Search Documents

By H. S. Choi, I. Iwasaki

The effect of temperature as a parameter in ore flotation has not been systematically studied, although for some ores it has been known for many years that selectivity and grade of concentrates can be improved by conditioning or flotation at moderately or substantially elevated temperatures. In 1934 Coghill and Clemmer' stated that "elevated temperature seems to make hard water more tolerable" in soap flotation, and a cursory examination of the literature indicates that some earlier investigators were aware of beneficial results obtained by floating above room or mill-water temperatures. Tartaron,2 Mitchell et aL.,3 and particularly Hamilton et al.' have shown that high pulp temperatures give high recovery and selectivity in soap flotation of fluorite from a variety of gangue minerals. As a result of the work of these and of other investigators, high-temperature flotation has been successfully applied to industrial flotation of fluorite. Falconer" stated: "The use of high temperature conditioning (above 35°C and preferably above 60°C) in connection with the soap flotation of nonsulphide ores, as covered in B. Kalinowski's French Patent No. 847,-215, Dec. 7, 1938, is claimed to provide more intense activation, better separation of values from gangue, and reduction in quantity of reagents." The various investigations quoted above clearly demonstrate the improvements to be realized by increasing the temperature at which fluorite is floated, and it is surprising that little or no information has been published on systematic investigation of the same method as applied to other ores. The present article describes comparative results obtained at room temperature and at elevated temperatures by otherwise conventional flotation of iron ores, by single-mineral flotation in the Hallimond tube, and by contact-angle measurements. It is not the purpose of this article to evaluate the commercial feasibility of high-temperature flotation of iron ores, although preliminary calculations show that the cost should not be excessive and that the gains to be realized may well outweigh the extra cost of heating the pulp. LABORATORY FLOTATION TESTS Experimental: All flotation tests reported in this article that use a laboratory Fagergren cell were made on ore A (either containing the primary slimes or deslimed at 20µ as specified) following the preparatory procedures described elsewhere- or this particular ore. Ore A contained hematite, goethite (limonite), quartz, chert, and minor quantities of magnetite. Confirmatory tests made on other ores show that the same general principles apply to ores of similar mineralogy and structure. Conditioning was performed by adding the collector, as a soap, to the vigorously stirred and heated pulp. Conditioning time was 5 min, the pulp contained 60 pct solids, and the equivalent of 0.5 Ib of fatty acid was added per ton of original (unde-slimed) ore. The pH of the pulps ranged from 6.8 to 7.1 (25°C measurement) during conditioning. The pH was adjusted in the flotation cell by addition of either NaOH or H2SO4, the values reported being those of the pulp cooled to 25°C. During conditioning and flotation the pulp temperatures were controlled within l° to 2° by immersion of Variac-controlled Calrod elements in the conditioning beaker and in the cell, and by the use of water, heated to the appropriate temperature, for transferring pulp, adjusting pulp volume, and washing. Selectivity indexes have been calculated on the same basis as those reported in the article by Cooke, Iwasaki, and Choi." Results: Table I gives the results obtained by floating deslimed ore A with pure oleic acid at 25" and 50°C, and Fig. 1 shows the selectivity indexes plotted against pH of flotation. Inspection of Table I

Jan 1, 1961

By H. E. Cline, T. H. Alden

A study zvas made of rate-sensitive plastic deformation and superplasticity in alloys of lead and tin. These alloys (lead, PO-19 pct Sn, Sn-38 pct Pb, Sn-2 pct Pb, tin) were extruded, aged at room temperature, or melted and resolidified to produce a variety of ~nicrostrnctures. Flow stress us strain rate data were obtained frorn tension tests for strain rates between 10-6 and 1 min-1. The curve log o .us log £ was S-shaped jor fine-grained materials and approxinzately linear for coarse-grained nzaterials. At constant grain size, the behavior was relatively insensitive to conposition. High rate sensitivity (d log o/d log k) and superplasticity occurred at intermediate strain rates in fine-grained materials and are believed to be associated with a transition with strain rate in the mode of plastic flow. This transition was shifted to higher strain rates with increasing temperataire or decrensing grain size. The high rate rneclzanisrn is presunzed to be slip, while rnetallographic evidence sug-gests that the low rate lnechanism is pain boundary sliding. PEARSON' discovered that extruded eutectic alloys of Pb-Sn and Bi-Sn could be elongated as much as 2000 pct in tension. The ability for stretching decreased with aging time or annealing to increase the grain size. At high strain rates, or if the material was in the cast condition, normal ductility was observed. Following deformation of the extruded Pb-Sn eutectic at low rates, Pearson observed an equiaxed granular structure on an initially flat surface, while rapid straining produced elongated grains. He attributed the large deformation in the extruded alloys to the persistence of extremely small grains to a temperature sufficiently high for inter granular flow. Avery and backofen2 measured the strain rate sensitivity of the flow stress, m = d In old In 6, in the Pb-Sn eutectic and established a correlation between m and the tensile elongation. In the extruded eutectic alloy the strain rate sensitivity was 0.1 to 0.2 at rapid rates and the elongation was small, while at low rates m increased to 0.4 to 0.6 and superplastic elongation was observed. They also noted a grain size effect. In the case of the cast Pb-Sn eutectic the strain rate sensitivity remained at 0.1 over the range of strain rates of their experiment (3 x 10"3 to 2 min-I). These authors suggested that diffusional (Nabarro-Herring) creep was the mechanism by which deformation occurred at low strain rates, while climb-controlled creep occurred at high rates. Two predictions of this model are that, at low strain rates, the strain rate sensitivity approaches 1, i.e., Newtonian viscosity, and that the strain rate at constant stress varies as D/L2, where D is the coefficient of self-diffusion and L the grain size. More recently, a mechanical and microstructural investigation of the dilute superplastic alloy, Sn-5 pct Bi, has been done.3 The results show that the high strain rate sensitivity is associated with a transition with strain rate of the mechanism of plastic flow. At low strain rates, grain boundary sliding and its associated accommodation processes were evident, while at high strain rates quasi-uniform slip was concluded to be the dominant deformation process. The following experiments were performed to extend our knowledge of the phenomena of superplasticity to a larger range of strain rates, compositions, temperatures, and microstructures in the Pb-Sn alloy system. The question of why a cast structure does not exhibit viscous behavior although it appears to have a fine microstructure2 was investigated.

