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By H. M. Howe, E. C. Groesbeck

Fig. 1 shows a volute aging break which developed spontaneously in a hardened and tempered steel helmet between 19 and 38 days after it had been tested ballistically. A similar break, shown in Fig. 2, developed spontaneously in a similar helmet about 40 days after the ballistic testing. In this case the rupture occurred abruptly and with a loud report. The path of rupture in this second case, though much the less regular, is the more interesting of the two, in that it is an approximation to two parallel volutes centered at the point of impact of the projectile, just below D. Several weeks later, after the photograph for Fig. 1 was taken, a similar doubling of the volute crack occurred in this helmet, starting from the end of the eyelash crack near A and spreading thence to the left contra-clockwise for about 1/2 in. The negatives from which these pictures are made have not been touched up in any way, save writing the letters on them. In both cases the trajectory of the bullet was normal to the initial surface at the point of impact, and in both the helmet passed the ballistic test without detectable cracking, under a velocity of impact not far below that which usually causes perforation. The initial surface itself was very nearly spherical throughout the region covered by the break.

Jan 1, 1920

By M. Semchyshen, G. A. Timmons

P. A. Beck (University of Illinois, Urbana, 111.)—An interesting result of this work is the fact that in cold rolled molybdenum sheet complete loss of work hardening is obtainable on annealing, without change in texture. The retainment of the cross-rolling texture on soft-annealing is particularly significant, since this is essentially a single orientation texture, where texture retainment could be achieved by only one of the two niechanisms which produce this effect in aluminum,16 namely by recrystallization in situ. Recrystallization in situ was originally discovered by Collins and Mathewson (1940) and by Crussard (1944) as a phenomenon taking place on annealing in relatively mildly deformed single crystals of aluminum. It now appears to be a major (in many cases the major) mechanism of annealing of severely cold rolled poly-crystalline material, not only in aluminum,le but in metals as different in character as beryllium," tita- nium,'" and molybdenum. All these data now confirm the general validity, at least for more or less pure metals, of the interpretation of the annealing process given a few years ago by Smith.'" The whole question of recrystallization is now reopened. Indeed, it appears that recrystallization, as defined traditionally, may not occur at all, since at the time "deformed material" is absorbed by "recrystallized grains," it has already become completely strain free by recovery and "recrystallization in situ."

Jan 1, 1953

By Edward L. Clark, Garrett A. Muilenburg

THE first record of the discovery of iron ore in Missouri was Marquette's observation in 1673 of brown iron ore, or limonite, in the Mississippi River bluffs just north of the mouth of Apple Creek in southeastern Perry County. There is no record of any attempt to mine or smelt Missouri iron ores until 1815, when the Ashebran furnace was erected at the Stouts Creek shut-in near Arcadia, Iron County. Some limonite was treated in this furnace, the first iron furnace west of Ohio, but most of the ore was hematite from Shepherd Mountain and adjacent deposits. Eight years later, in 1823, the Perry furnace five miles north of Caledonia, Washington County, was constructed to smelt limonite ore. It was not until 1890 to 1900, however, that these ores attracted considerable attention. Nearly 300,000 tons had been produced by 1911, and this production had come from 24 counties in the Ozark region. For the next two decades, until 1931, essentially all activities ceased. During the depression years of the thirties when employment was low many people turned to the brown ores for subsistence; consequently production was increased. World War II produced another stimulus to the industry. The availability of risk capital in the past three years has revived interest in these deposits, although no appreciable increase in production has resulted.

Jan 1, 1954

By J. Intrater, E. S. Machlin

In a study of grain boundary sliding in superpure Copper (99.999 pct),&apos; bicrystals of a specific shape were used, Fig. 1. That shape was adopted in order to minimize the deformation of grains on both sides of the boundary due to clamping. Another requirement was to obtain bicrystals with a rnicroscopically straight boundary, Fig. 2. Single crystals of predetermined orientation (growth axis parallel to <310>) were grown in a graphite mold from seed crystals. The apparatus for growing single crystals consisted of a vacuum system, argon purification train, vycor tube (in which a graphite mold was placed), a carriage for the induction coi1,and a Lepel (7-1/2 KW) high-frequency converter. The graphite mold was heated by induction and the charge in turn was heated by conduction. The induction coil was moved by means of a motor at a speed of 1 1/2 in. per hr. Single crystals of two different orientations were grown from the melt in one-half of a split graphite mold, Fig. 3(a). Two such crystals were then placed in contact with each other in another split mold, Fig. 3(b) using tapered inserts. The pair of crystals was then remelted starting 2 in. from the top to insure that the whole top portion of the crystals was maintained molten. By moving the induction coil

