Caracterização mecânica e microestrutural de um aço de baixo carbono
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Data
2008-06-23
Autores
Elisei, Cristina de Carvalho Ares [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As necessidades do mercado por materiais mais resistentes e econômicos resultaram na pesquisa e desenvolvimento de novos aços. Neste contexto surgiram os aços de alta resistência e baixa liga que podem ter microconstituintes diferenciados dependendo do processamento térmico ou termomecânico aplicado. Por meio desses processamentos, a formação de estruturas multifásicas, bainíticas ou bifásicas tem sido conseguida. Este trabalho tem como objetivo caracterizar o efeito de diferentes tratamentos térmicos sobre as propriedades mecânicas obtidas do ensaio de tração e impacto e microestruturais de um aço microligado com baixo teor de carbono e silício. Para isto, foi realizado um tratamento de austenitização a partir de 950ºC, seguido de tratamento isotérmico a 500ºC para a obtenção do constituinte bainítico. Para a obtenção da estrutura multifásica foram realizados dois tratamentos de recozimento intercrítico (760ºC e 800ºC) seguidos de tratamento isotérmico a 500ºC por dois tempos de permanência (3 e 10 minutos), foram também realizados dois tratamentos de têmpera intercrítica (760ºC e 800ºC) para obtenção da estrutura bifásica foram realizados. Para a caracterização microestrutural foram utilizadas a microscopia óptica, eletrônica de varredura e de força atômica. Foram necessárias a utilização de diferentes reagentes químicos (Nital a 2%, metabissulfito de sódio, LePera e a técnica de Heat tinting), para a identificação das fases por microscopia óptica. O nital foi utilizado para realçar os contornos de grão tanto para a realização da microscopia eletrônica de varredura, microscopia de força atômica, assim como para a realização das medidas de tamanho e grão ferrítico. Pelos resultados obtidos pode-se verificar a obtenção das estruturas desejadas de cada tratamento, principalmente de austenita retida partindo-se de...
The needs of the industries by more strength and economic materials have been generated research and development of new steels. In this context came the high-strength and low alloy steels that may have different constituents depending on the heat processing or thermomechanical applied. Through these processes the formation of multiphase, bainitics or dual-phases structures have been achieved. This study aimed to characterize the effect of different treatments on the mechanical properties obtained from the testing of tensile and impact of a steel and microstructural microalloy low carbon and silicon. For this was done a treatment of austempering to 950°C followed by isothermal treatment to 500ºC to obtain the bainitic constituent. To obtain the structure of multiphase two intercritical treatments (760°C and 800°C) followed by isothermal treatment to 500ºC for two times (3 and 10 minutes) were made. And two quenching treatments (760°C and 800°C) to obtain the dual phase structure were made. For the microstructural characterization were used optical microscopy, electronic scanning and atomic force. As required the use of different chemical etchants (nitric acid to 2%, sodium metabisulphite, LePera and the heat tinting technique) to identify the phases through optical microscopy, and the nitric acid was used to highlight the grain for both attainment of scanning electron microscopy, atomic force microscope, as well as to carry out the measures of grain size and ferritic. Through the results can be the achievement of desired structures of each treatment mainly the verification of obtaining retained austenite on steel with low silicon and aluminum and that small variations in microconstituents can affect the mechanical properties of the material . You can also observe and identify the phases obtained in the heat treatments with the aid of microscopy techniques already mentioned.
The needs of the industries by more strength and economic materials have been generated research and development of new steels. In this context came the high-strength and low alloy steels that may have different constituents depending on the heat processing or thermomechanical applied. Through these processes the formation of multiphase, bainitics or dual-phases structures have been achieved. This study aimed to characterize the effect of different treatments on the mechanical properties obtained from the testing of tensile and impact of a steel and microstructural microalloy low carbon and silicon. For this was done a treatment of austempering to 950°C followed by isothermal treatment to 500ºC to obtain the bainitic constituent. To obtain the structure of multiphase two intercritical treatments (760°C and 800°C) followed by isothermal treatment to 500ºC for two times (3 and 10 minutes) were made. And two quenching treatments (760°C and 800°C) to obtain the dual phase structure were made. For the microstructural characterization were used optical microscopy, electronic scanning and atomic force. As required the use of different chemical etchants (nitric acid to 2%, sodium metabisulphite, LePera and the heat tinting technique) to identify the phases through optical microscopy, and the nitric acid was used to highlight the grain for both attainment of scanning electron microscopy, atomic force microscope, as well as to carry out the measures of grain size and ferritic. Through the results can be the achievement of desired structures of each treatment mainly the verification of obtaining retained austenite on steel with low silicon and aluminum and that small variations in microconstituents can affect the mechanical properties of the material . You can also observe and identify the phases obtained in the heat treatments with the aid of microscopy techniques already mentioned.
Descrição
Palavras-chave
Aço-carbono, Aço - Estruturas
Como citar
ELISEI, Cristina de Carvalho Ares. Caracterização mecânica e microestrutural de um aço de baixo carbono. 2008. 188 f. Tese (doutorado) - Universidade Estadual Paulista, Faculdade de Engenharia, 2008.