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By V. A. Evans, D. L. Hellier

Introduction Preparing a report on fluorspar economics in the US could have been somewhat complicated at one time. This was because the number of producers, both large and small, derived production from different locations through-out the western US and the southern Illinois and western Kentucky fluorspar districts. Companies, such as Allied Chemical and Williamson Mining, operated in the Jamestown district of Colorado. In Walden and Salida, CO, the Colorado Fluorspar Co. operated mines and mills. In New Mexico, both Du Pont and Allied had mines and mills. In the Illinois-Kentucky district, US Steel, Rosiclare Lead and Fluorspar, Minerva Oil Co., and Marathon Oil all produced spar for the US market. Now all of the companies are out of the fluorspar business and, with the closing of the Seaforth Mineral Co.'s Inverness Mining Co., only Ozark-Mahoning Co. survives as a domestic producer. History Ozark-Mahoning Co., as it now exists, was formed in 1946 by the merger of Ozark Chemical Co. and Mahoning Mining Co. Ozark Chemical Co. was started in the 1920s to produce sulfuric acid for two refineries located in Tulsa, OK. Mahoning Mining was originally formed by the founders of Ozark Chemical Co. and the Youngstown Sheet and Tube Co. to produce fluorspar and associated minerals from properties in the southern Illinois and western Kentucky fluorspar district. In 1937, Mahoning Mining started an exploration program, employing contractor-operated churn drills to look for reserves in Hardin and Pope Counties in southern Illinois. Based on known reserves in the area and the results of the exploration program, work was started in the fall of 1938 to build a selective flotation plant at Rosiclare, IL. The mill was completed and put into operation in August of 1939. The company's first mining efforts were in the Cave-In-Rock district just north of Cave-In-Rock, IL. The deposits in this area were of the Manto or bedded type. They have been the mainstay of the company's operations in the Illinois-Kentucky fluorspar district. In 1950-51, the company expanded its operations by purchasing fluorspar properties from Colorado Fluorspar Co. at Walden, CO. This location was operated from 1952 through 1958 and from 1968 through 1973 when it was closed permanently. In 1974, Ozark-Mahoning Co. was purchased by Pennwalt Corp. Presently, it is a wholly-owned subsidiary of that corporation. As the only major domestic producer of fluorspar in the US today, the company's ability to survive under the flood of imported material is directly related to the four major segments of its operations. These are: exploration, mining productivity, maintenance, and marketing. All are done in-house. Exploration The Southern Illinois fluorspar district is located in the most complexly faulted area of the central US. The formations are sedimentary in nature and range in age from Devonian through Pennsylvanian. The deposits are small, they range in size from a few thousand tons up to 900 kt (1 million st), with the average minable deposit being around 544 kt (600,000 st). The ore occurs in both nearly vertical vein deposits and in Manto or flat lying bedded deposits. Due to the relatively small size of the deposits and the depth at which they occur, a good low-cost exploration program is essential to ensure that new finds of ore are equal to the mining extraction rate. Ozark maintains a leased land position in Pope and Hardin Counties that will fluctuate somewhere between a low of 40 km2 (10,000 acres) up to a high of 129 km2 (32,000 acres), depending on total size of tracts leased. Most all lands are obtained through a standard lease purchase option, with a small minimum royalty per acre during the normal 10-year option period. All leases are standard and without deviation to control land cost. All land leasing is done through Ozark's geological staff, who also

