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By W. Rostoker

IN the course of the development of the phase equilibrium diagram for the system Zr-Cr,' the structure of an as-cast allov having the composition ZrCr2 was analyzed and established to be isomorphous with MgZn2 (C14, hexagonal lattice, 12 atoms per unit cell). In a recent paper on the same system, Hayes, Roberson, and Davies' report for the ZrCr2 phase an isomorphy with MgCu2 (C15, cubic lattice, 24 atoms per unit cell). It appeared that this conflict might be resolved by assuming a high and low temperature modification for ZrCr2. That this was the case with the phase TiCr2 has recently been demonstrated by Levinger." Specimens of ZrCr2 annealed at 1200°, 1100°, 994", 900°, 834", 800°, and 700°C, respectively, and subsequently quenched were examined by X-ray diffraction analysis. It was successfully demonstrated that a transition from the MgZn, structure at lower temperatures to the MgCu, structure did occur at some temperature between 900" and 994°C. Table I lists the observed structures at the various annealing temperatures. In Table II, a summary of line spacings and intensities is given for each of the allotropic modifications. The first six lines of the MgCu2 structures have been located in the table to illustrate the close similarity between the patterns. Lattice parameters of the two modifications were calculated by a least squares solution of equations for interplanar spacings for a series of high angle lines. The results are as follows: MgZn2 type - c = 8.262 kX, A = 5.079 kX. MgCu2 type — a = 7.195 kX. It is interesting to note that TiCr2 behaves in reverse fashion yn that the MgCu, structure is the low temperature modification and the MgZn2 structure is the high temperature modification. References lR. F. Domagala, D. J. McPherson, and M. Hansen: This issue p. 279. 'E. T. Hayes, A. H. Roberson, M. H. Davies: Trans. AIME (1952) 194, p. 304; Journal of Metals (March 1952). 3B. W. Levinger: Trans. AIME (1953) 197, pp. 195-196; Journal of Metals (February 1953).

Jan 1, 1954

By David Russell, Courtland Lee

FOREWOHD-Americans have been able to create wealth from the nation's natural resources to an extent unprecedented in recorded history, thanks largely to the existence of a free market and of a rational body of laws. The General Mining Law of 1872, for instance, by establishing the rules of the game, was quite effective in channeling the ability of Americans to discover and develop mineral deposits. Another example was the Mineral Leasing Act of 1920 which made available the more easily discovered mineral deposits by spelling out the conditions and rules under which miners could obtain leases on federal lands.

Jan 5, 1977

By D. J. Rose, W. M. Armstrong, A. C. D. Chaklader

The wetiability of single crystals of MgO by specimens of vacuum-cast iron was studied using the sessile drop technique in vacuo at 1550ºC. Formation of FeO at the liquid-vapor interface caused the contact angle (6) to decrease from 117 to 65 deg during the first minute. After cooling, all specimens possessed a peculiar annular interfacial deposit of Fe,O,. Within the annulus the interface showed no sign of chemical attack. Chemical reaction occurred where the iron was alloyed with Ti, V, Cr, Nb(Cb), Ta, cmd Zr. Vnriation of 6 with alloy concentration was studied. Although vanadium md chromium improved the wettability of MgO by iron, the effect of Zr, Ti, Nb, and Ta was indeterminable because the 8 derived from sessile drop considerations was that of the metal against a restrictive peripheral volume of liquid oxide wetting the substrate. INTEREST in the nature of metal-ceramic interactions has been stimulated by progressive development of metal-ceramic combinations. One of the more valuable methods used for bond investigation is the sessile drop technique. Recent attempts to improve wettability through solute additions to the drop have revealed that the solute may a) react with the oxide creating new compounds at the solid-liquid interface, b) adsorb at the interface in a monolayer formation, or c) distribute throughout the drop uniformly causing no wettability variation. This work, part m in a series1,2 of investigations of interface reactions between metals and ceramics, embraces a study of the Fe-MgO system. MgO possesses a large negative free energy of formation (-173 kcal per g mole 0, at 1550ºC) compared to FeO at this temperature (-73 kcal per g mole 02). Hence the electronegativity difference between the drop and substrate allows selection from an extensive group of metal solutes with intermediate electronegativity differences that would, in the absence of chemical reactions, be expected to adsorb pre- ferentially at the solid-liquid interface. However, the high oxygen pressure of MgO in vacuo creates an oxidation environment which influences the solute behavior. Recent studies of the Fe-MgO systemJ74 have been restricted by chemical reactions that obscured observations. In view of the current interest in liquid-phase sintering of metal-ceramic combinations under partial oxidizing conditions,5 a more comprehensive study of the Fe-MgO system seemed beneficial. EXPERIMENTAL PROCEDURE 1) Specimen Preparation. Optical-grade MgO single crystals and Ferrovac vacuum-cast iron were used in all experiments. A spectrographic analysis of the iron indicated 0.008 C, 0.05 V, 0.005 Mo, 0.01 Ti, 0.002 S, 0.01 Cr, 0.001 Mg, 0.01 Si, 0.003 A1 (wt pct). The MgO crystals were cleaved along (100) planes into plates approximately 20 by 20 by 1 mm. Following annealing in vactto at 1100°C for 3 hr, surface irregularities were removed by a chemical etch in phosphoric acid at 100°C. The iron rod was machined into small cylinders approximately 0.250 in. in diam and length and these were carefully cleaned in organic and acidic solutions to remove surface impurities. All specimens were weighed to the nearest 0.1 mg. 2) Apparatus. The apparatus described in detail by previous authors1,2 was modified for this work. A Polaroid Land Camera was incorporated into the optical system so that drop measurements at ten-second intervals after melting were possible with ultra-high-speed self-develop ing film. 3) Procedure. The iron cylinders were placed upright on the MgO plates and positioned in the molybdenum susceptor. After furnace assembly the system was pumped down to a vacuum of 1 µ and flushed with H2 at 800°C. The system was again evacuated to 5 x 10-5 mm of mercury and the temperature raised to 1550°C within 2 min. The molten drops were photographed at appropriate time intervals. TWO min after melting the iron vapor pressure caused gas discharge, or corona, within the tube. The specimens were then slowly cooled to room temperature, sectioned and examined metallographi-cally. X-ray identification of interfacial reaction products was attempted by the powder diffraction technique. Alloying elements (Ti, V, Cr, Zr, Ta, Nb) were added to the iron in various concentrations up

