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By C. Norman Cochran

The pllnse diagvam for the NaF-AlF3 system was used to calcutate an ionic model for the NaF-AlF3 system. Assuming an ideal solution,a series of simultaneous equations expressing equilibria be-tween solid and liquid phases at the euleclic, perilec-tic, and melting points were solved for the activities of the ionic species, the dissociation constants, and the entropies and heats of fusion. The calculations suggest the existence of A13F1415 ions in addition to the F-1+AlF6-3 , and AlF4-4 ions previously proposed by others. The calculaled valnes give better agreement with vapor pressures than the previous model without Al3Fl14-5. Additional possible vefinements of the model are proposed. CRYOSCOPIC1 investigations and density data2 for the NaF-A1F3 system have previously been used to study the dissociation mechanism of Na3A1F6 and to derive equilibrium constants for its dissociation to NaF and NaAlF,. Depending primarily on the heat of fusion assumed for cryolite, the dissociation constants ranged between 0.02 and 0.18 from cryoscopic studies, and from 0.09 at 1273°K to 0.16 at 1363°K from density data. In most cases the values were unable to reproduce satisfactorily the experimental liquidus lines very far on the A1F3 side of the Na3A1Fe composition. This suggested the existence of at least one other ionized compound in the melt besides NaA1F4 in the Na3A1F6-A1F3 side of the system. This is assumed to be liquid Na&13F14 (chiolite), which is already established as a stable solid in phase studies of this system. MODEL FOR THE MELT The melt is assumed to be an ideal solution with ion activities equal to anion fractions. The only cation in the model is sodium so that Temkin and simple anionic activities are identical. Although the compounds are completely ionized to Na' and the respective anion in the melt, molecular rather than ionic notation is used throughout this work. The Na3A1Fe is assumed to dissociate to NaA1F4 and NaF as in the former model, and Na&13F14 to dissociate to Na3A1Fe and NaA1F4. Other valid dissociation equilibria can be written involving these four compounds, but all of these can be obtained by combinations of the two described dissociation reactions and, thus, are automatically considered in these calculations. The model allows for no free AlF3 so that compositions for NAIF3 > 0.5 (mole fraction A1F3 on the NaF-A1F3 basis) cannot be treated. The question of the existence of free AlF3 in the melt will be discussed again later. The constants in the model were evaluated from points along the entire known liquidus line of the NaF-A1F3 system. Previous work employed only the liquidus line or densi- ties near the Na3A1F, composition. The liquidus line compositions used in the solution of the model are from unpublished work by Mr. P. A. Foster, Jr., for compositions between the Na3A1F6 melting point and the Na&13F14-A1F3 eutectic, and from the published works of Grjotheim,1 Phillips,3 and Foster4 for the remainder of the system. The relationships used in solving for the desired dissociation constants and heats and entropies of fusion are listed in Table I, and the points along the liquidus line at which each apply are indicated to the right of the relationships. The mole fractions of each of the separate species in the melt are symbolized by N. Relationships [I] and [2] are the respective dissocia-ation constants, Kl and K2, of Na3AIF6 and Na5A13F14 for this model. For simplicity, these constants will be assumed to be independent of temperature. Relationship [3] follows from the assumption of the ideal solution. The expression relating the values of N to the experimental values of NAIf3, is given in Relationship (41. Relationships [5], [6], and [7] each state the equilibrium between a compound in the melt and its pure solid phase for the portion of the liquidus lines where it precipitates. The heats of melting, AH,, and entropies of melting, AS,, used in [5], [6], and [7] are assumed to be independent of temperature. The compositions and temperatures of all five invariant points (two melting points, two eutectics, and one peritectic) along the liquidus lines from NAIF3 = 0 to NAIF3 = 0.5 were employed in the solution. The eutectic and peritectic compositions were particularly useful because each of these is involved in one more equation than other points along the liquidus lines and thus reduces the number of points required to solve for the constants. Also, their use assures that the inflection points in the derived liquidus line will correspond exactly with those on the experimental liquidus line. The total number of equations is 5k1 — 1, where n is the number of experimental composition points used. The number of unknowns is 4n + 5 (4n- 3 values of N, 3 values each of AH, and AS,, and 2 values of K). Thus, six points must be used in the solution to obtain an equal number of equations and unknowns. The one additional required experimental composition was taken on the liquidus line between the Na3A1Fe melting point and the Na3A1F6-Na5A13F14 peritectic. Previous work indicated this was a difficult portion of the curve to fit. The temperature used for the point was 1161°K, the same as for the NaF-Na3A1Fe eutectic. This choice of temperature gave two points with identical NNa3AIF6 values which simplifies the algebraic solution. The second point at this temperature is denoted 1161°'K. PROCEDURE FOR SOLUTION OF EQUATIONS Values were assumed for NNa,AIF and NNaF at the NaF-Na3A1F6 eutectic at 1161°k. By an iterative procedure, the corresponding values for NNa5A13F14 and NNaAlF4 at 1161°K were determined from 131 and 141. A value was assumed for NNaAlF4 at 1161°'K and

