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By J. R. Thompson

It is common practice, and certainly good business as all of us know, to take care of plant operating equipment. Machinery of any type requires periodic inspection and planned maintenance. With this thought in mind a plant operator should at the end of every shutdown period make regular belt inspections and plan for later appropriate care and maintenance. The points mentioned below are understood well by all of us but are sometimes forgotten because belt conveyors are comparatively easy to operate. Maintenance of any conveyor belt is dependent upon the fundamental characteristics of the two component parts-cover and carcass.

Jan 6, 1950

By W. M. McKewan

Magnetite pellets were reduced in flowing hydrogen at pressures up to 40 atm over a temperature range of 350° to 500°C. The rate of weight loss of oxygen per unit area of the reaction surface was found to be constant with time at each temperature and pressure. The reaction rate was found to be directly proportional to hydrogen pressure up to 1 atm and to approach a maximum rate at high pressures. The results can be explained by considering the reaction surface to be sparsely occupied by adsorbed hydrogen at low pressures and saturated at high pressures. PREVIOUS investigation1,2 have shown that the reduction of iron oxides in hydrogen is controlled at the reaction interface. Under fixed conditions of temperature, hydrogen pressure, and gas composition, the reduction rate is constant with time, per unit surface area of residual oxide, and is directly proportional to the hydrogen pressure up to one atmosphere. The reduction rate of a sphere of iron oxide can be described3 by the following equation which takes into account the changing reaction surface area: where ro and do are the initial radius and density of the sphere; t is time; R is the fractional reduction; and R, is the reduction rate constant with units mass per area per time. The quantityis actually the fractional thickness of the reduced layer in terms of fractional reduction R. It was found in a previous investigation2 of the reduction of magnetite pellets in H2-H,O-N, mixtures, that the reaction rate was directly proportional to the hydrogen partial pressure up to 1 atm at a constant ratio of water vapor to hydrogen. Water vapor poisoned the oxide surface by an oxidizing reaction and markedly slowed the reduction. The enthalpy of activation was found to be + 13,600 cal per mole. It was also found that the magnetite reduced to meta-stable wüstite before proceeding to iron metal. The following equation was derived from absolute reaction-rate theory4,8 to expfain the experimental data: where Ro is the reduction rate in mg cm-2 min-'; KO contains the conversion units; Ph2 and PH2O are the hydrogen and water vapor partial pressures in atmospheres; Ke is the equilibrium constant for the Fe,O,/FeO equilibrium; Kp is the equilibrium constant for the poisoning reaction of water vapor; L is the total number of active sites; k and h are Boltzmann's and Planck's constants; and AF is the free energy of activation. Tenenbaum zind Joseph5 studied the reduction of iron ore by hydrogen at pressures over 1 atm. They showed that increasing the hydrogen pressure materially increased the rate of reduction. This is in accordance with the work of Diepschlag,6 who found that the rate of reduction of iron ores by either carbon monoxide or hydrogen was much greater at higher pressures. He used pressures as high as 7 atm. In order to further understand the mechanism of the reduction of iron oxide by hydrogen it was decided to study the effect of increasing the hydrogen pressure on rebduction rates of magnetite pellets. EXPERIMENTAL PROCEDURE The dense magnetite pellets used in these experiments were made in the following manner. Reagent-grade ferric oxide was moistened with water and hand-rolled into spherical pellets. The pellets were heated slowly to 550°C in an atmosphere of 10 pct H2-90 pct CO, and held for 1 hr. They were then heated slowly to 1370°C in an atmosphere of 2 pct H2-98 pct CO, then cooled slowly in the same atmosphere. The sintered pellets were crystalline magnetite with an apparent density of about 4.9 gm per cm3. They were about 0.9 cm in diam. The porosity of the pellets, which was discontinuous in nature, was akrout 6 pct. The pellets were suspended from a quartz spring balance in a vertical tube furnace. The equipment is shown in Fig. 1. Essentially the furnace consists of a 12-in. OD stainless steel outer shell and a 3-in. ID inconel inner shell. The kanthal wound 22 in. long, 1 1/2, in. ID alumina reaction tube is inside the inconel inner shell. Prepurified hydrogen sweeps the reaction tube to remove the water vapor formed during the reaction. The hydrogen is static in the rest of the furnace. The sample is placed at the bottom of the furnace in a nickel wire mesh basket suspended by nickel wire from the quartz spring. The furnace is then sealed, evacuated, and refilled with argon several times to remove all traces of oxygen. It is then evacuated, filled with