Jan 11, 1986

By D. C. Hilty, W. Crafts

J. Chipman—It has been my privilege to discuss this work with the authors on several occasions and to observe at first hand the experimental methods employed. I wish, therefore, to emphasize certain points which they have mentioned only briefly with regard to the experimental techniques. The rotating induction furnace as here employed interposes liquid metal between slag and refractory thus preventing the two nonmetallic parts of the system from reaching equilibrium with one another. It is therefore impossible for the metallic phase to be completely in equilibrium with both the slag and the crucible. The metal also acts as a partially permeable membrane allowing certain components, including oxygen, to diffuse from slag to crucible. This transfer results in building up on the face of the crucible a layer of material whose composition is in part dependent on that of the bath. Reactions between the layer and the solid refractory are slow, as evidenced by the rather good life of the crucible. Hence it seems probable that the layer is more nearly in equilibrium with the metal than with the underlying crucible material and that, once it is established under a bath of a given composition, its further reactions with that bath are slow. Additions to slag or bath may be followed by changes in the layer; and time must be allowed for virtual completion of such changes, before it can be assumed that slag and metal are in equilibrium. We may judge from the results reported that, in general, this was the case and that the data represent at least quite close approximations to slag-metal equilibrium. Data on deoxidation and on oxygen solubility are no better than the analytical methods employed. The vacuum fusion method as used by the authors seems entirely adequate for the samples analyzed. I have had frequent occasion to compare results with their laboratory, always with very satisfactory agreement. The determination of aluminum at very low concentrations is perhaps an even more difficult procedure. Here also the colorimetric method used has been worked out with great care and is undoubtedly the most dependable method available. The discrepancy between observed and calculated deoxidation or solubility lines is not to be explained as the result of experimental errors, either in the sampling or analysis of the metal. Nor is it to be blamed upon inaccuracies in the several kinds of indirect data upon which the calculated results were based. It is true that both the observed and the calculated lines admit of some uncertainty as to their exact locations, but the uncertainties are small compared to the wide gap which separates the two lines. The authors have pointed out the real cause of the discrepancy. In all of their experiments the solid phase was not Al2O3 but a mixed oxide containing iron and aluminum. This suggests an extension of the calculated values to include equilibrium with the spinel FeO . A12O3. The free energies of FeO and A12O3 are known, that of the spinel is not. However, it cannot differ greatly from that of its component oxides for even in the more stable spinel, chromite, the free energy of formation from the oxides is less than 10,000 cal. For purposes of calculation we shall call this free energy X and solve for values of X lying between zero and 10,000 cal. The other data required are taken from the forthcoming revision of "Basic Open Hearth Steelmaking" and are given in the following equations in which underlined symbols indicate elements dissolved in liquid steel and the standard concentrations are 1 pct. ?F° at 1600°C, cal ?LA = 2 Al + 3 O; + 107,200 FeO = Fe + 0; + 5,460 FeO + A12O3 = Fe + 2A1 + 4 0; + 112,660 — X The corresponding equilibrium concentrations are shown in fig. 21. The line marked A12O3 corresponds to the first equation, those marked FeO . AL2O3 correspond to the last, with X = 0, 5000 and 10,000 cal, respectively. The two upper lines represent the data of Hilty and Crafts and of Wentrup and Hieber. The points are the observations of Hilty and Crafts in the presence of 0.50 pct Mn.