Jan 1, 1968

By J. E. Hove

The high temperature physical properties of graphite are reviewed and interpreted in the light of present day knowledge of the mechanisms affecting these properties. The thermal and mechanical behaviors only are discussed and, whenever possible, comparisons are made with other refractory materials. Possible further studies are indicated, including some carbide work. AS long as the term high temperature implied only temperatures up to about 1000°C, the materials problems which arose could usually be handled by fairly conventional metal alloy types, such as the Co-Cr-Ni superalloys, for which there exists a great deal of technology. Perhaps this temperature can still be considered an upper limit for normal applications, but it is certainly true that the number of abnormal applications is increasing rapidly. The advent, in recent years, of ram-jet and rocket missiles and of high power nuclear reactor heat sources has raised a host of questions concerning the basic problem of what material to use in the temperature range up to 2000°C and higher. While there are, of course, many metals, in the second and third transition series, which melt at considerably higher temperatures than this, these metals are, at present, pretty well excluded from practical use by other considerations, such as re-crystallization, chemical activity, or excessive plastic deformation. The behavior of metals, from the standpoint of dislocation theory, is just beginning to be understood and thus there is some hope for the future development of very high temperature metals, but the immediate problems would most logically appear to have solutions involving the nonmetals, such as the refractory ceramics and graphite. For this reason, there is presently a great deal of engineering and experimental research being performed on the latter materials, much of this research being exploratory in the sense of gathering new property data. The situation, so far as graphite is concerned, is somewhat more fortunate than with the other refractory solids in the sense that a great deal is already known about its basic properties. This stems both from the fact that the carbon-carbon bond has been of interest to chemists for a long time (and graphite can be considered as a very large aromatic molecule, if desired) and the fact that its properties, both as a function of temperature and of radiation damage, are of critical importance to nuclear reactor designers. It is still true, of course, that such fundamental questions as why graphite remains solid to such a high temperature and why it has such a high thermal conductivity cannot entirely be answered at the present time. It is, nonetheless, meaningful and instructive to consider such problems in the light of existing knowledge. This is what the present paper will attempt to do. Before going on, it may be appropriate to classify graphite and justify its discussion before readers primarily interested in metals. Graphite is comparatively unique among materials in that there is always a property or group of properties which precludes calling it either a metal, a semiconductor, or a ceramic. It has the high electrical and thermal conductivities of a metal, but the artificial, poly-crystalline types show a negative thermal coefficient of electrical resistivity, generally characteristic of semiconductors. On the other hand, semiconductors, by definition, show an ever increasing resistivity as the temperature is lowered, whereas graphite approaches a finite, and, indeed, a rather low resistivity in the region of 10°K and, furthermore, a good single crystal of graphite has a positive temperature coefficient, as for a metal.' On still another hand, its porosity and brittleness at lower temperatures would put graphite in the ceramic class although, unlike most ceramics, it is readily machinable and has a high resistance to thermal shock. All things considered, it is probably more nearly appropriate to call graphite a metal than anything else. Although certainly outstanding in some ways, graphite has its peculiarities and, especially if the reader is unfamiliar with the data, it is probably valuable to review some representative property variations at high temperature. This review is meant to be mainly illustrative and no attempt has been made to be exhaustive. Review of High Temperature Properties At ordinary pressures, graphite does not melt, but sublimes directly into the gaseous phase at about 3700°C. Although the phase equilibrium diagram is still in some doubt, graphite will melt, at a slightly higher temperature, at pressures in excess of about 100 atm. The chief difficulty of using graphite in an oxidizing atmosphere is that the reaction rate becomes quite high at fairly low temperatures. If a threshold oxidation temperature2 is defined as the temperature at which graphite loses 1 pet of its weight in 24 hr, the value in air is 450°, the value in steam is 700°, and the value in carbon dioxide is 900°C. Efforts are presently being made to raise this threshold temperature either by impregnation with a retardant of some type (sodium tung-state and phosphoric acid, for example) or by a suitable metal or oxide coating. It is probably fair to say that, to date, these attempts have not shown any outstanding success in all respects. Most commercial graphites are fabricated by impregnating a carbon flour (say of coke or lampblack particles) with some type of hydrocarbon