Jan 1, 1960

By C. K. Leith, W. J. Mead

One of the most significant developments in the iron industry in recent years has been the discovery and opening of enormous reserves of low-grade ore in eastern and northeastern Cuba. The two principal fields are the Mayari and the Moa, situated on Nipe bag, in the Province of Oriente. A less well-known district of the same type is that of Baracoa, at the east of the island, and another is in Csmaguey Province in central Cuba. In the comprehensive estimates of the iron-ore reserves of the world, published during the summer of 1910 by the International Geological Congress in Sweden,&apos; these Cuban deposits are estimated at about 2,000,000,000 tons. Certain it is that the reserve is a large one. The Spanish-American Iron Co., the Juragua Iron Co. (Bethlehem Steel Co.), the U. S. Steel Corporation, and others have been active in this exploration. The Spanish-American Iron Co. has established a port for the handling of these ores at Felton, has built a railway 16 miles to the ore-fields, and has operied up deposits for steam-shovel mining. Its expenditures have reached an aggregate of about $6,000,000 in preparation for the handling of these ores. Shipment of the ore to Sparrow&apos;s Point, Md., has begun and may be expected to rise to a considerable amount in the near future.

Jan 1, 1912

By T. H. Courtney, G. W. Pearsall, J. Wulff

The mechanism, of the decrease in transition temperature of Nb3Sn was studied. Presintered Nb3Sn powder compacts were heated in a dynamic vacuum at elevated temperatures. Loss of tin resulted from these heat treatments and transition temperature as a function of tin loss was discontinuous at a critical value of tin loss. In general, decreases in transition temperature were correlated with deviations from AS a class, the A15 structure-type (also known as Cr3O or ß W) compounds have the highest superconducting transition temperatures.&apos; In this class are stoichiometry and presence of vacancies in niobium sites. The effect of vacancy distribution on the physical properties of Nh3Sn is considered. It is concluded that the close-packed atomic A chain in the A3B A15 structure must be preserved both in coutinuity and direction if good superconducting properties are to he obtained. tempting to associate these high transition temperatures with the most unique crystallographic feature of the A3B structure: the three close-packed, orthogonal chains of A atoms.&apos;0"&apos; There are at least three principal mechanisms by which the perfection of these "A-atom chains" could be interrupted: changing stoichiometry, inducing disorder, or introducing vacancies. Departures from stoichiometry in either direction in V3Ga lower the transition temperature.7&apos;8 In niobium-

Jan 1, 1965

By J. J. Scott

During 1967 wage settlements and strikes ran at a high rate and it has been estimated that union gains of 4 ½ % to 5% per year have been attained in many instances. When these events are coupled with the need to operate on lower grade and deeper deposits the need for technological advances in underground mining becomes obvious. Emphasis has been on ways to reduce the number of manshifts required per ton of product. Most significant advances have been made in rapid advance of primary mine openings, development of mobile, rubber-tired, front-end loaders and hauling units, high-speed drilling with rotary and rotary percussive units and a serious look at nuclear devices to break large volumes of ore cheaply. Boring Developments in bit manufacture and metallurgy have allowed continuous boring-type machines to be used on harder formations than was deemed feasible in the past. Hecla Mining Co. has been using raise boring equipment for drilling 9 7/8 in. diam pilot holes in raises which are later reamed in an upward direction to 48 in. diam. The machine used is a J. S. Robbins model 42R raise borer which has been used successfully to drill two relatively long 48-in. diam holes. The first was 520 ft in length at a dip of 76º, and the second was a 785-ft vertical hole.

Jan 2, 1968

By T. R. Wright

THE Corporation operates concentrators in four camps: Casapalca. Morococha, Cerro de Pa-co, and Mahr. The present concentrator at Cerro de Pasco is the newest having been completed in 1943. and that at Casapalca the oldest, having been built originally as a gravity concentrator, in 1889. Prior to 1925 the Corporation&apos;s milling operations were confined to the beneficiation of silver-bearing copper ores, and treatment of these ore: by flotation was started in 1918. Although fairly large deposits of complex, fine-grained lead-zinc ores existed, little progress had been made in the treatment of such ores--in Peru or elsewhere-until the early &apos;twentics. The Casapalca concentrator began the selettive concentration of complex leadzinc ores by all-flotation methods in 1925, or contemporaneously with the commercial development of selective lead-zinc flotation in the United State:.

