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By Gerhard Derge, Arthur H. Grobe, Harold Markus

The high corrosion resistance possessed by tin under most circumstances, combined with its generally satisfactory appearance and useful physical properties, has led to many and varied uses for the metal. These uses have been partly limited by the fact that tin is an expensive metal, therefore many applications have been developed in which tin has been employed in combination with lead, either by coating, as in tin-lined collapsible tubes, or by the formation of alloys containing various proportions of tin-rich and lead-rich phases, as tcrne plate. A detailed knowledge of the corrosion characteristics of the tin-lead couple therefore is of general interest and has become specially important at the present time, when every effort is being made to conserve tin as much as possible. The present study has been limited to carbonate solutions with a pH range from 8.4 to 11.2 so that the results may be related to earlier work on the corrosion of tin and its alloys. 1-3,6 In these papers, the effects of a number of anion and cation additions to these solutions have been observed. Apparatus and Method The electrodes for the corrosion cell were cut from rolled sheet about 1/16 in. thick. The length of all specimens was held constant at 7 in., while the width was varied from M to 2 in. These electrodes were fastened to brass electrode supports, which were attached to rubber stoppers fitting into tall-type one-liter Pyrex beakers that contained the electrolyte. The lead electrodes were prepared from Omaha pig* and the tin was rolled from a slab of Chempur.† After cutting to size, the sheets were polished with No. I emery paper and cleaned with carbon tetrachloride. The edges, back and upper parts of the specimen were coated with a synthetic lacquer, which was supplemented with beeswax for the lead electrodes. The binding posts were coated with beeswax after the electrodes had been clamped. The pH of the electrolyte was controlled by adjusting the ratio of carbonate to bicarbonate. Approximately 600 ml. of electrolyte was used in each beaker. The entire assembly was placed in an oil bath thermostatically adjusted to operate at 30°C. + 0.1". Potentials were measured against a saturated calomel electrode connected to the cell by an agar-agar salt bridge. The carbonate solution used in the salt bridge was the same as that used in the corrosion cell. Currents were measured with a milliam-

Jan 1, 1942

By Harold Markus, Arthur H. Grobe, Gerhard Derge

The high corrosion resistance possessed by tin under most circumstances, combined with its generally satisfactory appearance and useful physical properties, has led to many and varied uses for the metal. These uses have been partly limited by the fact that tin is an expensive metal, therefore many applications have been developed in which tin has been employed in combination with lead, either by coating, as in tin-lined collapsible tubes, or by the formation of alloys containing various proportions of tin-rich and lead-rich phases, as tcrne plate. A detailed knowledge of the corrosion characteristics of the tin-lead couple therefore is of general interest and has become specially important at the present time, when every effort is being made to conserve tin as much as possible. The present study has been limited to carbonate solutions with a pH range from 8.4 to 11.2 so that the results may be related to earlier work on the corrosion of tin and its alloys. 1-3,6 In these papers, the effects of a number of anion and cation additions to these solutions have been observed. Apparatus and Method The electrodes for the corrosion cell were cut from rolled sheet about 1/16 in. thick. The length of all specimens was held constant at 7 in., while the width was varied from M to 2 in. These electrodes were fastened to brass electrode supports, which were attached to rubber stoppers fitting into tall-type one-liter Pyrex beakers that contained the electrolyte. The lead electrodes were prepared from Omaha pig* and the tin was rolled from a slab of Chempur.† After cutting to size, the sheets were polished with No. I emery paper and cleaned with carbon tetrachloride. The edges, back and upper parts of the specimen were coated with a synthetic lacquer, which was supplemented with beeswax for the lead electrodes. The binding posts were coated with beeswax after the electrodes had been clamped. The pH of the electrolyte was controlled by adjusting the ratio of carbonate to bicarbonate. Approximately 600 ml. of electrolyte was used in each beaker. The entire assembly was placed in an oil bath thermostatically adjusted to operate at 30°C. + 0.1". Potentials were measured against a saturated calomel electrode connected to the cell by an agar-agar salt bridge. The carbonate solution used in the salt bridge was the same as that used in the corrosion cell. Currents were measured with a milliam-