Jan 1, 1962

By R. H. Gautschi, F. C. Langenberg

Rare-earth additions were made to laboratory heats of Type 310 stainless to observe their effect on as-cast ingot structure, nitrogen and sulfur contents, and nonmetallic inclusions. Lanthanum had a grain-refining effect in 30-lb ingots, but results with 200-lb ingots were inconsistent. Cerium, lanthanum, and misch metal lowered the sulfur content when the sulfur exceeded 0.015 pct and the rare-earth addition was greater than 0.1 pct. The rare-eardh content in the metal dropped very rapidly within the first few minutes after the addition. The size, shape, and distribution of nonmetallic inclusions was not changed in 30-lb ingots, but changes were noticed in larger ingots. RARE-earth* additions have been made to austenitic Cr-Ni and Cr-Mn steels to improve their hot workability. The high alloy content of these steels often results in a considerable resistance to deformation and inherent hot shortness at rolling temperatures, particularly in larger ingots. Rare earths in the metallic, oxide, or halide form are usually added to the steel in the ladle after deoxidation although they can be added in the furnace prior to tap or in the molds during teeming. The literature- indicates that the effects of rare-earth treatments on these stainless steels are not consistent, and sometimes even contradictory. Since no mechanism has been presented which satisfactorily accounts for the claimed improvements, the effects of rare earths are a qualitative matter. The work described in this paper was initiated to expand the knowledge of the effects of rare-earth additions on melting variables such as ingot structure, chemical analysis, and nonmetallic inclusions. REVIEW OF LITERATURE Ingot Structure—Rare-earth additions to stainless steels have been reported to cause a change in primary ingot structure in that there are fewer coarse columnar grains. However, the results are inconsistent. While one investigation1 has shown a large reduction in coarse columnar crystals, another2 has been unable to observe this effect, particularly when small ingots were poured. Post and coworkers3 observed ingot structures for a number of years and found that the columnar type of structure is not definitely a cause of any particular trouble in rolling or hammering, provided the alloy is ductile. Knapp and Bolkcom4 found rare-earth additions to be quite effective in preventing grain coarsening in Type 310 stainless steel. Chemical Analysis—Many effects of rare-earth treatment on chemical analysis have been claimed in the literature. Russell5 observed that some sulfur is removed by rare-earth metals, and that a high initial sulfur content improved the efficiency of sulfur removal. Lillieqvist and Mickelson6 report that rare-earth treatment causes sulfur removal in basic open-hearth furnaces, but not in basic lined induction furnaces. Knapp and Bolkcom found no sulfur removal in acid open-hearth and acid electric furnaces, probably because the acid slag can not retain sul-fides. snellmann7 showed that sulfur could be lowered apprecfably with rare-earth additions; however, a sulfur reversion occurred with time. Langenberg and chipman8 studied the reaction CeS(s) = Ce(in Fe) + S(in Fe), and found the solubilit product [%Ce] [%S] equal to (1.5 + 0.5) X 10-3'at 1600°C. Results in 17 Cr-9 Ni stainless were about the same as those in iron. Beaver2 treated chromium-nickel steels with 0.3 pct misch metal and observed some reduction in the oxygen content. He also noted an inconsistent but beneficial effect of rare earths when tramp elements were present in amounts sufficient to cause difficulty in hot working. It is not known whether rare earths reduce the content of the tramp elements or change the form in which these elements appear in the final structure. No quantitative data are available concerning a possible effect of rare-earth treatment on hydrogen and nitrogen contents. However, Schwartzbart and sheehan9 stated that additions of rare earths had no effect on impact properties when the nitrogen content was low (0.006 pct), but served to counteract the adverse effects of high nitrogen content (0.030 pct) on these properties. Knapp and Bolkcom4 analyzed open-hearth heats in the treated and untreated conditions and found the nitrogen content (0.006 pct) to be unaffected. These two results lead to the speculation that rare-earth additions can reduce the nitrogen content to a certain level. Decker and coworkers10 have observed that small amounts of boron or zirconium, picked up from magnesia or zirconia crucibles, increased high-tem-