Jan 1, 1945

By J. Fred Johnson

MORE ORE is mined in the Bingham District than in any other mining district in Utah. In addition to the open-pit operations of the Utah Copper Co., there have been, many large underground mines. Until recent years the principal production was from the Jordan and Commercial limestones, but in the last eight years valuable ore deposits have been developed in the so-called alphabetical or "A," "B," "C," and "D" limestones, mainly by the U. S. Smelting, Refining & Mining Co. The value of these developments has led the company just mentioned to acquire large holdings in the district and within the last year to install at the Niagara shaft a hoist capable of going to a vertical depth of 4000 ft., or 1800 ft. deeper than the present lowest level. Ore from Bingham has been the chief factor in enabling the

Jan 1, 1934

By Nelson Severinghaus

THIS Rock Chapel plant of Consolidated Quarries Corporation (Fig. 1) is three miles northeast of Lithonia, DeKalb County, Georgia. It was opened about eight years ago for crushed stone aggregate. This paper reviews a number of experiments that have been tried in drilling and blasting, and gives the practice in use today. It also present, several theories on the action of explosives in this type of blasting. [ ] The rock worked is a bare dome of granite gneiss about 3000 ft. in diameter, rising 150 ft. above the surrounding ground (Fig. 2). It is uniform in composition and quality, without seams, and extends downward to unknown depth below the quarry floor. A water well drilled 600 ft. remained in the same rock. The principal difficulty encountered in blasting is an easy split, which tends to break clown the rock in large blocks.

Jan 1, 1938

By J. D. Hunt, D. T. J. Hurle

A uariety of eutectic structures are formed in faceted/nonfaceted eutectics. The various structures are explained in terms of the absence or presence of small facets in the liquid groove. Regular structures are produced when, for purely geometric reasons facels cannot form. The presence of a facet in the liquid groove leads to the formation of an irregular or a cell-like complex regular structure, due to the relative immobility of the groove. A classification of eutectics was proposed by Hunt and jackson, based on the presence or absence of facets on the primary phases (the absence of facets may be predicted from the dimensionless entropy of melting2). Eutectics were divided into three groups: 1) eutectics in which both phases grow in a nonfaceted manner; 2) eutectics in which one phase grows faceted, the other nonfaceted; 3) eutectics in which both phases grow faceted. It was suggested that regular1 rodlike or lamellar structures1 should be formed in the first group, that irregular or complex regular structures1 should be formed in the&apos; second, and that irregular structures1 should be formed in the third. Recently it has been shown that the structural classification is incomplete. Regular rodlike structures (InSb-NiSb eutectic3), or broken lamellar structure (Bi-Zn eutectic, Fig. 8), are formed in alloys of the second group when the faceted phase has a large volume fraction. Hunt and jackson&apos; argued that regular structures could form in faceted/nonfaceted systems, but that such structures would be unstable in the presence of microfacets on the lamella of the faceting phase, because the growth rate at a point on such a facet would depend on the kinetic undercooling at the point of nu-cleation on the facet, and not on the local kinetic undercooling. In these circumstances it would not be possible to consistently balance the compositional and kinetic undercooling over a lamellar structure and thus obtain a stable isothermal interface. In this paper we discuss in detail the origin of the various structures formed in faceted/nonfaceted systems, pointing out that the most important factor promoting the formation of a regular structure is the absence of a facet in the liquid groove. 1) FACET FORMATION IN SINGLE-PHASE MATERIALS Facets form when there is an energy barrier for the addition of a new solid layer on an existing solid. When a barrier is present,2 growth proceeds by the lateral movement of steps across a crystallographic plane. The rate-controlling stage of the process occurs when the step is first formed. Hulme and Mullin6 have shown that faceting in single-phase materials can only occur when both interface curvatures are convex with respect to the solid and when the surface is tangential to the facet plane. When even one of the curvatures is concave a facet does not form because new layers of solid from adjacent regions can always feed the facet plane, Fig. 1. Growth under these conditions is then as easy as elsewhere. Similar considerations will apply to eutectic growth; consequently the shape of the faceted phase is extremely important. 2) LAMELLAR SPACING CHANGES IN EUTECTICS Jackson and Hunt7 have shown that the interface undercooling AT of a growing lamellar interface (neglecting kinetic undercooling) is related to the lamellar spacing, A, and growth velocity, v, by an expression of the form: where m, Ql, and nL are constants of the system given in Ref. 7. Eq. [I] is plotted for fixed v in Fig. 2. Jackson and Hunt postulate that a regular eutectic grows near, but to the right of the minimum in the AT vs A curve. They argue that the spacing cannot be to the left of the minimum because the interface is then unstable to fluctuations in A. It cannot grow too far to the right, because when the spacing becomes too wide an isothermal interface can no longer be maintained over the large-volume-fraction phase.7 It is argued that during any change in growth rate the lamellar spacing remains in the permitted range by the movement of lamellar faults. When the spacing is too wide, the fault, shown in Fig. 3, moves to the left; when the spacing is too narrow it moves to the right. The faults, however, have to be formed. heir formation has been shown to occur when local regions deviate considerably from the spacing defined by the lamellar When the spacing is locally too narrow (it passes to the left of the minimum, Fig. 2), pinching off of the narrow phase occurs. When the spacing is locally too wide, the interface on the large volume-fraction phase can no longer be maintained as an iso-

