Caracterização da ductilidade em fluência dos aços inoxidáveis AISI 321 e AISI 441 pela metodologia Sag Test
Characterization of the creep-ductility of AISI 321 and AISI 441 stainless steels applying the Sag Test methodology
Denilson Pereira Melo, Paulo Sérgio Moreira, Geraldo Lúcio de Faria
Resumo
As regulamentações ambientais estão cada vez mais rigorosas em relação à emissão de gases pelos automóveis. Por esse motivo, as grandes montadoras tiveram que pensar em soluções para continuar oferecendo motores potentes, mas menos poluentes. Nesse cenário, há uma tendência mundial de se substituir os clássicos motores aspirados por motores turbinados. Com a implementação do sistema turbo, as temperaturas máximas de trabalho de alguns componentes do escapamento aumentam de 900 °C para 1050 °C e, consequentemente, a seleção de materiais para a manufatura dos mesmos é algo crítico. Nesse contexto, esse trabalho avaliou a ductilidade em fluência (Sag Test) do aço inoxidável ferrítico AISI 441, geralmente utilizado na manufatura de coletores e catalizadores de veículos com motores aspirados, comparando-o com o desempenho do aço inoxidável austenítico AISI 321. Concluiu-se que o comportamento em fluência dos aços AISI 321 e AISI 441 são semelhantes nas temperaturas de 900 °C e 950 °C. Entretanto, na temperatura de 1000 °C o aço AISI 441 apresentou uma expressiva mudança de comportamento, atingindo uma flecha máxima de 26 mm após 100 h de ensaio, enquanto o aço AISI 321 apresentou apenas 5 mm. Baseado nos resultados obtidos, pode-se afirmar que o aço AISI 441 apresenta desempenho limitado em fluência para aplicação em escapamentos automotivos com motorização turbo.
Palavras-chave
Abstract
Environmental regulations are increasingly strict in relation to the emission of pollutants by vehicles. For this reason, the car manufacturers had to think about solutions to continue offering powerful, but less polluting engines. In this scenario, there is a worldwide trend to replace the classic aspirated engines with turbocharged engines. Due to the implementation of the turbo system, the maximum working temperatures of some exhaust components increase from 900 °C to 1050 °C and, consequently, the material selection for their manufacture is critical. In this context, this work evaluated the creep behavior (Sag Test) of the ferritic stainless steel AISI 441, generally used in the manufacture of collectors and catalysts for aspirated engine vehicles, comparing it with the performance of AISI 321 austenitic stainless steel. The creep behaviors of AISI 321 and AISI 441 steels are similar at 900 °C and 950 °C. However, at 1000 °C, AISI 441 steel presented a significant behavior change, reaching a maximum deflection of 26 mm after 100 h of testing, while AISI 321 steel presented only 5 mm. Based on the obtained results, it can be stated that AISI 441 steel presents limited creep performance for application in automotive exhausts with turbo engine.
Keywords
Referências
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Submetido em:
31/07/2020
Aceito em:
02/12/2020
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