Jan 1, 1968

By E. J. Koval

Practical miscible displacement processes will be characterized by lingering of the solvent into the oil. The lingering process is brought on by viscosity differences, and can be accentuated by channeling and longitudinal dispersion. The effects of these factors on the efficiency of unstable completely miscible displacements are combined in what is called the K-factor method. This method, analogous to the Buckley-Leverett method, predicts recovery and solvent cut as a function of pore volumes of solvent injected. Experimental data are included and show excellent agreement with theory for a wide variety of sandstone cores and viscosity ratios. INTRODUCTION Theoretical considerations,1 laboratory experiments,2 and pilot tests3 lead to the conclusion that miscible displacements in the field will be unstable In an unstable miscible displacement, the solvent fingers through the oil. This fingering leads to early breakthrough of the solvent and an extended period during which both oil and solvent are produced. For such a system, there appear to be four principal factors which bring about or accentuate the effects of instability: longitudinal dispersion (including geometrical effects), channeling, viscosity differences and gravity differences. Other factors, such as diffusion and flooding rate, can also influence the effects of instability, but at the flooding rates considered in this report, circa 15 ft/D, they are unimportant. Longitudinal dispersion can be thought of as a spreading of the solvent front caused by the presence of microscopic inhomogeneities. Channeling of the solvent occurs when a porous medium has macroscopic inhomogeneities; i.e., gross permeability variations. Viscosity differences lead to fingering of the less viscous solvent. This difference in viscosity accelerates the growth of fingers along paths previously developed because of permeability variations. Gravity differences lead to overriding by the usually less dense solvent. Al- though gravity effects are generally small at a flooding rate of 15 ft/D, they would, nevertheless, unnecessarily complicate the interpretation of flooding experiments. For this reason, all the experiments reported herein were done with matched density fluids. Fingering and the resultant poor areal sweep were recognized early as the dominant influences on the efficiency and the economics of miscible displacement processes. Much research effort has been spent on ways to minimize fingering and increase areal sweep such as the use of graded viscosity slugs4 or water slugs. Some researchers attempted to work out ways to prevent fingering completely; i.e., to achieve a stable displacement through gravity or latitudinal dispersion stabilization. l Others did not attempt to control fingering but obtained an economic process by merely recycling the solvent and sweeping pattern by pattern.6 During this period, all aspects of fingering came under close scrutiny. Some researchers reported on how fingering looks2 and how it is affected by viscosity ratio,7 geometry,7 and slug size.2,* Peaceman and Rachfordg suggested a mathematical approach to the prediction of unstable miscible displacements in relatively homogeneous sand packs, but their work cannot be extended conveniently to heterogeneous systems. Hence for a heterogeneous system, no method is presently available for predicting solvent cut and recovery as functions of pore volumes of solvent injected. The purpose of this investigation was to attempt to fill in the gap in our knowledge concerning the prediction of performance of unstable miscible dis placements. Necessarily, the system selected for study was a relatively simple one. The restrictions placed on the system were: (1) The system was linear; (2) The solvent was miscible in all proportions with the oil in place; (3) The solvent was continuously injected into the porous medium; (4) Gravitational effects were eliminated by matching densities and (5) All the flood rates were high and constant at 15 ft/D to avoid any small rate effect and to minimize any diffusion effects. To simplify and to indicate that both longitudinal dispersion and channeling arise from permeability variations, the effects which they cause or influence have been termed heterogeneity effects. The use of

By Matti J. Saarivirta

The relative machinabilities of the precipitation-hardenable Cu-0.9 pct Cr, Cu-0.25 pct Zr, and Cu-0.9 pct Cr-0.25 pct Zr alloys are improved from 18 to 80 pct by 0.75 to 1.25 pct Pb. The Lead also improves the tensile strength, hardness, ad resistance to softening of the Cu-Cr and Cu-Cr-Zr alloys. When the alloy containing 0.7 to 2.2 pct Cr, 0.10 to 0.25 pct Zr, 0.75 to 1.25 pct Pb, and balance copper is solution-annealed at 1000°C (1830°F) and then aged at 525°C (Y75°F), tensile strength of 65,000 psi, 16 pct elongation, 62Rb hardness, and 84 to 87pct IACS electrical conductivity are obtained. The copper base Cu-Cr, Cu-Zr, and Cu-Cr-Zr alloys have high electrical and thermal conductivities, high strength and resistance to softening at elevated temperatures, but their machinability is poor, i.e., close to that of the pure copper. In the manufacture of various components such as welding electrodes or electrical and thermal conductors it is ofter desirable that the alloy have good machinability for high production rates and long tool life. Thus, alloys that combine these properties may be used not only for existing applications, but for new ones where good machinability is a requirement. This investigation was undertaken to improve machinability without impairing other desirable characteristics of the Cu-Cr, Cu-Zr, and Cu-Cr-Zr alloys. These commercial alloys contain about 0.4 to 1.2 pct Cr, 0.10 to 0.25 pct Zr, and balance copper. Lead was selected as an element that should improve the machinability and possibly other characteristics of the alloy. WORK PROCEDURE This investigation began with a study of the effect of lead on the hardness, tensile strength, electrical conductivity, and machinability of the binary alloy containing 0.10 to 1.30 pct Cr and balance copper. This was followed by an investigation of the effect of lead on the Cu-0.1 to 0.4 pct Zr and Cu-Cr-Zr alloys. The alloys were made from initially oxygen-free copper and for comparison some castings were made from phosphorus-deoxidized Lake Copper. Commercially pure chromium, zirconium, and lead were used for alloying. In melting the chromium was added to molten copper at 1400°C (2550°F), the heat held for 15 min at temperature, and the temperature then lowered to 1350°C (2460°F) when the other elements were added. The alloys were held for 15 min at this temperature and cast into a cast-iron mold. One-kilogram, 3-in.-diam castings were made. An argon cover was maintained during melting and casting to prevent oxidation. The chemical compositions of the alloys are shown in Table I. The micro structure and properties of the alloys were studied in the cast and wrought conditions prior to and after various solution-annealing and heat-treating cycles. The relative machinability was determined as a function of the lead content and compared with the free-machining Cu-lpct Pb alloy. To determine the machinability, 13/16-in.-diam cast specimens were cut by a machine hack saw using a constant cutting speed of 50 fpm, a fixed feed force, and a new blade for each alloy specimen. Molybdenum highspeed steel saw blades, 0.032 in. thick with 14 teeth per in., were used in all tests. No cutting fluid was used. Five tests were made on each specimen and the average elapsed time per test was taken as a measure of the relative machinability for that alloy. The variation of cutting time for each alloy was less than 110 pct.