Jan 1, 1969

By A. H. Daane, A. S. Wilson

The U-Cr system is of the simple eutectic type with some solid solubility of chromium in r and ß uranium. The eutectic occurs at 20 atomic pet Cr and melts at 859°C. The maximum solubility of chromium in y uranium is 4 atomic pet at the eutectic temperature, and in ß uranium the solubility is estimated to be 1 atomic pet. y-ß and ß-a transformations were found to occur at 737°estimatedt° and 612°C respectively. DURING 1944 and 1945, the U-Cr constitution diagram was studied in this laboratory as a part of a research program on uranium metallurgy in the Manhattan Project, and the work was described in a Manhattan Project report issued in December 1945. This paper is based on that report, which has been declassified. Prior to this study, it had been shown by other Manhattan Project workers that the low Cr-U alloys could be quenched to retain the form of uranium. Experimental The uranium used in this work was massive metal prepared in this laboratory and contained less than 0.1 pct of other elements. The chromium was 200 mesh powder obtained from the A. D. McKay Co. and was found on analysis to be 99.5 pct Cr with 0.3 pct Fe the major impurity. Alloys, weighing 400 to 600 g, were prepared by induction heating the components to 1700°C in slip-cast ZrO, crucibles in a vacuum of 3x103 mm Hg. TO prevent too violent agitation of the melt by the induction field with subsequent crucible breakage and sample loss, the ZrO2 crucible was placed in a graphite crucible, which was surrounded by a layer of powdered carbon insulation 2 to 3 cm thick. Polished vertical sections of the alloys were examined microscopically to confirm their homogeneity. Heating and cooling curves were taken on the alloys by reheating them in ZrO, crucibles to 1200°C and inserting a mullite-protected chromel-alumel thermocouple into the melt by means of a slip seal in the vacuum head of the furnace. A recording potentiometer traced the curves which had a slope of from 3" to 6" per min. Samples of the alloys were prepared for metallo-graphic examination by conventional mechanical polishing techniques followed by an electrolytic polish in an ethylene glycol-phosphoric acid-ethyl alcohol bath. The structure of the alloys was brought out clearly by this procedure so that no further etching was required. Samples for chemical analysis were taken from drillings from the top, center, and bottom sections of the alloys. The uranium was determined by titra-tion with Ce(SO1)2, while the chromium was titrated with FeSO,; the uranium and chromium totaled at least 99.6 pct in all of the alloys prepared. X-ray samples were prepared by filing bulk specimens in a helium-filled glove box and annealing the resulting powder in a zirconium-gettered helium atmosphere. A 114.6 mm diam Debye-Scherrer camera and a Weyland nonsymmetrical self-focusing camera were used with filtered copper radiation to obtain the powder X-ray diffraction data. Results The data obtained in this study have been combined to construct the constitution diagram of the U-Cr system shown in Fig. 1 where the arrests observed in cooling curves are indicated by dots. The liquidus arrest was quite distinct in thermal data taken on alloys in the range 0 to 20 atomic pct Cr. The eutectic arrest was not observed in studies on the 2.5 and 4.5 pct Cr samples but appeared in the 7.5 pct samples, which suggested some solubility of chromium in y uranium. On quenching from 859 °C, the 2.5 pct sample showed but one phase while the 4.5 pct sample contained a small amount of the eutectic along the grain boundaries; see Figs. 2 and 3. From this the maximum solubility of chromium in r uranium has been set at 4 pct. X-ray studies on these samples showed that the r phase was not retained at room temperature by quenching, but in each case a pattern was observed .which has been identified with the ß phase of uranium. Thermal data show the y-ß transformation of uranium lowered to 737°C as a consequence of this solubility. On quenching from the ß range (660°C), precipitation of chromium in the primary uranium is observed in the 2.5 and 4.5 pct Cr samples (see Figs. 4 and 5),