Jan 1, 1963

By E. H. Rose

From the more distant members and some not so distant, the plaint is often heard that they cannot justify the expense and time required to attend the AIME Annual Meeting. Almost invariably, the reason given takes this form: "I just don't see that I would get enough out of it." Often the would-be clincher is added: "Besides, the meat of it all comes out in print anyway." Not long ago, a group of us who have seldom missed a meeting in recent years fell to discussing this phenomenon, and found ourselves in emphatic agreement that anyone holding such a belief indicates by his first remark that he does not know how to attend a convention, and by his second, proves it. He is, by and large, the man who has never been there, and of him, there are many.

Jan 1, 1949

By Mark Eisner

ONE'S JOB is the watershed down which the rest of one's life tends to flow write the Lynds in the first pages of their classic social study, "Middletown in Transition." Certainly engineers will confirm this statement after a check among those in their own profession with whose lives they are at all familiar. I have no hesitancy in acknowledging the truth of their observation for the men and women who are engaged in the profession of the law. It has been often remarked that American public life is overrun with members of the law profession. The highest public office in the land, that of President. has been occupied by lawyers almost to the exclusion of citizens of any of the other professions. Twenty-two Presidents of the United States out of the total of 31, were members of the bar. For the most part, members of Congress, the governors of the states, the state legislators and the mayors and other local leaders, men who occupy important positions of responsibility and public trust, have had legal training. Now this fact is no mere accident. Those who were fitted for the "job" of the practice of the law are favorably placed with respect to their participation in public life. Thus public service and public office is the watershed down which the "lawyer's" life tends to flow.

Jan 1, 1940

By David T. Peterson

Calcium metal was found to deoxidize thorizcm at 1000° to 1200° C. The reaction kinetics were determilled and related to the diffusion coefficients of oxygen in thorium. The solubility of oxygen in thorium, the minimum oxygen concentration, and the diffusion coefficient were determined from 1000° to 1200°C. This firocess results in the lowest oxygen concentrations zohich have been reported for thorium metal. FOR many years it has been known that calcium metal will reduce thorium oxide to thorium metal. This reaction has been the basis for several methods of preparing thorium metal. From the equations giv-by Kubaschewski and vans, ' AF" for the reaction Cao, + Tho,(,) - CaO(,, + Th(,) was calculated and found to be -3.4 kcal at 1000°C, -2.5 kcal at llOO°C, and -2.0 kcal at 1200°c. Thorium is very slightly soluble in liquid calcium, and the solubility of calcium in solid thorium is very low. Consequently these metals would be in essentially their reference states. If thorium containing oxygen were equilibrated with liquid calcium between 1000° and 1200°C, the oxygen content of the thorium would have to be below the solubility limit in thorium. Oxygen is one of the impurities most difficult to remove from thorium and is the most abundant impurity in metal prepared by almost all known methods. Fortunately, oxygen does not have a large influence on the properties of thorium because the solubility in solid thorium is very low. EvenT in thorium containing 100 ppm of 0, particles of thorium oxide can be observed in the microstructure. In view of the incompatibility of thorium oxide and liquid calcium and the low solubility of thorium oxide in thorium, the deoxidation of thorium by this method was investigated. For thorium containing an amount of oxygen well in excess of the solubility limit, the reaction should proceed in the following sequence. The oxygen content of the thorium matrix near the surface would be depleted by the diffusion of oxygen to the surface. At the surface, the oxygen would react with calcium to form calcium oxide. To maintain equilibrium within the thorium, thorium oxide would dissolve to keep the matrix saturated. Consequently, the thorium-oxide particles would disappear first at the surface and then the particle-free rim would grow in thickness. If the rate-controlling step were the diffusion of oxygen through this layer of thorium which was growing in thickness in direct proportion to the amount of oxygen removed, the well known parabolic time law should be observed. If the oxygen concentration at the surface of the thorium and at the inner surface of the deoxidized rim were known, the diffusion coefficient of oxygen in thorium could be calculated from the parabolic rate constant. EXPERIMENTAL PROCEDURE The thorium metal used in this study was prepared by calcium reduction of ThF, by the method described by Wilhelm.' The analysis of this metal is given in Table I. The carbon was determined by combustion, the oxygen by the HC1-insoluble residue method, nitrogen by the Kjeldahl method, and the other elements by emission spectroscopy. A section of this ingot was hot rolled at 600°C to 1/4 and 1/8-in. thick plates. Specimens approximately 7/8 in. square were cut from these plates, and all surfaces of the specimens were cleaned and smoothed by filing with a clean file. Individual specimens were placed in 1-in. diam by 2-in.-long tantalum capsules. Approximately 1 g of clean, high-purity calcium was placed in the capsules and an end closure arc-welded in place. The tantalum capsules were sealed in Inconel crucibles to protect the reactive metals from oxidation. The entire loading procedure was done in a glove box filled with pure argon. The loaded crucibles were placed in a muffle furnace, controlled within 2OC of the desired temperature, for a measured length of time. After the specimen had cooled to room temperature, it was sectioned perpendicular to the large faces and through the mid-point of two of the sides. The sectioned specimen was mounted and polished through Linde A abrasive. The rim which was free of thorium-oxide particles could be clearly observed microscopically as mechanically polished. Twenty measurements of the thickness of the rim were made at equally spaced points far enough from the end of the

