Caracterização microestrutural de um aço aar m-201 grau e, em engate ferroviário fixo tipo "F", após magnetização por PRODS no ensaio com partículas magnéticas
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Data
2016-08-04
Autores
Baptistella, Marco Antonio [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Atualmente, as cargas aplicadas nos eixos de vagões ferroviários têm sofrido aumento de esforços devido ao choque e tração no engate ferroviário. Neste trabalho o estudo foi realizado no engate tipo “F”, que tem maior utilização e interesse por parte da ferrovia, por se tratar de um engate rotativo e utilizado para descarregamento de vagões com os mais diversos tipos de carga. Este trabalho tem como objetivo, verificar se existem transformações da microestrutura no material do engate, e possíveis gerações de trincas, através do estudo do aço AAR M-201 Grau E, após o ensaio de partículas magnéticas, com corrente alternada através da aplicação de Prods. A faixa de amperagem variou-se de 100 a 1000 ampères e como meio de resfriamento, utilizou-se a água a temperatura ambiente e o ar forçado. A preparação foi feita partindo de um engate Tipo “F” completo, fornecido por um operador logístico, a cauda foi magnetizada por inteiro e depois separados os corpos de prova por corte de serra, refrigerado para não haver aquecimento. Para a caracterização microestrutural, utilizou-se uma preparação metalográfica de laboratório de bancada e ataque com Nital 2%, e fez-se uso de microscopia ótica convencional e microscopia eletrônica de varredura (MEV). Através da utilização da microscopia ótica e da microscopia eletrônica de varredura (MEV), pode-se verificar a microestrutura nas áreas que sofreram alterações microestruturais. Concluiu-se que o aço do engate, AAR M-201 grau E, após a magnetização por Prods de 300 a 1000 ampères, apresentou alteração microestrutural, onde observou-se uma estrutura de martensita acicular não revenida e geração de trincas, a mesma alteração microstrutural foi observada em amostras com resfriamento ao ar, porém sem a geração de trincas, em ampliações de 50 vezes foi nítido o efeito de queima provocado pelo Prods no material, bem como sua extensão, evidenciando áreas centrais de atuação do Prods, zonas de transição e áreas não afetadas. As trincas tiveram comportamento de propagação intergranular, para ampliações de 9300 vezes em MEV, pode-se observar que as mesmas se propagaram somente nas áreas com martensita e contornaram as áreas com maior presença da fase ferrítica.
Currently, the applied loads on the axles of railway cars has been increasing efforts due to shock and traction in railway coupling. In this work, the study was performed on the coupling type "F", which has increased use and interest on the part of the railway, because it is a rotary coupling and used for unloading of wagons with the most diverse types of cargo. This work aims, check for microstructural changes on the coupling material, and possible generation of cracks through the study of steel AAR M-201 grade and after the test of magnetic particles with alternating current by applying Prods. As amperage range, was varied from 100 to 1000 amps and as cooling medium water was used at room temperature and forced air. The preparation was made starting from a coupling type "F" full, provided by a logistics operator, the tail was magnetized in full and then separate the specimens by cutting saw, cooled to no heating. For microstructural characterization, we used a metallographic preparation of benchtop laboratory and attack Nital 2%, and was made use of conventional optical microscopy and scanning electron microscopy (SEM). By using light microscopy and scanning electron microscopy (SEM), you can check the microstructure in areas that suffered microstructural changes. It was concluded that the coupling of steel, AAR M-201 grade And after magnetization by Prods 300-1000 amps, presented change microstructural where there was a martensite acicular structure not tempered and generation of cracks, the same change microstructural was observed in air to cooling with samples, but without generating cracks at magnifications of 50 times was clear the burning effect caused by Prods in the material as well as its extension, showing the central areas of the Prods activities, transition zones and unaffected areas. The intergranular crack propagation behavior had to 9300 times magnification under SEM, it can be seen that they have spread only in areas with martensite and rounded areas with the greatest presence of the ferritic phase.
Currently, the applied loads on the axles of railway cars has been increasing efforts due to shock and traction in railway coupling. In this work, the study was performed on the coupling type "F", which has increased use and interest on the part of the railway, because it is a rotary coupling and used for unloading of wagons with the most diverse types of cargo. This work aims, check for microstructural changes on the coupling material, and possible generation of cracks through the study of steel AAR M-201 grade and after the test of magnetic particles with alternating current by applying Prods. As amperage range, was varied from 100 to 1000 amps and as cooling medium water was used at room temperature and forced air. The preparation was made starting from a coupling type "F" full, provided by a logistics operator, the tail was magnetized in full and then separate the specimens by cutting saw, cooled to no heating. For microstructural characterization, we used a metallographic preparation of benchtop laboratory and attack Nital 2%, and was made use of conventional optical microscopy and scanning electron microscopy (SEM). By using light microscopy and scanning electron microscopy (SEM), you can check the microstructure in areas that suffered microstructural changes. It was concluded that the coupling of steel, AAR M-201 grade And after magnetization by Prods 300-1000 amps, presented change microstructural where there was a martensite acicular structure not tempered and generation of cracks, the same change microstructural was observed in air to cooling with samples, but without generating cracks at magnifications of 50 times was clear the burning effect caused by Prods in the material as well as its extension, showing the central areas of the Prods activities, transition zones and unaffected areas. The intergranular crack propagation behavior had to 9300 times magnification under SEM, it can be seen that they have spread only in areas with martensite and rounded areas with the greatest presence of the ferritic phase.
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Palavras-chave
Aço ferroviário, Microscopia ótica, Magnetização, Prods, Indústria ferroviária, Partículas magnéticas, Rail steel, Magnetization, Railway industry, Magnetic particles