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By Layton C. Binon

Exploration budgets are commonly determined by "rules of thumb" such as a percentage of earnings or other fiscal measure. An appropriate exploration budget is the amount needed to achieve the goals of the company. It can be determined by discounting the income expected from achieved goals. Budgets for individual projects are determined in a similar manner except that risk of failure is included in the computation.

Jan 1, 1981

By Antonio Segatori, Bjørn Holmedal, Kai Zhang, Trond Aukrust, Knut Marthinsen

"The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion set-up, which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices of model parameters were employed and evaluated for texture predictions. With an appropriate choice of crystal plasticity model and model parameters, the deformation texture can mainly be predicted, although the accurate intensities are hard to reproduce. The corresponding recrystallization textures, either generated through spontaneous recrystallization of the extruded profiles or through post-extrusion annealing, are far more challenging to reproduce with available recrystallization models.INTRODUCTION Extrusion is a widely applied thermal-mechanical process to produce aluminium profiles. The properties of the profiles, for example mechanical, fatigue, fracture, corrosion as well surface appearance, are strongly dependent on the underlying microstructure and texture, and the requirements with respect to these aspects may vary with applications (Ralston et al., 2010; Dumoulin et al., 2012; Donati et al., 2013). Moreover, it is often a challenge to produce extrusions with a consistent and homogenous grain structure and texture along as well as through the cross section of the profiles. It is thus vital to understand and be able to predict (model) how different microstructures and textures are formed and how they evolve during and after extrusion, as basis for controlling the final appearance and properties of extruded profiles."

Jan 1, 2018

By G W. Scott, H M. Lukey

The Lake Superior Region has been a producer of iron ore for over 150 years. Early mining operations concentrated on direct shipping ores, which are the result of post-depositional upgrading principally by deep weathering. As direct shipping ore reserves became depleted, the focus changed to the production of iron ore pellets from taconite. The post-depositional processes responsible for upgrading taconite are regional metamorphism, contact metamorphism and hydrothermal processes (Clout and Simonson, 2005). While these processes are important in iron ore genesis they can also contribute to liberation problems and in some instances reduced pellet quality (Han, 2004). Low-grade metamorphic mineral assemblages can negatively impact liberation and pellet quality. Low-grade iron formation may contain a suite of carbonate minerals including ankerite, dolomite, kutnohorite, siderite and magnesiosiderite. Variation in the distribution and composition of siderite and magnesiosiderite makes controlling the MgO content of pellets difficult. Carbonate minerals also require calcination in the pellet induration process, which requires additional heat to be added to the system, slowing down the induration process and reducing throughput. Prediction of carbonate mineralogy and carbonate mineral chemistry is an important goal of ore characterisation for pelletising properties. Contact metamorphism causes changes in mineralogy and grain size (Klein, 1973; Gunderson and Schwartz, 1962). Increasing the grain size of magnetite should improve its liberation characteristics. However, plant grinding targets may not allow the coarse-grained, more easily liberating magnetite ores to increase throughput and can actually result in decreased throughput due to recirculation. While magnetite and martite ores are well understood (Lukey, Johnson and Scott, 2007) late open-space filling microplaty haematite ores are not. These ores, while composed of similar minerals, have a unique genesis that results in fine grain size and complex textures that present liberation challenges and often make interpreting laboratory metallurgical test results more difficult.

Jan 1, 2007

RÉSUMÉ Cet article traite d’une analyse technique et économique du concept du triage optique en vue d’améliorer la rentabilité des opérations minières. Le principe du tri optique et les principaux systèmes et modules servant au fonctionnement de l’appareil de triage sont décrits. un modèle a été développé pour analyser l’intérêt économique d’une opération de triage optique. L’étude est basée sur des données provenant d’une halde de minerai à faible teneur en or, déposé à la surface, et de minerai extrait des opérations souterraines courantes de la mine Beaufor au Québec. Les résultats de cette analyse indiquent que l’opération de triage optique permet d’améliorer grandement la performance économique; l’opération devient alors rentable pour des teneurs en or relativement petites.