Jan 1, 1962

By R. I. Jaffee, E. S. Bartlett, D. N. Williams

The oxidation resistance and fabricability of molybdenum powder-metallurgy alloys containing up to 20 wt pct nickel in the form of a fine dispersion were studied. The effects of dispersion distribution and of amount and type (pure nickel or nickel compounds) of additive were considered. A definite improvement in oxidation resistance was observed, but the amount of improvement fell far short of requirements for an oxidation-resistant alloy. Fabricability by hot-rolling was limited. INVESTIGATIONS at Ohio State university1 and Battelle Memorial institute2 have indicated that the attainment of a truly oxidation-resistant molybdenum-base alloy for high-temperature service, with the coincident retention of high-temperature strength and toughness, will be a difficult, if not impossible, feat. Among the most promising alloy systems studied was the molybdenum-nickel system shown in Fig. 1. Alloys in this system show good oxidation resistance at temperatures well above the normal melting point of molybdenum trioxide because of the regenerative formation of protective nickel-molyb-date (NiMoO4) on the surface of the alloy during exposure at high temperatures. Unfortunately, the required alloy content to obtain oxidation resistant molybdenum-nickel alloys far exceeds the limits of the narrow terminal solid-solution boundary, and closely approaches the peri-tectic composition involving the brittle intermetal-lic compound, MoNi. Because of the peritectic reaction, fusion alloys are characteristically brittle, since the MoNi phase, being the last to form, tends to occur as a continuous grain-boundary network around each molybdenum grain. An added problem with this system is that the protective nickel-molybdate layer formed at high temperatures is unstable, undergoing one or more allotropic modifications upon cooling. The volume changes associated with this modification during cooling are such as to cause violent expulsion of the protective molybdate coating from the surface of the piece. This is, of course, quite detrimental in material exposed to cyclic temperature during service. The research reported here resulted from an attempt to overcome the aforementioned problems associated with the molybdenum-nickel alloys primarily by controlling the amount, size, and location of the MoNi phase. By using powder-metallurgy techniques of alloy preparation and sintering the blended molybdenum-nickel powder mixtures at a temperature below the peritectic reaction temperature, molybdenum-nickel alloys with a randomly dispersed MoNi phase were produced. MATERIALS The molybdenum powder used in the preparation of alloys for this study was commercial hydrogen reduced, minus 325-mesh (Tyler) material. Master alloys, by which nickel was added, consisted of elemental carbonyl nickel powder (12 average particle size), an alloy of 50 wt pct Ni-50 wt pct Cr, and compounds of MoNi, Ni,Si, and Ni2B. The nickel-chromium powder was prepared by filing a vacuum-arc-melted ingot, separating impurities magnetically, and screening to minus 200-mesh. The MoNi powder was prepared by pulverizing a hydrogen-sintered powder-metallurgy compact to minus 325-mesh material. Further sizing of this powder for study of effects of dispersion distribution was accomplished by air classification of the minus 325-mesh powder. The Ni2Si and Ni2B powders were prepared by crushing vacuum-sintered powder-metallurgy compacts to minus 200-mesh material. EXPERIMENTAL PROCEDURE Specimen Preparation—The general procedure followed in the preparation of alloys for testing is described as follows: 1) Blending. Either hand-blending of the powders in a ceramic mortar and pestle for X 1/2 or mechanical blending was used. Hand-blending seemed preferable for optimum homogeneity. 2) Compacting. Most of the blended powders were pressed to green compacts at pressures of 15 tons per sq in. in a single-action die, although some were pressed at 80 tons per sq in. A 1 X 11/4 X 1/4-in. green compact was the standard size for oxidation test material, and 7 X 1/2 X 1/4-in. compacts were used for fabricability test specimens. 3) Sintering. All green compacts were sinteredat