Jan 1, 1951

By Arnulf Muan, D. P. Masse

PHASE relations in the system CoO-SiO2 have been determined as a basis for further investigations of thermodynamic properties of olivine solid solutions involving Co2SiO4 as a component. Previous data on the system CoO-SiO2 are incomplete or uncertain. Biltz and Lemke1 determined the melting point of cobalt orthosilicate as 1345°C , but Asanti and Kohlmeyer2 have later found a considerably higher temperature, 1420°C. The latter authors also studied melting relations of one mixture on the CO side and two mixtures on the SiO2 side of the orthosilicate composition and sketched a tentative phase diagram for a limited composition range of the system. However, no phase identification was carried out, and the authors left unanswered the question of the possible existence of a stable meta-silicate phase. Greig3 showed that a 90 wt pct SiO2-10 wt pct Co mixture at 1725°C consists of two immiscible liquid phases. The quenching technique was used in the present investigation. Mixtures of high-purity cobalt oxide ("Fisher Certified") and dehydrated silicic acid ("Baker Analyzed") were equilibrated in air atmosphere. The samples were then quenched to room temperature and the phases present were identified by microscopic and X-ray examination. The samples were kept in small envelopes made from thin (0.0004 in.) platinum foil. Thermodynamic data which have become available recently for Pt-Co alloys4 were used to check that the losses of COO from the oxide samples by alloying of cobalt with platinum in the present investigation were too small to change significantly the compositions of the oxide material during the equilibration. A vertical tube furnace with an 80 pct Pt 20 pct Rh resistance winding was used in runs up to 1510°C. Temperatures in these runs were measured with a Pt vs 90 pct Pt 10 pct Rh thermocouple calibrated against the melting point of diopside (CaMgSi2O6, 1391.5?C). The given temperatures as measured by this technique are estimated to be accurate to *5°C. Quench runs at temperatures above 1650°C were made with a modified Roberts and Morey5 strip furnace, using strip resistors composed of a 60 pct Pt-40 pct Rh alloy. Temperatures were measured with an optical pyrometer which was calibrated against the liquidus temperature of a mixture composed of 10 wt pct CaO, 90 wt pct SiO2 (1707°C). The temperatures measured with this technique have an estimated accuracy of +15°C. The results are shown graphically in Fig. 1. Only one intermediate phase, the orthosilicate Co2SiO4 with olivine-type structure, is stable in addition to the end members cobalt oxide and silica. The melting point of the orthosilicate was found to be 1415" ± 5°C. The metastilicate CoSiO3 is not stable at the temperatures of the present investigation. The two eutectic points in the system CoO-SiO2 where COO plus olivine, and olivine plus silica, coexist with liquid were found to be 72 wt pct COO and 1407°C and 63 wt pct COO and 1381°C, respectively. The melting point of cobalt oxide in air was taken as 1745?C, based on the previous data of Aukrust and Muan.6 Within limits of error (+ 5?C), identical eutectic temperatures to those determined in air were found when two representative mixtures were equilibrated at 1 atm O2 pressure and in an atmosphere of 84 vol pct CO2, 16 vol pct H2. This suggests that changes in oxidation state of cobalt in the condensed phases are not significant as far as their effect on the phase relations are concerned. This inference was substantiated by failure to detect7 any "excess oxygen" (i.e., oxygen in excess of that contained in Co2SiO4) in a sample of orthosilicate composition equilibrated in air 10°C above the liquidus temperature and subsequently quenched to room temperature. This work was carried out as part of a research program sponsored by the U.S. Atomic Energy Commission under Contract No. AT(30-1)-2781.

Jan 1, 1965

By A. Spearing

According to a 2000 NIOSH report, about 100 million rock anchors are installed annually in coal mines in the USA. Most coal mines have conditions that are conducive to corrosion of the rock anchor and ancillaries (such as plates), yet the effect of this on the performance of the anchors has not been adequately researched and its effects are not understood or quantified in the USA. There is considerable research into corrosion in civil engineering applications on surface and underground but the corrosion of coal mine rock anchors is not necessarily the same because: ? In underground civil structures, water ingress is usually stopped as part of the construction process. ? Many rock bolts in mines are only partially resin grouted leaving part of the reinforcing member exposed to corrosive conditions. All cable bolts in coal mines are only partially resin grouted. ? Even when mine bolts are fully grouted, shrinkage cracks occur and the rock stresses can change due to adjacent mining that can cause the resin column around the bolt to fracture further under external shear or tensile stresses. Most coal mines therefore have ideal conditions for bolt corrosion.

Jan 1, 2010

By K. Biswas, P. Tsang, S. S. Peng

A survey was undertaken in late 1993 and early 1994 to gain insight into the current status of pillar-design practice in underground coal mines in the United States. A total of 552 room-and-pillar mines and 75 longwall mines were surveyed to collect general, geological and mine-plan information. The collected information was critically analyzed with special emphasis on the pillar-design criteria adopted in these mines. A safety factor analysis was also carried out for the pillars in the room-and-pillar mines.