Jan 1, 2010

William Kent, New York, N. Y.:—The Institute may congratulate itself on the opportunity of reading the splendid address of President Brunton. It is an admirable summary of the progress that has been made in the mining and metallurgical arts in recent years. The paper rightly gives the chief credit for this progress to the aid which has been rendered to these arts by the advances in mechanics, chemistry, and electricity. It is notable that most of the headings in Mr. Brunton's address refer to the work of the mechanical engineer, the electrical engineer, and the chemist, rather than to that of the specialist in mining-operations. It seems that the most successful mining engineer of the present day is the one who makes the most intelligent application of the inventions and designs of engineers and others who are not directly engaged in mining. A tabulation of the headings of the address, grouped as below, shows this most clearly. Work of the Mechanical Engineer—Rock-drills, hoisting-machinery, tramming, pumping, ventilation, dredging, Sampling, concentration, briquetting, fume-recovery. Work of the Electrical Engineer—Electric machinery for hoisting, pumping, tramming, lighting and signaling, electric transmission, electric smelting. Work of the Chemist and Metallurgist—Explosives, chlorina-tion, cyanidation, roasting, lead-smelting, and copper-smelting. Work of the Geologist—Economic geology. Work of the Mining Engineer—Mine-mapping, surface-mining, timbering, tunneling; and planning and supervision of the work in general. The mining engineer of the present day, who is in responsible charge of a large plant, finds his chief work not in doing those things he was trained to do as a specialist, but in making use of the knowledge of geologists, chemists, and electrical and

Jan 1, 1910

By Nitin Bhavsar, Kaushik Vakil, Lakshmikanth Reddy, Sanjay Sarkar, Tathavadkar. Vilas, Bhavin Desai, Raghavendra Adiga

Gold and platinum group metals (PGM) do not dissolve in sulfate electrolyte from anode during electro-refining of primary copper. The PGM form solid ‘slimes’ which accumulates at bottom of the electrolytic cell. Typically, 8 to 10 ppm silver is present in copper cathodes, which is equivalent to almost 2% of silver loss during electro-refining. The silver can be cemented with cathode copper as soon as it is dissolved into the electrolyte from anode or during entrapment of slime particles in cathode. Over a period of time, the concentrates grade has deteriorated and change in type & amount of impurities in concentrate has resulted in higher silver loss during refining process. Therefore, an in-depth investigation was carried out in both fire- and electro-refining processes to understand the root causes of higher silver loss in copper cathodes. The detailed characterization and the plant data analysis were carried out. The results of study revealed that higher silver loss in 3rd crop cathodes as compared to 1st and 2nd crop cathodes from same anode. In anode silver was present in two forms, dissolved in copper (solid solution) and in slime phases such as Cu2-xAgxSeTe. SEM-EDX study of anode cross section confirmed higher silver and oxygen content in central region (core) of anode as compared that in both air and mold sides. This is due to non-uniform cooling of anode which was confirmed by the solidification modeling. Higher concentration of oxygen & silver at core of anode rised Ag+ concentration in electrolyte and slime particles during 3rd crop. The results of study were used to optimize the anode cooling process and also electrolyte chemistry to reduce the silver loss. The details of study carried out are discussed in this paper using the results of modeling, characterization and experimental studies. INTRODUCTION In the electrolytic refining of copper, fire refined copper anodes are used as raw material. Anodes contains copper of the range 99.5 to 99.6%, rest being the impurities. Hence, the purpose of the refining is (1) to remove the impurities so that final cathode conforms to the LME specifications and also (2) to recover the precious metal from the anode copper. When anode is dissolved, most of the impurities reports to the anode slime settled at the bottom of the cell, and rest dissolves in the electrolyte. Dissolved impurities remains in electrolyte and are removed during electrolyte recycling. However, sometime dissolved impurities and slime particles get entrapped in cathode due to disturbances in operational conditions. Metals dissolving in the electrolyte are the elements such as Ni, Co, Fe, Zn. The electrode potential of As, Sb and Bi being close to that of copper, these elements partly dissolve in the electrolyte. Noble metals like Ag, Au, Pt and Pd are generally insoluble and are thus expected to report to the anode slime. A small amount of the sliver content from the anode is dissolved in the electrolyte. Because the dissolved silver electroplates on the cathode at a smaller applied potential than copper, the cathode typically contains up to 8 ppm of silver. This is referred to as ‘silver loss’ in cathode (Cooper, 1987). Fortunately, silver is a rather benign impurity in copper due to its electrical conductivity being higher than copper. However, higher silver loss in cathode is loss of revenue for Copper smelter due to significant difference in their LME price.