Jan 1, 1959

By Robert S. Shoemaker

At this Symposium on Gold which is sponsored by The Metallurgical Society of AIME and the International Precious Metals Institute many distinguished authors will present the latest developments in the metallurgy of gold and in operating practices at mines and in refineries. It seems appropriate then, as the introduction to this volume to recall some of the history of gold and the metallurgical developments which have been accomplished, especially during the past 100 years and some of the people who have contributed so much to the metallurgy of gold. Of all the elements gold has been the most sought after since the earliest times. Perhaps the quotation from Virgil's Aeneid best describes man's desire for gold but Pliny the Elder also put it very well when he wrote in 79 A.D. that "Gold is the first of man's follies, silver the second". This quest for gold has markedly influenced man's history and through the efforts of the early philosophers and alchemists to turn base metals into gold the foundations for modern chemistry were laid. The pages of history literally teem with references to gold. Gold is the first metal mentioned in the Bible and was the source of Croesus wealth as well as the death of King Midas whose touch turned everything into gold. And of course almost everyone has heard of Jason's Argonauts and the golden fleece. They are the subject of one of the many drawings in Agricola's De Re Metallica published in 1556. The Argonauts were probably prospectors seeking the source of the placers in the region near-the Black Sea. The time was about 1200 B.C. and the placer miners recovered gold by trapping the particles in sheep's fleeces placed in sluices. After drying, the fleeces were shaken to recover the gold. Gold is not hydrophilic, or wetted by water and thus the oils in the wool aided in collecting the particles. Here we have perhaps the earliest reference to surface chemistry and the basis for concentration of gold by flotation.

Jan 1, 1984

By J. A. Botin, K. H. Singh

INTRODUCTION The Alfredo underground mine is one of the three mining operations of Rio Tinto Minera, S.A., all near the community of Rio Tinto in Huelva province of southwest Spain. The other two operations are Corta Atalaya open pit (Pyrite ore) and Cerro Colorado open pit (Copper ore 1. Underground mining of Alfredo Mine for pyrites started in the nineteenth century and continued without interruption until 1979 when it was discontinued due to economical reasons. In 1972, a new project was started for the mining of copper bearing ores on the footwall of the pyrite deposit. This copper ore is locally named “Cloritas” and it forms a nearly vertical and tabular shaped orebody which forms an envelope at the footwall of the San Dionisio pyrite orebody. Mining of the Cloritas commenced in 1975 using cut and fill stoping. In 1977, the original project was completely revised which led to the introduction of a bulk mining system to achieve a planned production of 3,000 tonnes of ore per day. This paper covers the economic and planning aspects of the mine and discusses the evolution of the mining method for the Cloritas orebody. A GENERAL DESCRIPTION OF THE CLORITAS OREBODY The “Masa San Dionisio” (figure 1 ) is a massive sulphide orebody located in the town of Rio Tinto, about 90 kilometres west of Sevilla, Spain. Extensive vein-type sulphide mineralization exists in the volcanic host rocks of the Masa San Dionisio. Within this area of stockwork veins, there is a higher concentration of copper in the form of chalcopyrite in a zone adjacent to and paralleling the contact with the massive sulphides. This copper envelope is locally referred to as the "Cloritas Orebody” and the ore within it is called "Cloritas”. The main zone of the Cloritas orebody, (figure 11, is tabular and nearly vertical having a length of 375-400 m east-west, a thickness of 20-50 m north-south, and a vertical extension of 500 m from the surface. In addition to this area, there is a second less important low grade area called zone 2A located to the north of the main zone below 26 Level which, in some sections, is not fully separated from the main zone. MINING METHODS Mining in Rio Tinto area can be traced back to the Phoenecians and the Romans. Modern day mining started with the demand for sulphuric acid during the last half of the nineteenth century. By 1971, more than 33 million tonnes of pyrite had been mined out of Alfredo Mine, (San Dionisio Orebody), using labor intensive drift and fill methods and also by open pit method. During the last decade, underground mining of the pyrite had become uneconomic due to lower prices and a slackening demand for pyrite, and the underground mining operations for pyrite were finally stopped in 1979. In 1971, a major change in the long range mining plans for Masa San Dionisio was established. Between 1971 and 1975, underground mining of pyrites was progressively reduced while open pit extraction was increased in

Jan 1, 1981

In Mr. Weed's interesting paper, frequent reference is made to the Cananea copper-deposits, which are said to have been so vigorously exploited that they produced 14,000,000 Ib. of copper in 1901. The ore-bodies which yielded this large quantity of metal are described as a product of contact-metamorphism, and in Mr. Weed's genetic classification of such deposits, they receive a place under the sub-heading, "Deposits impregnating and replacing beds of contact-zone."* They are considered by Mr. Weed to represent a special type under this head, and are further classified as: " l. Chalcopyrite deposits: (a) Pyrrhotite ores; (6) Magnetite ores, Cananea type." In condensing much information into a comparatively small space, the presentation of a subject may be so abbreviated as to detract from its clearness. The situation at La Cananea, considering its importance from an economic as well as scientific standpoint, may he worthy of more detailed description. As Mr. Weed rightly remarks, " structural differences are so important, and have SO marked a bearing, not alone on the theory of their genesis, hut also on the working of the deposits and a determination of their value as mines, that they merit a full discussion."† It is my present purpose: (1) to show that it is doubtful whether the copper of La Cananea is mined, except to a limited