Jan 1, 1942

By R. Maddi, I. R. Kramer

The delay time for the initiation of slip was studied in single crystals of a brass, aluminum, and ß brass. A delay time for slip was found in ß brass when the specimens were tested below room temperature; however, one was not found for a brass or aluminum. A general theory for the existence of the brittle transition temperature is proposed. A LTHOUGH a considerable amount of effort has A been devoted to the study of the deformation and fracture of single crystals, the vast majority of the work was concerned with static tests or with tests carried out at relatively slow strain rates. The necessity for the study of a possible incubation time for slip becomes apparent when the various theories which have been postulated for the elucidation of the mechanism of slip are considered. The existence of an incubation period would strongly indicate that slip occurs by a process of nucleation and growth; whereas the absence of an incubation would present rather convincing evidence that slip occurs by a cataclysmic process. In addition to shedding light on the process of plastic deformation, an understanding of the early stages of plastic deformation may be helpful in finding an explanation for the brittle behavior of the body-centered metals under certain conditions. It is well known that these metals, such as iron, molybdenum, tungsten, ß brass, etc., will become brittle as the test temperature is lowered or the strain rate is increased. In spite of the fact that this subject has received considerable attention since the turn of the century, no adequate theory exists today which explains the phenomenon. In the ductile temperature range the metal breaks with a "fibrous" fracture after considerable slip has taken place. In the brittle temperature range the metal fails essentially by cleavage on the {loo) planes: however, some plastic flow is always present even in the most brittle fractures. It is possible, as will be explained later, to ascribe this brittle behavior to the length of the incubation time for slip. Clark and Wood,' using polycrystalline metals, showed that a delay time existed for the yield point in mild steels and that the delay time depended upon the applied stress. These authors stated that the delay time was observed only with those materials for which the stress-strain curve showed a definite yield point. In their work only the mild steel specimens exhibited a delay time at the yield point, while the other materials studied-type 302 stainless steel, SAE 4130 normalized steel, SAE 4130 quenched and tempered steel, 24s-T aluminum—did not show a delay time. These authors' in an extension of their work, found that as the temperature was lowered the delay time was increased. It is, then, the purpose of this investigation to measure or to set an upper limit on the delay time for plastic flow in single crystals of a brass, aluminum, and ß brass. The delay time will also be studied as a function of temperature. The incubation time may be measured by determining the length of time the specimen will support a stress without slip occurring when the stress is greater than the static critical resolved shear stress. In order to accomplish these measurements use was made of a pendulum which was so designed that a single crystal specimen could be placed at various positions along its length. When a pendulum is struck by another pendulum of the same length, an elastic wave is transmitted down the bar with the velocity of sound in the material and is reflected from the far end of the bar. The reflected wave then travels back and unloads the stress until it reaches the impacted end of the bar and the two pendulums separate. The length of time that the specimen is subjected to the stress is equal to the time it takes for the stress wave to travel twice the distance from the specimen to the end of the bar. The stress applied to the specimen is governed by the velocity of impact of the two pendulums. The stress at which the specimen first suffers plastic: deformation was determined in these experiments by examining the specimen under the microscope for the first appearance of slip lines and by measuring the residual strain after each impact. In these experiments the critical resolved shear stress was approached from the low stress side and no attempt was made to determine it exactly. To determine it exactly, it would have been necessary to find that stress at which slip would have just started. However, since the stresses were increased in rather small increments the critical stress is believed to be approached rather closely, as will be seen from the experimental results. The critical stress will be taken as the highest stress obtained before the onset of plastic deformation. The stresses

