Estudo da relação microestrutura/propriedades mecânicas e tratamento térmico dos aços inoxidáveis austeníticos AISI 316l e 317l soldados pelo processo GTAW, em termos de ferrita delta

• Ano de defesa: 2016
• Autor(a) principal: Altieri, Welder Michael
• Orientador(a): Faldini, Sonia Braunstein
• Banca de defesa: Couto, Antonio Augusto , Andrade, Arnaldo Homobono Paes de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Presbiteriana Mackenzie
• Programa de Pós-Graduação: Engenharia de Materiais
• Departamento: Escola de Engenharia Mackenzie (EE)
• País: Brasil
• Palavras-chave em Português: aço inoxidável austenítico; ferrita delta; fase sigma
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: http://dspace.mackenzie.br/handle/10899/24228

Steel production is estimated to be over of 1,500 million tons per year. Among them, stainless steels stand out, having as one of their main characteristics the corrosion resistance, especially in aggressive environments. As with most steel alloys, stainless steels are classified according to their chemical composition, with austenitic stainless steels accounting for the largest manufacturing share among the category. Its choice is given due to the excellent properties, highlighting its corrosion resistance, toughness, weldability, etc. As one of the most employed, stainless steels are processed in different ways into the industry, with welding being one of the main ones. Different processes as well as different alloying elements provide to each type of steel a different property, since it has direct influence with its microstructure. It is known that austenitic stainless steels have a predominantly austenitic microstructure, but during solidification due to microsegregation of elements it can be altered. One of the main phases formed during solidification in austenitic stainless steels is known as delta ferrite, derived from the segregation of ferrite stabilizing elements. This phase tends to minimize the susceptibility of hot cracks during the solidification, as well as to increase the mechanical resistance, but to the detriment of the ductility, being one of the main mechanisms for the precipitation of intermetallic phases, like sigma phase, that has its precipitation accelerated by the presence of delta ferrite formations and is considered a deleterious phase, as it decreases the resistance and ductility parameters of the materials. This work analyzed the behavior of two distinct stainless steels, AISI 316L and 317L, in order to know the effects of these phases, as well as their nucleation mechanisms. May be concluded that the presence of stabilizing elements of ferrite, chromium and molybdenum, tend to accelerate the precipitation of the sigma phase at 850°C, as well as to delay the dissolution of the delta ferrite in the solution annealing condition, 1080°C. It is also observed that in the presence of these phases the material has its tensile strength increased, but with ductility reduction.