REGIS DE MATOS CURVELO DE BARROS
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Artigo IPEN-doc 30226 Residual stress and fracture toughness study in A516 Gr70 steel joints welded and repaired by arc processes2023 - BARROS, REGIS de M.C. de; NEVES, MAURICIO D.M. dasStructural components made of steel are used in several areas and require welding for assembly. In some situations, repair of the weld bead, also performed by electric arc welding, can be used to correct, and eliminate any discontinuities. However, electric arc welding causes the presence of residual stresses in the joint, which can impair its performance and not meet specific design requirements. In this paper, welded joints made of ASTM A 516 GR 70 steel plates, with a thickness of 30.5 mm, welded by the MAG—Metal Active Gas process (20% CO2) and using a “K” groove were analysed. The joints were manufactured with seven welding passes on each side of the groove. After welding, one batch underwent repair of the bead by TIG welding (Tungsten Insert Gas) and another batch underwent two repairs by TIG welding. Were presented results of the behaviour of the residual stress profile measured by X-ray diffraction and the Vickers microhardness profile in the joints as well the fracture toughness in the conditions only welded and submitted to repairs. The results indicated that the greater number of repair passes reduced the residual compressive stress values obtained in the material manufacturing process and caused a stabilization on the Vickers hardness values. It was concluded that compressive residual stresses did not play a major role in the R-curve results. The presence of discontinuities in the welded joint caused greater influence on the behaviour of the R curve.Resumo IPEN-doc 30165 Study of residual stresses and fracture toughness in welded and repaired joints using A516 Gr70 steel2023 - BARROS, REGIS de M.C. de; NEVES, MAURICIOThe properties of welded joints subjected to cyclic loading is an important subject in several áreas[1]. In this scenario, aiming to study this subject, welded joints made of ASTM A 516 GR 70 steel plates, with a thickness of 30.5 mm, welded by the MAG – Metal Active Gas process (20% CO2) with the use of a K-bevel were analyzed. to allow full penetration due to the high thickness [2]. The joints were manufactured with seven welding passes on each side of the chamfer. After welding, one set was subjected to a repair pass, for remelting the surface of the bead using the TIG (Tungsten Inert Gas) process, while another set was subjected to two repair passes. This study aimed to analyze aspects of welded and repaired joints: dimensions (height and width) of the bead, behavior of the residual stress profile measured by X-ray diffraction, Vickers microhardness profile and fatigue crack nucleation with based on ASTM E466 and E606 standards. The results indicated that the greater number of repair passes decreased the compressive residual stress values in the transverse and longitudinal directions, from -350 MPa to 50 MPa. There was greater uniformity in hardness Vickers values (value between 200 and 210 HV) with the use of cord repairs. It was observed that the fracture toughness presented values of 1500 J/mm (without repair) and 900 J/mm (one pass and two repair passes), lower than that found in the material without welding (3500 J/mm). Therefore, as the repair passes were performed, the residual stresses in the weld bead tended to positive values, the hardness tended to stabilize with values of 200 HV due to the increase in the number of repair passes and the fracture toughness decreased in the welded material when compared to the values of the non-welded material. There was no significant difference in fracture toughness between repair passes.Resumo IPEN-doc 29442 Estudo de tensões residuais em juntas soldadas e submetidas ao reparo usando o aço A516 Gr702022 - BARROS, R.d.; OLIVEIRA, R.R.; NEVES, M.D.Componentes estruturais fabricados em aço são usados em diversas áreas e necessitam de união por soldagem para sua montagem. No entanto, a soldagem provoca na junta, o aparecimento de tensões residuais, que podem prejudicar seu desempenho e não atender requisitos específicos de projeto. Neste trabalho foram analisadas juntas soldadas fabricadas em chapas do aço ASTM A 516 GR 70, com espessura de 30,5 mm, soldadas pelo processo MAG – Metal Active Gas (20% de CO2) e usando chanfro em “K”. As juntas foram fabricadas com sete passes de soldagem de cada lado do chanfro. Após a realização da soldagem, um lote foi submetido a um reparo do cordão por soldagem TIG (Tungsten Insert Gas) e um outro lote submetido a dois reparos por soldagem TIG. O presente trabalho teve como objetivo analisar nas juntas, apenas soldada e submetidas aos reparos, o comportamento do perfil da tensão residual medidas por difração de raios X e o perfil microdureza Vickers. Foram medidas as tensões residuais e a dureza Vickers em pelo menos 22 pontos equidistantes. Os resultados indicaram que, o maior número de passes de reparo diminuiu os valores de tensão residual de compressão, obtidas no processo de laminação a frio usado na fabricação do material e provocaram também redução nos valores de dureza Vickers. Portanto, à medida que foram realizados os passes de reparo as tensões residuais no cordão de soldagem passaram a ter característica de tração.