Jan 1, 1961

By A. U. Seybolt

The solubility limit of oxygen in columbium has been determined in the range between 775' and 1100°C by means of lattice parameter measurements and microscopic examination. The solubility is a function of temperature and varies, in the range given above, from 0.25 to 1.0 pct O, respectively. BECAUSE of the marked deleterious effect of oxygen upon the mechanical properties of some of the transition metals, it is desirable to know something about the solubility of oxygen in these metals. The brittleness caused by oxygen in solution is particularly marked in the case of the group VA elements, vanadium, columbium, and tantalum. The solubility of oxygen in vanadium has already been reported in an earlier paper,' and Wasilewski2 has given a value (0.9 wt pct) for the solid solubility of oxygen in tantalum at 1050°C. Brauer3 in 1941 investigated the Cb-0 system up to Cb2O5, but made no real effort to investigate the extent of oxygen solubility in the metal. He made the observation, however, that this solubility must be less than 4.76 atom pct (0.86 wt pct) oxygen. This estimate was made from X-ray diffraction results on the alloys CbO, CbO, and CbO; all alloys consisted of the terminal (Cb) solid solution plus CbO, but the last alloy containing 4.76 atom pct 0 showed only three very weak CbO lines. It is surprising that Brauer, by examining only three alloys, arrived at an estimate of the solubility which agrees very well with the results to be reported herein. Experimental Procedure A columbium strip obtained from Fansteel Metallurgical Products was cut into strips, 0.020x1/2x2 in. Two holes, about 3/16 in. in diameter, were made near the ends of the strips in order to hold them against a flat steel block for mounting in a General Electric X-ray spectrometer for lattice parameter measurements. The same holes were used to hang the specimens inside a fused silica vacuum furnace tube which was part of a Sieverts' gas absorption apparatus. The apparatus and method of adding oxygen gas has been previously described.1 According to the supplier, the columbium obtained had the analysis given in Table I. After degreasing the samples, approximately 0.001 in. was etched from each side of the samples in order to remove possible surface impurities from the last rolling operation. For this purpose the following cold acid pickle was found satisfactory: 8 parts HNO3, 2 parts H2O2 and 1 part HF. Various Cb-O compositions were obtained up to 0.75 wt pct O by the gas absorption and diffusion technique. After the sample had absorbed all the oxygen gas added at 1000°C, an additional 24 hr was allowed for homogenization. This treatment appeared to be adequate, as shown by the linearity of the lattice parameter-composition plot. More concentrated alloys were prepared by arc melting mixtures of Cb and Cb2O5 since it was very time-consuming to make Cb-0 alloys in the neighborhood of 1 pct O, or over, by the diffusion method. When the flat strip specimens were used, they were ready for the X-ray spectrometer after cooling from the Sieverts' apparatus. The cooling rate obtained by merely allowing the hot fused silica furnace tube to radiate to the atmosphere (when the furnace was lowered) was sufficiently fast to keep the dissolved oxygen in solution. Arc-melted alloys were reduced to —200 mesh powder in a diamond mortar, wrapped in tantalum foil, sealed off in evacuated fused silica tubes, and then heat treated as indicated in Table 11. The fused silica tubes were quickly immersed in cold water without breaking the tubes after the heat treatments. The tantalum foil prevented reaction between the fused silica and the sample; there was no reaction between the powdered samples and the foil at 1000°C, but some trouble was experienced at 1100°C. At this temperature level a reaction between the sample and the foil was sometimes observed, which resulted in erroneous parameter values. Experimental Results Hardness Tests: Since most of the X-ray samples were in the form of flat strip, it was convenient to obtain Vickers hardness numbers as a function of oxygen content. Compared to the V-O case,' oxygen hardens columbium much more slowly, presumably because of the larger octahedral volume in colum-bium (about 12.0 compared to 9.3Å3 in vanadium), hence, requiring less lattice strain for solution. The plot of VHN vs wt pct O is shown in Fig. 1.

