Simulação de curvas TRC de aços inoxidáveis dúplex utilizando DICTRA®
Carregando...
Citações na Scopus
Tipo de produção
Trabalho de Conclusão de Curso
Data
2021-06
Autores
Andrade, Rayanne Araujo
Orientador
Magnabosco, Rodrigo
Periódico
Título da Revista
ISSN da Revista
Título de Volume
Citação
Texto completo (DOI)
Palavras-chave
aço inoxidável dúplex,TRC,simulação computacional,DICTRA,thermo-calc
Resumo
O presente trabalho teve como objetivo a construção do diagrama TRC ( Transformação sob Resfriamento Contínuo) para o início da formação de sigma do aço inoxidável dúplex UNS S31083, aço superdúplex UNS S32750 e o aço hiperdúplex UNS S32707 atráves de simulações computacionais utilizando o software DICTRA®. Com o auxílio do Thermo-Calc® obteve-se o diagrama de equilíbrio para determinar a temperatura de solubilização para uma microestrutura composta por 50% ferrita e 50% austenita, e a composição química das fases. Deste modo, as simulações de cinética de formação da fase sigma via DICTRA® foram realizada para diferentes taxas de resfrimento, variando entre 0,001°C/s e 100°C/s, a partir da temperatura de solubilização anteriormente determinada. Foram desenvolvida três metodologias diferentes para a obtenção de curvas TRC. A primeira metodologia consiste em um resfriamento direto sem a presença do nitrogênio no sistema, o que causou grande retrocesso da austenita principalmente para os aços superdúplex e hiperdúplex. Por isso, a metodologia de 2 estágios foi desenvolvida. Esta metodologia consiste na divisão do resfriamento, onde a primeira etapa contém a presença do nitrogênio e acontece até a temperatura do inicio da formação da fase sigma apresentada no diagrama de equilíbrio, e a segunda etapa ocorre sem a presença do nitrogênio. Para o superdúplex esta metodologia funcionou a contento, contudo o método não foi aplicável para o aço hiperdúplex, sendo assim foi desenvolvida a metodologia de 2 estágios modificada, que tem praticamente o mesmo método da anterior, porém a temperatura da segunda etapa é aquela em que realmente se inicia a formação da fase sigma durante o resfriamento, e para determiná-la foi preciso utilizar uma pré-simulação. Esta metodologia foi eficaz e eliminou o problema do retrocesso da austenita. O diagrama TRC obteve a máxima cinética de formação na temperatura de 850°C para o aço dúplex, 900°C para o superdúplex e 950°C para o hiperdúplex valores equivalentes aos encontrados na literatura. Ao introduzir dados da literatura dos aços inoxidáveis dúplex no DICTRA®, e desenvolver curvas TRC e compará-las com as originais obteve-se resultados satisfatórios. Pode-se portanto afirmar que o DICTRA® mostrou capacitade de aplicar a metodologia de 2 estágios modificada de determinação de curvas TRC para variados sistemas.
The present work had as objective the construction of CCT (Continuous Cooling Transformation) diagrams for the beginning of sigma formation of the UNS S31083 duplex stainless steel, UNS S32750 super duplex steel, and UNS S32707 hyper duplex through computer simulations using DICTRA® software. With the aid of Thermo-Calc®, the equilibrium diagram was obtained to determine solution-treatment temperature for a microstructure composed of 50% ferrite and 50% austenite, and the chemical composition of the phases. Thus, simulations of kinetic formation of sigma phase DICTRA® were performed for different cooling rates, varying between 0.001°C/s and 100°C/s, based on the previously determined solubilization temperature. Three different methodologies were developed to obtain CCT curves. The first methodology consists of direct cooling without nitrogen in the system, which caused great retrocess of austenite, mainly for super duplex and hyper duplex steels. Therefore, the 2-stage methodology was developed. This methodology consists in the cooling division, where the first stage contains the presence of nitrogen and happens until the temperature of the beginning of the formation of the sigma phase presented in the equilibrium diagram, and the second stage occurs without the presence of nitrogen. For super duplex this methodology results in good agreement to the phenomena simulated, however, the method was not applicable for hyper duplex steel. A modified 2 stage methodology was developed, which has practically the same method as the previous one, however, the temperature of the second stage is the one that really represents the formation of the sigma phase during cooling, and to determine it is necessary to make a pre-simulation. This methodology was effective and eliminated the problem of austenite retrocess. CCT diagrams obtained the maximum formation kinetics at a temperature of 850°C for the duplex steel, 900°C for the super duplex, and 950°C for the hyper duplex, values in agreement to those found in the literature. By introducing data from the literature for duplex stainless steels in DICTRA®, developing CCT curves, and comparing them with the original ones, satisfactory results were obtained. Also, DICTRA® showed the ability to apply the modified 2-stage methodology to various duplex systems.
The present work had as objective the construction of CCT (Continuous Cooling Transformation) diagrams for the beginning of sigma formation of the UNS S31083 duplex stainless steel, UNS S32750 super duplex steel, and UNS S32707 hyper duplex through computer simulations using DICTRA® software. With the aid of Thermo-Calc®, the equilibrium diagram was obtained to determine solution-treatment temperature for a microstructure composed of 50% ferrite and 50% austenite, and the chemical composition of the phases. Thus, simulations of kinetic formation of sigma phase DICTRA® were performed for different cooling rates, varying between 0.001°C/s and 100°C/s, based on the previously determined solubilization temperature. Three different methodologies were developed to obtain CCT curves. The first methodology consists of direct cooling without nitrogen in the system, which caused great retrocess of austenite, mainly for super duplex and hyper duplex steels. Therefore, the 2-stage methodology was developed. This methodology consists in the cooling division, where the first stage contains the presence of nitrogen and happens until the temperature of the beginning of the formation of the sigma phase presented in the equilibrium diagram, and the second stage occurs without the presence of nitrogen. For super duplex this methodology results in good agreement to the phenomena simulated, however, the method was not applicable for hyper duplex steel. A modified 2 stage methodology was developed, which has practically the same method as the previous one, however, the temperature of the second stage is the one that really represents the formation of the sigma phase during cooling, and to determine it is necessary to make a pre-simulation. This methodology was effective and eliminated the problem of austenite retrocess. CCT diagrams obtained the maximum formation kinetics at a temperature of 850°C for the duplex steel, 900°C for the super duplex, and 950°C for the hyper duplex, values in agreement to those found in the literature. By introducing data from the literature for duplex stainless steels in DICTRA®, developing CCT curves, and comparing them with the original ones, satisfactory results were obtained. Also, DICTRA® showed the ability to apply the modified 2-stage methodology to various duplex systems.