Caracterização microestrutural e mecânica em juntas soldadas por arco submerso em chapas de aço microligado API 5l x70 utilizadas em minerodutos

• Autor(a) principal: Busso, Nicolangelo Del
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/24197
• topic: ARBL (Alta Resistência e Baixa Liga); aço API 5L X70; arco submerso; HSLA (High Strength Low Alloy); steel API 5L X70; submerged arc welding process; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

The present work investigates the possible changes that occur in the mechanical properties and microstructure of welded joints through the process of submerged arc in steel plates High Strength Low Alloy (HSLA) type API 5L X70, used in pipelines. These are usually constructed starting from calendered plates and welded through submerged arc process, forming 600 mm diameter pipes, with 12 m long. To reproduce faithfully the pipes manufacturing processes, for further characterization of test bodies were produced, welding plate supplied by USIMINAS, through the submerged arc welding, and withdrawing samples to perform the characterization of the regions of the weld metal (WM), the heat affected zone (HAZ) and the base metal (BM). Conventional tensile and Charpy V-Notch were performed to determine mechanical and impact properties of the tested materials, as well as macrograph tests and Optical microscopy (OM) and weld metal (WM), the heat affected zone (HAZ) and the base metal (BM). The metallographic examination showed banded microstructure consisting of polygonal ferrite, pearlite and bainite with small grain size. The results showed increased strength and hardness influenced by the presence of acicular ferrite. The fractography analysis after impact tests revealed ductile-brittle behavior. Impact tests were performed at temperatures of 0°C and -20°C, which exhibited significant toughness decrease, that is 260J to 202J for the BM, 106J to 81J for HAZ and 25J to 19J to the WM, while the Vickers hardness testing (HV10) was increased from the fusion zone to the base metal (194HV for WM, 202 HV for HAZ and 218 HV for BM).