Jan 1, 1956

By Warren W. Jamar, Philip D. Pearson

IN recent years, there have been many changes in mining operations in the Lake Superior district. To follow these trends on the Menominee Range of Michigan, information has been assembled from all of the iron informatior]mining operations in the area. There are 15 operating underground mines in the Iron River-Crystal Falls area of the Menominee Range. Within the past two years, two idle properties were reopened pasttwoyears,and are now producing, and a third and fourth are being reopened. Also, there are two siliceous openpits operated by independent companies outside this immediate area. Six companies operate the underground mines, employing some 1850 employees. Table I shows pertinent facts about these properties. During 1949, the largest mine in Iron County shipped 571,287 tons, and one of the newer mines shipped 39,378 tons, with a range total to 3,535,-373 tons. Since the Menominee Range was opened in the 1870&apos;s, the mines in Iron County have shipped 85,890,922 tons. From an operator&apos;s viewpoint rather than a geologist&apos;s, the ore is&apos; classified as semi-hard, composed of hematite and limonite. It is not as soft as the ores of the Marquette Range nor is it as hard as the hard ores of the Marquette and Vermillion Ranges. The ore bodies have slate hanging walls and slate footwalls. In most cases the hanging walls and footwalls are soft and high in sulphur. The sulphur comes from pyrite, and these slates will ignite when piled more than 6 to 8 ft high. Ore is mined on this range by: 1—Sub-level stop-ing; 2—Shrinkage stoping; 3—Sub-level caving; 4— Block caving; 5—Top slicing. The predominance of these methods is in the order named. Underground drilling is important in the mining cycle. Some changes made and trends toward future changes fall into four categories: Drill bits, drill steel, drill machines, and compressed air pressures. Several types of bits have been tried and are in use. They include the detachable tungsten carbide, insert bit; the intraset steel bit, which is a conventional steel rod with tungsten carbide insert; the one-use bit; and the multiple-use bit. For many years, detachable multiple-use bits have been standard. In tests conducted recently to im- prove drilling efficiency, this bit was used as the basis for comparison. Under existing conditions, a multiple-use bit can be resharpened about three times before it is discarded. A thorough test of 2-in. tungsten carbide threaded bits was conducted under various ground conditions. 1—The drilled footage ranged from 48 to 600 ft per bit; averaging 357 ft per bit. Under these same conditions, a multiple-use bit ranged from 8 to 80 ft per bit. 2—The bit cost was greater for the insert bit in each case. 3—The average drilling speed for the insert bit was 12 in. in 62 sec and for the multiple-use bit was 12 in. in 64 sec. In a second test, 2V4 -in. tungsten carbide bits with the large 1 3/16-in. thread were used in moderately soft ground on a 152-lb drifting drill on a long feed jumbo. 1—The drilled footage ranged from 450 to 5000 ft per bit, averaging 1810 ft per bit. Under these same conditions, a multiple-use bit averaged 64 ft per bit. 2—The bit cost was reduced by the use of the insert bit. 3—No increase in drilling speed was recorded. 4—Minimum footage obtained was caused by thread failure. To improve the thread life, thread size on the rod was increased and the bit was attached to the rod with a pipe wrench. After this, bits failed in equal proportions because of cracked skirts, broken inserts, and gage loss. Tungsten carbide bits are now used in the operation where this second test was conducted because labor costs were lowered as a result of reducing the number of bits being changed by the miners. At the same operation and under the same conditions as the second test, 1Y4-in. insert bits with standard 1-in. threads were used. These bits did not drill much more than 300 ft before thread failure and were then welded to the rods and used until total failure. Sometimes this footage was considerable, sometimes it was not. Chisel-type 2%-in. insert bits were