Jan 1, 2019

By D. Bahrami, W. K. Asante, G. L. Danko

It is prudent to interpret atmospheric monitoring signals in real time for checking the safe limits of the air conditions in underground mines. In gassy mines, real-time evaluation increases the safety of operations. In all mines, continuous monitoring and evaluation contributes to maintaining air conditions within healthy and safe limits. Signal interpretation for safety conditions in mines is difficult for many reasons. An increase in hazardous contaminant concentrations can be predicted by signal pattern recognition, root cause analysis of rapid changes toward deterioration, and forward prediction in time using algorithms and numerical models. The paper describes an early warning system for analyzing monitored signal patterns continuously in real time as well as forward predicting the various environmental and working conditions to recognize dangerous trends that may affect safety and health in underground mines. A dynamic, numerical ventilation model with heat and gas contaminant simulation components is used for the analysis of atmospheric data. Methods and test results are discussed with numerical examples for signal propagation prediction. Several mine examples are studied using controlled, synthetic data for malfunction simulations to evaluate time delays between the detection time of suspicious signal trends and the time of dangerous threshold crossing marking an accident scenario. Delay time is found in the order of 20 min in the examples, signifying the useful time period for preventive intervention between EWS warning and the likely breakout of a following accident.

By B. W. Lawrence

Shaft alignment requirements are consistently met using conventional shaft sinking methods. Little attention has been given to achieving similar alignment accuracies using rotary drilled shaft methods. Alignment of these shafts is difficult to control and guarantee. Bare shafts and shafts that use drum hoisting systems can accept some deviation. However, combining drilled shafts with Koepe hoist installations presents new accuracy requirements for drilled shafts. This paper describes the importance of verticality with practical examples, and discusses various methods of measuring verticality and their respective limitations.

Jan 1, 1989

By E. H. Timmerman, A. F. van Everdingen, J. J. McMahon

The prevent paper contains a method which combines the material balance equation' with the water influx equation' to obtain reliable values for the active oil originally in place and a quantitative evaluation of the cumulative water influx. The method is illustrated by an application to a reservoir without original gas cap. In the absence of an original gas cap. results may be obtained using only field production and pressure data, PVT analyses. and a minimum of subsurface information. CHARACTERISTICS OF RESERVOIR AND RESERVOIR FLUIDS Production in the field under review is obtained from the top of the Wilcox formation of Eocene age, at a depth of approximately 8,100 ft subsea. The structural map, Fig. 1, shows that the accumulation, half elliptical in shape with the long axis in east-west direction, is trapped to the north and on the upthrown side of a normal fault. A number of east-west faults with additional minor faulting in random directions are found in the general area, and seismic information and production performance indicate in this particular case the existence of a second fault a short distance downdip, with a strike more or less parallel to the fault controlling the accumulation. It is estimated that 1,830 acres were originally underlain by oil and that the maximum thickness of the original oil column, about 37 ft, was only slightly greater than the maximum thickness of the oil-bearing sand. Maximum net sand thickness was estimated at approximately 26 ft. From logging and subsurface information the gross sand volume has been placed at 37.400 acre-ft. which reduces to about 27,500 acre-ft after probable non-productive intervals have been deducted. The following table presents laboratory analyse; data for the Wilcox sand cores. Average Average Samples Considered Permeability Porosity All Samples 236 md ..19.9percent Samples with k>l md 256 md 20.5 per cent Samples with k>8 md 275 md 20.9 per cent Interstitial water was estimated at 15 per cent. The initial gas-oil ratio was approximately 900 cu ft/bbl. and the initial shrinkage factor was determined by the laboratory to

Jan 1, 1953

By C Fountain

Australian mining and engineering companies have increasingly been investing in the mining industry in Brazil. It is a country of enormous mineral and agricultural wealth, with a well-established mining sector. Some Brazilian mining companies and personnel have been journeying in the opposite direction. There are significant differences in the approaches to engineering between the Australian and Brazilian industries that can cause confusion for companies operating in the other country. These range from differing expectations during the various stages of feasibility studies to style of plant and contracting strategies during the construction phase of projects. Some of the differences are driven by tax regimes, labour costs, or different settlement patterns. Others are the result of different histories and pressures on the industries in the two nations.This paper describes some of the differences in approach found in the two countries and some of the reasons for them.