Jan 1, 1955

The regular activities of the Institute are financed mainly by income derived from members' dues, from advertising in MINING ENGINEERING, JOURNAL OF METALS, and JOURNAL OF PETROLEUM TECHNOLOGY, and from the sale of publications to the public In addition, collateral activities and special projects are financed each year by means of income - from endowed funds controlled and administered by the Institute. An active effort is being made to increase the endowment funds of the Institute through a standing committee, of which Wilfred Sykes is Chairman, and of which the other members are N G

Jan 1, 1952

The Jeffrey operation of Canadian Johns -Manville Co. , Ltd., at Asbestos, Quebec, is considered to be the world's largest asbestos mine. It accounts for approximately 37% of Canadian production of chysotile asbestos and about 13% of world production. Rated capacity is over 600,000 stpy (540,000 mtpy) of fiber, of which well over 90% is exported to the United States and seventy other countries. During the early 1970's the company completed a five-year modernization and expansion program which included the installation of a unique 72 in. by 93 in. gyratory crusher to handle the extremely blocky serpentinized peridotite ore. Because of the large diameter of this crusher the top ring of the shell was made in two halves which were bolted together. Hundred-ton trucks dump from two sides of the crusher into the 200 st (180 mt) dump pocket which is equipped with dust collecting ducts in the walls of the other two sides. The installation was designed to accommodate the eventual use of 200 -ton trucks. Crushed ore at a. size of 7 ½ in. (191 mm) falls into a uniquely designed crushed ore pocket equipped with three sloping steel sides and one vertical side, which make it totally live. Infrared heaters installed in back of the hopper sides prevent the ore from sticking to the steel. Another interesting feature is an eccentric removal bridge which is permanently mounted inside the crushed ore pocket. The two halves of the bridge are let down by electric winches to form a platform on which the eccentric cart travels and from where maintenance is done. Level indications in the crushed ore pocket are by radioactive indicators. Under the crushed ore pocket is a 72 in. by 28 ft (1.83 m by 8.5 m) apron feeder which operates at 7. 2 to 50 fpm (2. 3 to 15. 3 mpm). Crushed ore is discharged to a picking belt for tramp removal. A crossbelt magnetic separator is also mounted over this belt. Permanently mounted belt reels are also situated over the picking belt to facilitate the changing of this unit. A 60 in. (1. 52 m) wide takeaway belt then elevates the crushed ore to t.he surface facilities. Instead of discharging to a crushed ore stockpile, the takeaway conveyor delivers the ore to a 300-ton distribution bin. The ore is then screened and secondary crushed; and the plus ¾ in. (19 m) is "stored in a 3,000 ton bin while the minus ¾ in. is dried and then sent to storage. This system of directly screening primary crushed ore is similar to that used at both the Endako molybdenum and Gibraltar copper operations in British Columbia. While it would seem connecting processing equipment directly to a primary crusher would have an adverse effect on the crusher availability, the 94% of scheduled time this crusher

Jan 1, 1978

By John V. Beall

Cutting costs and increasing safety with new ideas is the byword with The Cleveland-Cliffs Iron Co. on the Marquette Range in Michigan. Among the new ideas being tried out are mechanical shaft mucking, prefabricated lagging to replace timber poles, Carset bits in shaft sinking, and rubber tired guide wheels on the ore skips. Plans are being made to stockpile ore with conveyor belts during the winter. In sinking the Mather "B" Shaft a 3/8-yd clamshell-type bucket is used for mucking. The clamshell is opened and closed by means of a verticallymounted hydraulic ram actuated by 5000 psi oil pressure. An Ingersoll Rand-type hoist is used to raise and lower the clamshell. The hoist is controlled by one member of the crew on the floor of the shaft. When the bucket is raised, the men swing it over the muck pile to the desired position and then it is lowered on to the broken rock. The 1400-lb weight of the bucket causes it to sink into the broken rock and it digs as the ram closes the bucket. The hydraulic ram is operated by a man on the lowest shaft steel set who controls a specially designed oil pump which supplies oil pressure. The clamshell is emptied.