Jan 1, 1997

By João Júnio Pereira Lino

Este trabalho tem como objetivo demonstrar a influência da laminação de desbaste durante o processo de laminação termomecânica de um aço microligado ao Nb, Ti e V, obtido em um laminador Steckel, nas suas propriedades mecânicas. Duas variações do plano de passe para realização da laminação de desbaste foram propostas. As variações consistiram na diferenciação da redução passe a passe de forma a obter diferentes refinamento de grão ao fim do processamento de desbaste. O processamento de um aço com composição química adequada à obtenção de propriedades mecânicas compatíveis com o grau LNE380 especificado na norma ABNT NBR 6656 é demonstrado. Foram alcançados limites de escoamento a 0,2% de deformação e a resistência à tração na condição 1 de 459MPa 563MPa e na condição 2 de 505MPa e 601MPa respectivamente, sendo que na condição 2 foram obtidos acréscimos de em torno de 40MPa em ambos LE e LR.

Oct 30, 2017

By Rafael Fagundes Ferreira

Aços Bake Hardening são aços laminados a frio com envelhecimento controlado. Estes aços caracterizam-se pela boa conformação e por apresentarem aumento de resistência mecânica devido ao envelhecimento, que ocorre por tratamento térmico. Nesse trabalho, corpos de prova de tração do material BH220 foram submetidos à pré-deformações que variam de 0 a 9% por tração uniaxial, posteriormente à tratamento de envelhecimento realizado em temperaturas que variam de 140°C a 210°C em tempos de aquecimento entre 5 minutos a 45 minutos. Foi confirmada que as temperaturas de envelhecimento, na faixa estudada de 140°C a 210°, alteram a variação do limite de escoamento devido ao fenômeno de difusão que é termicamente ativado. Nos resultados encontrados verifica-se que o tempo de aquecimento, dentro do intervalo testado, não é significativo.

Aug 16, 2017

By Matheus Fortes Stiborski

O emprego de materiais sinterizados para conformação massiva permite a utilização de forças menores permitindo que resultados similares sejam alcançados com maquinas de potência menor, outra vantagem é que o blank utilizado para esse processo não contém tensões residuais advindas do processo anterior. Para o processo foi necessário o levantamento das curvas de compressibilidade do material a ser estudado (pó de ferro puro), análise das propriedades do material sinterizado e posteriormente extrusão do material e caracterização do mesmo.

Aug 17, 2017

By M. D. Mwema

Copper oxide ores deposits in the Katanga province of the Democratic Republic of Congo (DRC) contain at variable level cobalt oxide minerals. In contrast to copper oxide minerals which readily dissolve in the sulphuric acid solution, the cobalt oxide bearings are difficult to dissolve, especially if cobalt is present in the third oxidation state (Co2O3). This species become soluble after reduction of Co+3in Co+2. In practice, the use of reducing agent is therefore necessary in order to transform the insoluble minerals into soluble cobalt sulphate species. The following reducing agents are currently used at the Shituru plant: ferrous ions, which are present in leach solutions, pulverised copper or sodium meta bisulphite (MBS). Due to the high consumption of reducing agents (0,8 t MBS/t of solubilized Co; 1,2 t Cu/t-Co), cobalt production is expensive. The use of sulphur dioxide as reducing agent was then investigated in order to reduce operating cost. This reagent also presents the advantage of sulphuric acid production during the leaching process. It has been added in the leaching vessel (tank). From the laboratory and industrial tests, selective leaching of cobalt (78%) has been performed. The cobalt leaching kinetic depend on sulphur dioxide dosage. Dissolution of copper, iron and manganese remained very low. No emanation of SO2 gas was observed during the process.