Jan 1, 1959

By D. G. Osborne

Transportation cost is a key factor in both the profitability and competitiveness of coal marketing. With coal exportation growing rapidly, moisture control is important. Although in some cases, too much moisture reduction can lead to losses in transportation and pollution problems, there is normally justification for reducing moisture by mechanical means as much as possible. This paper reviews current technology of dewatering coal fines and examines the comparative capabilities of screens, filters, and centrifuges. Financial considerations are stated and implications of capital and operating costs on selection are discussed.

Jan 1, 1985

By W. J. McGee

Most nations and states have conducted geological surveys, generally with the view of discovering and developing natural resources, sometimes with the aim of promoting science. In some cases, as in the first survey of Pennsylvania, the official geologist so far preceded the prospector and miner as to guide the discovery and exploitation of the commoner ores, mineral fuels and structural materials; but in most instances statesmen have only been awakened to the need of such a survey by the successful extraction of minerals;

Jan 1, 1893

By A. J. Lynch, N. W. Johnson, D. J. McKee

The behavior of nonsulfide gangue in chalcopyrite flotation circuits has been investigated. Plant and laboratory tests were conducted on five different ores. Linear relationships between the recovery rates of free nonsulfide gangue and water were observed. From pilot plant tests, there was evidence that the linear relationship was actually a linear approximation to a parabolic relationship. There was evidence that free nonsulfide gangue is transported from the pulp to the froth in the water and that the gangue is subjected to hydraulic classification in the froth column. A classification matrix has been proposed to define this behavior. This matrix is suitable for inclusion in a mathematical model of the process.

Jan 1, 1975

By Leland L. Mink, Roy E. Williams, Lewis M. McNay, Alfred T. Wallace

In 1968 the metal-mining industry of northern Idaho installed tailings ponds as a means of handling and treating mine wastes, metallurgical process wastes and domestic wastes. The installation of the ponds constituted a crash program to minimize pollution of the Coeur d'Alene River. The ponds provided an opportunity to investigate which combinations of wastes tailings ponds can be treated. The research data pertaining to tailings pond discharge lends insight into compliance with the recent EPA guideline for effluent quality.

Jan 7, 1973

Scientific elite of the Minerals Beneficiation Div. assembled in Denver, Colo., September 17 to 20 to commemorate the 50th Anniversary of Froth Flotation in the United States of America. In his warm address of welcome at the opening luncheon, John W. Vanderwilt, President, Colorado School of Mines, recalled his experience in Bonanza which coincided with the early days of flotation. In those years the scientific and engineering aspects of the process which we know today were little understood and operating the flotation circuit was considered an "art." Luncheon Chairman H. L. McNeill caught the flavor of the old days in an anecdote which recalled the mill nightmares to many present with the agonized words, "Oh God, what's happened to the concentrate now!" It was an appropriate gesture when he called the names of some of the flotation greats for presentation to the assembly; and many an "artist" there was among them!

Jan 10, 1961

By H. F. Ameen, F. M. Hamilton

Results of a laboratory investigation of some sintering variables are presented. The effect on physical properties of mix component variation and rate of cooling of the sinter is illustrated by crush and tumbler test results and data of reducibility tests and microscopic examination of sinters are shown. The results of using solid additions in the mix to improve bed permeability are given.

