Numerical simulation was used to predict the thermal behavior and the resulting microstructure at the heat-affected zone (HAZ) of a 170 mm diameter and 3.5 mm thickness super duplex stainless steel (SDSS) UNS S32750 tube. In order to evaluate the thermal response from the model, a usual welding situation involving interpass temperature (IT) and its influence on the HAZ microstructure was exploited. Thus, two superimposed autogenous welding passes were simulated, the first clockwise with the tube in the room temperature and the second, counterclockwise, with the tube at the temperature of 250oC. Even subjected to successive thermal cycles and high interpass temperature, the proportion and morphology of the phases at the HAZ and Fusion Zone (FZ) did not present significant differences when comparing the two welding passes. Meanwhile, nitrogen losses should be avoided during welding in order to obtain a balanced microstructure in DSS welds, contributing to guarantee satisfactory toughness in addition to resistance to pitting corrosion. The predictions from the simulation were validated by using experimental results obtained from the autogenous TIG (Tungsten Inert Gas) process.

Abstract With the growing industrialization, there is a constant increase in the world demand for iron ore, thus implying an increase in the volume of mining, resulting in the extraction of ores with higher levels of silicon, phosphorus and sulfur impurities. Therefore, it is highly relevant to use beneficiation techniques that allow the use of iron ores with high levels of impurities, and it is known that a widely used alternative is to perform a pre-treatment of iron ore particles in order to reach the limit of acceptable phosphorus before application in steel production. Therefore, this study aims to evaluate the pre-treatment process of iron ore particles aiming at reducing the phosphorus content using the bacterial strain burkolderia caribensis in contaminated iron ore samples. Through the rotatable central composite design technique, it was possible to evaluate the best conditions for the use of the bacterial strain to reduce the phosphorus content in the particles. The results indicated that the developed process has relevant applicability. The results contribute to a better understanding of the use of the bacterial strain as a pretreatment process to reduce the phosphorus content of iron ore particles and also to the development of new cleaner technologies.

With the growing industrialization, there is a constant increase in the world demand for steel, causing an increase on extraction of low-grade iron ores, which bear high levels of impurities. A feasible alternative is the use of residues from steel rolling processes (steelmaking mill scale) generated in the steel industry, which are composed of iron oxides consisting mainly of wustite (FeO), hematite (Fe2O3) and magnetite (Fe3O4). In line with the recycling of wastes, the application of heating by microwave energy in ironmaking processes consists in a promising new method developed in recent decades and is considered a cleaner technique. Therefore, this study aims to evaluate the self-reduction of mixtures composed of iron ore and steelmaking mill scale as iron source, together with coke fines as carbon source, heated using microwave energy. Through the rotational central composite design technique, it was possible to evaluate the best conditions for the use of steelmaking scale residue as well as the effect of the applied microwave energy power. The results indicated that the developed process has relevant utility with up to 41.48% of reduction obtained. The outcomes contribute to a better understanding of iron recovery from steelmaking residues in reduction processes using microwave energy for heating, providing significant insight for the development of new clean technologies.

Resumo: O aço AISI 316L e Inconel 718 são metais de ampla aplicação na indústria. O estudo da soldagem dissimilar entre esses dois materiais é tecnologicamente importante para melhorar o desempenho da junta. Concentramos este estudo na avaliação da soldabilidade dissimilar desses materiais. Três amostras de AISI 316L e Inconel 718 soldadas usando processo multipass GTAW (Gas Tungsten Arc Welding) com diferentes parâmetros foram analisadas. Foram realizadas caracterização microestrutural, medidas da fração volumétrica da ferrita δ e fase Laves, espaçamento entre as dendritas de austenita, além da medição e análise das dimensões do metal de solda e da microdureza. A medição das dimensões do metal de solda e do espaçamento entre as dendritas mostrou que maiores aportes térmicos aumentaram as zonas fundidas e o espaçamento entre as dendritas de austenita. A fração volumétrica de ferrita δ diminuiu com o aumento do aporte térmico, enquanto que a fração da fase Laves aumentou. A microdureza apresentou variação significativa na poça de fusão devido a mudanças nas fases e na composição, conforme evidenciado pela análise de EDS nas juntas dissimilares.