Jan 1, 2002

By Carlos Cristiano Carvalho Teixeira

No carregamento volumétrico de vagões, onde a variância de pesos carregados é relevante, ocorrem grandes limitações operacionais, que vão desde a percepção do volume em carregamento até a capacidade real de controle. Neste contexto, a diversidade de cenários é enorme: velocidades variadas (25% a 80% da capacidade), variação do minério, diferentes tipos de vagões, etc. Maximizar ou atingir o ponto ótimo com repetibilidade leva tempo e experiência. A solução considerou a aplicação intensa e avançada de instrumentação e recursos de automação, obtendo um resultado favorável de elevação da capacidade de controle sobre o peso em carregamento, nas diversas condições operacionais. A metodologia utilizada partiu de uma engenharia conceitual destacando o tratamento de riscos considerando as imprecisões e as técnicas avançadas de controle necessárias. Instrumentos e equipamentos também foram tratados dentro desses riscos, entre eles: balanças, radares 2D, identificação dos tipos de vagões, níveis dos silos, lasers para medições de precisão e para redundâncias, e ainda a simulação para testes do processo. Conclusão: 1. Maior capacidade de controle de peso carregado e menor variabilidade. 2. A imprevisibilidade na variação do material como desafio adicional para os automatismos. 3. Simuladores como diferencial na implantação da solução.

Aug 16, 2017

By Robert W. Waytulonis

Miners working in underground mines where diesel equipment is used are exposed to exhaust pollutants. These include carbon monoxide (CO), carbon dioxide (CO,), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), hundreds of different hydrocarbons (HC) and particulate matter. Evidence from animal inhalation studies and limited epidemiological investigations have led the National Institute for Occupational Safety and Health (NIOSH) to recommend that ‘... whole diesel exhaust be regarded as a potential occupational carcinogen ...’ NIOSH further stated that ‘... the excess cancer risk for workers exposed to diesel exhaust has not yet been quantified, but the probability of developing cancer should be decreased by minimizing exposure…’ The International Agency for Research on Cancer(IARC) reached a similar conclusion, saying that ‘... diesel engine exhaust is probably carcinogenic to humans.’ Before these declarations, there was insufficient evidence concerning the carcinogenicity of diesel exhaust. It was well known, though, that diesel exhaust caused less severe problems, such as headache, eye irritation and unpleasant odors. In 1988, a milestone was reached in the Mine Safety and Health Administration (MSHA) regulatory process. An advisory committee recommended a three-tier approach to regulating diesels used underground-approval of diesel equipment, safety and health. Diesel particulate matter may be specifically regulated. In addition, ambient air quality standards are being proposed that will establish a new standard for CO2 and lower the permissible exposure limits for the NO2, CO, SO2 and formaldehyde emissions that originate from diesels and other sources. Additional safety and emission restrictions are also proposed for diesel engines in coal mines. The goal of the US Bureau of Mines (USBM) diesel engine research program is to minimize the health and safety problems associated with underground diesel equipment use. Part of this program is focused on reducing exhaust emissions from diesel-powered equipment used in underground mines.

Jan 1, 1993

By Gabriela Moreira Lana

A radiação solar apresenta uma enorme variedade de aplicações de engenharia, dentre elas, a conversão em energia térmica em concentradores solares. Os tubos absorvedores dos concentradores solares podem ser recobertos por cromo negro, com o objetivo de otimizar a absorção energética e a durabilidade. Esse trabalho é parte de um estudo complexo sobre esse tipo de recobrimento. Foram desenvolvidos filmes de cromo negro por eletrodeposição sobre aço inoxidável AISI 304 e tratados termicamente a 600°C por 2 horas. Os filmes foram caracterizados antes e depois do tratamento térmico, utilizando-se microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e difração de raios X a baixo ângulo de incidência (GAXRD). Além do cromo, observou-se deposição de cobalto e elementos residuais do banho eletrolítico. O estudo da estrutura cristalina mostrou formação de óxidos após tratamento térmico. Microestruturalmente, foram observados filmes com estrutura lamelar ou nodular. O estudo permitiu sugerir modificações do banho eletrolítico, do substrato e métodos adicionais de caracterização.