Aug 8, 2011

By J. P. Baur

The sensitivity of radiochemical techniques makes possible the study of the initial stage sulfuric acid leaching kinetics of chalcopyrite and other copper sulfide minerals. High-grade Transvaal chalcopyrite was neutron irradiated in a TRIGA reactor to produce radioisotopes copper-64, iron-59, and sulfur-35. Dissolution rates were measured in the time interval zero to 60 minutes during which time significant anomalies were observed. First, an initial period of rapid dissolution lasting a few minutes; second, an arrest or "plateau" region usually lasting from 6 to 10 minutes; third, a second period of dissolution of lesser rate than the first. The effect of solution variables such as pH, oxygen partial pressure, and ferric ion concentration at different temperatures were measured. The initial rate data were correlated by considering the rapid reaction to be due to the dissolution of surface oxidation products or the formation of an iron depleted surface layer. The data for the second slower reaction have been explained to be due

Jan 1, 1972

By Jean Igor Margem

Nestes dias materiais ecológicos como compósitos com fibras naturais em matriz polimérica estão chamando a atenção de pesquisadores científicos, devido ao seu bom desempenho na substituição de materiais como madeira, polímeros à base de petróleo e outros. Neste trabalho foram avaliadas as propriedades de tração de compósitos de matriz epóxi reforçados com diferentes espécimes de fibras lignocelulósicas. Compósitos reforçados com até 30% em volume de fibras longas, contínuas e alinhadas de malva, sisal e bambu foram testados em uma máquina Instron a temperatura ambiente. A fratura foi analisada por SEM. Os resultados mostraram alterações significativas nas propriedades mecânicas com a quantidade dessas fibras. Estas propriedades mecânicas foram comparados com outros resultados em compósitos testados em ensaio de tração. A análise da fratura revelou uma fraca interação da interface fibra / matriz, o que poderia ser responsável por um maior desempenho de algumas propriedades.

Aug 17, 2017

By Raymond F. Moran

The history and development of the FMC Coke process has been reported in numerous presentations over the past 10 years (1, 2, 3, 4, 5, 6) but a short review is desirable, especially regarding the aspects that are influenced by the coal to be used. F'MC has been developing this process in pilot facilities since 1956 and in a modest sized plant in Kemmerer, Wyoming since 1960 (Figure I). This plant produces strong uniformly sized coke briquettes from a completely non-coking coal, namely Elkol, a sub-bituminous coal of the Adaville seam. Since operating commercially, over 300,000 tons have been produced, 90% of which has been used in electric phosphorus furnaces and some 10% of which went for trials in iron blast furnaces. We believe that this commercial use of non-coking coals is a unique experience in the history of coke manufacture.

Jan 1, 1975

By Aliakbar Golshani, Behnam Eslami

"Surface settlement adjacent to sensitive structures is a challenging issue in the tunnel engineering. In this study, 3D simulation of TBM excavation has been performed with the FLAC3D code and then the results compared with real monitoring data. Sensitivity analysis was carried out for all parameters affecting the surface settlement, such as the tail void grouting pressure (Pt), the face pressure (Pf), the tunnel diameter (D), overburden (q), shield thickness (t) and the length of the shield (L). The results show that the face pressure, tail void grouting and tunnel diameter have a considerable effect on the maximum ground displacement.In this paper, the monitoring data from Mashhad Metro was used to verify the numerical simulation. Data monitoring for about 47 sections between A2 and D2 stations was selected and a multiple regression analysis was performed. Based on this analysis, an empirical relationship was obtained for the coefficient of regression relationship which confirmed the sensitivity analysis.INTRODUCTIONThe surface settlement due to tunnel excavation is a complex issue, since the surface displacement is a function of several parameters that they are related to the excavation method, soil characteristics and TBM elements. Prediction of deformation is a very important issue, especially in urban areas, since these displacements may be affected the superficial structures. In recent studies, one of the most popular empirical relationships that is used to predict the surface displacement has gussian curve that it was suggested by Peck [1, 2]. An analytical relationship was proposed by Chow that its base assume was isotropic of soil, that surface settlement can be estimated based on the tunnel geometry and the shear modulus(G) [3]. Besides these methods numerical approaches such as the Finite Element Method (FEM) and the Finite Difference Method (FDM) have been used over the last twenty years, since numerical modeling has a high capability to simulation a complex soil conditions and irregular geometry [4]. In this study, all aspects of the EPB-TBM on Mashad Metro Line 2 were modeled and the most important influences on surface displacement in urban areas were determined [1, 3]."