Abstract: AISI 316L steel and Inconel 718 are metals of wide application in industries. The study of dissimilar welding between these two materials is technologically important to improve their joint performance. We focused this study on the evaluation of the dissimilar weldability of these materials. Three samples of AISI 316L and Inconel 718 welded using a multipass GTAW (Gas Tungsten Arc Welding) process with different parameters were analyzed. The microstructural characterization, measurements of the volumetric fraction of the δ ferrite and Laves phase, the spacing between austenite dendrites, in addition to measurement and analysis of dimensions of the welding zones and the microhardness were performed. The measurement of the weld metal dimensions and the dendrite spacing showed that higher heat inputs increased the dilution zones and the spacing between austenite dendrites. The volumetric fraction of the δ ferrite decreased with the increase of heat input, while the Laves phase fraction increased. The microhardness presented significant variation in the weld pool due to changes in the phases and composition, as evidenced by EDS analysis in the dissimilar joints.

Abstract The Direct Reduction (DR) process has been growing worldwide, and there are strong context suggestions that it will grow even more. One of these factors is the environmental pressure that occurs worldwide, and there are already projects to migrate Blast Furnace route steel plants to the Direct Reduction (DR) route, due to its smaller carbon footprint. Considering the importance of this process and the challenges of carrying out experimental tests on a pilot scale, an adequate way to evaluate the process and its impacts is through numerical simulations. There are different techniques applied to models that describe the counter-current reactor in the DR process, but none of them account for the clustering phenomenon. Clustering occurs because of the sintering of the metallic iron on the surface of the pellets in such a way that they attach to each other, forming clusters that hinder the gas flow through the shaft. The present study attempted to adapt a numerical model of a DR process to account for the effect of the cluster formation. Some clustering index equations from literature and some developed as part of this study were used and tested in the model, as a function of temperature, by varying the solid volume fraction in the control unit. The equation that resulted in the adjusted output closest to the current empirical value was implemented in the model and proved to be successful.

Hydroxyapatite (HA) nanopowders are attracting interest for surface application to ceramic biomaterials. In this study, we developed innovative and new viable synthesis routes of calcium phosphate nanopowders from the natural calcium carbonate of chicken eggshells. Following the four routes, alternative co-precipitation, vacuum process, brushite, and calcination, we obtained the HA samples, which were then characterized by different methods. The X-ray diffraction /Rietveld method showed the HA phases, monetite and brushite crystallinity with greater symmetry, and nanoscale. Transmission electron microscopy showed the morphology of nanoparticles functionalized nanoparticles smaller than 100 nm in routes A, B and D, and Fourier-transform infrared spectrophotometry and Raman spectroscopy identified the classic chemical groups of calcium phosphates by four routes mainly groups (PO4)3- and (CO3-). Scanning electron microscopy analysis revealed a good surface topography to future cell biointeraction in A, B and D routes, and thermogravimetric analysis showed the mass loss profile inherent to each synthesis route with slot at 200 °C. Hence, the eggshell HA and brushite and the specific monetite nanoparticles with different morphology can be prepared from the four new possible and viable routes using different methods.

The planning and execution of the adequate welding procedure for the superduplex stainless steel (SAF 2507 SDSS) in multiple passes is a complex technological task since thermal cycling may cause the precipitation of harmful phases, such as the sigma (σ) and chi (χ) phases. For this reason, technical standards limit the maximum interpass temperature (T.I.) in an extremely conservative manner at 100 °C. In order to investigate a possibly wider temperature range for this procedure, SAF 2507-SDSS tubes were subjected to autogenous Tungsten Inert Gas (TIG) welding with interpass temperatures ranging from 150°C to 400°C. The different welding zones were characterized by microscopy, Vickers microhardness, and polarization corrosion tests. The results indicated that in the Fusion Zone (FZ), columnar grains of ferrite were formed surrounded by allotriomorphic austenite (AA), besides intragranular austenite (AI) and Widmanstätten austenite (AW). The heat-affected zone (HAZ) had a lower ferrite content and was composed of equiaxed grains of ferrite, also surrounded by AA, besides AI and AW. Hardnesses varied between HV272 and HV293, regardless of the region or the interpass temperature used. Furthermore, the corrosion resistance has not been significantly affected by the interpass temperatures between 150 °C and 400°C.