Jan 12, 1950

By Jerome S. Nelson, William S. Johnson

Seismic investigations at pre-construction sites commonly are limited to obtaining velocities and thicknesses of subsurface intervals which are useful in estimating construction costs, but are sometimes difficult to apply to project designing. This paper shows through a case history of the San Bernardino Tunnel Intake Tower, a part of the California State Water Project, that dynamic rock properties and dynamic resonant frequencies can be determined and velocity models constructed from in situ field studies and that these are theoretically correct after simplifying assumptions are made. These data can be used to confirm and extend information obtained by conventional methods such as drilling and laboratory static testing.

Jan 1, 1971

By L. H. Robinson

Triaxial compression tests have been performed to determine the strength characteristics of limestone, sand-stone and shale rocks subjected to controlled stress conditions. This control tuns exercised by varying the liquid pressures within and around a plastic-encased rock specimen. The pressure in the pores of the rock was varied throughout the range from atmospheric to 15,000 psig; the external pressure was changed over the same range with various positive pressure differences between is and the intertnal pressure. The data show that the rock strength increased and the mode of failure changed as the pressuire. surrounding the rock became greater than the pressure in the pores of the rock. These observations and the resu1ts of microbit drilling experiments indicate that the increased rock strength under pressure may bc an important effect in reducing drilling rare, but that other factors are probably of even greater importance. INTRODUCTION A large part of the research conductcd to reducc thc cost of drilling is directed toward improving present drilling technology and dcveloping new drilling methods. In spite of the fact that drilling is essentiaIly the act of making rocks fail, many details of the mechanism of failure are not known. It seems probable, therefore, that continuing studies of the fundamentals of rock failure can lay a foundation for future improvements in drilling technology. One of the factors which affects rock failure is the stress applied to the rock. This effect has been known for many years.'.'.; As an example, stress studics have been published by engineers' concerned with the strength characteristics of concrete in large dams. More recently, a number of investigators4-12 have explored the effects of stress on the strength of geologic formations and the geologic implications of their findings. During the last few years some research'" on rock strengths has also been conductcd in an attempt to gain additional insight into the factors which affeet rock drillability. In detcrmining the strength characteristics of rocks under different stress conditions, investigators have conventionally used triaxial compression equipment. wherein a jacketed rock cylinder is uniformly loaded from all directions and then compressed longitudinally. The results of this work have demonstrated that the mode of failure (brittle or malleable) is dependent upon the loading pressure, and that the strength of the rock increases as the loading pressure increases. These results clearly manifest that the stress, which is determined by the loading pressure, affects rock strength, and this implies that rocks under stress should be stronger and hence harder to drill. During the drilling of a porous rock the stress conditions are determined not only by the pressure surrounding the portion of the rock undergoing failure (confining pressure) but also by the pressure of the interstitial fluids within the rock (pore pressure). The importancc of both these pressures on the drilling rate of rocks has already been demonstrated by a number of investigators. Murray and Cunningham" found in microbit drilling expcriments that at constant pore pressures the drilling ratc decreased as the hydrostatic pressure surrounding an unjacketed, impermeable rock increased. Later Eckel" found that for jacketed Iimestone specimens the differcnce between hydrostatic (wellbore) pressure and formation (pore) pressure had an important effect on drilling rate. These observations of the effect of pressure on drilling rate emphasize that for drilling studies triaxial compression tests should be conducted under conditions of confining and pore pressure which simulate conditions underground. In the past, triaxial tests have been made under conditions which do not reproduce those underground. In particular, most of the tests on porous materials have keen made at varying confining pressures but with atmospheric pore pressures. In only one group of tests' was any data on the effect of pore pressurc reported, and these few data were on materials not representiltive of those encountered in drilling earth formations. The research described herein was initiated to deter-mine the importance of both internal pore pressure and confining pressure on failure characteristics of limestone. sandstone and shales. Triaxial loading equipment was used to obtain strength data at pressures up to 15,000 psig. An additional objective of this research was to apply these results to drilling rate studies by comparing them with the previously published drilling data of Murray and Cunningham" and of Eckel12. The work reported here is but one step in determining and evaluating the fundamental mechanisms which control drilling rate. Additional research is needed to clarify other aspects of the drilling process. The better