Jan 1, 1969

By G. A. Vissac, R. G. Minet, N. E. Sylvander

R. G. Minet—The authors' description of the remarkable progress made in the last few years in applying the fluidized solids technique to the problem of lignite drying and carbonization clearly demonstrates that engineering techniques available today may make many processes practical and profitable which a few years ago were considered otherwise. As pointed out in the article, the future of the carbonization step hinges on the value and utilization of low temperature tar. On paper, at any rate, this tar looks like a valuable raw material for the chemical industry to use. Some 50 to 60 pct may be converted to pitch for electrodes, roofing, road tars, and other valuable products; the 25 to 30 pct tar acids could conceivably form a basis for a new low cost resin or plastic of the phenolformalde-hyde type. Yet these materials are so new and dissimilar from available sources that much work must be undertaken by the chemical industry before they will be accepted. Now that the work of Dr. Perry and his colleagues has made a large supply of low temperature tar a real possibility, I would expect the chemical industry to accelerate its work in this field. On the basis of certain data available in the literature it appears possible to produce a more aromatic tar, although in smaller yield, by operating at temperatures in the range of 1300" to 1500°F. Operating a fluidized bed process for lignite at these conditions should be technically possible, at least, and could produce a tar having more familiar characteristics. I wonder if Dr. Parry would care to comment on such a possibility. Incidentally, in our own work on carbonizing coking coals in fluidized beds, using Ohio, Pennsylvania, and West Virginia high volatile bituminous coals, we have obtained yields which agree with the correlation given for tar yields vs moisture and ash-free volatile Btu. Our data are slightly under the line, but certainly in the range of the correlation. We have also obtained evidence in support of the authors' statement as to the effect of air on the process. In our pilot plant all the heat required for carbonizing is released by internal combustion of char in the fluidized bed in normal operation. We are also equipped to obtain all carbonization heat by external electric heaters on the shell of the carbonizer while introducing only an inert gas to the process. We note no difference in tar yield or characteristics between the two operations. In the case of the gas, however, it appears that some hydrogen is consumed by the air combustion. We would be interested in hearing in a little more detail about the hot dust and char handling problems at Sandow. Have the authors found char subject to spontaneous combustion? Have they ever tried a coking coal in their pilot plant? V. F. Parry (author's reply)—Production of a more aromatic tar by operation of the carbonizer at 1300" to 1500°F does not appear to be economical. 1) The capacity of a reactor operating at 1500°F would be 30 to 50 pct less than the capacity at 932 °F and the cost of processing would increase materially. 2) The cracking of tar vapors in a reactor requires appreciable time to complete the reactions and it is doubtful that considering the very short time of residence of tar vapors within the reactor (4 to 10 sec after evolution) the basic character of the tar would be changed significantly. This is indicated from the data reported in Table XIV. 3) General studies have shown that it is advisable to operate at the minimum temperature to produce the maximum tar and minimum gas. 4) Operating problems and the maintenance of vessels and reactors, and the hazards of handling hot char, increase with the temperature of carbonization. It is technically possible to operate at temperatures as high as 1500°F, but in my opinion it is not economical or desirable. We believe that the primary tar must be won in the simplest way and then processed alone to change its character for production of desired products. It is interesting to have confirmation of our observations on the reaction of air with the products of carbonization. The major reaction is with the char, fol-