Jan 1, 1949

By M. D. Everell

A study has been made of the relationships between grinding selection functions and physical properties of rocks, particularly the failure loads of irregular particles and the compressive and tensile strengths of large regular specimens. The rocks used were limestones of various structures and impurity contents, a carbonatite, and a high-purity crystallized calcite. The selection functions were obtained from carefully performed grinding experiments on selected narrow size ranges in various grinding machines-a laboratory batch ball mill, a Hard grove grindability machine, and a mill of the type suggested by Yang, Mempel, and Fuerstenau. The specific rates of breakage during milling and the failure loads of irregular specimens correlated well for the rocks studied. The testing of irregular particles is suggested as a means of predicting the behavior of commercial mills.

Jan 1, 1973

By Thomas J. O’Neil

During the past five years, the mining industry has been subjected to new operating constraints that are unprecedented in number, scope, and urgency. The industry must operate in a safer, cleaner manner, yet produce more without large price increases. Compliance with any new sweeping legislation is always difficult-and particularly so in today's adverse economic climate, which is being aggravated by the steady stream of environmental control and tax-reform programs. In effect, while government is unwittingly but surely undercutting the country's productive capabilities, it blames industry for the resulting failure to meet consumer demand. Any such real or alleged failure then brings heightened bitterness from Congress. During the recent energy shortage, for instance, threats of nationalization were ventilated in public along with proposals to abolish the mineral depletion allowance.

Jan 11, 1974

By A. L. Mular

lnput energy-size modulus relation at small reduc-tion ratios is expressed by Et = (M, -Mt) k;. In some cases 13 is close to Schuhmann's distribution modulus a in value. Experimental results in conjunc-tion with the equation demonstrate the fact that energy input which produced fracture is not expended on unbroken starting material inside the mill at any time. Recently, schuhmann1 derived the Charles equation2 using the postulate that complex com-minution operations can be considered as a summa- tion of many comminution events. The fragments resulting from each event are assumed to follow the Gaudin-Schuhmamn distribution. In his derivation, Schuhmann implies that the size distribution of the total mass of a material is determined by the fraction of that mass actually subjected to comminution. Consider a feed to contain a volume, Vo, of uni- formly sized homogeneous material. After t seconds of grinding, let the volume of broken material be Vo - Vt where Vt is the volume of starting material not yet broken. The size distribution of the broken material is given by: where V is the cumulative volume less than size X, and k, is the size modulus of the broken material at time t. The distribution for the total volume at this

Jan 1, 1962

By Roger Thunvik, Carol Braester

Excavation of cavities below the ground water level induces water influx from the surrounding aquifer. An estimate of the rates of flow prior to excavation operations may be of valuable information for the mining engineer. The present paper deals with water influx into cavities of the tunnel type, e.g., mine galleries, tunnels, etc. The solution of the flow problem was obtained by a numerical finite difference method. The results are presented in dimensionless form as a function of the parameters characterizing the location of the cavity in the aquifer.

Jan 1, 1981

THERE are three chief production zones of tungsten ore in China. In the Province of Kiangsi mines are located at Kanchow, East River, and West River. Their combined production is understood to amount to 300 to 350 tons of ore per month, and their original exportation is made through the port of Kiukiang, largely to Shanghai. The second zone is in Kwangtung Province, the mines there being at Tayulin. Produc-tion reaches about 200 tons per month and cargo is gen-erally exported through the port of Hong Kong. In the Province of Hunan approximately 25 tons of ore are produced monthly in the mines at Ton-on. Tungsten ore from Kiangsi and Kwangtung Prov-inces is generally about 70 per cent WO, (tungstic acid), while that from Hunan is of lower quality, run-ning about 65 per cent WO3. Kiangsi ore is received from the mines in 100-1b. and Hunan in 224-lb. gunny sacks. No repacking is done except as it is made neces-sary by the condition of the sacks. Kiangsi Province contains the Chinese districts pro-ducing the largest amount of salable wolframite or tungsten. Many districts west and south of Kiangsi have been found to have wolframite deposits.-Com-merce Reports.

