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By Patrick Tassot

Increased worldwide highly competition in steel market imposes innovative measure for the steelmaker targeting cost reduction and climate-friendly steelmaking process in order to have the ability to withstand the pressure of the market. At the same time the demand for high purity and highest quality steels continues to grow from year to year, especially in the sector automotive in transportation of oil and gas, in the construction Industry and in the manufacture of heavy plate. As they allow producers to be up to the requirements while allowing expanding their product mix, new secondary metallurgical treatments have become a must additionally to standard equipment elements of steel plants modern. Most of these treatments occurs in the steel ladle increasing the pressure to ensure a reliable and as possible neutral reactor. Intelligent solutions for refractory lining ladles should integrate better adaptation to the operational process parameters and the high reliability/availability at the best cost/performance. This challenge has conducted Refratechnik to develop new concepts to overcome the frontier between shaped and unshaped materials and that’s what will be covered in this paper.

Aug 17, 2017

By Tracy Brettmann, Shailendra Endley, Jason Leary, Shashank Valluru

"Augered Cast-in-Place (ACIP) piles have long been used for deep foundation support in sands due to their high capacity and speed of installation. Very little information exists on the effects on capacity if the auger needs to be withdrawn from the hole prior to grouting. This condition can occur due to various reasons including grout plug ups, equipment issues, and grout supply delivery problems. It can become a major problem for the project team if this happens during production because the capacity of that pile is then in question, potentially resulting in re-design, installation of replacement piles and/or schedule delays. This paper compares the results of two high capacity test piles installed into a dense sand where one test pile was installed by first completely withdrawing the auger from the hole after drilling to the pile tip depth and the other test pile was installed utilizing conventional industry standard methods. Identical load tests were then performed on both piles to compare the effects of the two different installation procedures. The load test results were surprisingly similar in this case although the grout take required for the test pile installed in the pre-drilled hole was significantly higher to produce a similar grout return depth.IntroductionAugered Cast-in-Place (ACIP) piles are used extensively along the Texas Gulf Coast due to their combination of high capacity and speed of installation resulting in one of the most cost effective deep foundation systems relative to other options. Soil conditions in this region typically consist of alternating layers of sand and clay in the upper several hundred feet. ACIP piles are routinely installed to depths of over 100-ft to achieve the required capacity depending on the site specific soil conditions and therefore typically extend through and tip into sand layers. Occasionally, due to various reasons like equipment issues and plug-ups, the auger is withdrawn from the hole without grouting. Significant sand in the soil profile could lead to questions about the effect of the auger withdrawal on the pile capacity and load deflection relationship.This paper summarizes the results of two identical pile load tests performed on adjacent piles of the same length with the main difference being one was installed using the standard installation procedure and the other was installed by first completely withdrawing the auger from the hole after drilling to the pile tip depth. The load test results were then evaluated using load transfer analyses to estimate the effect of the withdrawal of the auger on the load-deflection characteristics and capacity."

Jan 1, 2017

By Nilo Nogueira da Silva

O objetivo deste trabalho foi investigar os efeitos da temperatura de laminação na microestrutura de um aço microligado ao Nióbio através de simulação por ensaios de torção a quente. Ensaios foram realizados com deformações em resfriamento contínuo para determinar as temperaturas de não recristalização da austenita (Tnr) e de início da transformação austenita-ferrita (Ar3). Foram realizados ensaios de torção simulando diferentes esquemas de laminação a quente em laminador Steckel, variando-se as temperaturas dos passes de acabamento. Foi observado, nas curvas tensão em função da deformação dos ensaios de torção, gradual encruamento da austenita quando a temperatura da última deformação foi inferior à 870°C. Foi também observado que o tamanho de grão ferrítico cresce com temperatura de laminação de acabamento.