Jan 1, 1953

By H. S. Auvil, L. D. Schmidt, H. G. Graham

"Several studies on the bulk density of coals prepared for byproduct-oven use were undertaken during the war by the Bureau of lanes in cooperation with the Office of the Solid Fuels Administrator and with the advice of the Coke Production Committee. The primary purpose of these studies was either to produce more uniform coke or to increase the throughput of existing facilities or both; the goal was increased Production of steel for war. As these studies were made, detailed reports were sent to the individual companies with whom the Bureau cooperated; also two reports,5/6/on the general subject of bulk-density control were published. In the course of the work, data were gathered that now prove of value in judging the merit of carious methods of testing bulk density and the limits of application of each method in byproduct-oven operations.Since the cessation of hostilities, the .Bureau section (Coke Production Survey Section) that conducted this work has been liquidated, but it was felt advisable to prepare a report on the accumulated experience so that it would be in a form available for the use of the industry and also as a base for any further research on the control of fluctuating bulk densities in coke ovens.It is hoped that the data and experiences recorded herein will be of material assistance to the many who have had difficulty in obtaining reproducible results in bulk-density testing. Since the data were gathered in the course of extending aid to individual plants in minimizing the deleterious effects of fluctuations in bulk density of oven charges on the quality and quantity of coke produced, certain desirable phases of an over-all investigation were not covered. However, on certain of these phases qualitative indications are available and the policy followed herein is that suggested by the American Society for Testing Materials Manual on Presentation of Data7/ that lacking quantitative information, relevant material should be included even though it ""may be qualitative in character, some may even be vague."""

May 1, 1946

By C. V. Sibbald

"This paper provides a description of the Highmont copper-molybdenum concentrator from primary crushing through grinding, flotation, tailings disposal and water reclamation. The unique features of the operation will be emphasized.IntroductionThe Highmont property is located in the southern portion of the Highland Valley adjacent to and east of Lornex and about 4 miles south of Bethlehem Copper. The plantsite is at an elevation of 5100 ft.Highmont acquired the property in 1966 and in 1969 Teck Corporation entered into an exploration agreement which contained the option to finance the property to production . A detailed feasibility study of the project was completed in 1971. A positive production decision was deferred at that time because of the prevailing soft copper market and relatively low molybdenum price. The development of a strong molybdenum market in late 1978 and early 1979 led to a re-examination of project economics, and a decision to proceed to production was made in April 1979.The Highmont ore zones occur adjacent to and on either side of an east-west-trending quartz porphyry dyke. The two major zones , the east and west pits, contain 122 million tons of ore assaying 0.27070 Cu and 0.029% Mo. Chalcopyrite, bornite and molybdenite are the minerals of economic interest. Chalcopyrite is the predominant copper mineral. Mineralization occurs primarily along fractures and is zoned according to fracture density. Some pyrite is present, but for the most part it is outside the ore zone. Surface oxidation is shallow throughout the orebody.Wright Engineers Limited were responsible for the major part of the engineering design. Site construction, which began in the spring of 1979, is under the direction of Commonwealth Construction. The first concentrator line is scheduled for completion late in 1980, the other for early in 1981."

Jan 1, 1981

By W. T. Cardwell

Physically absurd, triple-valued saturations appear in the straight-forward solution of the Buckley-Leverell equations for the displacement of oil by water or gas. From an engineering viewpoint, the triple value causen no difficulty. It is well known how it may be compensnted in order to obtain physically meaningful, numerical results. From a scientific viewpoint, the question still arises: What did the triple value mean? This paper explains how and why the triple value arose in non-capillary Buckley-Leverett theory. The discussion should serve as a background for the understanding and use of the modern method of characteristics in di.~pkzc(>ment theory. INTRODUCTION Displacement theory was introduced to petroleum technologists in 1 941 by Buckley and Leverett.' Their first equation, which they wrote down without derivation, was equivalent to the following: ?s/?t= - qr/F ?f/?r (1) where S = saturation of displacing fluid (a fraction) r = time q,. = total volumetric velocity of both the displacing phase and the phase being displaced (usually, but not necessarily, assumed to be a constant) F = porosity (a fraction) f - fraction of the total volumetric velocity that is the volumetric velocity of the displacing phase (assumed to he a function of S only x = distance. Buckley and Leverett called Eq. I "a material balance equation". Actually it is derived from both a continuity equation, or material balance equation, and Darcy's law. Buckley and Leverett jumped from their Eq. 1 immediately to their Eq. 2, which was the equivalent of the following: (?x/?t)x = qr/F df/ds = qr/F f'(s) (2) The jump from Eq. 1 to Eq. 2 involves apparently simple mathematics, but in that apparently simple mathematics lies a subtle point that is part of the key to the meaning of the triple value to be discussed here. Eq. 2 may be readily interpreted as saying that a point of constant saturation (on a saturation-vs-dis-tance curve) moves with a constant velocity that is proportional to the total volumetric rate, inversely proportional to the porosity, and is otherwise a function of the saturation itself. So that if one knows the derivativc with respect to saturation of the fractional flow function, f(S), for each saturation, one knows the velocity of each point of the moving saturation-vs-distance curve. The function f(S) can he determined experimentally and its derivative f'(S) can be calculated. It turns out that the experimentally derived f'(S) is not a monotonic function of S, but instead it has a definite maximum and declines away at both high and low saturations. This in turn means, in accordance with Eq. 2, that on a moving saturation-vs-distance curve, ccrtain intermediate saturations will travel faster than the saturations either higher or lower. The result is indicated in Fig. 1. In Fig. 1, the abscissas represent distances along a column of porous medium, which column is assumed to be uniform in cross-section perpendicular to the ab-scissal direction. The ordinates represent fractions of pore space occupied by the displacing phase, which may be either water or gas. It is assumed that the saturation is uniform over all planes perpendicular to the abscissal direction. The saturation is a function only of time and one space variable. Time variation of the saturation is represented by change in shape of a curve such as curve AGJ, which represents the initial saturation-vs-