Jan 1, 1928

HENRY G. MARTIN,* Chicago Heights, 111. (written discussion?).-. The object in taking three or more ladle tests is to secure a sample that will show the average composition of the heat, not primarily to investigate the lack of uniformity existing; however, the assumption that the samples are not of uniform composition -remains. In other words, we have three samples of steel of different composition, the par-ticles of which are not subject to extreme comminution so as to mix inti-mately, and yield an average homogeneous sample, if placed in one

Jan 11, 1919

By C. A. Queener, W. L. Mitchell

In recent years bismuth telluride has received considerable attention, primarily due to its value as a thermoelectric material. Since there seems to be little dependence of thermoelectric effect upon crystal orientation1 many of those who have previously worked with this material have been unconcerned with knowing its crystallographic angles to any degree of accuracy. However, when one studies deformation modes, lattice stresses, or the aniso-tropy of mechanical properties of a material, knowledge of the interplanar angles and their relationships as depicted in a stereographic projection becomes essential. Lange2 originally published crystallographic data which described the structure of bismuth telluride as rhombohedral with the space group A more recent work by Francombe3 presented data which corroborated and refined the original findings of Lange. In addition, Francombe established that there is no coexistence of rhombohedral and hexagonal lattices in bismuth telluride as was suggested by Vasenin and Konovalov,4 and that the structure can be treated as a pseu do hexagonal structure with an axial ratio, c/a, of 6.95 for convenience of presentation and study. The interplanar angles and standard projections for several unalloyed hexagonal metals have been previously published,5-9 but the present work appears to be unique in that it presents data for a rhombohedral compound in pseudohexagonal form. As a pseudohexagonal structure, this material has an extremely large axial ratio as compared to the usual range of approximately 1.5 to 1.9 for the hexagonal metals. Since the interplanar angles are a function only of c/a, the angular relations between various planes for Bi,Te3 will be grossly different

Jan 1, 1965

By C. A. Winkler, V. Hospadaruk

PREVIOUS papers from this laboratory have discussed the effect of chloride ion on the cathode polarization during electrodeposition of copper from copper sulphate-sulphuric acid electrolytes, in the presence and absence of gelatin. The steady state polarization'" was found to decrease sharply and pass through a minimum with increasing chloride ion concentration in the presence of gelatin. The minimum shifted to higher chloride ion concentrations and to higher polarization values with increase in current density or gelatin concentration, while an increase of temperature shifted the minimum toward lower halide concentrations and lower polarizations. Since these observations were made in acid-copper sulphate electrolytes that contained no other addend than gelatin, there was obviously the possibility that they were not applicable to deposition of copper from commercial electrolytes that contain a variety of other substances in relatively small amounts. In particular, it was of interest to determine whether the presence of arsenic, antimony, or bismuth in the electrolyte would materially alter the behavior. Experiments have now been made under a variety of conditions with systems containing these cations, and the results are summarized in the present paper. Experimental Polarization measurements were made at 24.5oC in a Haring cell in the manner described previously.' Electrolytes were made with doubly-distilled water, and contained 125 g per liter of copper sulphate and 100 g per liter sulphuric acid, both of reagent grade Eimer and Amend gelatin from a single stock was used throughout. Chloride ion was introduced as reagent grade sodium chloride, and arsenic, antimony, and bismuth by dissolving the chemically pure metal in hot concentrated sulphuric acid and adding appropriate amounts of the solutions to the electrolyte. Each cathode, of 1/16-in. thick rolled copper, was first etched in 40 pct nitric acid and washed thoroughly with distilled water. The surface was then brought to a standard condition4~9 by electrodeposition from an acid-copper sulphate electrolyte containing no gelatin, at a current density of 3 amp per sq dm for 30 min, followed by deposition at a current density of 2 amp per sq dm for l hr. As in previous studies, the cathode polarization eventually attained a steady-state value (15 to 75 min) such that further change in polarization did not exceed 0.2 mv per min. The polarization values recorded are those for the steady states. "Excess weights" were determined with arsenic and antimony present in the electrolyte, as the difference between the weights of the deposits obtained in the presence of these cations and those obtained in their absence, with the two cells connected in series. When gelatin was present along with the arsenic or antimony, it was also added to the electrolyte in the cell in series. Results and Discussion The results of the study are summarized in Figs. 1 to 6. From Fig. 1, top, it is evident that the presence of arsenic or antimony alone results in an increase of polarization, while bismuth alone causes a decrease. The presence of gelatin (25 mg per liter) rather drastically modifies all three cation effects, as indicated in the lower panels of the same figure. The addition of chloride ion, when no gelatin is present, causes comparable decreases in polarization in the presence of antimony and bismuth, but a relatively larger decrease when the electrolyte contains arsenic. It is interesting to note that the decrease in polarization brought about by addition of chloride when both arsenic and antimony are present parallels the behavior with arsenic alone, while the polarization in the electrolyte containing the cation mixture, without chloride added, corresponds to that for an electrolyte containing only the antimony cation. Similarly, the polarization at zero concentration of chloride in electrolyte containing arsenic and bismuth is that corresponding to an electrolyte containing arsenic alone. From Figs. 3a, 4a and 4b, it is clear that, in the presence of gelatin at a level of 25 mg per liter, the effect of chloride in the presence of arsenic and antimony, or a mixture of the two, becomes quite analogous to that observed in the absence of added cations. When both bismuth and gelatin are present (Fig. 5), the decrease in polarization with increased chloride concentration is virtually absent. This is perhaps a reflection of the large decrease in polarization brought about by the bismuth itself in the presence of gelatin. The shifts of the minimum in the polarization-chloride concentration curves brought about by changes of temperature (Fig. 3b), gelatin concentration (Figs. 3c and 4c) and current density (Fig. 3d) when the metal cations were present are all similar to the corresponding shifts observed in their absence." The approximately linear "excess weightv-anti-mony concentration relation recorded in Fig. 6 would seem to indicate that antimony is codeposited with copper to a considerable extent. On the other hand, only very limited amounts of arsenic appear to be adsorbed or codeposited.