By Charles L. Mantell, George Ferment

This investigation determined the jeasibility of current-potential curves as an analytical tool for monitoving manganese electroicinning solutions for metallic impurities. Nine metallic impurities were studied: trickel, cobalt, silver, copper, zinc, molybdenum, catlmiun magnesium, and sodium. The individual effect of each metallic irzplrl,iLy on the standard point-izatiorr was determined for a range of 'concentration. Not all of Ihe impurities affected the polarization curve; correlation between transition current and cotrcetztration of impurity. Molybdenum had an uncorrelated effect on the polarization curie. The effects of binary mixtures of impurities were studied to see if the transition current of the mixture could be predicted. Interactions occurred between impurities which prei'etzted the pvecliction the transition current of tile rrlisLitr.e by additive laws. The polarization curve was shown to be sensitive to metallic impurities which affect the current efficiency of a manganese cell. THE application of current-potential curves in manganese electrowinning is not new but played an important part in the conversion of an inoperative large-scale pilot plant into a continuous comnercial operation.1"" The effects of trace metallic impurities in manganese electrowinning solutions on cathode current-potential curves,5-19 specifically nine impurities (nickel, cobalt, silver, copper, zinc, molybdenum, cadmium, magnesium, and sodium) were studied for a range of concentrations. Cadmium, magnesium, and sodium had no effect. Nickel, cobalt, silver, copper, and zinc yielded a correlation between transition current and concentration of impurity: molybdenum had an uncorrelated effect. Binary mixtures of impurities were studied to de-termine if the transition current could be predicted from the values for the individual constituents. Interactions between impurities prevented the prediction of the transition current of the mixtures by an additive law. The polarization curve was shown to be sensitive to metallic impurities which affected the rurrent efficiency of a manganese cell. The electrowinning of manganese relies upon maintaining a high-purity electrolyte. Purification schemes were developed to remove all of the heavy metals, the magnesium and calcium. Concentration limits have been established for single impurities. With high-purity electrolytes, favorable cell efficiencies are consistently obtained; but with impure solutions there is a reduction in efficiency. With the rapid rise to commercial prominence of electrochemical processes, there has been a lag in developing rapid methods for determining whether an electrolyte is sufficiently pure for efficient electrolysis. The most sensitive test for impurities is the behavior of the electrochemical cell. Impure electrolytes will cause a serious reduction in cell efficiency, and in many cases metal deposition will be prevented or reversed. The effects of impurities are not usually evident until after long periods of electrolysis, resulting in a disruption of the process. A method which could predict the behavior of an electrolyte in terms of cell efficiency prior to reaching the commercial cell is needed. Van Arsdale and Maier," Allmand and Campbell,a1'22 and others attempted to develop an electrochemical process for manganese,"3"29 but all met with some degree of difficulty. Jacobs et a studied the effects of metallic impurities in manganese electrowinning. Plant methods were based on a 2-hr plating in a small electrolytic cell. The final method was based on a 24-hr plating run, performed in a relatively large test cell. Here, current efficiencies were calculated with and without impurities in the electrolyte, and the critical concentration was established as the maximum amount of impurity that the electrolyte could tolerate before there was a serious loss in efficiency. The amount of impurity that could be tolerated decreased as the plating time increased, indicating deposition of the impurity. This test duplicated the conditions of commercial practire, and was sensitive to impurities. Small amounts of impurities significantly affect the hydrogen overvoltage at a metal surface, increasing or decreasing it depending upon the nature of the impurity. ockris established the limit for the onset of poisoning at 10-l moles per liter. The effects of impurities were studied by potential-time curves at a constant current density. The technique did not lend itself to rapid analysis in that several hours were needed to establish stable potential-time curves. Serfass and coworkers3' developed calorimetric and spectrophotometric techniques for analyzing for trace impurities. Our method4'" is based on current-cathode potential curves produced by continuously changing the cell voltage at a programmed rate. Starting with a clean stainless-steel cathode, the cell voltage was initially adjusted to yield zero current: the program was then started and the current was plotted as a function of the cathode potential. Fig. 1 is a typical current-potential curve. In initial region A the hydrogen-evolution reaction predominates and the polarization curve