Jan 1, 1903

By H. E. Stauss, G. Sandoz

THE purpose of this note is to draw attention to the possibility that a melt may be contaminated by a material not in direct contact with it by means of gaseous intermediate agents. In recent years silicon has assumed a position of importance because of its use in rectifiers and transistors and close attention has been required to control of both purification and contamination during all stages of preparation.' This note reports the observation that a graphite heater may have contaminated silicon ingots without direct physical contact through reactions that developed gaseous products. Several ingots made with the equipment of Hino and Stauss,2 using a graphite heater in a dried helium atmosphere, were found to have a small amount of a very hard substance on the free surface. X-ray analysis by F. W. von Batchelder showed the sub- stance to be Sic. Similar contamination was not found when the heater was tantalum, indicating that the carbon had not come from an original impurity in the silicon powder. One source of the carbon could have been volatile matter released from the graphite heater. This heater had been used about ten times at the time of the observations. A second source of carbon could have been a direct reaction between the quartz crucible and the graphite heater to form CO, or an indirect reaction involving a crucible-melt interaction and volatile SiO as an intermediate product. Such reactions should have developed Sic on the heater; and in fact a yellow powder did form on the inside of the graphite heater although its composition could not be determined. References 'H. C. Torrey and C. A. Whitmer: Crystal Rectifiers (1948) Chapter 10. New York. McGraw-Hill Book Co. 2 J. Hino and H. E. Stauss: Trans. AIME (1952) 194, p. 656; Journal of Metals (June 1952).

Jan 1, 1954

By Paul L. Burkhart

THOUGH at an earlier period brief studies had been made by the Lehigh Navigation Coal Company Inc., it was not until 1924 that J. B. Warriner, then general manager, called for a comprehensive study of timber treatment, treating solutions, and related operations. Because of the impossibility of procuring accurate costs and other pertinent treating data, the American Wood Preserving Co. agreed to treat a car of mine timber at the Port Reading plant of the Reading Railroad. Fig. I shows the treating data collected at the treating plant on this timber, which was installed in two of the Lehigh mines in 1925. [ ] In the latter part of 1925, a survey of the tunnels and gangways of the company's Panther Valley mines was made to determine the proportion of gangways or tunnels timbered, cause of timber failures, approximate life of the average wood set and the approximate percentage of treated timber that it would be profitable for the company to use. Results of this survey appear in Table I. Because of the high percentage of timber that gave evidence of failure by rot, as noted in Table I, and a further study of the life of the sections where timbering was necessary, it was deemed advisable to fill 25 per cent of the yearly gangway timber requirement with treated timber. QUANTITIES AND TREATMENTS OF TREATED TIMBER PURCHASED In the early days of the program, none of the large treating companies would accept orders for small quantities of treated timber and the company was compelled to state the quantity of timber it would require at each operation in each month of the year. Table 2 is an example of the tabulation given to the various treating companies to assist them in making a yearly bid on the minimum quantity of timber required by the company during the year 1931. A bill of timber was calculated for each car, the weight of which would be between the minimum and maximum weight permitted for railroad-car loading. The treating company was paid for timber upon delivery at the operation specified. As extra cars of timber were required, they were ordered from the treating company, and payment was required on their receipt, on the basis of the piece or tonnage

Jan 1, 1942

By N. A. Gokcen, J. Chipman

Aluminum and oxygen dissolved in liquid iron were brought into equilibrium with pure alumina crucibles and atmospheres of known H2O and H2 contents to study the reactions: 1—Al2O3(s) = 2 Al + 3 0; 2—Al2o3(s) + 3H2(g) = 2Al+ 3H2o(g); and 3—H2(9) +O = H2O(g). Aluminum strongly reduces the activity coefficient of oxygen and similarly oxygen reduces that of aluminum. Values of the product [% All" • [% O]3 are much smaller than those found in previous experimental studies and are of the order of magnitude of the calculated values. ALUMINUM is the strongest deoxidizer commonly A used in steelmaking, but the extent to which it removes dissolved oxygen has been debatable. The relationship between aluminum and oxygen has not been determined reliably not only on account of the usual experimental difficulties at high temperatures but also because of uncertainties in the analyses of very small concentrations of oxygen and aluminum. The earliest experimental attempt of Herty and coworkers' was followed by a more systematic study of Wentrup and Hieber.' These authors added aluminum to liquid iron of high oxygen content in an induction furnace and considered that 10 min was sufficient to remove the deoxidation products from the melt. Parts of the melts thus obtained were poured into a copper mold and analyzed for total aluminum and oxygen (soluble plus insoluble forms), assuming that the insoluble parts were in solution at the temperatures from which samples were taken. It is conceivable that the furnace atmosphere in their experiments, consisting of mainly air at 20 mm Hg pressure, was a serious source of continuous oxidation and therefore that their oxygen concentrations were correspondingly high. Scattering of their data was explained to be well within the maximum inaccuracy of 10°C in the temperature measurements and errors of ±0.002 pct each in the oxygen and total aluminum analyses. Maximum and minimum deoxidation values, i.e., values of the product [% All' . [% O] differed by factors of 10 to 15; mean values of 9x10-11 and 7.5x10-9 ere reported at 1600" and 1700°C, respectively. Hilty and Craftsv determined the solubility of oxygen in liquid iron containing aluminum, using a rotating induction furnace. Pure alumina crucibles used in their experiments contained the liquid iron which in turn acted as a container for slags of varying compositions consisting mainly of Al2O3, Fe2O3, and FeO. The furnace was continuously flushed with argon, and additions of aluminum and Fe2O3 were made in the course of each experimental heat. The inner surfaces of their alumina crucibles were covered with a substance other than pure Al2O3, containing both iron oxide and alumina. Although frequent slag additions can change the composition of slag in the liquid iron cup formed by rotation, the inner surface of the crucible must depend upon the transfer of oxygen or aluminum through the liquid iron for any adjustment in composition. It is not clear that their metal was in equilibrium with the crucible wall, but it is clear that it was not in equilibrium with Al2O3. Their deoxidation product, [% A].]" • [% O]3, varied by a factor of more than 50; the average values of 2.8x10- and 1.0x10-7 were selected for temperatures of 1600" and 1700°C, respectively. Aside from the experimental determinations, attempts have been made to calculate the deoxidation constant for aluminum indirectly from thermody-namic data. Schenck4 combined the thermodynamic data for Al2O3 and dissolved oxygen in liquid iron by assuming an ideal solution. His calculated values are 2.0x10-15 and 3.2x10-13 at 1600" and 1700°C, respectively. Later, Chipman5 attempted to correct for the deviation from ideality and derived an expression which led to deoxidation values of 2.0x10-14 and 1.1x10-12 at 1600" and 1700°C, respectively. The errors in these treatments originate mainly from inaccuracies of thermal data and uncertainties regarding the activity coefficients of dissolved oxygen and aluminum. The purpose of this investigation was to study the equilibria represented in the following reactions in the presence of pure alumina: Al2O3(s) = 2Al + 3O K = aAl2.ao3 [1] Al2O3(s) + 3H2(g) = 2Al + 3H2O(g) H2O K2 = aAl2(H2O/H2 ) [2] H2(g) +O = H2O(g) K3 = 1/ao (H2) [3] The experimental method consisted of melting pure electrolytic iron, usually with an initial charge of aluminum, in pure dense alumina crucibles under a controlled atmosphere of H,O and H2 and holding