Jan 1, 1954

By Walter Miller

ALTHOUGH confident of its ability to meet any demands which may be made, the petroleum refining industry is not complacent about the situation and realizes that the quantities of petroleum products to be furnished are so enormous and so far beyond what was previously estimated that the full co-operative effort of the industry must be exerted. Establishment by the President in May of the Office of Petroleum Coordinator for Defense with Secretary of the Interior Ickes at its head, plus the formation of the Petroleum Industry Council for Defense, in November, provide the channels for united endeavor within the industry and the means for gearing that endeavor within the industry and the means for gearing that endeavor in full harmony with the nation?s needs. Great strides have been made and a rapid understanding of the situation and the magnitude of the task is being attained by all concerned.

Jan 1, 1942

By C. F. Riisness, E. R. Parker

THAT grain size has a great effect on the mechanical properties of metals has been recognized for a long time. Bassett and Davis1 in 1919 did excellent work in [ ] determining the effect of grain size on the hardness of brass. About the same time Jeffries2 and Sykes3 ascertained the effect of grain size on the strength and ductility of several metals at temperatures ranging from 80°K. to their melting points. When creep was recognized as an important property of metals, those engaged in the study of this property tried to determine the effect of grain size 4-9 on creep rates. Unfortunately, most of the investigations were conducted on only two grain sizes, often designated simply as "fine" and "coarse." It is well known that at high temperatures coarse-grained test bars creep less than fine-grained bars. The relation between grain size and size of test bar, [ ] however, has been frequently overlooked. In his early work, Jeffries2 showed that the number of grains in the cross section has a more important influence on the properties of the material than the actual grain size. More recently Hanson and Sandford10 and Pell-Walpole,11 in their measurements of the creep and tensile properties of tin, tested a wide range of grain sizes and correlated the grain size with the strength. Hanson9 later established the relation between the number of grains in the cross section and the. creep rate: At high temperatures, generally a coarse-grained structure is considered superior in creep to a fine-grained structure, but it is evident that for a given bar size continuously increasing the grain size will