Aug 8, 2018

By H. Yasuhara, N. Kinoshita, S. Nakashima, K. Kishida

"In this study, flow-through experiments in fractured rocks have been conducted under different stress, temperature, and pH conditions so as to understand the evolution of permeability induced by these conditions. Throughout the experiments, the confining pressures and temperatures are well-controlled. Effluent concentrations are also measured for the ten elements of Si, Al, K, Fe, Ca, Na, Mg, Ti, S, and Cl that are included mainly in the targeted rocks. In the early stage of the experiments, the fracture permeability measured abruptly decreases with time, and subsequently reaches quasi-steady state within a relatively short period. In contrast, the permeability in the intact rocks monotonically increases with time. The permeability increase and decrease are attributed likely to the relative dominance of mineral dissolution in the pore spaces and to that of mineral dissolution/crushing at the propping asperities within the fracture and/or mineral precipitation onto the free surfaces, respectively. The evolving rates and magnitudes of the permeability are likely to be controlled by the stress exerted over the contacting asperities, temperatures, and pH of the permeant. Thus, this complicated behavior should be attributed to the coupled chemically- and mechanically-induced effects, which should be examined in more detail for longer period to contribute to the safe entombment of radioactive wastes. INTRODUCTIONUnderstanding of the flow and transport characteristics of porous/fractured rocks is required for the safe and long-term geological isolation of energy-related by-products (i.e., high level radioactive wastes and anthropogenic CO2). Notably, under relatively high temperature and stress conditions, mechanically- and chemically-mediated processes may alter the pore structures in rocks, resulting in an irreversible evolution of the flow and transport behavior. Augmentation in permeability may result from mechanical dilation due to shearing and mineral dissolution within the pore spaces, while reduction may result from reversible or irreversible mechanical compaction, mineral dissolution at the contacting areas, and clogging of pore spaces by precipitation of secondary minerals."

Jan 1, 2015

By E. Hein, R. A. Dodd

The fatigue softening of prior strain-hardened poly crystalline copper has been determined by measuring changes inflow stress resulting from fatigue treatments. Tensile fatigue does not soften the metal, while the softening due to reversed stress fatigue depends on the extent to which fully reversed stressing is approached. True tensile fatigue is shown to be possible only in the case of long wire specimens. Annealing following fatiguing of strain-hardened metal shows that tensile fatigue is very effective in modifying normal recovery and recrys-tallization. OBSERVATIONS by Ludwik and Scheu,' Kenyon,' Polakowski and Palchoudhuri, Kemsley, and Broom and Ham,596 have shown beyond doubt that strain-hardened metals are softened by reversed-stress fatigue. To some extent the softening might be associated with a rearrangement of dislocations, but the results of Broom and Ham5 on the temperature dependency of the fatigue hardening of annealed copper, and those of McCammon and Rosenberg7 on the partial recovery at 100'C of fatigue-hardened copper suggest that point defects may be involved. Since lattice vacancies are the only species of point defect present in appreciable quantities in thermody-namic equilibrium, most attention has been accorded them in the various theories advanced to explain hardening and softening effects resulting from fatigue. Precise mechanisms remain uncertain, and while some effects may be due to single vacancies, defects arising from vacancy clusters may also contribute to the changes in properties. All types of plastic deformation result in point-defect formation, one frequently invoked formation mechanism involving the nonconservative motion of jogs formed by the intersection of, for example, mixed dislocations. But since fatigue deformation is thought to be a particularly effective way of forming point defects, additional mechanisms peculiar to fatigue must be sought. One possibility is that jogged loops contract during the unloading cycle to give rows of vacancies. A local high-vacancy concentration could conceivably promote polygonization and recovery by climb, and, therefore, could explain the fatigue softening of strain-hardened metals under appropriate conditions of temperature. Conversely, the experiments by Broom and Ham6 on the fatigue hardening of copper single crystals involving subsequent tensile testing of previously fatigued specimens, resulted in the observation of distinctly lowered yield points. This could be due to vacancy atmospheres associated with dislocations, possibly augmented by jogs on dislocations. In addition to the yield-point phenomenon, a post-yield hardening was observed, with a temperature-dependence resembling the friction-hardening of irradiated metals,9 this again suggesting a point-defect mechanism. An important development in this field has been the observation,10 by transmission electron microscopy, of high concentrations of prismatic loops in fatigued aluminum. By analogy with quenched aluminum filmso11 it seems certain that these loops originate in the collapse of vacancy clusters formed during deformation. Metals, such as copper, having a relatively low-stacking fault energy would tend to produce Frank sessile loops (in practice tetrahedral defects with stacking faults on all (111) planes) rather than the glissile prismatic loops observed in aluminum. The manner in which these various defects affect the different aspects of fatigue behavior has not yet been fully investigated. The present work was designed principally to indicate whether tensile fatigue gives rise to hardening and softening effects similar to those associated with reversed stress fatigue, and with the hope of providing additional information on the contribution of point defects to fatigue deformation. Despite the uncertain ty often associated with the interpretation of resistivity data, i.e., the relative contribution of stacking faults and other defects, such measurements are conveniently employed to study point defect pheno-