Resumo: Um desafio bem conhecido é prever as transformações que ocorrem durante a soldagem das ligas metálicas com o objetivo de controlar as propriedades da solda. Desta forma, este estudo apresenta um modelo Termo-Mecânico-Metalúrgico para predizer numericamente a história térmica, as transformações de fase no estado sólido, a microestrutura de solidificação e a distribuição de dureza durante e após a soldagem de aços de alta resistência e baixa liga. O modelo foi implementado numericamente em um código computacional próprio baseado no Método dos Volumes Finitos, o que permitiu rastrear e calcular dinamicamente as frações volumétricas de ferrita, perlita, bainita e martensita na zona afetada pelo calor, além da formação e determinação do espaçamento do braço dendrítico na zona de fusão, enquanto que a distribuição da dureza na zona afetada pelo calor foi calculada aplicando-se a regra da mistura de fases. Para tanto, soldas autógenas usando o processo Gas Tungsten Arc Welding de passe único foram simuladas numericamente e experimentalmente realizadas em amostras do aço de alta resistência e baixa liga AISI 4130, incluindo seu pré-aquecimento com o objetivo de avaliar a eficácia do modelo proposto para simular a soldagem de peças em diferentes condições térmicas iniciais, tendo sido obtida uma estreita concordância entre os resultados calculados e experimentais.

Abstract: A well-known challenge is to predict the transformations occurring during the metal alloys welding aiming to control the weldment properties. Thus, this study presents a Thermo-Mechanical-Metallurgical model to numerically predict the thermal history, the solid-state phase transformations, the solidification microstructure and the hardness distribution during and after the welding of high strength low-alloy steels. The model was numerically implemented in an in-house computational code based on the Finite Volume Method, which allowed to dynamically track and calculate the volume fractions of ferrite, pearlite, bainite and martensite at the heat-affected zone, besides the formation and determination of dendrite arm spacing at the fusion zone, whereas the hardness distribution at the heat-affected zone was calculated by applying the phase mixture rule. For this, single-pass autogenous Gas Tungsten Arc Welding welds were numerically simulated and experimentally carried out on high strength low-alloy AISI 4130 steel samples, including their preheating to evaluate the effectiveness of the proposed model to simulate the workpieces welding in different initial thermal conditions and a close agreement between the calculated and experimental results were obtained.

Abstract In recent decades, microwave energy has been successfully experimented for mining and metallurgy processes and is considered a promising new method for ironmaking. In this context, in the present work, self-reducing mixtures composed of fines of iron ore and coke were prepared, intending to evaluate the degree of reduction of iron ore using microwave energy, applying different contents of coke, levels of power, and reaction times. For this, the degree of reduction was assessed as a function of these variables. Additionally, the reduction kinetics was investigated using chemical and diffusional models, and the microstructure of the samples was evaluated using scanning electron microscopy (SEM). The highest degree of reduction obtained after the experiments was greater than 60% and a statistical investigation showed that the reaction time is the factor with the greatest influence on these results, followed by microwave power and coke content. The investigation of the reaction kinetics showed that the process is chemically controlled, depending on the gasification steps governed by the Boudouard reaction. The images obtained by SEM led to the conclusion that the temperature inside the sample reached 1200°C. Pig iron was found both in the form of whiskers and in the form of metallic droplets.

Abstract The stability of colloidal suspensions of engineered nanoparticles in the environment is of great interest for the risk assessment and treatment of hazardous materials. The relevance of this study is due to the evidence that engineered nanoparticles have been produced and used in commercial products in large scale, especially ZnO and TiO2, which are transported through the environmental components interacting with soil and water, representing the high potential impact on the ecosystems. In this research, we newly investigated the influence of nanoparticles of zinc oxide (NPZnO) on the behavior of nanoparticles of titania (NPTiO2). The impact of parameters such as pH, zeta potential, ionic strength, electric conductivity, suspended nanoparticles size of the colloidal suspensions containing hazardous nanoparticles on its stability, were studied using experimental and theoretical approaches. Leaching experiments were carried out within a sandy soil column model. It was found that the NPTiO2 in suspensions enhance the stability of the nanoparticles colloidal suspensions, keeping higher nanoparticles concentrations, while NPZnO promotes rapid aggregation, improving the soil particle collector efficiency with a lower concentration in equilibrium in the colloidal suspension, which can be used for promoting environmental impact attenuation and mitigation.

