http://repositorio.ufc.br/handle/riufc/500 2026-05-31T04:01:28Z http://repositorio.ufc.br/handle/riufc/86409 Título: Previsão computacional do teor de silício no ferro-gusa Autor(es): Xavier, João Victor Barroso Abstract: The silicon content of pig iron is one of the main indicators of its quality and the thermal state of the blast furnace. Furthermore, a high silicon content can damage industrial equipment, leading to the need for maintenance and, consequently, a loss of process efficiency. For these reasons, several studies have been developed over decades to predict and monitor the silicon content in pig iron, suggesting the use of data-driven models. In this context, this work tested models such as the logistic perceptron, multilayer perceptron artificial neural networks with up to two hidden layers, and different versions of support vector machines adapted for regression (SVR, TSVR, LSSVR) to predict the silicon content in pig iron. A technique for estimating the number of hidden neurons in neural networks based on singular value decomposition (SVD) was also investigated to reduce tuning time and computational cost. Among the neuron-based models, the neural network with one hidden layer presented the best balance between performance and computational cost, while the SVD-based technique provided a smaller hyperparameter testing window, therefore, it was used in a sensitivity analysis to study the influence of each input variable on the silicon content in pig iron. Tipo: Dissertação 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85985 Título: Desenvolvimento do fio-máquina com o aço 1010 para produção de vergalhão CA60 em laminadores a frio Autor(es): Gondim Júnior, Irannildo Walter Abstract: Today's steel market is increasingly competitive, where every extra minute of production is a huge gain in financial results. In 2022, a steel mill in Ceará used 5.5mm 1008 steel wire rod to produce 3.40mm CA60 rebars and 5.5mm 1012 steel wire rod to produce 4.20mm CA60 rebars, two different raw materials for two different products, However, these materials presented opportunities, such as difficulties in meeting the property requirements of the Brazilian standard ABNT NBR 7480, which sets out the minimum requirements for rebar, so there was a need to develop a new technology for producing this material. The aim of this work is to develop a wire rod in 1010 steel so that it is suitable for the hot rolling process and then the cold rolling process, so that during the hardening process it achieves the desired properties, significantly reducing the generation of non-conforming products, as well as having a single steel that would produce both 3.40mm and 4.20mm CA60 rebar. This development was carried out by producing a pilot batch of 30 tonnes of SAE 1010 steel, where three temperature values were tested during hot rolling and then subjected to the hardening process (cold rolling), reducing its section to 4.20mm and 3.40mm. This material was validated by means of tensile tests carried out on a calibrated machine using an extensometer, as well as characterising the material for each temperature parameter by measuring its grain size, which is a determining factor for characteristics such as the yield strength. The results showed that the higher the hot rolling temperature, the larger the grain size, which consequently improves the values of the material's elastic ratio, which is the breaking limit divided by the yield limit, a parameter that is normative and which is very difficult to achieve using different steels, especially 1012, thus showing that the hot rolling temperature is a determining factor for the cold rolling process, favouring the achievement of the appropriate elastic ratio for the product Tipo: Dissertação 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85303 Título: Thermomechanical modeling and simulation of an electric arc welding process: a computacional analysis of the influence of the element birth and death techinique Autor(es): Costa, Mateus Andrade de Sousa Abstract: Arc welding plays a vital role in modern industry, particularly in the fabrication of complex structures and components. While the process is widely employed and relatively straightforward, it is not without challenges. Welding can introduce residual stresses, distortions, and defects into the material, potentially compromising structural integrity, increasing costs, and necessitating rework. To address these challenges, this study conducts a detailed thermomechanical analysis of the welding process, exploring computational modeling as a viable alternative to traditional experimental methods. The research employs ANSYS® software and the Finite Element Method (FEM) to simulate the thermal and mechanical behavior of materials under specific welding conditions. The study focuses on single-pass butt welding of plates and pipes, incorporating filler metals and utilizing the Element Birth and Death Technique (EBDT) to simulate material addition during welding. By examining