Aug 17, 2017

By Alexandre Rodizio Bento

Os acidentes de trabalho estão cada vez mais presentes em indústrias de vários segmentos, inclusive no setor automotivo. Devido ao trabalho no chão de fábrica deste setor utilizar interferência humana em alguns processos e operações, onde o trabalhador compartilha o ambiente produtivo com máquinas automatizadas. Estas máquinas podem causar graves lesões temporárias ou permanentes no trabalhador, podendo chegar até a morte. Neste cenário, este trabalho apresenta um estudo da implantação da pirâmide de Heinrich como forma de informar e prevenir acidentes na indústria automotiva. É detalhado o processo de implantação da pirâmide na linha de produção. Esta implantação contribui na prevenção de acidentes, gera alertas de possíveis riscos, comportamentos inseguros e incidentes. Os resultados desta implementação acabam aumentando a segurança no ambiente de trabalho, reduz custo com acidentes dentro da indústria, que permite investir cada vez mais em métodos para prevenir e gerar um ambiente de trabalho livre de acidentes no setor automotivo.

Aug 8, 2018

By Fabio Schusterschitz da Silva Araújo

A unidade do Grupo SIMEC em Pindamonhangaba tem capacidade de produção de 560 mil toneladas/ano de produtos destinados à construção civil. Para abastecer a planta, é utilizada água de poço com pH, condutividade e alcalinidade altas, além de restrições quanto à disponibilidade. Isto gera desafios para o seu uso, e para a água de reposição do sistema de resfriamento dos moldes a água passa por um sistema de osmose reversa. No primeiro semestre de 2016, houve contaminação da água de molde, com a formação de uma incrustação de coloração branca, de aspecto oleoso e diferente das incrustações normalmente encontradas. Este fenômeno reduziu significativamente a vida dos moldes, o que levou à necessidade de paradas constantes para a troca e aumento significativos dos custos. Foi montado um grupo de trabalho de todas as áreas envolvidas, operação, manutenção e condicionamento químico para descobrir as causas e corrigir o problema. Este trabalho mostra as causas, as ações tomadas e os resultados obtidos.

Oct 30, 2017

By A. Boehm

"For recycling LD slag into the steel making process, the phosphorous containing calcium silcate phases have to be removed from iron oxide phases. One possible technical solution could be magnetic separation in a wide range of susceptibilities from ferromagnetic to paramagnetic. To check the feasibility of magnetic separation the distribution of the magnetic susceptibility in size classes as well as the liberation of the phosphorous containing phase were evaluated by a new method combining two dimensional physical property analysis with QEMSCAN analysis. The particle size classes of energy controlled comminution products were subdivided into fractions of defined magnetic susceptibility using a hand magnet of well known field properties (pick up method). On the one hand the susceptibility classes were wet assayed on the other hand analyzed by QEMSCAN followed by data evaluation using iDiscover 5.3.1(FEI), which was adapted to the data structure of two physical properties (size and magnetic mass susceptibility). The results allow the comparison of mass based (3D) cumulative distribution of grades from the wet assays with the area based (2D) distribution from QEMSCAN analysis, in order to control a systematic (size dependent) stereological error for this special type of material. As the physical separation property forms a crucial parameter the results from the liberation analysis by QEMSCAN can be interpreted more profound with respect to an expectable separation result. Once the various mineral compositions of the particles are assigned to the physical properties the Henry Reinhardt chart serves to predict the best possible separation result and thus the feasibility of a separation technique.INTRODUCTIONThe two Austrian steel plants operated by voestalpine AG produce about 650,000 t (voestalpine 2014) of LD slag in the course of steel production from pig iron according to the basic oxygen process blowing oxygen in the converter by an oxygen lance. The process is also known as the Linz Donawitz (LD) steelmaking process. By the addition of lime (CaO), carbon, phosphorus, silica, manganese and sulfur, which are present in the molten pig iron, shall be oxidized and bound in the slag either as oxide or silicate phases, or leave the slag in the gaseous phase (CO). The average chemical composition of the investigated LD slag is given in table 1."