RESUMO Introdução: A técnica de canulação do acesso vascular varia entre instituições de saúde, e as diretrizes sobre o acesso vascular dão pouca importância às técnicas de canulação. O objetivo deste estudo foi avaliar a técnica de canulação e determinar quais fatores estão associados a cada detalhe da técnica. Material e métodos: A canulação do acesso vascular foi avaliada em 260 pacientes em hemodiálise. Foram registrados o tipo e localização anatômica do acesso vascular, a técnica de canulação, a direção, a bitola e a distância entre as agulhas, além da direção do bisel e da rotação da agulha. Resultados: A fístula arteriovenosa foi o acesso vascular mais frequente (88%), a técnica de canulação mais utilizada foi a área (100%), a direção da agulha foi anterógrada na maioria dos casos (79,5%) e a distância média entre as pontas das agulhas foi de 7,57 ± 4,43 cm. Para enxertos arteriovenosos, a localização anatômica proximal (artéria braquial) e a canulação com agulhas 16G em posição anterógrada foram mais predominantes. Para as fístulas arteriovenosas, a localização anatômica distal (artéria radial) e a canulação através de agulhas 15G foram mais comuns. A canulação do acesso vascular na direção retrógrada foi associada a uma maior distância entre as agulhas (13,2 ± 4,4 v.s. 6,1 ± 3 cm, p < 0,001). O Kt / V foi maior quando a distância entre as agulhas foi superior a 5 cm (1,61 ± 0,3 vs. 1,47 ± 0,28, p < 0,01). Conclusões: A técnica de canulação do acesso vascular depende das características do acesso vascular e da experiência dos “canuladores”. Ensaios clínicos são necessários para a formulação de diretrizes para a canulação do acesso vascular.

ABSTRACT Introduction: The vascular access cannulation technique varies among clinics, and guidelines on vascular access give little importance to cannulation techniques. The objective of this study was to evaluate the cannulation technique and to determine which factors are associated with each detail of the technique. Material and methods: The vascular access cannulation was evaluated in 260 patients undergoing hemodialysis. The type and anatomical location of the vascular access, the cannulation technique, direction, gauge, and distance between needles, besides bevel direction and needle rotation were registered. Results: The arteriovenous fistula was the most frequent vascular access (88%), the most used cannulation technique was area (100%), the needle direction was anterograde in most cases (79.5%), and the mean distance between the tips of needles was 7.57±4.43 cm. For arteriovenous grafts, the proximal anatomical location (brachial artery) and cannulation with 16G needles in anterograde position were more predominant. For arteriovenous fistulas, the distal anatomical location (radial artery) and cannulation through 15G needles were more common. Cannulation of vascular access in retrograde direction was associated with a greater distance between needles (13.2 ± 4.4 vs 6.1 ± 3 cm, p < 0.001). Kt/V was higher when the distance between needles was higher than 5 cm (1.61 ± 0.3 vs. 1.47 ± 0.28, p < 0.01). Conclusions: The vascular access cannulation technique depends on the vascular access characteristics and expertise of cannulators. Clinical trials are required for the formulation of guidelines for vascular access cannulation.

ABSTRACT Radiation-induced brachial plexus neuropathy (RIBPN) is a rare and delayed non-traumatic injury to the brachial plexus, which occurs following radiation therapy to the chest wall, neck, and/or axilla in previously treated patients with cancer. The incidence of RIBPN is more common in patients treated for carcinoma of the breast and Hodgkin lymphoma. With the improvement in radiation techniques, the incidence of injury to the brachial plexus following radiotherapy has dramatically reduced. The currently reported incidence is 1.2% in women irradiated for breast cancer. The progression of symptoms is gradual in about two-thirds of cases; the patients may initially present with paresthesia followed by pain, and later progress to motor weakness in the affected limb. We present the case of a 68-year-old female patient with breast cancer submitted to surgery, chemotherapy, and radiotherapy in the year 2000. Eighteen years later, she developed symptoms and signs compatible with RIBPN and was successfully submitted to omentoplasty for pain control. Omentoplasty is an alternative treatment for RIBPN refractory to conservative treatment, which seems to be effective in improving neuropathic pain. However, postoperative worsening of the motor strength is a real possibility, and all candidates for this type of surgery must be informed about the risk of this complication.