Jan 1, 2016

By E. Maziar Sauber

In order to prepare a more desirable feedstock for a rare earth elements separation refinery, cerium, a penalty element in the refinery feedstock, should be removed from the mixed rare earth elements oxide or carbonate feedstock. In this study, cerium (III) to cerium (IV) oxidation by calcium hypochlorite and subsequent precipitation was used to remove cerium from a mixed rare earth elements chloride solution. A factorial design of experiments was used to determine the effect of process variables such as temperature, pH, and oxidizer addition on the oxidation of cerium (III) using synthetic solutions. Under certain test conditions, all of the cerium was successfully removed from the chloride solution, and some REE accompanied cerium and reported to the precipitate. This proposed technology can allow for low cost removal of cerium from mixed rare earth elements chlorides.

By William Hawker, James Vaughan, Jeff Chen, Antony van der Ent

"Nickel agromining utilizes hyperaccumulator plants (“metal crops”) to extract nickel from low-grade soils, a process that yields high-grade nickel bio-ore. This feedstock is further processed into a range of nickel products. The bio-ore is relatively free of impurities that complicate the traditional processing of laterite nickel ores. In this paper, current primary nickel processing routes and proposed nickel bio-ore processing options are summarised. A novel pyro-hydrometallurgical route demonstrated at the laboratory scale is described. This process produces a precipitated nickel hydroxide product and takes advantage of the water-soluble basic compounds in the ash to minimise reagent requirements, thereby making it suitable for small-scale implementation in close proximity to the nickel farm. In this process, nickel is precipitated from the leach solution using the basic ash wash liquor. Leaching nickel from ash generated from open air burning requires strong acid and long residence times to obtain high recoveries due to its complex nature and distribution of nickel in multiple phases. This process can be improved by optimising the ashing process with respect to nickel leachability.INTRODUCTIONHyperaccumulator plants have the unique capacity to ‘biopurify’ and concentrate certain trace elements (e.g. nickel) from the soil into their biomass (Reeves 2003; van der Ent et al., 2015). Cultivating these plants as ‘metal crops’ by periodically harvesting and incinerating their biomass generates a high-grade bio-ore (Chaney et al. 1998; Li et al. 2003). This process is called phytomining or ‘agromining’ which is an emerging technology for extracting nickel from sub-economic resources (van der Ent et al., 2015). Potential near-term applications of the technology include implementation on land ahead of processing of the underlying ore-body (Willis 2015), as a mine-site rehabilitation strategy or as an alternative crop for farmers on land that is not suitable for normal food crops. In the longer term, nickel agromining could provide a significant supplement to the nickel supply chain. Critical to the success of agromining is effective bio-ore processing. Due to the unique chemical composition of this feedstock material, existing processes are not very efficient. Our current research efforts aim to develop new process options that overcome limitations of previously trialled routes. In this paper we summarise conventional nickel process routes and proposed new options for producing agromined nickel."

Jan 1, 2016

By C. Garcia, A. Potulska, J. J. Opazo, T. Comi

"The Sierra Gorda SCM sulfide ore processing plant began commissioning in the third quarter of 2014. Located in the Atacama Desert in northern Chile, the project is an open pit mine and Copper-Molybdenum processing plant is one of the most highly-instrumented operations in the world. It is the first hard rock operation in Chile and the second in South America to utilize HPGR technology. It is a significant Molybdenum resource especially in the first five years and the Molybdenum separation plant is complex. Designed to process up to 60 million lbs. of fine Molybdenum per year, it uses the latest technology and equipment to ensure superior recovery and product quality. It also has gas handling and alarm systems to fulfil the Company’s vision of “Zero Harm”. This paper discusses the overall operation and issues relating to the concentrator start-up. These include a review of the mineral processing design, the unified process control center and management information systems, and the correlation of geological and metallurgical performance data (mine-to-mill) for use in anticipating and preparing for treatment of diverse ore deliveries. INTRODUCTION Sierra Gorda SCM is a joint venture partnership with KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining, and Sumitomo Corporation (Japan) operating in northern Chile. The Sierra Gorda open pit mine and Copper-Molybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, well-instrumented mine in Chile. This paper contains a general review of the project including geology and history. This was a very fast-track project going from greenfield site acquisition to mill start-up in 10 years. Highly-experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied. The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (see Figure 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km from the village of Sierra Gorda at an elevation of approximately 1,700 m above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic, and Escondida, to name a few."