By Whiten W. J

The control of mineral processing plants incorporates a number of off-line and on-line actions by plant personnel to obtain satisfactory plant performance. In general, off-line actions centre around intensive data analysis, while on-line activities are either automated control actions or prompted by qualitative interpretations of quantitative and qualitative information. Data sets obtained by various data logging devices and laboratory analysis of samples in many modem plants may be very large and are often unmanageable. This paper presents a method of analysing the data sets typically found in mineral processing, based on cluster analysis. The results of this analysis leads to a more complete understanding of operations in comparison with existing analysis tools used in mineral processing.Improved process configuration, optimised control strategies and in some cases, direct use of the results in monitoring process unit operations may be achieved.

Jan 1, 1992

By Rospigliosi RT, Krouse HR

The San Vicente stratabound zinc-lead rhythmite deposit, Peru, is hosted in carbonates of the Late Triassic - Early Jurassic Pucara Group. These strata were deposited in a large, shallow water, carbonate platform which extended nearly continuously for 150 kilometers (north-south) in the eastern part of the Pucara basin.The distinctive sulfide-bearing rhythmites occur in three dolomite units which, from bottom to top, include the San Judas horizon with one sulfide-bearing manto; the San Vicente horizon with seven sulfide-bearing mantos including the main ore horizon; and the Alfonso horizon with three sulfide-bearing mantos. The dark gray sulfide-bearing dolostone layers range in thickness from a few millimeters to a few centimeters and contain variable amounts of carbonaceous material, pyrite, quartz, fine-grained sphalerite and galena. They are bordered on each side by selvages of yellow to red-brown coarse-grained sphalerite containing minor amounts of galena. Coarsely crystalline white or gray sparry dolomite is found between the coarse-grained sphalerite layers. Although commonly stratiform and uniform in thickness, the dark layers curve, "pinch out," coalesce, and form "islands" and "peninsulas."Mineral replacement textures, the paragenetic sequence, and presence of sparry dolomite, bitumen, intraformational breccias and isotope data support a hydrothermal replacement origin by metal-bearing solutions that deposited the ore and related minerals in space previously occupied by dolomite and evaporite minerals. The alignment of the Zn -Pb deposits, and at San Vicente the orientation of the mantos, the spatially and temporally associated igneous sills and the tourmaline-bearing sandstone support hydrothermal mineralization driven by a magmatic heat source in a tensional regime.