Jan 1, 1967

By L. F. Mondolfo, B. E. Sundquist

The crystallographic orientation relationships resulting when lead is nucleated from the liquid by Ni, Cu, Ag, and Ge were determined. For each nucleating agent several definite orientatioz relationships were found. These relationships seemed to be controlled by good symmetry relations and low crystallographic disregistry between mating planes. For any given nucleating agent the under colling for nucleation was found fairly constant and independent of the orientation relationship and consequent disregistry. It was also found that, upon re melting and refreezing the Pb, the orientation relationship was changed. These findings prove that crystallographic disregistry is not the controlling factor in heterogeneous nucleation from the liquid. The results of this investigation tend to confirm the theory presented in a preceding paper that heterogeneous nucleation starts with the formation of an adsorbed layer of nucleated metal on the nucleat-ing impurity. Evidence is given that cavities in the nucleating agent act as centers of nucleation. IT has long been known' that solid extraneous particles are active in catalyzing phase transformations that occur in a system, particularly condensation and crystallization. It is well established that these heterogeneities act as catalysts by providing surfaces upon which nuclei of the precipitating phase can form with activation energies smaller than those required for homogeneous nucleation. Numerous investigations have shown that in this process of heterogeneous nucleation: a) the nucleus forms with one, or several, definite crystallographic orientation relationships with the nucleating phase2-4 and b) that there is a small range of undercoolings or super saturations characteristic of the nucleation of a given solid on a given Substrate.5-10 Turnbull and vonnegut11 have developed a theory based on theories developed by Volmer12 and Turn-bull and Fisher1= for heterogeneous nucleation from gases and liquids, that relates the super saturation or undercooling required for nucleation to the dis-registry between the lattices of the nucleus and the nucleating agent. This theory predicts that nucleation should occur with the orientation relationship between the nucleus and nucleating agent that minimizes the disregistry. Further, it predicts that the undercooling or super saturation necessary for nucleation should be a function of the disregistry. Numerous investigations have dealt with the orientation relationships resulting from the condensation of vapors onto crystalline solid substrates2,3 and a few with the nucleation of one phase by a second phase in solidification4,14. Others have dealt with the supersaturation8-10 and undercooling5-7 associated with nucleation in condensation and solidification respectively. However, there is virtually no report that gives both of these factors for the same system. In this investigation a study was made of the undercoolings and orientation relationships resulting when Pb is nucleated from the liquid by Ni, Cu, Ag, and Ge. It was the purpose of this investigation to check the Turnbull-Vonnegut theory, i.e., the importance of crystallographic disregistry between nucleating catalyst and nucleated metal. The results indicate that disregistry is not an important factor in nucleation and that the nucleation process is probably somewhat more complex than current theories suggest. EXPERMENTAL PROCEDURE Small single crystals of nickel, copper, silver, and germanium were prepared from materials of four to five nines purity, and the Pb used was also 99.999+ pet pure. Cu and Ag single crystals were prepared by sealing small chips of Cu or Ag in an evacuated quartz capsule and heating the capsule at 2000°F for 1 hr before cooling. Nickel crystals of 200 diam were also prepared in evacuated quartz capsules, but melting was done by heating the capsules in an oxy-acetylene flame for a few minutes. These spheres were invariably polycrystalline so