Jan 1, 1962

By J. W. Thompson

ORES PROCESS OF ORE CONCENTRATION-PATENTABILITY. The patent issued to Sulman, Pickard, and Ballot, November 6, 1905, and assigned to Minerals Separation and Minerals Separation American Syndicate, for new and useful improvements in ore concen- tration, its object being to separate metalliferous matter from gangue by means of oils and fatty acids that have a preferential affinity for such metalliferous matter, the principal feature of which is "agitat- ing the mixture to cause the oil-coated mineral to form a froth," was clearly anticipated by other patents, and each step in the process described in the Sulman, Pickard, and Ballot patent is fully described in more than one of the prior patents, with the single exception of the reduced quantity of oil used; but the discovery that the small fraction of oil is sufficient to produce flotation of the metalliferous matter can not be made by itself or in combination, the subject of a patent. Hyde v. Minerals Separation, 214 Fed., 100, p. 109, May, 1914. ACTION FOR CONVERSION OF MINERALS. In an action by the grantor of a certain mine and mining property against his grantee to recover damages for the conversion of a quantity of ore that the grantor before the conveyance had mined and extracted from the mine and placed on the dump near the mine, the plaintiff is not entitled to recover where it appears that at the time the ore was placed on the dump the mine was owned and operated by a mining company and that at the time the ore was taken out of the mine the company had no intention of doing anything with it but simply deposited it on the dump as waste and to give an opportunity to develop the mine and get better ore to send to the smelter, and that

Jan 1, 1915

By J. Marin, H. A. B. Wiseman

This paper presents results of an experimental study dealing with the plastic stress-strain relations of aluminum alloy 14s-T6 subjected to combined biaxial tension and compression stresses. Plastic stress-strain relations for both constant and various types of variable stress ratios were determined and a comparison made with the simple flow theory of plasticity. THIS investigation was undertaken for two main purposes: 1—to obtain plastic stress-strain relations for Alcoa 14s-T6 when subjected to various combinations of biaxial stresses, and 2—to determine the validity of the flow theory in predicting plastic stress-strain relations for combined stresses. The biaxial stresses used were tension combined with compression. These stresses were produced by subjecting a thin-walled tube to axial tension and torsion. Various types of combined stress conditions were investigated. To provide control test data and information on the influence of biaxial stresses on the strength, the usual constant stress ratio type tests were made. These tests showed that the biaxial yield strength agrees approximately with the distortion energy theory. However, the Prager semi-empirical theory agrees best with the test results. For these constant stress ratio tests the plastic stress-strain relations were found to agree approximately with the flow theory. (For constant stress ratio the flow and deformation type theories are identical.) In view of the fact that the constant stress ratio tests cannot distinguish between the flow and deformation theories, a number of variable and special biaxial stress tests were made. These tests showed that the flow theory is inadequate, since large differences exist between the experimental and theoretical results. Special tests were also conducted to check the validity of the isotropic yielding assumption. This assumption is made in the linear-type flow theory. In these tests specimens were loaded in tension to predetermined values beyond the proportional limit stress. The tension load was removed from the specimen and the specimen was subsequently loaded in torsion to fracture. Other tests were applied with the order of torque and tension loading reversed. The nominal stress-strain curves for these two tests approximately coincide indicating that the assumption of isotropic yielding is valid. In addition, these tests verified the requirement by the slip theory of plasticity that prestraining below 140 pct of the proportioned limit stress in either torsion or tension did not influence the subsequent plastic stress-strain relations in tension or torsion. Another type of test was conducted to check the assumption that the axes of principal stress and strain coincide during plastic flow and variable stress conditions. These tests were conducted by applying combinations of axial tension, internal pressure, and torsional loads such that the axes of maximum principal stress could be rotated through 90" during the loading path. The results of those tests showed that the angle between the axes of principal stress and strain varied greatly and that the assumption of coincidence between axes of principal stress and strain is not valid. Introduction In various metal processes including forming of sheets, rolling of bars, and extrusion of rods, metals are subjected to stresses beyond the yield strength of the material. Often these stresses are not simple stresses acting in one direction, but are combined stresses acting in more than one direction. Structural and machine members are often subjected to combined stresses. To adequately determine the factors of safety for these members, it is necessary to know the plastic stress-strain relations of the material used for various combined stress conditions. Various theories have been proposed for predicting the plastic stress-strain relations for combined stress in terms of the simple tension plastic stress-strain relation for the material. To determine which theory might be adequate, test results must be obtained for various combined stress conditions, in order to compare the actual with the assumed theoretical behavior. Although there is considerable test data available for combined stress conditions in which the principal stress ratios are constant, relatively little test information is available for vari-