Jan 1, 1952

By A. L. Mincher, W. F. Sheely

Mechanical properties of columbium have been studied over the temperature range of -196 to 1093oC. The decreased strengthening influence of cold-work at temperatures below ambient has been interpreted in terms of the Peierls-Nabarro effect. Maxima in the rate of strain hardening observed during tensile testing in the range 250-600°C. have been correlated with interstitial impurities to indicate the temperature ranges at which carbon, oxygen, and nitrogen, respectively, are responsible for strain aging. THE growing need for structural materials for use above the useful service temperatures of the iron-, nickel-, or cobalt-base alloys has caused the refractory metals to be considered as potential engineering materials. These metals, which include columbium, tantalum, molybdenum, and tungsten, are called refractory because the lowest melting point among them,that of columbium, is about 1000°C higher than the average melting temperatures of conventional high-temperature alloys. They are all body-centered cubic transition metals and, as such, their mechanical properties have basic characteristics which distinguish them from the face-centered cubic metals. For example, all show a much steeper rise in strength with decreasing temperature below room temperature than do the face-centered cubic metals, and their mechanical properties are strongly influenced by interstitially dissolved impurities. In order that these new metals may be used efficiently, it is necessary that their characteristics of behavior be fully known. In this paper, the mechanical properties of columbium will be examined over a wide range of temperatures. In particular, the influences of cold-work and individual species of interstitial impurity atoms on mechanical properties will be described, and basic mechanisms which may control the observed characteristics will be explored. EXPERIMENTAL The material used in this investigation was Union Carbide Metals Co. columbium roundels consolidated to four 4-in. diam ingots, three by consumable-electrode arc melting and one ingot by electron beam melting. Impurity contents of the ingots and methods of ingot conversion and treatment are summarized in Table I. The only metallic impurity occurring in any significant quantity was tantalum at about 0.1 pct. Iron, silicon, titanium, and zirconium were each less than 0.015 pct; boron was 1 ppm or less. This should have no appreciable influence on properties. The electron beam melted material, being the purest, will be used as the basis for comparison in the discussions to follow. Tensile tests were conducted from-196 to 1093oC, on both cold-worked and fully recrystallized arc-melted and electron-beam melted columbium using standard 1/4-in. diam, 1-in. long gage length test specimens. A strain-rate of 0.005 in. per in. per min was employed until the 0.2 pct yield strength was achieved and then the strain-rate was increased to 0.05 in. per in. per min for the balance of the test. Samples were protected in an inert atmosphere at tests above 300°C. The tensile properties obtained on the electron-beam melted columbium, E, in both the cold-swaged and recrystallized conditions are given in Fig. 1. The yield strength data of Dyson, et al.,&apos; obtained on recrystallized electron beam melted columbium and the tensile strength data reported by Tottle2 on powder metallurgy columbium are included in Fig. 1. The material used by Tottle had been purified by vacuum sintering. There is excellent agreement between Dyson&apos;s data and those obtained in the present investigation. The tensile strengths obtained by Tottle were slightly greater than those obtained in this investigation on electron-beam melted columbium but varied with temperature in a similar manner. Tottle&apos;s data showed a maximum in tensile strength near 500°C, as did our data on electron-beam melted material, and also showed a small maximum at 300°C. The significance of these maxima will become evident later in the discussion. The tensile properties of cold-swaged and recrys-tallized arc melted columbium are plotted in Fig. 2. It was found that the properties of the recrystallized arc-melted columbium from all three heats showed very close agreement except at temperatures between about 500" and 800°C. A reason for this range of disagreement will be suggested in the discussion. The generally good agreement, however, attests to the ability of cold-working and subsequent recrystal-lization to erase the effects of the three different primary breakdown procedures and to produce nearly equivalent structures in the samples derived from the three different heats. wesse13 reported tensile data on columbium having interstitial impurity contents between those of the

Jan 1, 1962

By Ira A. Stark

Use of clay-working machinery in the metallurgical industry is by no means new. Extrusion- agglomeration as a basic operation in the non-ferrous field has a history of more than 50 years. This article advocates using the technique in the ferrous field where it might serve a useful purpose in today&apos;s operations. Many of the processes involved in production of iron ores result in fine powders, with a considerable percentage running finer than 200 mesh. In many instances, mining and related processing operations are located far from furnace operations. Shipping the powdered ore is impractical since handling losses and furnace losses from dusting would be excessive and powdered material must be agglomerated. The agglomerate must withstand the handling involved in transportation and here the continuous pugmill-extruder can be used to form a strong dense product.

