Efeitos de tratamentos térmicos de têmpera com austenitização intercrítica na microestrutura, partição de elementos e temperatura Ms em um aço TRIP780
Effects of quenching heat treatments with intercritical austenitizing in the microstructure, elements partition and Ms temperature in a TRIP780 steel
Natália Aparecida Barbosa Pimenta, Charles Henrique Xavier Morais Magalhães, Pablo Henrique Kelly Campos, Geraldo Lúcio de Faria
Resumo
Neste trabalho, o efeito de tratamentos térmicos de têmpera com austenitização intercrítica sobre a microestrutura, partição de elementos e temperatura Ms foi estudado para um aço TRIP780. Por meio de dados dilatométricos e caracterização microestrutural, diferentes ciclos térmicos de têmpera com austenitização intercrítica foram avaliados. Os resultados obtidos experimentalmente foram comparados com aqueles obtidos por meio de simulações computacionais no equilíbrio. Concluiu-se que, quanto menor a temperatura de austenitização intercrítica, menor é a fração de austenita formada tanto no equilíbrio quanto fora dele. Verificou-se ainda que, quanto menor a fração de austenita formada, maior é a concentração de C e Mn na referida fase, assim como menor é a concentração de Si. Esse cenário favorece a formação de bainita durante a têmpera e diminui significativamente a temperatura Ms . Os resultados obtidos apontam que o conhecimento dos efeitos da austenitização intercrítica em um aço C-Mn-Si tem grande potencial para ser aplicado com o objetivo de se definir ciclos térmicos que favoreçam a estabilidade da austenita e permitam o ajuste fino da temperatura Ms , possibilitando que tratamentos térmicos atuais, como têmpera e partição, possam ser empregados com significativas chances de sucesso.
Palavras-chave
Abstract
In this work, the effect of quenching heat treatments with intercritical austenitizing on the microstructure, element partition and Ms temperature was studied for a TRIP780 steel. Using dilatometric data and microstructural characterization, different quenching cycles with intercritical austenitizing were evaluated. The results experimentally obtained were compared with those obtained by in-equilibrium computational simulations. It was concluded that the lower the intercritical temperature, the lower the austenite fraction in both conditions: in- and non-equilibrium. It was also found that the lower the austenite fraction, the higher its C and Mn contents, as well as the lower its Si concentration. This scenario favors the formation of bainite during quenching and significantly decreases the Ms temperature. These results show that the knowledge about the effects of intercritical austenitizing on a C-Mn-Si steel has great potential to be applied in order to define thermal cycles that favor the austenite stability and allow the fine adjustment of the Ms temperature, making it possible that important and actual heat treatments, such as quenching and partitioning, can be used with great chance of success.
Keywords
Referências
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Submetido em:
01/09/2020
Aceito em:
18/01/2021
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