Jan 1, 1954

By W. H. Tomlinson

One of the more important functions of the Federal Bureau of Mines is conservation of the life and health of employees of the mineral and allied industries. Since its very beginning the Bureau has encouraged competition between mine rescue and first-aid teams as a means of stimulating interest in safety and accident-prevention work. In addition to sponsoring competition on a national and international scale during the past 45 years, the Bureau has also assisted State mining departments, mining companies, and mining organizations in holding State, district, company, and other local meets. This assistance includes providing instructors to train teams, judges, and other contest officials. The Bureau has also furnished problems and outlines for working them, judges I discount sheets (scorecards), contest rules, and problem judges. In fact, Bureau representatives participate in nearly all State, district, and company contests and have bad complete charge of some contests.

Jan 1, 1956

By Christopher Newman, Zach Agioutantis, Gabriel S. Esterhuizen

"As conventional underground deposits are continuing to be depleted, mining operations have been forced to produce at greater depths and in more geologically and geometrically challenging conditions. Over the past decade, there has been a global increase in the application of cemented paste backfill (CPB) material as a means of ground support in open stope mining operations. Although CPB has been extensively used within the industry, there are many fundamental factors affecting the design of safe and economical fill structures that are still not well understood. A critical design issue with respect to backfilled stopes is determining the stress state within the fill material as well as the surrounding rock.This paper details the development of a reliable numerical model for the simulation of stress distributions around the excavated stope area, as well as through the backfill material. Through discussions on modeling parameters and output results, one is provided with insights into the mechanisms of stress redistribution allowing for further accuracies in simulating the behavior of the CPB material as well as its interaction with the surrounding rockmass.INTRODUCTION AND BACKGROUNDModern technological innovations with respect to material processing, cementitious composition and chemical additives, and material transportation have provided the mining industry with a ground support material that greatly reduces mine waste costs, while, when used appropriately, increases reserve production and mine stability. As mining operations continue to produce in more complex geologic and geometric conditions, cemented paste backfill (CPB) has become commonly employed within primary-secondary excavation-support sequencing allowing for total extraction of the mining reserve. As shown in Figure 1, primary stopes are initially excavated and then backfilled in a two-staged pour: plug and final pours. The plug (initial pour), is initially placed at the bottom of the stope with a CPB material of heightened cementitious material. While the plug provides a strong foundation on which to build the rest of the CPB structure, it also provides protection against barricade breakthroughs (Li and Aubertin, 2009), as well as providing operations a means of underhand stope-and-fill mining through the use of an artificial sill pillar (Hughes, et al., 2011). Following placement, the plug is allowed to cure to a designated design strength. Upon completion of the plug, a less cementitious “final” pour material is used to backfill the rest of the excavated area."