different mesh element orders (linear and quadratic), the analysis evaluates temperature distributions, residual stresses, and deformations while also considering computational efficiency. The results revealed that EBDT increased test duration by 16.5%, and a significantly temperature difference (665ºC with EBDT vs. 348ºC without) during heat source passage. Mesh element order notably influenced outcomes: quadratic elements reduced the element count by 85%, balancing accuracy and computational efficiency, while refined linear elements increased execution time by up to 90%. For the heat-affected zone (HAZ), simulations without EBDT may suffice, but weld bead analysis requires further validation, particularly in multi-pass welding, where reheating alters stress distributions. The methodology was validated through comparisons with analytical, numerical, and experimental data available in the literature, confirming its robustness for structural analysis and process optimization. This research contributes to the theoretical understanding of arc welding, offering a computational framework that effectively balances precision and cost. The study lays a strong foundation for future investigations, especially in exploring the complexities of multi-pass welding. Tipo: Dissertação 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/83941 Título: Weldabilty evaluation of corrosion-resistant alloy weld metals for high-temperature service in oil and gas industry using trans-varestraint test Autor(es): Sousa, Ana Beatriz Ferreira Abstract: The flare in the oil and gas industry is responsible for burning harmful gases, ensuring safety. Flares are commonly made of austenitic stainless steels (ASSs), which are highly recommended for application at high temperatures and in reducing/oxidising atmospheres. Despite this, several failure cases of ASS components utilised in oil and gas production and refining have been reported in the literature, mostly related to metallurgical phenomena occurring due to harsh operation conditions. The processes of fabrication and repair per welding may also cause failures once the welding leads to nonequilibrium solidification, microsegregation of alloy elements, and potential rejection of impurities from the solid toward the interdendritic liquid, which are critical factors for the occurrence of solidification cracking. Therefore, this work aimed to assess the weldability through Trans-Varestraint Test (TVT) of consumable electrodes which can be employed in the fabrication and repair of flare components. The welds were made with the shielded metal arc welding (SMAW) using three filler metals: the ASS electrodes AWS E310-15 and AWS E347-17 and the nickel-based alloy electrode AWS ENiCrFe-2. The ASSs AISI 310S and AISI 304H were applied as the base metals. The TVTs was performed with strain levels ranging from 0.5% to 8%. The weldability was evaluated based on the susceptibility of the weld metal to solidification cracking, which was determined through the critical strain, saturated strain, maximum crack length, maximum crack distance, total crack length, and critical strain speed. Additionally, samples of the fusion zones resulting from each welded combination were investigated by light optical microscopy and scanning electron microscopy, with a focus on correlating the microstructural characteristics to the resistance to solidification cracking. Electron backscatter diffraction (EBSD) analysis was used to determine the effects of stress applied during TVT on the microstructures of the weld metals. Considering all the results analysed, the ranking from least to most susceptible to solidification cracking was as follows: (AISI 310S + AWS E347-17) > (AISI 304H + AWS E347-17) > (AISI 304H + AWS E310-15) > (AISI 310S + AWS E310-15) > (AISI 310S + AWS ENiCrFe-2) > (AISI 304H + AWS ENiCrFe- 2). The weld metals most resistant to solidification cracking resulted from the tests with the AWS E347-17 electrode, for which solidification occurred in the primary ferrite/secondary austenite mode. These fusion zones consisted of a combination of austenite and δ-ferrite, and the presence of δ-ferrite is known to be beneficial for preventing solidification cracking. The welds with the AWS E310-15 electrode solidified in the fully austenitic mode, which is favourable for solidification cracking. The fusion zones of tests using the AWS ENiCrFe-2 filler metal were composed of the γ-Ni fcc phase, and evidence of the precipitation of Nb(C,N) was found in the interdendritic volumes. The formation of secondary phases may have some influence on the cracking propensity, explaining the lower resistance to solidification cracking of these weld metals. The EBSD results showed higher misorientation levels surrounding the cracks and on subgrain boundaries. This may be attributed to the severe deformation level at which the microstructure was subjected to cracking. The regions where dislocations accumulate eventually became subgrain boundaries. Tipo: Dissertação 2024-01-01T00:00:00Z