Jan 1, 1957

By J. F. Held

In a study of the influence of cold rolling on mechani cal properties of steel, it was found that the specific rolling procedure influenced crystallographic orientation. Properties developed by several rolling modes were determined and related to crystallographic orientation. Sanzples were cold-rolled various amounts on a laboratory mill. When palm oil was used as a lubricant, the crystallographic orientation was homogeneous throughout the thickness of the samples. Other samples were rolled without lubrication. Variations in intensity of the recrystallization texture components persisted throughout more than 50 pct of the volume of these samples. When the average plastic strain ratio, which is dependent upon crystallogvaphic orientation, was plotted as a function of percent reduction, a maximum was found at 40 pct in the samples which contained the observed texture variation. No maximum was found for the samples with the homogeneous texture distribution. Other mechanical properties, such as tensile strength and yield strength, were not influenced by the variation in crystallopaphic orientation. MECHANICAL properties of steel sheets depend, in general, upon the structural properties of the steel. For example, the Petch equation describes the relationship between yield strength and grain size. Other properties, such as hardness, vary with chemical composition. The plastic strain ratio, or R value, has been found to be dependent upon crystallographic orientation . In the course of investigating the effect of cold rolling on mechanical properties, it was found that a previously reported relationship between percent cold reduction and R value was not always observed. Published data had shown that the optimum cold reduction for best R values is 70 pct for aluminum killed steel.' However, by altering the rolling conditions, the optimum reduction can be shifted to much lower values, or it can be moved to very high values. This paper describes the rolling conditions that lead to shifting of the optimum cold reduction. The effect of rolling conditions on the various structure parameters and the resulting mechanical properties are evaluated. EXPERIMENTAL PROCEDURE Samples of three low-carbon aluminum killed steels were cold-rolled various amounts on a 9-in.-diam 2-high laboratory mill. Hot-mill thermal practice and steel chemistries are listed in Table I. Steel A was rolled with palm oil lubrication and heavy reductions on each pass; i.e., a total reduction of 75 pct was ac- complished with a maximum of five passes. Steel B was rolled without lubrication, and light reductions were given on each pass. After approximately 75 pct reduction, it was necessary to use a small amount of light oil to achieve any additional reduction in thickness. Following cold reduction, the samples were box-annealed at 1300°F for 10 hr. The heating rate between 800" and 1300°F was 50°F per hr, and the cooling rate following the soak period was 50°F per hr. Tensile specimens were machined from the annealed material and these were used to measure yield strength, tensile strength, and the plastic strain ratio (R value). Recrystallization textures were determined by an inverse pole figure technique.*'3 Integrated intensities of the (110), (002), (112), and (222) reflections were recorded for those planes lying parallel to the sheet surface. Examinations were made on both surfaces of each sample, and also at various levels beneath each surface to approximately 0.010 in. depth by etching techniques. RESULTS R Values. The R values obtained in steels A and B are shown as a function of percent cold reduction in Fig. 1. No optimum cold reduction was observed in steel A, rolled with palm oil lubrication. It is likely, however, that an optimum reduction would have occurred had higher reductions than 88 pct been employed. The optimum reduction in steel B occurred at 40 pct. The behavior in both of these steels is quite

Jan 1, 1968

By F. Paredes, W. R. Holman, R. W. Crawford

The diffusion coefficient for hydrogen in the ß titanium alloy containing 13 pct V, 11 pct CY, and 3 pct A1 was measured over the temperature range 20° to 500°C. Results fit the expression: D= 1.58 x lgs exp-------==-----) cm2,sec THE diffusion coefficient for hydrogen in the metastable ß-phase titanium alloy containing 13 pct V, 11 pct Cr, and 3 pct A1 was measured as part of an investigation of the effects of hydrogen on the mechanical properties of titanium alloys. Several theories on the mechanisms of hydrogen embrittle-ment include diffusion of hydrogen at ambient temperature as an important step in the embrittling process.'-5 In hydrogen-contaminated a-ß titanium alloys, it has been postulated that the rate-controlling step may be the rate at which hydrogen diffuses from the ß phase to stress- or strain-nucleated brittle hydride platelets at the a-ß interface.' However, embrittlement of the all-ß alloy investigated in this work may proceed by a different mechanism, since this alloy can be embrittled without the formation of detectable hydride platelets.6 Troiano has suggested that in this case the mechanism of delayed failure or embrittlement is similar to that proposed for high-strength steel, i.e., repeated crack initiation caused by a decrease in bonding energy as hydrogen diffuses to points of high tri-axial stress at the root of a notch. In both types of alloy the rate of embrittlement is believed to be controlled by diffusion of hydrogen in the ß phase. Accurate hydrogen-diffusion data in the vicinity of room temperature should therefore be of some assistance in understanding the mechanisms of embrittlement in these two classes of titanium alloys. Diffusion of hydrogen in pure titanium has been studied by Wasilewski and Kehl7 at temperatures above 500°C. Their measurements on diffusion in the ß phase were extended below the ß-a transformation temperature (882°C) to approximately 600°C. This was possible because of the 8 stabilizing effect of hydrogen. No results at lower temperatures have been published and there are no data in the literature on hydrogen diffusion in the ß -phase alloy used in this program. Hydrogen diffusion in metals is generally investigated by measuring the rate of transport of hydrogen past a solid-gas interface, i.e., by absorption, permeation, or degassing-rate measurements. These methods produce accurate diffusion data when bulk diffusion is the rate-determining step in the over-all process. However, at the lower temperatures of interest in hydrogen-embrittlement studies or under conditions where surface films are present, the measured rates may be surface-controlled and the calculated diffusion coefficients will be in error. Surface effects were eliminated in the present work by using a modification of the common welded-couple technique m which two bars with uniform but different compositions are joined before the diffusion anneal." The same type of step change in the initial concentration vs distance curve was produced by electrolytically hydrogenating thin-strip specimens which had been electrically insulated over half of their length. Concentration vs distance curves were determined, after appropriate diffusion-annealing treatments, by vacuum-extraction analyses of transverse samples sheared from the strips. Diffusion coefficients were calculated by the methods of Grube.M This technique was feasible because of the large concentrations of hydrogen which can be charged into p -phase alloys without the formation of hydrides15'16 and because of the extremely low degassing rates observed when hydrogenated titanium alloys are heated in air. EXPERIMENTAL WORK The diffusion couples were cut from a 0.022-in.-thick mi ll-annealed sheet.* Strips 8 in. long by 1/2

Jan 1, 1965

By Alfred E. Hunt

In a paper written for the Boston meeting of February, 1888 (Trans., xvi., 693), on "Some Recent Improvements in OpenHearth Steel Practice," the writer described the reducing agent used by the Carbon Iron Company as "a peculiar graphite from Cranston, near Providence, R. I." Upon an application pending at that time, a patent has since been issued as number 259,795, to Mr. Matthew Graff, for the use of solid carbonaceous matter in the form of coke, charcoal, gas carbon, bituminous or anthracite coal, ground to the size of coarse sand and then coated with a mash of lime, magnesia, clay, or other material of a like character, as an agent to reduce metallic oxides. An amount of this prepared carbonaceous matter equal to from 25 to 30 per cent. of the weight of the ore treated is required to perform the complete reduction. The idea is that the carbonaceous matter is protected against rapid combustion by a suitable coating of some inert material, so that, in effect, its action as a reducing agent will be similar to that of the Cranston graphite previously used, allowing the solid carbon to remain without combustion in intimate mixture with the iron oxide at a temperature sufficiently high to reduce the ore and in some cases to melt the matrix in which the iron is held. In the present practice of the Carbon Iron Company, the use of graphite, except for the formation of bottoms of the reverberatory furnaces in which the reduction is performed, has been entirely abandoned, and " retarded coke," as it is called at the works, has taken its place. Five hundred and fifty pounds of Connellsville coke is ground in a pan to 16-mesh fineness, or is taken in the form of ordinary coke-dust, and made into a hollow basin on the mixingfloor ; and seven bucketfuls of a wash composed of equal parts of lime and fire-clay, mixed in water to the consistency of thin cream,