Jan 1, 2018

By Xiaolu Ye

"Comprehensive utilization of Bi and Sn from the tin-associated polymetallic tailings by “gravity separation – flotation combination process” has been studied, which was verified that the novel process is an effective method to deal with the high content pyrrhotite tin-associated polymetallic tailings. In this investigation, ore property analysis and magnetism analysis of pyrrhotite were conducted to research and develop reasonable beneficiation flowsheet. The results of ore property analysis present that pyrrhotite was not closely related to bismuth and tin minerals. Particle size analysis results indicated that pyrrhotite was mainly in the form of fine particles. The magnetic analysis results show that pyrrhotite was distribution in all the three types of pyrrhotite in a single mining area, which indicated that variable magnetism of with different crystal structure pyrrhotite. The process of “low intensity magnetic separation - high intensity magnetic separation” shown an excellent adaption for the high content pyrrhotite tin-associated polymetallic ore compared with the single flotation process based on the magnetism variable of pyrrhotite. The results of whole process test indicated that a bismuth coarse concentrate assaying 5.63% of Bi at 81.77% recovery was obtained, which treat the conditions for the Bi-S separation flotation. In addition, the content of sulfur in the tin concentrate decreased from 2.5% to 1.5%, which provided a new reference for other tin-associated polymetallic tailings. INTRODUCTION Tin has been applied extensively in catalytic chemistry, gas sensors, tin plating, and plumbing. Tin-bearing polymetallic ores have been the important deposit types to recycle tin with the rapid depletion of mineral resources. The comprehensive utilization of the associated elements has been a preoccupation for the mineral processing researchers."

Jan 1, 2018

By Shu Xinqian, Zhou Weining, Shan Zhiqiang, Feng Jifu

"Modified calcination conditions on the extraction of rubidium resources from muscovite (KAlz[AlSi301o](OH)2) ore are systematically studied. The impact of various factors on the rubidium leaching rate is also analyzed, including the agent types, roasting time, the mass ratio, roasting temperature, etc. The results indicate that the best agent is a combination of sodium chloride and calcium chloride, its mass ratio ofmuscovite/NaCl/CaClz is 1:0.25:0.25. Calcined at 8500 for 30 minutes, the rubidium leaching rate is up to 90%. The reaction of muscovite ore with the chlorinating agent CaC12 has been studied by TG/DSC, the calcined intermediates are identified by XRD, and the surface morphology before and after leaching is characterized by SEM. Rubidium chloride products can be obtained with a purity of 92% by using t-BAMBP extraction, hydrochloric acid reextraction and purification.IntroductionRubidium is one ofrare alkali metals, which is found in 1981 by German R.W. Bunsen and G.R. Kirchhof. Rubidium includes the following features: atomic number is 37, each atom weight 85, the body-centred cubic lattice, each unit cell has two metal atoms, and the density is 1.532g/cm3. The properties of low melting point (312.46 K) and malleability make rubidium have a strong chemical activity and photoemission. Rubidium provides a main material for manufacturing phototube with a wide range oflight waves, which possess high sensitivity and stability. Efforts are being made to carry out research on rubidium ion gngine, magnetic flux generators and thermoelectric transudcer, etc. Rubidium exists in muscovite ore(KA12[AlSh01o](OH)2 (monoclinic system and hexagonal layered structure) as isomorphism and replace the large radius of the potassium atoms, as well as part of rubidium locate between structure layers. The complex components bring great difficulty in comprehensive recycling."

Jan 1, 2013

By Z Hu

The technique of reclaiming disturbed land by use of a hydraulic dredge pump (HDP) (which is a set of hydraulic machines for earthwork), termed 'digging deep to fill shallow has been used in the reclamation of subsidence areas in Chinese coal mines. This paper discusses the operational principle of the technique and summarises its reclamation procedures, which are being used in current reclamation practice. The soil condition reclaimed by the HDP was studied. The results showed that the pioneer crops to be planted in the reclaimed soil should be the ‘pulse’ family crops, and that improvements to the reclaimed soil and the HDP technique itself are needed. Bused on the analysis of the previous technical processes, a new rational technical model for the HDP reclamation method is presented in this paper.

