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Soldagem & Inspeção, Volume: 27, Published: 2022
  • Evaluation of the Effect of Heat Input and Cooling Rate of Rail Flash-Butt Welding using Finite Element Method Simulation Technical Papers

    Pereira, Henrique Boschetti; Echeverri, Edwan Anderson Ariza; Alves, Luiz Henrique Dias; Goldenstein, Hélio

    Abstract in Portuguese:

    Resumo Simulações pelo método dos elementos finitos (MEF) foram realizadas para entender os efeitos das taxas de aquecimento/resfriamento na distribuição de tensões residuais. Dois parâmetros de material dos trilhos foram usados, enquanto as condições de contorno permaneceram constantes: tamanho da zona afetada pelo calor, temperatura máxima e taxa de extração de aquecimento. Para complementar a análise, foi realizada uma solda de topo por centelhamento de um trilho Premium com parâmetros de soldagem ajustado para obter uma baixa extensão de zona afetada pelo calor, sem resfriamento forçado, para examinar a microestrutura formada nas regiões críticas na alma e no extremo do patim. Os resultados mostraram que houve concentração de tensões residuais verticais na região da alma, enquanto a presença de tensão residual de compressão no sentido horizontal foi predominantemente superficial na região do trilho superior. Ao usar dois parâmetros de simulação de materiais semelhantes (trilhos), os resultados foram substancialmente diferentes. Os exames metalográficos mostraram que não havia presença de microconstituintes aciculares (martensita/bainita). Além disso, foi observada ferrita pro-eutetóide na região central, cementita em contorno de grão austenítico prévio na região próxima a AC3 e esferoidização quase completa na região de sítio de esferoidização máxima da alma. Em contrapartida, na região do extremo do patim, apresentou microestrutura completamente perlítica na região central e próxima a AC3 e menor volume de esferoidização na região de máxima esferoidização, provavelmente devido à maior taxa de resfriamento nesta região.

    Abstract in English:

    Abstract Simulations using the finite element method (FEM) were done to understand the effects of heating/cooling rates on the distribution of residual stresses. Two material parameters from rails were used while the boundary conditions remained constant: heat-affected zone size, maximum temperature and heating extraction rate. To complement the analysis, a flash-butt weld of a Premium rail was done with welding parameters adjusted to obtain a narrow HAZ, without forced cooling, to examine the microstructure formed in the critical regions in the web and the edge of the rail foot. The results showed that there was a concentration of vertical residual stresses in the web region, while the presence of horizontal compression residual stresses was mostly superficial in the rail head region. The main result from the simulation sets was that when using two simulation parameters with similar materials (rails) substantially different results were obtained. Metallographic examinations showed that there was no presence of acicular microconstituents (martensite/bainite). In the rail web, proeutectoid ferrite was observed in the central region, cementite in a previous austenitic grain boundary, in the region that reached temperatures close to AC3, and almost complete spheroidization in the region of maximum spheroidization. In contrast, in the rail foot edge region, there was a completely pearlitic microstructure, in the central region and in the zone that reached temperatures close to AC3, and a lower volume of spheroidization in the region where maximum spheroidization is typically observed, probably due to the higher cooling rate in this region.
  • Influencia de la Atmosfera de N2 en los Parámetros Operacionales y la Microestructura del Depósito en el Recargue Duro con FCAW Artículos Científicos

    García-Jacomino, Jorge Luis; Ferraresi, Valtair Antonio; Cruz-Crespo, Amado; Scotti, Americo

    Abstract in Portuguese:

    Abstract The study of the influence of the nitrogen atmosphere on the behavior of the welding parameters (current and voltage) and on the properties of the deposits of self-protected tubular wires used in the FCAW process for the recharging of pieces and parts subjected to severe abrasion is debated. Three filler materials are evaluated for this type of application: one with high chromium, another with high chromium and alloyed with niobium and the third with lower chromium content and also alloyed with titanium. Deposits are made under the conditions indicated by the manufacturers for the wires (in terms of regime parameters) with and without nitrogen gas protection, using a constant voltage mode welding source. The use of additional gaseous protection (N2) modifies the welding parameters while modifying the microstructure, influencing the mechanical properties of the deposits. The deposits were characterized by optical microscopy, confirming the influence of nitrogen on the operational behavior and on the deposits for the three wires used.