Jan 1, 2016

By Jilai Xue, Jun Zhu, Liang Liu

"Separation removal of fluorite and calcite from scheelite is a difficult technical operation in current industrial practice with a heating process causing large energy consumption and high production costs. In this work, the floatation separation at room temperature were carried out using two types of skarn scheelite ores. The results showed that CaO and Na203 are better than NaOH as a regulator in pH value. In the rough floatation and first cleaning floatation, CaO (500g/t), Na203 (3000g/t) were used as a pH regulator, waterglass (4000g/t) was as a gangue depressant, oleic acid or sodium oleate were used as a collector. The degree of the obtained W03 concentrate was more than 65% (commercial product).IntroductionThe mainly gangue in scheelite are quartz, calcite, barite and some rare metal ores. There are three main types of scheelite for floatation: scheelite--quartz (silicate minerals) type, scheelite-calcite/ fluorite type, scheelite--calcite/fluorite/barite type. Generally speaking, scheelite--quartz type is separated easily, and others are difficult, on the contrary. The last two kinds of scheelite are always called scheelite--calcite/fluorite (barite) type, because there are similar floatation ability and floatation process between them. Scheelite, calcite and fluorite have same cation - Ca2+, it makes them have close floatation property [1]. Separation removal of fluorite and calcite from scheelite is a difficult technical operation in current industrial practice.The traditional separation method is a heating floatation process (Petrov's process) [2]. It can deal with many kinds of scheelite, and can be obtained stable quality ofW03 concentrate. On the other hand Petrov's process causes large energy consumption, high production costs and bad operational environments. Since 1980s, scheelite ambient temperature floatation has become the mainstream of study [3]. Nowadays more and more studies on scheelite floatation focus on complex reagent system [4, 5], rigid operating rules and at the same time development new regulator [1, 5]. Some research show there are new regulators can concentrate scheelite efficiently, but it may cause high costs, potential pollution and difficulty to spread. Oleic acid and sodium oleate used as collector have high adsorption capacity to scheelite, but same to calcite and fluorite[6]. So, it would not get ideal effect for separation of scheelite. In this work, the floatation separation at room temperature were carried out using two kinds of skarn scheelite ores. Calcium oxide and sodium carbonate was used as a pH value regulator, waterglass was used as a depressant and Oleic acid/sodium oleate was used as a collector. The result of experiment showed that the degree of the obtained W03 concentrate was more than 65% by one time ambient temperature roughing floatation, several times ambient temperature cleaning process."

Jan 1, 2014

By José Britti Bacalhau

Na conformação de plásticos de alto desempenho, cuja demanda cresce continuamente nos setores automotivo e de eletrodomésticos, é necessário aços com elevada resistência mecânica e excelente polibilidade. O aço DIN 1.2711 e suas modificações são materiais encontrados no mercado que atendem tais necessidades, porém não foram projetados para essa aplicação. O presente trabalho discute as características de um novo aço desenvolvido especificamente para moldes plásticos de alto desempenho. Foram produzidos em escala piloto, dois lingotes de 55 kg, sendo um deles o DIN 1.2711 que serviu de referência, e o outro com a nova composição química. A curva TRC dos materiais foi determinada por dilatometria, e sua usinabilidade avaliando o volume de material removido em relação ao desgaste da ferramenta de corte em fresamento. Caracterizações microestruturais por MO, MEV e dureza também foram realizadas. O Novo Aço apresenta elevada homogeneidade microestrutural e de dureza, boa temperabilidade e usinabilidade superior ao DIN 1.2711. A segunda etapa constou na produção de um bloco forjado em escala industrial a partir de um lingote de 35 toneladas, e na validação dos dados experimentais em empresas fabricantes ou usuários de moldes, as quais comprovaram a superior usinabilidade do Novo Aço em aproximadamente 50% ao DIN 1.2711. Devido à boa combinação de propriedades de manufatura o Novo Aço se torna uma interessante opção para o aumento da competitividade das ferramentarias e usuários finais de moldes plásticos.