Jan 1, 1954

By Michael Tenenbaum

THE importance of semikilled steel as a high tonnage grade has long been recognized. The increasing severity of the applications for which semikilled steel is used makes it desirable to obtain further information regarding the features of open hearth practice and ingot structure that can affect steel performance in subsequent rolling and fabricating operations. Accordingly, an investigation is being carried out studying the structure of various types of semikilled steel ingots. This paper reviews some of the observations made and information gathered in this investigation. By definition, semikilled steel may be considered to include all nonrimming steels in which the natural shrinkage occurring during ingot solidification is offset to an appreciable degree by gas formation. Accordingly, this type of steel includes the entire range intermediate between rimmed and fully killed steel. The resultant ingot structures range from those of steels that have been capped to suppress a weak rimming action to those steels that have been killed in the furnace or ladle to the extent that no mold deoxidizer is required. A survey reported to the 1946 AIME Open Hearth Conference' reviewed the practices being used at 28 major plants for the deoxidation of semikilled steel. It was found that most plants divide the deoxidizing additions between the ladle and the mold many of the plants adding only minor amounts of deoxidizer to the bath or none at all. Silicon, aluminum and titanium were the only elements used for ladle and mold deoxidation. Mold deoxidizers were added as capping additions or as uniformly fed additions. Several practices were reported in which the steel was deoxidized in the ladle to the extent that little or no mold deoxidation was needed. No reference was made to grades capped by using special mold designs or special closures over the top of molds. Accordingly, specific examples of this type of practice will not be considered in this paper. It appeared from this survey of deoxidation practice that semikilled steel can be divided into three types, namely, capped semikilled, in which aluminum is added near the end of pour or after shut-off, intermediate semikilled steels, in which aluminum is fed uniformly throughout the pour, and semikilled steels requiring no mold deoxidation. In an attempt to cover the ingot structures obtained by the range of practices reported in the preceding survey, three series of experimental heats were made using increasing amounts of aluminum, silicon and titanium for ladle deoxidizers. The ladle deoxidizers were added as stick aluminum, 50 pct ferrosilicon and 20 pct ferrotitanium (4 pct carbon), respectively. Two methods of studying ingot structures were used. Ingots were removed from production, burned longitudinally and machined to allow observation of the central pipe and coarse blowholes. During the machining operation much of the finely porous subsurface structure was obliterated. Accordingly, observations were also made

Jan 1, 1947

Jan. 7, 1952, AIME, Boston Section, Massachusetts Institute of Technology, Campus Room, Graduate House, Cambridge, Mass. Jan. 8, Society for Applied Spectroscopy, 6 pm, supper, Tosca's; 8 pm, meeting, Socony-Vacuum Training Center, 63 Park Row, New York. Jan. 9, AIME, Chicago Section, Chicago Bar Assn., 29 S. La Salle St., Chicago. Jan. 13-15, Institute of Scrap Iron & Steel, Waldorf-Astoria, New York. Jan. 14-1.6, AIME, Minnesota Section, Hotel Duluth, Minn. Jan. 14-18, SAE, annual meeting, Hotel Book-Cadillac, Detroit. Jan. 1.6-18, Society of Plastic Engineers, Inc., annual national technical conference, Edgewater Beach Hotel, Chicago. Jan. 17, AIME, New York Section, Mining Club, 33 Broadway, New York. Jan. 1.7, AIME, Utah Section, Newhouse Hotel, Salt Lake City.