Jan 1, 1990

By D. K. Sarkar, J. Perron, J. D. Brassard

"Nearly perfect spherical shaped water drops rolling-off from the surface of lotus leaf is one of the beauties of nature. This kind of surface is called superhydrophobic, since the water does not like it. Physically, a superhydrophobic surface provides a contact angle (CA) of water over 150°. The combinations of both mico-nanostructure topography as well as low surface energy are essential to have such high CA on a surface. Nano-micro structured superhydrophobic surfaces have been developed in different methods. (i) Monodispersed fluorinated silica nanoparticles have been synthetized via Stöber Sol-Gel process and deposited on various surfaces, such as aluminium or glass, to obtain transparent superhydrophobic thin films. (ii) Similarly, zinc stearate nanocomposite coating has been fabricated by spray process on the same substrates. These thin films are found mechanically robust with drag reduction of coefficient 16% lower than as-received surfaces. (iii) By electrodepositing pure zinc on steel surfaces and further coating it with diluted room-temperature vulcanized silicone rubber, the surface become superhydrophobic. This superhydrophobic surface protects the steel against corrosion by increasing the polarization resistance from 1.5 k? on steel to 44.4 k?. This coating also reduced the ice adhesion on the steel surface 6.3 times as compared to bare steel substrates. Globally, these superhydrophobic surfaces have tremendous applications against corrosion reductions, drag reductions and ice adhesion reductions.INTRODUCTIONSuperhydrophobic coatings are increasingly attractive to the industry and academia due to their unique self-cleaning properties as a result of their water repelling characteristics. Fabrication of superhydrophobic coating is an inspiration from nature as water is seen to repel on many natural surfaces such as those of the lotus leaves, butterfly wings, water striders’ legs, and so on (Gao & Jiang, 2004; J. Huang, Wang & Wang, 2006; Neinhuis & Barthlott, 1997; Zheng, Gao & Jiang, 2007). This non-wetting phenomenon is well understood on lotus leaves, shown on the Figure 1 (a), and it is considered as the basis of the studies of superhydrophobicity. The existence of this binary structure on the surface of the lotus leaves allows a large amount of air entrapment and consequently reduces the contact area of water on it and the presence of low surface energy waxy components with reduced affinity to water together leads to the superhydrophobic properties. The phenomenon is shown on Figure 1 (b). Cassie and Baxter (Cassie & Baxter, 1944) as well as Wenzel (Wenzel, 1936) proposed two mathematical models to explain the wetting phenomena on rough surfaces that leads to superhydrophobic properties. By definition, superhydrophobic surfaces are characterized by a water contact angle value = 150° with the rolling off of water drops from the surfaces (Sarkar & Saleema, 2010). Superhydrophobic surfaces find tremendous importance in the technological world where it can applied in domains such as anti-corrosion, anti-biofouling, electrowetting, icephobic and even in drag reductions (Bushnell & Moore, 1991; Cao, Jones, Sikka, Wu & Gao, 2009; Carlborg & van der Wijngaart, 2010; Carré & Mittal, 2009; Y. Huang, Sarkar & Chen, 2010a; R. Karmouch, Coude, Abel & Ross, 2009). However, the most important challenge faced by industries is their feasibility large scale in an effective an economical manner."

Jan 1, 2016

By Gordon F. Revey

In underground construction and mining work, situations occasionally occur where hard rock or concrete must be excavated at locations near critical structures or utilities. Fearing damage from blasting, contractors and engineers often explore the viability of using mechanical methods or expansive concrete to facilitate the excavation work. However, for moderate to large excavations, the prolonged duration and high cost of using these methods is often impractical. In these situations, under the right conditions, controlled blasting and blast-management methods can be used to speedup the work and lessen costs. The process of determining whether or not blasting is practical is often complex, particularly when risks are high. In this paper, general methods of conducting blasting risk evaluations and outlined and considerations for blast design and risk management are reviewed. This paper also includes three blasting case histories demonstrating how these techniques were used at recent projects. In the first case, a cautious blasting program was developed to facilitate the removal of concrete and rock within a large section of an active mineshaft. The second case involved critical blasting to excavate a dry lake-tap connection between a tunnel and a shaft at the Southern Nevada Water Intake No. 2 project in Henderson, Nevada. The third case history describes how novel blasting methods were used to carefully drop a 2,721,500-kg (6,000,000-lb) concrete caisson into a1.2-m (4-ft) rock socket at the Detroit Outfall No. 2 project in Detroit, MI.

