Caracterização microestrutural em função da temperatura de serviço de tubos de aços HP-Modificados ao Nb e Ti envelhecidos em fornos de reforma a vapor

• Ano de defesa: 2017
• Autor(a) principal: Queiroz, Fábio dos Santos.
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio de Janeiro; Brasil; Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia; Programa de Pós-graduação em Planejamento Energético; UFRJ
• Palavras-chave em Português: Planejamento Energético; Aços HP; Tubo de forno de reforma; CNPQ::ENGENHARIAS::ENGENHARIA DE PRODUCAO
• Link de acesso: http://hdl.handle.net/11422/8303

Hydrogen is produced in reforming furnaces inside tubes, which are currently manufactured with HP-Nb and HP-NbTi steels. The service temperature of these tubes causes different degrees of metallurgical aging along their lengths. The purpose of the present work is to characterize the aging of these steels at different temperatures, taking into account the effects ofNb and Ti additions, to establish an aging classification criterion for these alloys. For this, four deactivated reforming tubes were analyzed, presenting compositionswith low Nb or high Nb and with or without micro additions of Ti. It was verified that the aging stage classification criterion for HP steels can be based on the one used for HK steels, considering, however, three factors: NbC "Chinese script" morphology in stage I, except for those steels with Ti or Zr; secondary precipitation in the aging stages II and III as a function of Cr/Nb ratio; and a more uniform distribution of secondary precipitation for steels with high Nb in the absence of Ti in aging stage IV.