Jan 1, 1952

By T. P. Harrington, P. G. Doctor, K. A. Prisbrey

Crushing and grinding ore consumes so much energy that it represents a major component of total processing costs. While it has been estimated that only about 0.6% of the total energy expended in grinding is actually used to create new surfaces, accurate measurement of this quantity is difficult. If energy expended in crushing and grinding could be more directly measured, alternatives for increasing efficiency of the processes could be evaluated more effectively. Since the energy intensity associated with rock fracture is related to fracture sonority, it should be possible to use this sound (acoustic emission) to measure the actual energy expended. However, it is difficult to apply this approach because the mill environment is so noisy. To make the approach practical, a method for differentiating acoustic emissions caused by rock fracture from those caused by extraneous noises must be found. Pattern recognition analysis may provide such a method. This paper presents the results of pattern recognition analysis to make two types of differentiations: acoustic emissions caused by crushing two types of minerals (quartz and chrysocolla) and those caused by two extraneous noise sources, and acoustic emissions produced by each mineral.

Jan 1, 1982

By Marvin P. Barnes

The Sacaton open pit copper mine has recently been placed into production. Some problems have been encountered in maintaining grade control due to differences between early block estimates and actual production grade. A study was made using three methods for computing grade for 50' x 50' x 40' size blocks from exploration and development drill holes; 1) The polygonal method, 2) The inverse distance squared method, and 3) The geostatistical kriging method. The results of each were compared against a control block file created by using the assay results of all blast holes drilled in the ore over three benches of the new pit. Results indicate that the kriging technique gave better estimates for grade of individual blocks than did the other two methods for this particular deposit.

Jan 1, 1977

By Reynold Q. Shotts

CHEMICAL methods, based on the relative rates of oxidation of fusain, bright coal, and dull coal by nitric acid, have been devised to determine these coal components.1-4 Results obtained by oxidation methods for fusain have been checked against results obtained from microscopic methods5, 6on duplicate samples of the same coals, but to the author's knowledge this has not been done for bright and dull coal components. For this reason it is not certain that the two methods of analysis identify essentially the same chemical or physical units. It would be highly desirable to see results of the application of both methods to duplicate samples, but in the absence of any such data the author has attacked the problem indirectly. From the U. S. Bureau of Mines samples were obtained of three Alabama coals which the USBM had analyzed optically and reported on over the past 30 years. These samples were subjected to analyses by oxidation rate methods. Results of this work, and comparisons with the USBM analyses, have been published." This was the first indirect approach to the problem. The present report attempts a second indirect approach by way of internal validation. By nitric oxidation samples of two whole coals were carefully analyzed for fusain, bright coal, and dull coal. One coal was analyzed in duplicate. Duplicate portions of each of the coals were divided into three density fractions by means of heavy liquids. A duplicate portion of one of the coals was divided by sieving into three size fractions. Each fraction was analyzed by oxidation and its percentage composition calculated in terms of fusain, bright coal, and dull coal. Because the weight percent of each fraction was known, a material balance calculation for the whole coal was also made. The resulting reconstituted analysis of the whole coal could be compared to that determined by direct analysis. In addition, specific reaction rate constants were determined for each component and for each whole coal or fraction. Arbitrary reactivity indexes were calculated by dividing by 100 the sum of the products of the percent of each component in the coal and its specific reaction rate constant. The resulting figure was an average reactivity index for each coal or fraction. Weighting the reactivity indexes for each fraction by the percent of the fraction in the coal gave a reactivity index for each whole coal which could be compared to that calculated directly from the whole coal analysis. If oxidation analyses really delineate definite physical entities within the coal, or even definite groups of similar entities, reconstituted analyses calculated from fraction analyses should check closely those made of the whole coal. It probably is true that optical methods identify and describe a greater variety of components than do chemical methods and that variations are wide in the appearance and quantity of those components identified optically. Chemical methods based upon differences in oxidation reaction rates would of necessity be less discriminating, as between similar components, than would optical methods. The procedures followed for oxidizing the samples, analyzing the residues, plotting and calculating the percentage of each component, and calculating its specific reaction rate constant have been fully described.'-' In brief the method originally proposed by Fuchs et al.1 for the determination of fusain consists of the oxidation of small samples of coal in boiling 8N nitric acid in a condenser-fitted flask. After boiling for periods of 1/2 to 4 hr, the unoxidized residue is filtered and washed. The washed residue is treated with normal sodium hydroxide, diluted, and allowed to stand for several hours. The resulting brown liquor is removed, and the filtered residue dried, weighed, ignited, and weighed again. The ash-free residue is expressed as a percent of original dry, ash-free coal. The percent residue is plotted against time, and the extrapolation of this line to zero time gives the percentage of dry ash-free fusain present in the original sample. The shape of the resulting time plots has been explained' by the assumption that they are the result of two different types of reaction, the first part representing a first order reaction with rate a func-