Jan 1, 2001

By Chris Twigge-Molecey

As emission constraints for metallurgical plants become more difficult to meet; control of major, multi-vessel, flue systems become more critical. Control instabilities can result in significant loss of system capacity or emissions to the environment. This paper will discuss the use of dynamic simulation techniques to optimize both the design and control strategies for these systems. A significant ,safety hazard is associated with pressure excursions from process upsets or equipment failures. Pressure rise rates of up to 10 kPajsec can occur. These cannot-be followed by conventional controls. Fail-safe high speed venting is required to protect both the furnaces and operating personnel'. Design options, sizing techniques and practical problems are discussed.

Jan 1, 1992

By Abhishek Kumar, T. G. Sitharam, Surender Singh

The height of tailings pond (TP) embankments is frequently raised to accommodate the ever-increasing volume of tailings released by the mining industries. Excess pore water pressure (EPWP) may develop during the height-raising operations, which can affect the overall stability of TP. This article presents a detailed stability analysis for the embankments of an existing TP, the height of which was increased twice utilizing downstream (D/S) and upstream (U/S) construction techniques. A rigorous two-dimensional transient fully coupled-stress-pore pressure analysis is performed in the finite element-based package RS2 to examine the build-up of EPWP during different stages of construction. Furthermore, an attempt is made to investigate the feasibility of future height raising, with due consideration given to the influence of embankment raising rates. Results from the analysis show a development of higher EPWP within the tailings deposit in comparison to the embankments of TP, indicating the development of an undrained-like condition. The study further reveals that the development of EPWP is highly affected by the rate at which embankments of TP are being raised. A higher rate of embankment-raising results in the development of greater EPWP in comparison to a lower embankment-raising rate, which may lead to the ultimate collapse of TP. Furthermore, based on the stability analysis, the height of existing TP can be further raised by 4 m (two lifts of 2 m height) utilizing the U/S construction technique. A thorough cost and benefit analyses are however required before implementing the results of the current analysis since the storage capacity of TP is reduced while raising by the U/S method.

May 16, 2023

By C. Han

The analytical results of Dagushan grinding workshop primary grinding operation product show that the size fraction of -0.079mm is 32.88%, the size fraction of -0.01mm is 9.97%, the rate of -0.01mm size fraction and -0.079mm size fraction is 30.32%. It means that there is too much -0.01mm size fraction in primary grinding operation product and fall out that there will not be a better result in following operations. Several tests have been carried out to control the size distributing of the primary grinding operation product according to confirm the appropriate conditions of grinding operation. Integrate with theoretic count, grinding property tests show that the appropriate rev ratio of ball mill should be between 85% and 90% so as to get better size distributing. Based on the results of grinding property tests, the shocking property tests simulated the momentum of different diameter steel balls in the ball mill have been carried out. It showed that if want to get better size distributing the appropriate diameter of steel ball should be 110mm. The tests result shows that regulate diameter of steel ball and rev ratio of ball mill could control the size distributing. Contrast to the technical parameters of ball mill in grinding operation now, there are some significant advices are given for practice and industrial tests.

Jan 1, 2014

By M. P. Filion, K. Ferguson, L. L. Sirois

Acidic drainage is the largest single environmental problem facing the Canadian mining industry today. Technologies to prevent acidic drainage from occurring in wasterock piles and tailings sites, and on the walls of open pits and underground mines, need to be developed and demonstrated. There are two groups in Canada which have accepted this challenge: the national Mine Environment Neutral Drainage (MEND) program and the British Columbia Acid Mine Drainage (BCAMD) Task Force. This paper summarizes the activities of these two organizations.

