic system. AFMAG is not conventional insofar as an artificial transmitter is not required. Only a receiving and detecting device is employed. The electromagnetic fields measured are those from millions of electrical discharges in the atmosphere (e.g;..- lightning strokes). Their random distribution in time and space make these fields difficult to employ and it is only with recent advances in the electronics of geophysical instrumentation that this has become possible. A second reason for AFMAG and one of its

Jan 1, 1961

By M. B. Mirza, F. D. Wright

Models of photoelastic material were made to simulate a mine roof that had cracked over the edge of the pillars and at the center of the span. Models were restrained from moving laterally outward so they acted as flat arches. Uniform loading was approximated by loading the models along the bottom at eight points spaced equally along the span. It was found that for models with depth to span ratios of 1:3 to 1:6, the maximum stress at the top of the center crack could be calculated directly by the following formula: Elastic stresses in mine roofs composed of sedimentary beds are usually computed by assuming that the immediate roof bed acts as a fully restrained beam uniformly loaded by its own weight and by overlying strata. Very little work has been done to analyze stresses in roof beds or beams which contain vertical (normal to the span) or nearly vertical cracks. Yet every mining engineer has walked safely under roofs that show such cracks. As far back as 1933, Bucky' made model studies of the effect of vertical cracks on the behavior of horizontal strata. He did not make any analysis of the stresses but did show that a cracked beam will stand safely under certain conditions, and also showed that a beam restrained at the ends can crack over the supports and in the middle without collapsing as long as the ends of the beam are not free to move laterally outward. The beam, or rather, part of the beam, acts like a flat arch and supports itself by pushing outward at its supports. In 1941 Evans2 treated analytically the problem of a beam cracked along so many planes perpendicular to the axis of the beam that no tensile stress can operate. He named this type of beam a "voussoir-beam" by analogy to the voussoir-arch. In 1962 ~a~cocks~ modified Evans's solution by including the effect of the shear stress component of the resultant force at the abutment. This paper gives the results of a photoelastic study of the stresses in a beam containing vertical cracks in the center of the span and over the supports. A

Jan 1, 1963

Jan 1, 1967