Jan 1, 1889

By Richard Lee

SINCE the economics in the blast furnace resulting from enriching iron ores are so great, much attention, has been paid during the past few years to the various methods of concentrating lean ores, and, as the concentrated ore is usually of extreme fineness, various methods . of agglomeration and sintering, of more or less value, have been put 'into operation. The resulting agglomerated concentrates are generally obtained in the form of briquettes or nodules. The briquettes naturally divide themselves into two classes: (1) those made by the mixture of some binding agent, and then formed into briquettes under great pressure; and (2) those made by sintering the concentrates, the latter either being formed into bricks before exposure to heat or the sintered mass broken into fragments afterward. Of the first class I will not speak, as they are not used on an extensive scale in this country. The second class of briquettes, or those made by sintering, are simply masses of melted or fused silicate and oxide of iron mingled with more or less silicates of aluminum, lime, and magnesia. The fact that the material in a briquette is sintered is proof positive that there are no pores in the material. There are, however, quite a number of holes of greater or less diameter through the substance of the briquette. They are not pores in the common acceptance of that term as applied to ores by furnacemen, as the sides of the holes and channels are fused. In reality the material is simply mill cinder. It is practically untouched by the gases in the upper part of the furnace, and the iron has to be reduced by solid carbon in the boshes and hearth. Briquettes sometimes show a little saving in fuel in the furnace over an ore mixture of large lumps, but that saving is made simply because, owing to the numerous holes and channels through the mass, the briquette is practically composed of numerous small or fine lumps, and, as is well known, the finer the

Jan 10, 1913

By Klaus Detert, Joseph Ziebs

The progress of primary recrystallization has been studied in alloys of nickel with 0.01, 0.1, and 1.0 at. pct Ta. It can be shown that in one particular alloy containing 0.1 Ta and 0.02 02 a large grain structure (0.5 mm diameter) could he developed by primary recrystallization in thin sheetswhich were cold-worked to 97.5 pct reduction in thickness. Electron transmission microscopy demmstrates that this phenonmena was linked to the occurrence of fine precipitates at subboundaries. A discussion of how fine precipitates can exert under certain circumstances a rather distinct retarding effect on nucleation rate is included. IN a former investigation, the recrystallization and texture formation in a series of binary nickel alloys including pure nickel were studied.' Nickel alloys with some tantalum added displayed peculiarities during primary recrystallization which have been studied in more detail by the present investigation. The alloys were prepared by powder-metallurgy techniques similar to the previous investigations.' Pure metal powders were thoroughly mixed to obtain alloys with 0.01, 0.1, and 1.0 at. pct Ta, referred to as alloy A, B, or C, respectively. The metallic impurities were kept below 0.005 at. pct except iron and cobalt with slightly higher values, by using highly purified nickel and tantalum powders.' The mixtures were pressed into bars and sintered at a temperature of 1300°C. The sintering atmosphere was either high vacuum, dry hydrogen, or wet hydrogen. The sintered rectangular bars were rolled 60 pct to a thickness of 3 mm, then annealed under dry hydrogen at 1000°C and again cold-rolled to about 97.5 pct reduction of thickness. After this heavy deformation, the sheet thickness was 0.07 5 mm. In order to study primary recrystallization which occurred in measurable times between 400" and 600°C, samples of the rolled sheets were annealed in a salt bath at various temperatures for various times in order to study the progress of recrystallization by hardness measurements and microscopic examination. For optical observation, the samples were polished and etched in a solution of 65 cu cm HNO3, and 18 cu cm acetic acid in 20 to 100 cu cm H2O, depending of the particular sample and annealing treatment. For transmission electron microscopic observations, thin foils were prepared by the combined window and Bollmann techniques.273 The electrolyte consisted of 23 pct perchloric acid and 77 pct acetic acid held at 15°C. Polishing was performed at a current density of 0.4 amp per sq cm. The examination of the thin films was accomplished by a Siemens Elmiscope-type electron microscope operating with an accelerating voltage of 100 kv. RESULTS The progress of primary recrystallization was very accurately followed in these alloys in order to establish the time when recrystallization started and ended during an isothermal anneal. Table I gives some of the data obtained by these studies. The time for beginning is a mean value, where somewhat less than 5 pct of the matrix has recrys-tallized. The end of recrystallization is the time when at least 95 pct of the matrix has recrystal-lized. Listed are three different B alloys, with 0.1 Ta distinguished by different sintering atmospheres which influence the rate of primary recrystallization. By the above method, the state of the grain structure when primary recrystallization was completed, but grain coarsening had not started, could be clearly defined. The average grain diameter of the recrystallized matrix is also given in Table I. The grain size did not depend on the temperature of the isothermal anneal. With one exception the grain size of the primary recrystallized matrix was found to be rather fine