Jan 1, 1962

By J. O. Brittain, E. P. Lautenschlager, D. A. Kiewit

Compression tests were run in the temperature range of 700° to 900°C ox 0' phase NiAl intermetal-lic alloys of several grain sizes. At these temperatures the minimum strengths were observed at the stoichiometric composition. While significant increases in strength occurved in both the low-nickel (vacancy) and high-nickel (substitutional) regions, the highest strengths were found in the high-nickel region. During deformation serrated flow was sometimes observed in the low-nickel alloys. After deformation transgranular cvacking and deformation striations were observed in all compositions tested. AS part of a general investigation of the properties of NiAl inter metallic compounds, a preliminary study of the role of point defects upon plasticity was made by high-temperature compression tests on ß' NiAl specimens of several grain sizes and compositions. ß' NiAl is an intermetallic compound having a CsCl structure and a rather wide range of composition from A1-45 at. pct to 60 at. pct Ni.1 According to Bradley and Taylor2 and to cooper,' it possesses a defect lattice in which departures from stoichiometry in the direction of decreased nickel content lead to the presence of vacant nickel sites (although Cooper's work indicates that a small amount of substitution also occurs) whereas departures on the high-nickel side lead to substitution of nickel on aluminum sites. NiAl forms congru-ently from the melt at approximately 1650°C,1 and thus has a higher melting point than either of its component elements. Up to this time, although this and other high-melting intermetallic compounds have been suggested for elevated-temperature usage,4 only the hardness4 and a few tensile-strength measurements5 have been reported for NiAl at high temperatures. In the present investigation the effects of composition upon the compressive-strength properties in a range of 700° to 900°C have been measured for NiAl of several grain sizes. EXPERIMENTAL PROCEDURES The alloys were made as described elsewhere6 from an A1-46.8 at. pct Ni master alloy furnished by the International Nickel Co. with additions of high-purity nickel and aluminum. The charges were vacuum-induction-melted in A12O3 crucibles with small amounts of helium added to the atmosphere to suppress vaporization. They were cooled slowly from the melting temperature to achieve uniform grain size. In order to refine the as-grown grain size a special rolling technique was developed. Alloys were packed into 0.10-in. wall-type 302 stainless-steel tubes which were partially filled with magnesium oxide to prevent bonding between the alloy and the steel jacket. The ends of the tubes were closed by hot forging, and the packets were then hot-rolled. The alloys with greater than 50 at. pct Ni were rolled at 1100°C, but it was found necessary to increase the temperature to 1350° C before alloys with less than 50 at. pct Ni would roll without cracking. With these temperatures, reductions as high as 48 pct were achieved in a single pass. The rolled alloys will hereafter be referred to as "fine grained" whereas the as-grown material will be designated "coarse-grained''. The compression specimens were made by cutting square cross-sectional pieces, approximately 3/16 by 3/16 by 1/2 in., with a water-cooled diamond cut-off wheel from the as-grown or the rolled alloys. Specimens were ground to their final dimensions by polishing through 3/0 grit silicon carbide papers. The final shape was a rectangular parallelepiped of square cross section having a height-to-width ratio of 3:1. Compression testing was carried out in a compression rig of our own design mounted on an In-stron Floor Model. The specimen chamber could be heated to 1000°C and was controlled within ±2°C. The compression rig was enclosed within a bell jar and was maintained at a 50 µ of mercury vacuum throughout the duration of the test. The test cham -ber was heated from room to test temperature within 15 min. Specimens were then held at the test temperature 30 min prior to testing. Previous experiments indicated that no grain growth would occur within this time. An Instron Variable Crosshead speed unit was used to adjust for small variations in specimen lengths in order to have a constant initial strain rate, €, for all specimens of a group. For the fine-grained specimens the strain rate was changed rapidly at constant temperature by a factor of 10 with the speed lever on the Instron. For a given € the compression data was analyzed in terms of true plastic strain (E) and true compressive stress (0).

Jan 1, 1965

By C. H. Curtis

THE valuable mineral content of the current feed to the Miami concentrator is as follows: copper, 0.7 pct total; molybdenum, 0.01. Flotation of this ore yields a sulphide concentrate containing: chalcocite, 44 pct; molybdenite, 0.5; pyrite, 50.0; insol, 5.5. A combination of potassium ethyl xanthate and pentasol amyl xanthate as collectors, and pine oil, as frother, are used in this flotation. Rejection of pyrite is encouraged by holding the amount of collectors used to the minimum consistent with copper recovery and by operating at high alkalinity (equivalent to 0.35-0.40 lb CaO per ton solution of pH 11.0).

Jan 1, 1950

By R. H. Heinen

Introduction Drilling is the initial operating step In open pit mining. It goes hand-in-hand with the blasting operations to ensure adequately broken material for the excavation equipment employed. The drilling effectiveness is highly dependent on the quality of the drill evaluation. This discussion will center on the parameters that are needed to evaluate drill requirements for a new mine The procedure that is generated can, however, be used to evaluate whether to expand existing operations and replace existing equipment. Methods of breaking ground, other than blasthole drilling and blasting, such as ripping, will not be discussed. The importance of correct drill evaluation extends to the other facets of open pit mining. Inadequate fragmentation, the direct result of poor drilling and blasting techniques, results in oversized, hard digging for the excavating equipment. The result is higher secondary blasting costs, reduced excavation efficiencies, higher excavation costs, higher road repair costs, and higher haulage equipment costs. The main objective of evaluating drill fleet requirements, therefore, is to determine the equipment needed to minimize the operational constraints, caused by blasthole drilling, on other facets of open pit mining at the lowest cash flow costs.