Abstract Demand for iron ore worldwide has been steadily increasing, thus implying an increase in the volume of mining resulting in the extraction of ores with higher levels of silicon, phosphorus and sulfur impurities. An extensively used alternative is to perform a pre-treatment of the particles in order to reach the acceptable phosphorus limit in iron ore before its use in steel production. This study aims at the evaluation of the heating process and decrease of the phosphorus content of the particles using microwave energy in iron ore samples percolated by sulfuric acid followed by the leaching technique as a feasible route for the remotion of the phosphorus content in iron ore particles. Using the scanning electron microscopy (SEM) and statistical analysis techniques, it was possible to observe the characteristics of the iron ore particles after treatment with microwave energy. The results indicated that the developed process is feasible. The results of the kinetic simulation contribute to a better understanding of the phenomena of heating using microwave energy and also to the development of new cleaner technologies aiming to improve the efficiency of the acid baking - leaching technique for the reduction of the phosphorus content in iron ore particles.

Abstract Resistance Seam Welding (RSEW) is commonly used in continuous steel processing for joining steel coils. Experimental studies focused on the welding process quality controls are justified by their wide application and influence on the performance of steelmaking processes. The present study focuses on the continuous annealing line welding process using as sample, a low carbon steel (0.07%C) with 0.21 mm thickness. The work proposes a correlation of thermal input, electric current parameter and thermogram monitoring during RSEW procedures. A methodology was developed to determine the real thermal profiles values by means of association of the thermograms with the sample emissivity curve. Three heat input levels were used, 3.64 J.mm-1, 5.09 J.mm-1, and 6.38 J.mm-1, respectively, for typical C-Mn steel. The thermal welding profile obtained experimentally exhibited linear correlation coefficients (R) of 0.99 with the electric current welding parameter and (R) of 0.99 with the calculated thermal input, respectively. The welds metallurgical characterizations results, expressed through the ductility and welds nuggets analysis, were conducted to correlate the welds quality with the welding thermal input. The Erichsen cupping test showed that the higher the thermal input corresponds to higher ductility of the welds. Nevertheless, the heat input of 5.09 J.mm-1 indicated better-balanced properties: ductility, weld nugget discontinuity, nugget size, and no expulsion of the melt material.

Resumo: Aços AISI 316 e AISI 316L possuem ampla aplicação industrial, por isso a importância de avaliar a soldabilidade dessas ligas. Neste estudo, foi feita análise comparativa entre as amostras de ambos os aços soldados com aportes de 0,5, 1,5 e 2,5 kJ/mm utilizando processo TIG autógeno. Foi analisada a variação do aporte térmico sobre a morfologia do cordão de solda, o espaçamento entre ferritas δ, a fração volumétrica de ferrita δ e a microdureza na zona fundida. Os resultados mostraram que as dimensões do metal de solda, o espaçamento entre as ferritas e a fração volumétrica de ferrita δ tornam-se maiores com o aumento do aporte. As amostras soldadas do aço AISI 316L apresentaram maior espaçamento entre ferritas δ e maiores frações de ferrita δ que o aço AISI 316. Quanto à microdureza, o estudo mostrou que quanto mais próximo do centro da zona fundida, maior é o valor de microdureza, sendo a microdureza do aço AISI 316 maior que a do aço AISI 316L. Através de modelagem computacional foi possível avaliar a distribuição de temperatura ao longo das chapas soldadas e comparar o ciclo térmico obtido por simulação com o ciclo calculado experimentalmente para o aporte de 0,5 kJ/mm.

Abstract AISI 316 and AISI 316L steels have wide industrial application, so the importance of evaluating the weldability of these alloys. In this study, comparative analysis was made between the samples of both welded steels with heat inputs of 0.5, 1.5 and 2.5 kJ/mm using autogenous TIG process. The variation of heat input on weld bead morphology, the spacing between δ ferrite bands, the volumetric fraction of ferrite δ and the microhardness in the molted zone were analyzed. The results showed that the dimensions of the welding metal, the spacing between ferrite bands and the volumetric fraction of ferrite δ become larger with the increase of the heat input. The welded samples of AISI 316L steel presented larger ferrite band spacing and larger δ ferrite fractions than AISI 316 steel. As for microhardness, the study showed that the closer to the center of the molted zone, the greater the microhardness value and the hardness of AISI 316 steel higher than that of AISI 316L steel. Through computational modeling it was possible to evaluate the temperature distribution along the welded plates and compare the thermal cycle obtained by simulation with the experimentally calculated cycle for the input of 0.5 kJ/mm.