Jan 1, 1965

By O. W. Rees, Gilbert H. Cady

Unit coal calorific values represent a close approach to pure coal values; they possess characteristics theoretically inherent in the latter values. They are essentially uniform in the same seam for areas possessing essentially uniform geological environment. They are higher in older than in younger coals in most cases, and in deeper than in shallower coals. In general, they display characteristics closely in accordance with expectation assuming that they are essentially indices of rank. Because it possesses these characteristics, the unit coal value is essentially a standard value, characteristic of each bed in each local region. Hence it can be used as a basis for determining the accuracy of results in newly established laboratories, or when new equipment is installed, or in checking the results of different laboratories, or even in determining the character of coal as mined or prepared if ash, moisture and sulfur values are known. DISCUSSION (A. C. Callen presiding) R. P. Hunson,§ Wayland, Ky. (written discussion).—One of the interesting observatioris made by the authors is that there is a more or less definite correlation between unit coal calorific values and the geological environment of the coal bed. It is very interesting to note that, in general, the unit B.t.u. value increases with the increase in the probable original depth of burial, and that each seam tends to increase in calorific value toward the areas of diastrophic instability. It is generally conceded that Parr's formula, for determining unit coal values, is about as accurate as any formula subsequently proposed for the same purpose. In his formula, Professor Parr did not differentiate between the sulfur present as iron pyrites and that present as organic sulfur. However, the practical application of the formula has shown that this is of little consequence. I agree with the authors that unit coal calorific values are useful ill determining the accuracy of calorimetric determinations, and in determining the character of the

Jan 1, 1934

By P. G. Shewmon

A novel technique for determining the surface energy (?) and its derivative with respect to orientation, (?') is described. Essentially it involves the 'floating" of a wedge on the substrate, said wedge being made of a material which is not wet or only slightly wet by the substrate, i. e., as a greased needle "floats" on water. A thermodynamic analysis of a system in which the wedge is supported entirely by surface energy is given. If the original suyface is not at a cusp orientation, the surface tension is directly measurable from the groove angle formed. If the original surface is at a cusp orientation, there may or may not be a groove depending on the relative value of ?' and the weight of the wedge. Experiments primarily on copper and silver showed that sapphire, quartz and refractory metal wedges were wet while graphite wedges were not. The technique was demonstrated to work using graphite wedges, but the results obtained were not as eccurate as those obtained by other workers using the wire-creep experiments. It is concluded that the technique might prove most useful with non-metals where ?' is large and filament creep experiments would be quite difficult. If an absolute value of the surface free energy (?) of a metal is to be determined, the most reliable methods used to date measure an average over the various orientations exposed on a polycrystalline sample. For example, ? for silver, gold, and copper have been measured by determining the force required to just keep a thin wire,' or foil,' specimen from contracting under the influence of ?. Herring 3 has predicted and experiment confirms, that the sensitivity of this method is inversely proportional to the grain size.' Thus it cannot be used to measure ? for a particular orientation by using a foil single crystal or a very coarse-grained specimen. An accurate value if ? for tungsten averaged over a range of orientations has been determined using a field emission technique. The same techniques cannot or have not been used to measure ? for non-metallic solids, and as a result the values available are much less accurate.4 This Paper resents a means of making an absolute determination of ? for a particular surface orientation on any solid, as long as the given surface orientation does not break up into other orientations during an anneal. Experimentally ? is found to vary with orientation and at a few low index orientations it is found to have a cusped minimum, i.e., the derivative of ? with respect to the orientation of the surface changes discontinuously at the low index orientation, see Fig. 1. The slope of a plot of ? vs orientation (herein designated ?') is called the torque on the surface, since it tends to rotate the exposed surface toward the low index orientation, or if the surface is at the cusp orientation it opposes any force tending to rotate the surface out of the low index orientation. The ratio ?'/? has been determined for a few metals, but in cases where this ratio is high there is presently no means of determining either ?'/? or the absolute value of ?' for the orientations present on an annealed surface. The technique discussed herein also provides a means of determining an absolute value of ?' for those orientations which deviate only infinitesimally from a cusp orientation. It should work best on surfaces where ?'/? is large; that is, for cases where no other technique is available for measuring ?'. Aside from trying to learn more about surfaces through measuring ? and ?', the primary reason for wanting values of ? or ?' is to study adsorption. From measurements of the variation of ? for a particular orientation with the concentration of an impurity, one can obtain the number of impurity atoms adsorbed per unit area (Ti) on that orientation using the Gibbs adsorption equation.' where µi is the chemical potential of the adsorbed impurity. Thus, if absolute values of ? could be obtained for the free surface of a given surface orientation as a function of µi, ri could be determined for the given orientation. Furthermore, by equilibrating a grain boundary with the given surface at various values of ki, one could also determine ri for the grain boundary. Similarly Robertson 6 has pointed out that if y is taken to be a continuous function of and µi, then a2 ?/a @a µ2 = a2 ?/a pi a +. Thus, at all orientations away from cusps the following equation holds From a measurement of ?' vs ki, it is thus possible

Jan 1, 1963

By R. T. Mishler

I wish to express my keen appreciation of the article on the above subject by Coe and C1evenger.l It has been doubly interesting to me, for the reason that the experience recorded and the principles evolved practically parallel the results of similar investigations made by myself and others at The Lucky Tiger Mine, El Tigre, Sonora, Mex. An outline of the work at El Tigre may aid in confirming the principles expressed by Coe and Clevenger. El Tigre has the unenviable distinction of possessing a slime with a much lower settling rate than any recorded in the article discussed. Under most favorable conditions the settling rate is about one-third that reported for the Liberty Bell mill, and one-tenth that reported for the Nipissing, Golden Cycle, and Presidio mills. This slow settling characteristic of Tigre ore has necessitated careful investigation of settling phenomena throughout the various evolutions of the plant. Previous Settling Investigation at Tigre During construction work at the mill, the metallurgical engineer in charge, D. L. H. Forbes, ran a series of experiments on settling. His tests proved that deep settling tanks were not ordinarily necessary. The use of tanks 2 or 3 ft. in depth was suggested.2 Later experiments demonstrated that the following principles of settling applied to Tigre pulp.3 1. In settling dilute pulp, settling rates are independent of pulp depth. 2. In settling thick pulp, settling rates are approximately proportional to pulp depth.4