Jan 1, 1979

By Martin C. Kuhn, Lawrence G. Stevens, J. Mark Richardson

The majority of the world's known and anticipated reserves of nickel ores are lateritic deposits At present, there are several different process alternatives for recovering nickel and other desired metal values from laterite ores An overview is given of the selective reduction roast/ammoniacal leach process, one of the processes in commercial operation.

Jan 1, 1981

By C. Alstetter, V. Kerlins

By using alloys with subzero Ms temperatures, this investigation demonstrates that the amount of decomposition of martensite during the quench from austenite may be considerable and especially so in specimens of large cross -sections and high Ms temperatures. The activation energy for decomposition as measured dilutometrically is PREVTOUS investigations of the initial decomposition of Fe-C system martensite have invariably been limited to alloys having M, temperatures above a function of the amount of transformation which has taken place. The amount of transformation is a linear finction of log time. A correction term to the activation energy is derived for dilatometric measurements in which no end-point of the transformation is detected. room temperature. In such alloys the martensite is tempered during the quench to an extent dictated by the quench rate and temperature of formation. This tempering, called quench-tempering, Q-tempering, self-tempering, or auto-tempering, although frequently acknowledged, has not been studied or treated quantitatively. To do so one should obtain absolutely untempered martensite and study its decomposition. This as-formed martensite could be obtained either by extremely rapid quenching, requiring very thin specimens, or by lowering the martensite formation temperature range. The second alternative is more effective, because

Jan 1, 1963

By John Birkinbine

The favor with which the members of the Institute received Mr. Fernow's paper upon the use of charbon roux in the manufacture of iron has encouraged me to present this paper, in the hope of having the discussion upon the manufacture and use of the oldest and undoubtedly the best fuel for producing pig iron continued. Owing to the advances made in employing anthracite coal, bituminous coal, or coke, or mixtures of them, we are apt to forget how much of our present development is due to the pioneers in iron manufacture and the fuel which they employed in the production of pig iron. In Mr. Swank's last compilation of the iron and steel works of the United States, the furnace capacity of the country is given as 5,868,000 tons, of which 1,000,000 tons can be made in the 264 charcoal furnaces. In other words, over one-third of the furnaces now in existence use charcoal for fuel, and produce more than onesixth of the iron made. If to this is added the 130,000 tons of blooms and billets turned out by the 122 forges and bloomaries, the importance of the charcoal industries will be appreciated.

Jan 1, 1879

By Robert D. Coale, Reinhart P. Ehrlich, Terry L. Thompson

The copper concentrate slurry pipeline and pumping system of the Bougainville Copper Ltd. facilities on Bougainville Island in Papua New Guinea, is discussed. Development work necessary for the pipeline design is dealt with including a description of the 17-mile by 6-in. pipeline and pumping system as it was installed. The commissioning of the pipeline is reviewed as well as current operating performance, including data on corrosion, pump parts life, and manpower requirements.

Jan 1, 1977

By J. A. Herbst, J. L. Sepulveda, J. D. Miller

Lead cake, a zinc smelter flue dust residue, consists primarily of lead sulfate. Characteristic properties of lead cake were determined in order to aid the understanding of reaction mechanisms involved in bismuth removal from lead cake by sulfuric acid digestion. Sp gr (specific gravity) measurements, surface area measurements, and photomicrographs revealed that the particles of lead cake are quite porous and seem to consist of an agglomeration of submicron grains (0.4 pm) fused together in a manner similar to cement clinker. Analysis of experimental rate data, which was independent of particle size, indicates that the dissolution reaction involves two distinct, rate limiting steps. The initial stage of reaction appears to be limited mainly by intergranular diffusion of the reactant, hydrogen ion, while the latter stage of reaction appears to be controlled by diffusion of soluble reaction products through the reaction product layer of the individual grains.

Jan 1, 1979