    Abstract in Spanish:

    Resumen Se aborda el estudio de la influencia de la atmosfera de nitrógeno sobre el comportamiento de los parámetros de soldadura (corriente y tensión) y en las propiedades de los depósitos de alambres tubulares auto-protegidos utilizados en el proceso FCAW para el recargue de piezas y partes sometidas a abrasión severa. Son evaluados tres materiales de aporte para este tipo de aplicación: Uno de alto cromo, otro de alto cromo y aleado con niobio y el tercero con menores contenidos de cromo y aleado también con titanio. Se realizan depósitos en las condiciones indicadas por los fabricantes para los alambres (en cuanto a parámetros de régimen) con y sin protección de gas nitrógeno, mediante fuente de soldadura en modo de tensión constante. El uso de protección gaseosa adicional (N2) modifica los parámetros de soldadura a la vez que modifica la microestructura, influyendo en las propiedades mecánicas de los depósitos. Los depósitos obtenidos fueron caracterizados por microscopia óptica, confirmando la influencia del nitrógeno sobre el comportamiento operacional y sobre los depósitos para los tres alambres utilizados.
  • Computational Simulations of Metal Additive Manufacturing Processes: An Introductory Review Artigos Técnicos

    Farias, Rodrigo Martins; Vilarinho, Louriel Oliveira

    Abstract in Portuguese:

    Resumo Os processos de Manufatura Aditiva (MA) de Metais permitem criar peças tridimensionais através da adição progressiva de finas camadas de material. Estes processos se enquadram em duas grandes categorias, denominadas Fusão em Leito de Pó e Deposição por Energia Direcionada. A compreensão física dos processos de MA pode fornecer uma visão holística sobre as sensibilidades aos parâmetros de processo. Já a modelagem computacional destes processos não só pode fornecer uma visão importante dos fenômenos físicos que levam às propriedades finais do material e à qualidade do produto, mas também os meios para explorar o espaço de projeto, visando criar produtos funcionais. Esta revisão introdutória foca na MA de materiais metálicos, particularmente nas questões de modelagem física e numérica. São apresentadas considerações sobre os diversos fenômenos físicos atuantes, métodos computacionais mais empregados, técnicas para realizar a modelagem e suas respectivas validações, demonstrando os desafios e limitações atuais, assim como as perspectivas futuras da simulação computacional aplicada aos processos de MA.

    Abstract in English:

    Abstract Additive Manufacturing (AM) processes of metals allow creating three-dimensional parts through the progressive addition of thin layers of material. These processes fall into two major categories, called Powder Bed Fusion and Directed Energy Deposition. Physical understanding of the AM processes can provide a holistic view of the sensitivity to process parameters. Computational modeling of these processes can not only provide an important view of the physical phenomena that lead to the final properties of the material and quality of the product, but also the means to explore the design space, in order to create functional products. This introductory review focuses on the AM of metallic materials, particularly on issues of physical and numerical modeling. Considerations are presented about the various physical phenomena at work, most used computational methods, techniques to perform the modeling and their respective validations, demonstrating the current challenges and limitations, as well as the future perspectives for computer simulations applied to AM processes.
  • Evolution of Process Automation in Welding Cells: A Literature Review Artigos Técnicos

    Faria, Isabella Cristina Souza; Filleti, Remo Augusto Padovezi; Helleno, André Luís

    Abstract in Portuguese:

    Resumo: O processo de soldagem é um método de união de materiais metálicos por meio do aquecimento até uma temperatura adequada. Esse processo é crucial na manufatura de diversos componentes, desde a microeletrônica até componentes estruturais de máquinas pesadas. Com o advento da automação industrial, houve o início da utilização de robôs de solda na indústria, visando uma maior produtividade, qualidade e acuracidade do processo. A partir do século XXI, com a chegada da Indústria 4.0, é possível enxergar novas oportunidades de melhoria no processo de solda, tais como a introdução do sistema CPS (Cyber Physical System), a realidade aumentada e a realidade virtual. Tais técnicas permitem não só a automatização da operação de soldagem, mas também um maior controle do processo, cruzando informações do método planejado com a operação real de modo dinâmico e adaptativo. Nesse contexto de diversificado portifólio de tecnologias usadas no processo de soldagem, o presente trabalho se propõe a realizar uma revisão da literatura com o objetivo de mapear as principais evoluções tecnológicas da automação dos processos de soldagem a arco nos últimos anos.

    Abstract in English:

    Abstract: Welding is a method of joining metallic materials by heating them until an appropriate temperature. This process is crucial for the manufacturing of several components, from microelectronics to structural components of heavy machinery. With the advent of industrial automation, welding robots were developed and implemented in industry, aiming to increase productivity, quality, and accuracy of the process. With the dawning of the 21st century and arrival of Industry 4.0, new opportunities for improvement in the welding process arose, such as the Cyber Physical Systems – CPS, augmented reality, and virtual reality. These techniques go beyond the welding operation automation, by providing greater control of the process control, crossing information of the planned method with the actual operation, in a dynamic and adaptive way. In this context of manifold welding technologies, the present work carries out a literature review with the objective of mapping the main technological developments of arc welding automation over time.
  • Effect of post welding heat treatment on the weld quality of micro plasma arc welded SS-316L thin sheet Technical Papers

    Prasad, Srikant; Pal, Sukhomay; Robi, P. S.