Jan 1, 1918

By R. Van A. Norris

Although mechanical appliances for the ventilation of mines have been known siuce very early times (one being mentioned in Agricola's De Re Metnllica, 1657), it is only within the last forty years that such appliances have been generally used. A great number of different ventilators have been invented and used, but the varions forms of centrifugal machines having proved their efficiency, have now almost conlpletely replaced all others. Most if not all of the machines in use in this country are of this class, being either open-periphery fans, or closed, with chimney and spiral casing, of a more or less modified Guibal type. The theory of such machines has been demonstrated by Mr. Daniel Murgue in Theories and Practice of Centrifugal Ventilating Machines, translated by A. L. Steavenson. His statement may be condensed thus : Let a = orifice in a thin plate, of such area that its resistance to the passage of a given quantity of air equals the resist ance of the mine. I o = orifice in a thin plate of such area that its resistance to the passage of' a given quantity of air equals that of the machine. Q = quantity of air passing in cubic feet per minute. V = velocity of air passing through a. Vo = velocity of air passing through o. h = head iu feet air-column to produce velocity IT h, = head in feet air-column to produce velocity V,.

Jan 1, 1892

By J. S. Ll. Leach, M. B. Bever

THE system copper-nickel exhibits complete solid and liquid miscibility1 The thermodynamic properties of such a system would not be expected to deviate greatly from ideality. Although the evidence is conflicting, anomalies in the composition dependence of various physical properties of solid copper-nickel alloys suggest that mixing may not be ideal.' From measurements of the Hall coefficient it has been concluded that clustering occurs in these alloys. ' Considerations involving the phase diagram of the ternary system copper-nickel-chromium have led Mei-jering3 to predict a positive heat of formation for solid copper-nickel alloys. An electrochemical investigation of the activity of nickel in copper-nickel alloys showed unexpectedly large positive deviations from ideality.4 wagner5 has proposed that if the entropy can be considered ideal, these measurements would yield the following equation for the heat of mixing at 700°C H" = 3380 x,vl (l-xVi) cal per g atom [I1 The heat of formation at 722°C of solid copper-nickel alloys of the equiatomic composition has been measured in a reaction calorimeter as 540 cal per g atom. This note reports calorimetric measurements of the heat effects on dissolution of some copper-nickel ndon: in tin. These measurements were preliminary to a larger investigation, which was later discontinued. From them the heats of formation of the alloys can be calculated, if certain assumptions are

Jan 1, 1960

By Henry M. Howe

in Cast-Iron. It has been generally accepted that the presence of silicon in cast-iron leads to the formation of graphite; and this has been explained by saying that the silicon lowers the solvent power of iron for carbon at and somewhat below the freezing-point, so that, in the presence of silicon, the iron is unable to retain in solution or combination the whole of the carbon with which it has united while molten, and therefore expels the excess of carbon in the form of graphite, during and immediately after solidification. Probably the best way to study this question would be to examine pure cast-irons, i.e., those containing nothing but iron, carbon and silicon, which at the same time should have been saturated with carbon when molten. But the data for such a study are not at hand; so we must turn to commercial pig-irons as they are made in the blast-furnace, and before their composition has been changed by remelting. Much evidence has been offered of late, tending to oppose the theory of the action of silicon above set forth. Some of this evidence will be examined here. 1. Mr. Bachman's Results. In particular, Mr. F. E. Bachman† has published a collection of analyses of cast-iron, in which the proportion of graphite at first appears to be nearly independent of the proportion of silicon present. Thus, in his Table LI., we find that with pro-

Jan 1, 1901

By Byron W. Cheever

In the Journal of the Iron and Steel Institute for 1881 (vol. ii., page 379), will be found an article upon this subject. The analyses there reported mere of samples taken from an ingot made especially rich in impurities and then cast in a sand-mould in order to give the elements a better chance to redistribute themselves, on account of the steel solidifying more slowly than when cast in an iron mould. Wishing to ascertain how much, if any, segregation takes place when the steel is cast in the ordinary way, I placed the subject in the hands of Mr. W. J. Olcott, a graduate of the Michigan University, who has carefully collected and analyzed samples taken from different parts of ingots and billets. In this undertaking he found himself somewhat embarrassed on account of being distant from steel-works, and therefore unable to supervise the selection of samples. He found, however, a competent and willing aid in the person of E. F. Wood, M.E., chemist of the Pittsburgh Bessemer Steel Company, Limited, who has spared no pains in collecting the desired samples and furnishing drawings and descriptions of the ingots from which the samples were taken. The following are the results obtained: Ingot No. 1. This ingot was about 5 feet long and 13 X 131/4 inches at the point of fracture, which was 2 feet from the bottom. The samples

Jan 1, 1885

By Eugene S. Perry

The only outstanding development in Montana oil or gas fields during 1935 was the extension of the Cut Bank oil and gas field 7 miles southward. This field is now about 20 miles long and 3 to 8 miles wide, with 218 producing oil wells and 39 producing gas wells. Average daily production of the oil field during December, 1935, was about 6700 bbl.; total production for the year 1935 was approximately 2,020,770 barrels. The Cut Bank field in northern Montana is in a flat to rolling glaciated area used mainly for grazing purposes. Oil and gas occurs in sandstones and shaly sandstones in the Kootenai (Dakota) formation of Lower Cretaceous age at depths ranging from 2700 to 3000 ft. Prominent anticlinal or domal structure is not present, but small plunging anticlines occur locally. Strata dip westward from 75 to 200 ft. per mile. The field lies on the western flank of the Sweetgrass arch, a broad gentle upwarp over 150 miles long. Localization of oil and gas appears to be due either to pinching or lensing out of the sandstone beds, or else silting of the sandstones with clay minerals so that porosity becomes low. Within the field offset wells show marked variation in initial production, which suggests that differences in porosity of sandstone is the controlling factor. The gas-producing portion of the field is entirely updip (east) from the oil-producing portion, and the producing horizons are the same. Initial production of oil wells ranged from about 50 to about 200 bbl. per day, and initial open flow of gas wells ranged from about one million to about 37 million cubic feet per day, with an average of 11 million cubic feet. Initial gas pressures were slightly greater than 700 lb. per sq. in. Oil is brought to the surface by pumping. Both rotary and standard churn-drilling equipment are used. In the remaining 14 oil and gas fields but little new activity took place other than the drilling of offset wells and wells in proven territory. Continuation of "acid treatment" of wells in the Kevin and Pondera oil fields led to reconditioning of many old wells and the drilling of a number of new wells within these fields. Acid treatment of the oil-bearing horizon, which is the dolomitized and silicified Madison limestone of Mississippian age, has proved quite satisfactory, and some "bone dry"