Jan 1, 1956

By M. J. Blackburn

The phasal equilibria in TI':Al alloys has been studied Ry transmission electron microscopy, electron diffraction, and X-ray diffraction. It is shown that three-phase fields exist below the transformation, viz.: a disordered hexagonal solid solution a; an ordered hexagonal phase based on Ti3Al, aa; and a two-phase region. (a + (YZ) , occurring between the single-plzuse fields. The size. disiribution, and morphology of- the a, phase in the two-phase region is shown to be dependent upon the alloy composition and heat treatement. The ordering process in the a, phase leads to the formation of anliphase domain boundary networks; the contrast and stability of these networks is shown to be dependent on alloy composition. A new and relatively simple phase diagralil for the systemm is constructed. The phasal equilibrium at the titanium-rich end of the Ti:Al system has long been the subject of considerable controversy. crossleyl has recently reviewed the phase diagrams that have been advanced for the system and in his turn proposed yet another one. There would seem to be general agreement that a phase exists at a composition at or near Ti& with an ordered hexagonal DO,,-type structure. However, several other phases have been proposed; for instance, Ence and ~ar~olin's' diagram includes two phases, Ti2A1 and Ti3A1, in the region up to 25 at. pct Al. The position of the proposed phase boundaries varies over a considerable compositional and temperature range, a point graphically illustrated in Fig. 1 of Crossley's paper.' It is perhaps germane to briefly examine the techniques used by other workers in the establishment of the phase structure. These fall into three categories: 1) X-ray diffraction, the only limitation of which is the rather low intensity of superlattice reflections in this system.3 Thus, superlattice reflections become increasingly difficult to detect in the more dilute aluminum alloys. 2) A considerable amount of optical microscopy has been performed"2'4 and it will be shown in a later section that many of the obscure mi-crostructures that have been observed can be attributed to hydrogen contamination. It is concluded, therefore, that such observations should be interpreted with considerable care. 3) The variation of some physical property with aluminum content has been measured.5"7 These methods are a useful indication of the existence of a transformation, but are usually insufficient in themselves to identify the transformation. The results using these techniques will be considered in more detail in the discussion. In this paper, the phase structure of alloys containing up to 25 at. pct A1 has been studied by transmission electron microscopy and X-ray techniques, and the results are used to generate a new and relatively simple diagram for the titanium-rich end of the Ti:Al system. EXPERIMENTAL A series of alloys containing 5.05, 10.16, 13.39, 13.99, 14.40, 20.83, and 25.05 at. pct A1 were obtained in the form of hot-rolled sheet 0.02 in. thick. These alloys contained 0.10 to 0.15 pct 0. Thirty-gram arc-melted buttons were prepared from iodide titanium and 99.99 A1 which contained 16.1, 16.9, 18.2, 19.0, 21.6, 22.2, 23.0, and 23.9 at. pct A1 and had an average oxygen content of 0.03 pct 0. The differences in oxygen content did not appear to influence the nature of the phase transformations which were found. Oxygen content may affect the temperature of these transformations, but insufficient samples of the high-purity alloys were examined to answer this question. The heat treatment of alloys was performed in dynamic atmosphere and vacuum furnaces or in helium -filled silica capsules. A special vacuum furnace was constructed to provide a high quenching rate in which rates of 4000°C per sec were obtained using water as the quenching medium. As pointed out by Crossley,' it is important to avoid heat treatment in the a - [} phase field as the resultant segregation of the alloy into the two phases containing different amounts of aluminum can persist through subsequent treatments leading to ambiguous results. It will be demonstrated later that step cooling of specimens from the a phase region can also lead to anomalous effects. Thus, all solution treatments were carried out in either the a or 3 phase fields followed by water quenching and subsequent isothermal annealing at various temperatures. X-ray analyses were performed on a diffractometer on fine-grained bulk specimens. The value of long-range order parameter, S, wa_s calculated from the integrated intensity of the (1211) reflection. In general, the intensity of the (1011) superlattice reflection was compared with that of the (2021) fundamental reflection to correct for experimental differences between measurements. Thin foils for electron microscopical examination were produced by electropolishing using the technique described in an earlier paper.8 Dark-field techniques were employed to a large degree in this investigation using the gun-tilt method. Finally it should be noted that the lattice parameters of the D01,-type superlattice are approximately related to the disordered hexagonal phase parameters by Crf - c, and 2ad - a, where the subscripts s and d refer to the ordered and disordered unit cells, respectively.

Jan 1, 1968

By F. S. McNicholas, M. S. Walker, V. C. Rogers

During the year of 1944 and the first half of 1945, the Climax Molybdenum Co. made a study of some of the problems in block and panel caving, with the use of a scale model. The experiments dealt essentially with the type of rock and conditions at Climax, but some experiments were carried out to simulate conditions found in other mines. Most of the previous experiments on the caving characteristics of rock have dealt with sedimentary or broken igneous material. The series of experiments described here was designed to show the caving action of unbroken igneous rock. Con- siderable difficulty was experienced in duplicating unbroken material in the model. The results obtained are believed to be relatively correct, but verification must necessarily come from future mine operation. Observations in the mine and glory hole, together with statistical data, were used as criteria for creating similar conditions in the model. In 1913, George R. Lehman' experimented with broken material in a model for the Inspiration Consolidated Copper Co. and, more recently, P. B. Bucky2 experimented with broken material with a capping of mill tailings. Mr. Lehman's model represented a maximum ore height of 70 ft. capped by 55 ft. of waste. He varied the draw-hole spacing from 6¼ ft. to 8? ft. and 12½ ft. The material used graduated from fines to 30-in. maximum size. Some of his conclusions were: "(I) The less the distance between chute centers, the greater the extraction (Fig. I); (2) the higher the ore column, the greater the extraction; (3) the less the amount drawn at a time from each chute, uniformly, the greater the extraction of clean ore before the capping appeared, but not the greater the total extraction to a I per cent copper final product." (Fig. 2.) Professor Bucky concluded, in part: "(I) Drawing of ore may take place at any time from any finger and in any amount without affecting materially: (a)

Jan 1, 1946