Jan 1, 1990

By M. L. Holzworth, Philip R. Sperry, Paul A. Beck

INTRODUCTION THE basic work of Z. Jeffries1,2,3 has long ago established the main features of grain growth in the presence of a dispersed second phase. Working with sintered specimens of initially fine grained tungsten, to which various amounts of thoria have been added, Jeffries found that grain growth was inhabited, that is, practically prevented, up to a certain annealing temperature. When this temperature, which increased with the thoria content, was exceeded, extremely large grains developed abruptly from the fine grained matrix. Such a "coarsening temperature" was later found by Gross mann13,14 in certain types of steel, while Bain showed" that in other steels grain growth was gradual, without inhibition and abrupt coarsening. Later work16,17,18,19,21 demonstrated the connection between coarsening and aluminum additions. The viewpoint that the direct cause of inhibition and coarsening in aluminum killed steels is a fine dispersion of aluminum oxide21 appears to be held quite generally, although some doubts have been voiced even very recently.20 In steels with Ti additions the titanium carbide phase is considered responsible for the inhibition effects found.20 The coarsening temperature increases, with the titanium content. That coarsening may occur, as a result of certain heat treatments, even in low carbon rimmed sheet steel, was shown by Samuels,22 He also detected coarsening in a steel ingot of similar composition, after giving it the same heat treatment as that used by him for the sheet material, In this instance the identity of the inhibiting phase has not been determined, However, Tangerding found 23 that even the few small carbide particles, which occur in carbonyl iron, have a very marked inhibitive effect. As a result of an oxidizing anneal at 850°C, large grains begin to form at the surface of the carbonyl iron specimen, and gradually grow inward as the subsurface oxidation of the carbide particles progresses and eliminates the obstruction, The carbide particles can be removed also by annealing in hydrogen, with similar results. But if the oxidizing anneal of 10 hr at 850°C in air, is followed by annealing in hydrogen for 75 hr at the same temperature, grain growth is more spectacular; usually the whole specimen is transformed into a single crystal (approx. 1,5 cm X 5 cm). The reversed procedure, that is, hydrogen annealing followed by oxidizing annealing leads to smaller grains. Tangerding arrived at the logical conclusion that there must have been in his specimens some additional obstruction to grain growth resulting from a minor impurity, other than carbon. It seems likely that this obstruction was caused by an oxide formed during the oxidizing anneal and gradually reduced during the subsequent hydrogen-annealing. Other instances of grain growth inhibition of varying severity, associated with a dispersed second phase, have been described by several authors. Notable examples: lead with 0.06 pct Cu or Ni,24 cartridge brass with 0.12 pct Cr,25 or with up to 0.15

Jan 1, 1948

By Jose Dermeval, Denilson Coutinho, Thiago Vitali, Daniel Pereira

Con el objetivo de recuperar la casiterita y los minerales portadores de niobatos que se pierden en los relaves de la planta de preconcentración por espirales de la minera Taboca, se probaron tecnologías de separación centrífuga de alta intensidad y magnética de alto campo. El gran desafío de la compañía es generar valor a partir de rocas con contenido muy pequeño, con media del 0,19 % para el estaño y del 0,23 % para los óxidos de niobio y tántalo. Sin embargo, ganar ese desafío es posible, a través del perfeccionamiento constante de los procesos de producción utilizados en las plantas. En este caso fue posible incrementar las recuperaciones de estaño del 68,7 % al 80,0 % y la recuperación de niobio y tantalio salió de niveles del 44,5 % al 68,0 %.

Sep 20, 2019

By J. A. Allan

OCCURRENCES of salt in Alberta have been mentioned and described by the writer in 1929 (l) and by Cole in 1930 (2). Brine springs occur at a number of places along the valley of Athabaska river north of latitude 56 degrees, and also on the south margin of Salt prairie, twenty-five miles west of Fitzgerald in the vicinity of the 60th parallel of latitude, which is the boundary between Alberta and the Northwest Territories. These salt springs were visited by Sir James Richardson in 1820, and in the same year D. W. Harmon stated that " ... clown Salt river there are several places where almost any quantity of excellent dean white salt may be taken with as much ease as sand along the seashore" (3). One hundred years later, in 1920, when the writer first visited these springs, the "dean white salt" which had accumulated about the springs was about 400 tons ( 4). This paper deals with a thick deposit of rock-salt which has been proved by drilling in the vicinity of McMurray. Particular attention will be given to a well drilled at Waterways early in 1936 by Industrial Minerals, Limited, when a continuous bed of rock-salt was penetrated with a thickness of 199 feet. As this paper is being presented, a salt plant is being completed and a production well is being drilled at the plant. < is salt deposit is in the vicinity of McMurray, close to the junction of the Clearwater and Athabaska rivets, in township 89, range 9, west of the 4th meridian. McMurray is about 240 miles northeast from Edmonton. As shown on Figure 1, Clearwater river, which rises at Methy portage, in Saskatchewan, enters Athabaska river at McMurray. Some three miles above the mouth of Clearwater river, the Hangingstone enters from the southwest. Waterways, where the latest salt development has taken place, is situated at the end of the Northern Alberta railway, a distance of 304 miles from Edmonton. This railway reaches the bottom of the Clearwater valley at Draper station, about 3 miles east of Waterways and near the mouth of Deep creek. The Draper bituminous sand plant is approximately half a mile east of Draper station. About one mile south of the townsite of McMurray, Horse river enters the Athabaska from the east.

