Precipitação de fase sigma em tubos formadores de espiras manufaturados em aço inoxidável duplex UNS S32750 e sua relação com a formação de canais preferenciais por desgaste
Sigma phase precipitation on laying head pipes made of UNS S32750 duplex stainless steel and its influence on the formation of preferential wear channels
Guilherme Duarte Moreira; Juliana de Fátima Maia; Geraldo Lúcio de Faria
Resumo
Tubos formadores de espiras são componentes essenciais no processo de laminação de fio máquina. Eles são responsáveis por modificar a geometria dos fios de seção longitudinal reta para helicoidal. Como os mesmos trabalham na faixa de temperatura entre 900 °C e 950 °C, eles são fabricados em aços com características muito específicas no que diz respeito à evolução microestrutural e desempenho em desgaste, sendo o aço inoxidável duplex UNS S32750 um destaque atual. Entretanto, na indústria, há constantes relatos de que tubos fabricados a partir deste aço apresentam desempenhos em serviço muito diferentes (grande variabilidade), com alguns tubos sendo substituídos com um tempo de vida útil até 90% menor do que o esperado. Como a literatura a respeito do tema é muito restrita, este trabalho se propôs a avaliar o efeito da precipitação de fase sigma na temperatura de 950 °C e a relação entre a evolução microestrutural a quente do aço UNS S32750 e a formação de canais preferenciais por desgaste nas paredes internas do tubo; estes essenciais para o bom desempenho do componente. Por meio de simulações computacionais e físicas, foi possível mostrar que esta relação existe e que, em função dela, a definição do diâmetro do fio máquina a ser processado nos 10 primeiros minutos de operação do tubo, assim como da velocidade de operação, é fundamental para se garantir que o mesmo tenha um bom desempenho em serviço.
Palavras-chave
Abstract
Laying head pipes are essential components in the wire rod rolling process. They are responsible for transforming wires from a straight longitudinal section to a helical shape. As they operate between 900 °C and 950 °C, these pipes are manufactured using steels with specific characteristics in terms of microstructural evolution and wear performance, with the duplex stainless steel UNS S32750 being a current highlight. However, there have been consistent reports in the industry that pipes made from this steel exhibit highly variable performance in service, with some of them experiencing a lifespan up to 90% shorter than expected. Due to the limited literature on this subject, this study aimed to evaluate the effect of sigma phase precipitation at 950 °C and investigate if there is any relationship between the high-temperature microstructural evolution of UNS S32750 steel and the controlled formation of preferential wear channels on the inner walls of the pipe, crucial for the component’s performance. Applying computational and physical simulations, it was possible to demonstrate that such a relationship exists and that, as a result, defining the wire rod diameter to be processed within the first 10 minutes of pipe operation, as well as the operational speed, is fundamental to ensure its high in service performance
Keywords
Referências
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Submetido em:
21/07/2023
Aceito em:
27/02/2024
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