Jan 1, 2015

By Niédson José da Silva

Ligas com memória de forma (LMF) são materiais ativos que apresentam como característica a resposta a impulsos externos, recuperando deformações aparentemente plásticas. Esses materiais têm forte potencial aplicativo como atuadores termomecânicos em diversos setores industriais, sendo de interesse o aperfeiçoamento de suas propriedades termomecânicas. A conformação mecânica do ECAE (Equal Channel Angular Extrusion) resulta em melhorias quanto às propriedades mecânicas destas ligas. Esta melhoria está relacionada à redução de tamanho de grãos devido ao cisalhamento interno que estes sofrem ao passar pelos canais interceptantes, apesar de não ocorrer nenhuma alteração na área da seção transversal do corpo de prova. Neste trabalho, realizou-se a fabricação de ligas com memória de forma da família NiTi e da matriz para a extrusão em canal angular. A conformação mecânica foi realizada numa máquina de ensaios universal. O resultado desse estudo foi a observação da melhoria das propriedades mecânicas e alteração das temperaturas de transformação, as quais são essenciais para a utilização do efeito de memória de forma. Essa análise se torna relevante quando da aplicação desse tipo de material em situações em que se requer elevada resistência mecânica aliada a eficácia dos fenômenos de memória de forma.

Aug 8, 2018

By Charles Henrique Xavier Morais Magalhães

Os Aços Inoxidáveis Duplex possuem uma estrutura constituída basicamente por ferrita e austenita na proporção aproximada de 50%. Este trabalho estudou a influência da temperatura de um tratamento térmico na morfologia e fração de ferrita e austenita no aço UNS S32304. Os tratamentos térmicos realizados consistiram no aquecimento das amostras, desde a temperatura ambiente até a temperatura de 1250°C, seguido de um resfriamento lento em um segundo forno estável em uma determinada temperatura. As amostras permaneceram neste segundo forno por um intervalo de tempo necessário para que suas temperaturas atingissem exatamente um valor desejado, sendo então imediatamente retiradas e resfriadas em água a 20°C para preservar a estrutura resultante do ciclo térmico aplicado. As amostras foram metalograficamente preparadas, atacadas e analisadas com o auxílio de um microscópio ótico. As frações de fases medidas por MO se aproximaram dos resultados obtidos por simulação utilizando o software Thermo-Calc. A morfologia das fases variou significativamente com a diminuição da temperatura de tratamento, uma vez que a austenita se mostrou mais fragmentada nas temperaturas mais baixas, porém o bandeamento não deixou de existir na estrutura.A transformação da ferrita em austenita se mostrou fortemente dependente do tempo.

Aug 16, 2017

By Rafael Malagutti Leandro

O objetivo deste trabalho é avaliar a influência do tempo e temperatura de tratamento térmico de solubilização no tamanho de grão e na fração de ferrita de um aço inoxidável dúplex UNS S31803 (SAF 2205). A chapa do aço em estudo foi laminada com 22% de redução de espessura antes de ser solubilizada a 1.000°C, 1.100°C e 1.200°C, por tempos de até 96 h. A fração de ferrita das amostras foi obtida por medidas magnéticas em ferritoscópio e por estereologia quantitativa. Já o tamanho de grão foi determinado por estereologia quantitativa de imagens obtidas por microscopia óptica. Observou-se o aumento da fração de ferrita em função da temperatura de tratamento, como esperado, e foi realizado comparativo entre as duas técnicas de determinação da fração de ferrita com simulações de equilíbrio em Thermo-Calc®. O intercepto médio das amostras solubilizadas a 1.000°C manteve-se praticamente constante em todos os tempos de solubilização estudados, em aproximadamente 9 micrômetros; após 5h de solubilização a 1.100°C, e após 30 min a 1.200°C, contudo, observou-se significativo crescimento de grão nas amostras.

Aug 7, 2018