Jan 1, 1937

By W. W. Adams

Three hundred and twenty-eight mines and quarries, representing 36 States, took part in the twelfth yearly accident-prevention contest conducted by the United States Bureau of Mines and known as the National Safety Competition. Four underground mines and one open-cut mine (which represents the quarry and open-cut mine group), each the leader in its group, were awarded the ?Sentinels of Safety? trophy. Relative standing in the contest" was determined by the number of days lost from accidents in proportion to the total number of man-hours worked. Since 1925, when the National Safety Competition was inaugurated, an increasing interest has been taken in it by mining and quarrying companies as a means of stimulating mine and quarry safety by competition among similar plants. Each participating plant can, on a basis of its standing and record in the contest, determine to what extent its safety program is succeeding or to what extent it needs strengthening. With this information, each company that has a low standing in the contest can intensify its safety-promotion efforts the following year to obtain a lower rate and possibly win the trophy or achieve honorable mention in the competition. Except for 1929, the National Safety Competition of 1936 represented more man-hours of employment than any other year since the yearly contests began.

Jan 1, 1937

By W. W. Adams

Three hundred and twenty-eight mines and quarries, representing 36 States, took part in the twelfth yearly accident-prevention contest conducted by the United States Bureau of Mines and known as the National Safety Competition. Four underground mines and one open-cut mine (which represents the quarry and open-cut mine group), each the leader in its group, were awarded the ?Sentinels of Safety? trophy. Relative standing in the contest" was determined by the number of days lost from accidents in proportion to the total number of man-hours worked. Since 1925, when the National Safety Competition was inaugurated, an increasing interest has been taken in it by mining and quarrying companies as a means of stimulating mine and quarry safety by competition among similar plants. Each participating plant can, on a basis of its standing and record in the contest, determine to what extent its safety program is succeeding or to what extent it needs strengthening. With this information, each company that has a low standing in the contest can intensify its safety-promotion efforts the following year to obtain a? lower rate and possibly win the trophy or achieve honorable mention in the competition. Except for 1929, the National Safety Competition of 1936 represented more man-hours of employment than any other year since the yearly contests began.

Jan 1, 1937

By Alexander L. Field

This paper contains an account of experimental results obtained in an extensive investigation of steels containing zirconium. There recently appeared&apos; an announcement by F. M. Becket, at whose suggestion and under whose general direction this investigation was made, a statement of the outstanding features of the work and a brief explanation of the factors that led to its inception. It is not possible, in a paper of this character, to record all of the operating and test data collected, which includes the production of more than 350 heats of steel. The difficulty of a complete presentation is increased by the fact that several lines of experimentation are too incomplete to warrant publication of the results at the present time. In addition to the methods of manufacture and test employed in the work, there is described experimental evidence on which are based certain definite conclusions regarding the remarkable effects brought about by the presence in steel of relatively small percentages of zirconium. When added to a molten steel bath, zirconium combines chemically with dissolved oxygen, nitrogen, and sulfur, in the order named, and is capable of neutralizing the embrittling effect of phosphorus in whole or in part; although in the case of phosphorus there is no evidence so far of actual chemical combination. These effects arc not in the nature of suppositions supported by theory, nor is their existence deduced merely on the basis of analytical evidence. In each phase of its relation to or reaction with the four impurities mentioned, zirconium affects beneficiauy the mechanical properties of the steel to which it is added, in a manner which it is one of the purposes of this paper to explain in terms of a tentative working theory.

Jan 1, 1923