Aug 16, 2017

By Marcelo Cervantes Del Rio Baptista

Nos últimos anos a indústria siderúrgica no Brasil vem sofrendo um processo lento e cruel de encolhimento de sua participação no PIB, em decorrência de diversos fatores políticos e econômicos. Apesar do grande esforço por parte das empresas, a capacidade de produção de aço pouco cresceu neste período, permitindo que as despesas cresçam mais rápido do que as receitas. Esses fatores têm mostrado aos profissionais do setor que a mudança do cenário só ocorrerá ao se produzir com o máximo de eficiência. O objetivo deste trabalho é demonstrar que a lubrificação tem grande participação no aumento da produtividade e redução de custos da manutenção. Em suma, será apresentado um estudo sobre como a lubrificação correta influencia no aumento da produtividade das siderúrgicas. Com base nos resultados dos testes realizados em duas grandes empresas do setor, este trabalho demonstra o aumento significativo de performance no Mandril da bobinadeira e mancais dos convertedores, após estudo detalhado da lubrificação.

Aug 17, 2017

By Alencar de Andrade Soares

Este trabalho tem como objetivo descrever as ações que foram tomadas pela TKCSA com o objetivo de restabelecer a capacidade operacional plena do Gasômetro (BFG), pela sua estabilidade e, por conseguinte a sua continuidade operacional. Desde seu start-up, ambos os Gasômetros apresentaram vários problemas que impediram sua operação em plena capacidade; provocaram várias paradas para realinhamento, rebalanceamento, bem como repopeamento. Estas ocorrências interferiram fortemente na Geração de energia do complexo, devido a instabilidade dos Gasômetros, causada por irregular movimentação do pistão, provocando sua descentralização e desnivelamentos fora das tolerâncias aceitáveis, o que levou a TKCSA a limitar a operação dos Gasômetros e, mesmo assim ; sempre que descentralizava e ou desnivelava, era necessário novos ajustes (repopeamento e rebalanceamento). Tais eventos nestes importantes equipamentos, levaram a CSA a tomar várias ações conforme preconiza o IGEM (Instituition of Gas Engineer) passando por reparos estruturais e culminando com a troca do sistema de selagem dos Gasômetros.

Sep 25, 2017

By Carlos Alberto Perim

Os aços baixo carbono microligados representam uma parcela significativa da produção de placas de aço na ArcelorMittal Tubarão e sua participação na produção total tem sido crescente ao longo dos últimos anos. Entretanto, grande parte da necessidade do mercado por este tipo de material se dá em larguras pequenas, o que inviabiliza a sua produção em equipamentos de grande escala, como é o caso da ArcelorMittal Tubarão. Neste trabalho será apresentado um resumo das ações tomadas na ArcelorMittal Tubarão visando viabilizar a produção deste tipo de aço em pequenas larguras, através do aumento de sua velocidade de lingotamento e análise constante da qualidade interna das placas. Uma vez consolidado o aumento de velocidade, com a consequente redução do tempo de lingotamento, foi possível reavaliar a aceitação de placas com menor largura e padronizar esta nova condição. Também, durante a execução deste trabalho, foram reavaliados os critérios de retirada de amostras para os ensaios de macro-ataque nos aços de baixo carbono e baixa liga.

Jul 30, 2018