Jan 1, 1944

By B. Silliman

THESE ores occur in the Laurentian rocks in the town of Clifton, St. Lawrence County, New York. The Clifton Mining Company have opened these magnetites upon their estate of 23,000 acres, on the waters of the Grasse River, an affluent of the St. Lawrence, which flows for about nine miles across the estate, exposing a section of the formation, and affording ample water-power at numerous points. In approaching this district from De Kalb Junction, upon the Watertown and Ogdensburg Railway, the observer passes from the zone of the specular ores, which abound to a great extent in Jefferson County, across a belt of non-metal-liferous limestones, continuing for some miles intermingled with metamorphic rocks, and gradually giving place to heavy beds of granitic and porphyritic gneiss, the weathered surfaces of which present a gray and rough appearance, from the washing out of the feldspar; leaving the quartz very prominent, and completely disguising the real character of the rock, which, when freshly broken, has a lively reddish appearance from the predominance of flesh-colored and red feldspar. Beds of fine-grained quartzite appear also intercalated in the granitic gneiss. These are the dominating rocks of the magnetite region, but the magnetite is always found, so far as the speaker's observation extended, associated with beds of calcite, carrying hornblende, black and green, biotite, and brown garnet interspersed with yellow and magnetic pyrites. The strike of these rocks is about northeast, and their dip about 40° to 45° southeast.

Jan 1, 1873

By P. Gobin, J. Perez, P. Peguin

The strain-amplitude- dependent part of the internal friction of alluminum after several ther momechanical treatments has been measured in the I-cycle range and at the ambient temperature. The internal friction in the outer layer of the torsional specimen us stress is computed from the experimental data. The curues obtained are analyzed in tevnzs of u coirzbinntion of AH and p, which aye, respectively, due to the vecersible unpinning from weak pills and to the plastic strain. Considerirlg the notion of thermally activated unpinning and repinning, it is shown that in our experimental conditions tlze dislocation lines acl as in the H model of Granato and Liiclze. It is also seen that the internal friction p which appears at higher- strains call be described by a simple expression which is in good agreement with our results. A qualitative interpretatiorz is proposed by combining these new types of intelpnal fviction. We define the internal friction 6 as half the ratio of the dissipated energy aW during one cycle to the maximum supplied strain energy W of a material submitted to a periodic stress. Experiment and theory show that internal friction varies with stress above a critical value.' Below this value the internal friction is strain-amplitude-independent and is often masked by an experimental background; so we shall call it AB. ~bove this critical value, the internal friction is strain-amplitude-dependent. This quantity is usually called aH:' and it can be explained as a thermal unpinning of dislocations.3-6 Furthermore, at higher stresses, a rapid increase of internal friction appears. This phenomenon could be caused by the plastic strain,' so we shall call it Ap. It seems interesting to us to study the influence of several t her momechanical treatments on the curve internal friction 6 vs strain E, in order to study the variation of AH and p with the concentration and the repartition of linear and point defects. In order to try to explain the results obtained, we shall propose and discuss models for H and hp and shall show that we obtain a combination of these two types of internal friction. 1) EXPERIMENTAL PROCEDURE 1) Preparation and Treatment of Specimens. We

Jan 1, 1968

By D. A. Woodford

In a constant-load creep test, if the density of nlobile dislocations is assumed constant for strains exceeding that corvesponding to the minimum creep rate, it is shown that the creep rate may be approximated by the equation where E is the nominal strain, o0. is the initial stress, and a' the stress fov unit dislocation velocity. The constant C contains the mean density of mobile dislocations and n is a measure of the stress sensitivity of dislocation celocity. This equation is shoum to be applicable to published data on an alloy steel and on nickel. The degree of plastic instability and hence the creep ductility is dependent on the calue of n for these materials. When instability becomes gross and local macroscopic necking occurs, the assumptions are no longer valid. On the basis of this equation, and the strain-time relation derived from it, a method of predicting the creep behavior at different stresses is suggested. MOst analyses of creep data have been concerned with time-dependent transient creep or time-independ- ent secondary creep in constant-stress tests. The far more widely used constant-load test has been neglected in terms of a mechanistic approach. In general, since the strains involved are usually small, the same laws for transient creep may be applied to both types of tests. However, there is no steady-state creep in a constant-load test since the stress increases continuously. Any apparent steady state observed on a strain-time plot is either fortuitous or illusory, and is generally revealed as a continuously varying creep rate on a carefully constructed strain rate vs time plot.* Transient creep may be understood in terms of a simple differential equation representing the change in mobile dislocation density with time:' where p is the density of mobile dislocations. The first term on the right is related to first-order kinetics of dislocation multiDlication and the second to second-order kinetics of exhaustion. On the basis of this equation, several authors2-4 have found good agreement with experimental transient creep curves for a number of materials. When k1p = k2p2, a steady-state creep

Jan 1, 1968