Jan 6, 1959

By Irvin Mayes, Maher E. Tadros

The effects of particle properties and dispersion on the filtration behavior of magnesiumhydroxide, silica, and polystyrene suspensions in aqueous media were examined. It was found that effective separation of particles can be achieved using filter media with larger pore diameters than the size of the particles. The addition of electrolytes, at concentrations lower than the critical coagulation concentration, to suspensions of polystyrene or silica resulted in an increase of the cake resistance. This result was interpreted in terms of a decrease in the effective particle size due to the increase in ionic strength. For magnesium hydroxide, an increase in the absolute value of the surface charge was associated with an increase in cake resistance and a decrease in cake compressibility. Low cake resistance values were obtained with suspensions of large particles with low surface charge and blocky morphology.

Jan 1, 1980

By E. Richard Randolph, Rolland L. Blake, Stanley H. Ward, Gerald J. Anderson

During the last 30 years the inductive electro- magnetic method has been used chiefly in the search for massive sulphide mineralization. This application has met with varying degrees of success and in recent years has resulted in discovery of several large orebodies. Little has been written concerning its use in exploration for soft iron ores, but one of the present authors has reported on experiments with massive magnetic deposits. To augment the exploration tools available to geologists in delineating iron orebodies, Cleveland-Cliffs Iron Co. and McPhar Geophysics Ltd. undertook in 1953 to apply the inductive electromagnetic method to Cleveland-Cliffs properties in the Lake Superior region. As a result of this project, equipment has been developed that enables simultaneous transmission of two audio frequency waves, and the field technique and interpretative procedure involved have furthered exploration in the district significantly.

Nov 1, 1955

By F. F. Aplan, G. Simkovich

Zinc oxide, an n-type semiconductor, and nickel oxide, a p-type semiconductor, were studied in electrostatic separation experiments in pure and doped forms. In addition, pure potassium chloride and potassium chloride containing one volume per cent silver were also investigated. It was found, in agreement with theory, that the presence of dopants in the oxides could either increase or decrease the electrical conductivity of the base compounds and, thus, control the response of these particles to electrostatic separation. Further, it was shown that the same dopant in the n- and p-type semiconductors produced opposite conductivity effects; again in accord with theory. Finally, it was found that the presence of dispersed silver particles in the normally insulator phase potassium chloride produced sufficient electronic conductivity to cause the silver containing particles to respond as would materials possessing "medium-type" conductivities.

Jan 1, 1980

By J. I. Budnick, W. B. Ittner III, D. P. Seraphim

A reliable technique has been developed for producing single crystals of tantalum in the form of small diameter wires. By suitably heat treating these and polycrystal samples, first in an oxygen atmosphere and finally in vacuum, it has been found possible to reduce residual resistivities to 10-3 microhm-cm. The purity of these samples is thus comparable to the purities obtained in zone-refined silver, copper, and aluminum. THE growth and purification of pure single crystals of the transition metals is, in general, difficult. The high melting and annealing temperatures of these metals make it necessary to employ rather special techniques in any crystallization process. In addition, the transition metals show a great affinity for and are easily contaminated by nitrogen, oxygen, and carbon. Recently, however. a number of investigators have been successful in growing,

Jan 1, 1961

By Edward H. Williams

In the middle of the eighteenth century John Frazier and wife, Sarah Ingraham, removed from Boston, Mass., to Philadelphia, Pa., where he was held in such esteem that we find him one of the Committee which arranged the ball at Washington&apos;s inauguration. Their son, John Nalbro Frazier, was prosperous in his mercantile career and fortunate in his wife, Anne West, who was an important personage in the early life of Professor Frazier. This cultured lady brought into the family an atmosphere of religious enthusiasm, of thoroughness and of unity of purpose. Her son, Benjamin West Frazier, inherited her traits and displayed them during a short and active life. Like his father, he engaged in mercantile pursuits, and was a member of the firm of Zimmerman, Frazier & Co. In their interests he lived for a short time in Montevideo, and on

Jan 1, 1906