    Abstract in English:

    Abstract High thermal gradient formed during the fusion welding process results in development of undesirable residual stress in the weldments. This stress is developed due to restraint by the parent metal during weld solidification. The high heat input results in non-uniform heat distribution across the weld region in other words non-uniform microstructural development across the weld region and hence the mechanical properties of the joint are often not uniform. In order to avoid inhomogeneity in the mechanical properties and also to reduce/eliminate undesirable residual stress, the welded samples are given post welding heat treatment. In this research, 500 µm thin SS-316L sheets are welded using micro plasma arc welding process and then the welded specimens are heat treated. The welding experiments are conducted by varying welding speed, welding current and stand-off distance. Weld bead microstructure, micro-hardness, ultimate tensile strength (UTS), yield strength and percentage elongation are determined before and after heat treatment. The effects of welding heat input and process parameters on the measured weld qualities are studied. Analysis of variance is also performed to estimate the influence of factors and their interaction on the weld quality. The post weld heat treatment results in an increase in the grain size of the HAZ and is found in the range of 38.96 µm to 56.22 µm whereas for as-welded samples it is in the range of 29.88 µm to 50.40 µm. The average UTS value of the heat treated samples is increased by 9.9% compared to the as-welded samples. The hardness of the fusion zone varies in the range of 175-215 HV.
  • Effect of Square Pin Tool on Friction Stir Welded AA 6061-T6 from the Perspective of Revolution Pitch Technical Papers

    Banik, Abhijit; Debnath, Tapas; Barma, John Deb; Saha, Subhash Chandra

    Abstract in English:

    Abstract The phenomenon of revolution pitch was studied on AA 6061-T6 with a square pin tool for friction stir welding (FSW). The tool rotational speed and traverse speed were varied at four levels and selected in a manner so that the revolution pitch could comprise both lower and higher magnitude of variation when compared among them. An attempt was made to investigate the material flow from the macrostructure of both vertical (transverse to welding direction) and horizontal (parallel to the weld surface) cross-section. The study showed a significant amount of variation in terms of spindle torque, forces, material flow, and tensile properties. The increased material flow was noticed in the top surface of the weld from advancing to the retreating side at increased revolution pitch. Whereas an increased material flow was observed in the downward direction through the retreating side of the nugget. At increased revolution pitch a clear division in the onion ring was noticed towards the retreating side. The variation of torque, force and material flow showed a consistent trend for a higher change in revolution pitch. As the revolution pitch increased finer nugget grains were obtained causing increased tensile properties.
  • Double-layer technique for welding subsea joints without post welding heat treatment Technical Papers

    Oliveira, George Luiz Gomes de; Miranda, Hélio Cordeiro de; Miranda, Edvan Cordeiro de; Pinheiro, Pedro Helton Magalhães

    Abstract in English:

    Abstract Welded joints for subsea systems are usually buttered with a nickel alloy, heat-treated and then joined together. Although the majority of these joints have been successful throughout their service, some have suffered catastrophic failure, leading to investigations into the possible causes. The use of heat treatment has been considered the primary cause for failure in this type of joint. The main objective of this article is, with background on the methodology used on Double-Layer Controlled Deposition Technique – DL-CDT, along with the LPTS decision diagrams, to determine the relations between the buttering parameters that allow the welding of subaquatic joints, and the low need for heat treatment. MIG single-bead-on-plate welding was executed on samples of AISI 8630M steel. The welded samples were submitted to metallographic analyses of their geometric and microstructural characteristics and the confection of decision diagrams. Among the 200 possible relationships between the buttering parameters, only one presented positive gaps over all criteria. Grain refinements were observed in the HAZ of joints buttered for the parameters approved by the decision diagrams, while for the joints submitted to the Post Welding Heat Treatment (PWHT) peaks of microhardness on the buttering interface were found, which may result in fragilization of that region.
Associação Brasileira de Soldagem Rua Dr Guilherme Bannitz, 126 conj 42, 04532-060 - São Paulo/SP Brasil, Tel.: (55 11) 3045 5040, Fax: (55 11) 3045 8578 - São Paulo - SP - Brazil
E-mail: abs@abs-soldagem.org.br