Jan 1, 1936

By Eugene S. Perry

The only outstanding development in Montana oil or gas fields during 1935 was the extension of the Cut Bank oil and gas field 7 miles southward. This field is now about 20 miles long and 3 to 8 miles wide, with 218 producing oil wells and 39 producing gas wells. Average daily production of the oil field during December, 1935, was about 6700 bbl.; total production for the year 1935 was approximately 2,020,770 barrels. The Cut Bank field in northern Montana is in a flat to rolling glaciated area used mainly for grazing purposes. Oil and gas occurs in sandstones and shaly sandstones in the Kootenai (Dakota) formation of Lower Cretaceous age at depths ranging from 2700 to 3000 ft. Prominent anticlinal or domal structure is not present, but small plunging anticlines occur locally. Strata dip westward from 75 to 200 ft. per mile. The field lies on the western flank of the Sweetgrass arch, a broad gentle upwarp over 150 miles long. Localization of oil and gas appears to be due either to pinching or lensing out of the sandstone beds, or else silting of the sandstones with clay minerals so that porosity becomes low. Within the field offset wells show marked variation in initial production, which suggests that differences in porosity of sandstone is the controlling factor. The gas-producing portion of the field is entirely updip (east) from the oil-producing portion, and the producing horizons are the same. Initial production of oil wells ranged from about 50 to about 200 bbl. per day, and initial open flow of gas wells ranged from about one million to about 37 million cubic feet per day, with an average of 11 million cubic feet. Initial gas pressures were slightly greater than 700 lb. per sq. in. Oil is brought to the surface by pumping. Both rotary and standard churn-drilling equipment are used. In the remaining 14 oil and gas fields but little new activity took place other than the drilling of offset wells and wells in proven territory. Continuation of "acid treatment" of wells in the Kevin and Pondera oil fields led to reconditioning of many old wells and the drilling of a number of new wells within these fields. Acid treatment of the oil-bearing horizon, which is the dolomitized and silicified Madison limestone of Mississippian age, has proved quite satisfactory, and some "bone dry"

Jan 1, 1936

By S. E. Haszko

Fused alumina or silica crucibles were used as the containing vessel. X-ray powder photographs were taken with CrKa radiation and the use of Straumanis type Norelco cameras of 114.6 mm diam. Crystallographic data for these compounds are shown in Table I. These results are in agreement with others of this series reported previousiy by Wernick and Geller.l The abnormally large atomic volume of Eu and Yb metal3 is manifested in EuA12 and YbAl2, when one compares them with the compounds reported in Ref. 1. However, the behavior of Yb in the Ni compound is the same as that observed in Ni5Yb having the Cu5Ca structure.4 Thus, it appears that Yb has a valence closer to 3 only in the Ni compounds; i.e.. the 2s and Id electrons are lost to the conduction band. 1,4 Europium in EuAl2, appears to have a valence closer to 2. In previous work.' X-ray patterns of ingots of NdCo2 indicated a multiphase material with faint indication of the presence of a phase having the MgCu2 structure. It was thought that NdCo2 formed peri-tectically from the melt, resulting in a multiphase system when cooled under nonequilibrium conditions. An X-ray pattern of a sample from a melt cooled more slowly than in past work showed that the major phase was NdCo2. The lattice constant, Table 1, is in excellent agreement with the value one can predict from the data of Ref 1. One of the other phases was identified as Co,Nd. The author wishes to thank J. H. Wernick for his guidance in this work, and D. Dorsi for the preparation of these compounds. 'J. H. Wernick and S. Geller: AIME Trans., in press. 'J. H. Wernick and S. E. Haszko: to be published. 'F. H. Spedding and A. II. Daane: Progress in Nuclear Energy, Series 5, Eds.: H. M. Finniston and J. P. Howe, McGraw-Hill Book Co., 1956. 'S. E. Haszko: to be published. 'J. H. Wernick and S. Geller: unpublished work. 6J. 11. Wernick and S. Geller: Acla Cryst., 1959, vol. 12, p. '162. The Influence of Hydrogen on the Lattice Parameters of Ti-Sn Alloys A. Coucoulas and H. Margolin A reinvestigation of the lattice parameters of Ti-Sn alloys by the present authors has revealed consistently higher c and a values than those obtained by Worrier. The difference is most pronounced in the c-parameters which are, therefore, used as a basis of comparison. This discrepancy was not due to air contamination, since precautions were taken to exclude this possibility. Specimens for Debye-Scherrer photograms were prepared by arc-melting 15-g buttons of Bureau of Mines titanium and 99.99 pct Sn, with compositions of 6, 8, 10, and 12 at. pct Sn. These buttons were forged under an oxygen-acetylene torch to 1/8-in. sq rods to produce relatively fine grained material. Scale and some surface were ground off, and the rods, after wrapping in molybdenum and titanium sheet, were vacuum annealed 15 min at 800 °C to remove hydrogen. Heat treatment of one of the samples at 875°C to produce ß and reveal a at the surface showed no surface contamination. Following the vacuum treatment, the specimens were wrapped in molybdenum and annealed for 1week at 800°C under two atmospheres of argon. After water-quenching, the rods were ground so that the thickness tapered to 0.1 mm at the tips. The ground specimens were then recapsuled as previously and reannealed 1 hr at 800°C to remove cold work. The

Jan 1, 1961