Jan 4, 1996

By H. R. Stahl

FIVE mills are operated in Southeast Missouri by the St. Joseph Lead Co.; these have a total rated capacity of 24,300 tons per day divided as follows: Federal, 12,000 tons; Leadwood, 4800 tons; Desloge, 3600 tons; Bonne Terre, 2400 tons; and Mine La Motte, 1500 tons. These concentrators are similar in a general way, differing mainly in size and type of equipment and in minor variations in flow sheet. No attempt is made rigidly to standardize procedure in the various mills in spite of a general similarity in the ores. Each mill may be regarded as a separate laboratory in which new ideas and changes may be tried. A generalized description of the process is given, noting important differences in procedure at the various plants. The concentration process may be divided into five main stages: dry crushing, wet grinding, desliming and classification, tabling, and flotation.

Jan 1, 1947

By Uwe Wilhelm

Pittini Group has contracted Danieli in 2011 for the supply and replacement of the existing EAF at Ferriere Nord Plant in Osoppo. This was a very challenging project: giving the fact that the Meltshop was operating already under very high performance level, there were many elements involved for the project to improve (reduce the amount of charges, promote highest possible chemical energy utilization, allow best optimization on existing transformer power, modification on Drop Out box and Water Cooled Duct, Hydraulic System for EAF, Scrap Bucket design to fit to new EAF with existing loading and transport system, Automation System Review and Upgrade) as well as limitations of the existing installation (limited space, lifting capacity building and cranes and the required solutions for fast shell and roof exchange). All furnace parts, as well as installation engineering, were developed and discussed carefully with the Customer to either provide proven and reliable concepts, but also to define solutions for fast installation/maintenance access and quick exchange for offline turnaround. In the end, from disassembly of existing equipment up to the first heat of the new furnace, only 38 days were necessary. First heat was made on January 24th 2013, on the 6th production day 32 heats where produced at nominal design capacity and 28 days after start up 100,000 t liquid steel have already been produced.

Jul 30, 2018

By John D. Sullivan

ALUMINUM and magnesium plants in the United States underwent enormous wartime expansion which made many wonder if ghost plants would result when industry swung back to a peacetime basis. Production capacity of primary aluminum ingots was stepped up from 150,000 tons annually to about 1,150,000 tons; magnesium production increased from 2500 tons in 1936 to nearly 200,000 in 1943, with a production capacity of some 300,000 tons. Not only was primary metal production enlarged but also the capacity of prime fabrications such as castings, forgings, extrusions, and sheets was correspondingly increased. In mid-December it was estimated that production of primary aluminum ingots in the United States in 1946 will be about 410,000 tons while consumption will be about 500,000, close to half of the wartime consumption. The 1946 estimated consumption of secondary aluminum is 200,000 tons. The critical shortage of soda ash is hindering production of primary metal, and the outlook for an early relief of this shortage is dark.

Jan 1, 1947

By AIME AIME

T HE Executive Board of the American Engineering Council held its fourth meeting at St. Louis on the first anniversary of the organizing conference which met in Washington on June 3,1920. Representatives of a number of the leading engineering organizations in the vicinity of St. Louis were present by invitation. The members of the Executive Board were guests of the Associated Engineering Societies of St. Louis. They were given a delightful ride about the city and were entertained at the Glen Echo Country Club at dinner. The special committee that had been appointed to draft resolutions to Mr. Hoover submitted the following, which were adopted : WHEREAS, our President, Herbert Hoover, has been appointed Secretary of Commerce in the Cabinet of the President of the United States, and WHEREAS, in consequence of his acceptance of this high public office, he has deemed it necessary to tender his resignation as President of The Federated American Engineering Societies.

Jan 1, 1921

By G. H. LeFevre

THE Metal Sales Department, with offices in New York, is responsible for the sale of the Company's products, with the exception of gold and coal. At present the department handles the sales of lead, zinc, silver, antimonial lead, , cadmium, bismuth, arsenic trioxide, and tellurium; gold is shipped direct to the United States Mint and coal is marketed by United States Fuel Company's own sales organization. The department keeps in close touch with the metal markets and collects information on marketing conditions, which it makes available to other departments of the Company. The electrolytic lead produced at the U. S. S. Lead Refinery, Inc., is a high-uality product marketed as corroding grade under the "U. S. S.-ELECTRO" brand. It is largely sold to manufacturers of paints, pigments, lead oxides, and storage batteries.

Jan 1, 1948

By Antonella Rocha Ponseggi

O desenvolvimento dos materiais dos eletrodos (anodo e catodo) e do eletrólito de células a combustível de óxido sólido (SOFC) com o intuito de que estas possam operar de forma estável com combustíveis diferentes do hidrogênio é um objetivo central da pesquisa em SOFC. Dessa forma, o objetivo deste trabalho é evidenciar as características microestruturais e o desempenho de materiais para uso de combustíveis hidrocarbônicos e alcoóis em SOFC. Neste trabalho são avaliados, à luz da caracterização eletroquímica e elétrica de SOFC unitárias e estruturas em bicamadas anodo-eletrólito, sistemas materiais do tipo Ni/Cu-Céria/YSZ-LSM sob a alimentação de diferentes combustíveis. Os melhores resultados foram obtidos com o uso de hidrogênio ou etanol, mas novos desenvolvimentos em engenharia microestrutural são prementes. Também ficou evidenciado os problemas de degradação e instabilidade advindos da presença de sulfurados no biogás combustível.

Aug 16, 2017

By Marcos Vinícios da Silva Cavalcante

A permeabilidade de um leito de partículas esféricas é uma função direta dos espaços vazios, ?, formados pelo empacotamento destas partículas que compõe o leito. Na literatura são encontrados estudos que envolveram leitos com um ou até dois diâmetros de partículas esféricas, contudo na pelotização o produto do disco pelotizador é uma população de aglomerados esféricos, também chamados de pelotas, com diversos diâmetros diferentes tornando a previsibilidade da medição de ? imprecisa. Este estudo tem como objetivo entender qual a faixa de percentual de espaços vazios, %?, existem nos leitos encontrados na indústria de pelotização, e ainda a relação desta métrica com alguns parâmetros de controle operacional e ainda indicar testes na linha de produção para otimizar a produção de pelotas e também controlar os custos de produção.

Aug 16, 2017

By W. A. Wood, W. H. Reimann

A study is made of the creep that can be induced in armco iron at room temperature by superposing small amplitudes of alternating torsion on a tensile creep load. It is shown that the creep differs from that in comparable tests on copper in being trmsient only. At the same time, though transient, the creep can produce extensions of some 10 pct under creep loads less than the tensile yield stress of the material. The creep can be largely suppressed b$ applying cyclic strain of suitable amplitude before applying the creep load and the metal thereby stabilized. At room temperature, plastic flow in a metal under steady load is normally limited by strain-hardening processes. However, if a small cyclic stress is superposed on the steady load these processes may be more or less neutralized and, as shown in recent investigations,'-4 plastic flow may continue. In this way annealed copper, for example, can be induced to creep continuously to fracture under loads as small as 1 tsi. Dislocation mechanisms possibly responsible for this room-temperature creep have been usefully reviewed by Feltner.But discussion so far has been based mainly on creep as it is found in close-packed metals initially in the annealed state, and their behavior may not be general. In fact, recent work shows that the form of creep in annealed copper is different from that even in cold-worked copper;7 the creep thus depends on the dislocation pattern already in a metal as well as on the metal itself. This paper describes the creep in annealed armco iron, tested in the same way as the above-mentioned copper. One object was to see how creep in a typical bcc metal compared with that in the annealed close-packed metals. Another object was to utilize the fact that a bcc metal like iron has a more pronounced elastic range than close-packed metals like copper and to find to what extent the creep load or superposed cyclic stress had to exceed their re-

Jan 1, 1964