AUSTENITE SOFTENING IN THE FINISHING STAGE OF T.M.C.P. OF
HIGH NIOBIUM-LOW MANGANESE MICROALLOYED STEELS

Antonio Augusto Gorni; José Herbert Dolabela da Silveira; Kenji Camey; Emanuelle Garcia Reis

doi:10.4322/2176-1523.20202242

Original Article

AUSTENITE SOFTENING IN THE FINISHING STAGE OF T.M.C.P. OF HIGH NIOBIUM-LOW MANGANESE MICROALLOYED STEELS

AMACIAMENTO DA AUSTENITA DURANTE A FASE DE ACABAMENTO DO PROCESSAMENTO TERMOMECÂNICO DE AÇOS MICROLIGADOS COM ALTO NIÓBIO E BAIXO MANGANÊS

Antonio Augusto Gorni, José Herbert Dolabela da Silveira, Kenji Camey, Emanuelle Garcia Reis

http://dx.doi.org/10.4322/2176-1523.20202242 Tecnol. Metal. Mater. Min., vol.17, n2, p.112-117, 2020

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Abstract

Recently several studies have been developed on the use of microalloyed steels with low Mn content (below 1%) in the controlled rolling of heavy plates for the manufacture of pipes. However, lower Mn contents should lead to the acceleration of NbCN precipitation kinetics during rolling, reducing the soluble Nb content in austenite. This fact, plus the heavy and fast passes applied under virtually isothermal conditions in a heavy plate rolling mill, increases the risk of partial recrystallization during the finishing stage of the controlled rolling, since strain hardening of austenite becomes significant and the interaction between precipitation and recrystallization is increasingly delayed. The objective of this study was to analyze the evolution of mean flow stress during the finishing stage of controlled rolling in these low Mn, high Nb microalloyed steels to better understand the metallurgical mechanisms acting during this process.

Keywords

Controlled Rolling; Low Mn high Nb microalloyed steels; Austenite recrystallization; NbCN precipitation.

Resumo

Recentemente foram desenvolvidos estudos sobre o uso de aços microligados com baixo teor de Mn (abaixo de 1%) na laminação controlada de chapas grossas para a manufatura de tubos de grande diâmetro. Contudo, menores teores de Mn podem levar à aceleração da precipitação de NbCN durante a laminação, levando a uma redução no teor de Nb solúvel presente na austenita. Este fato, mais os rápidos e pesados passes aplicados sob condições virtualmente isotérmicas num laminador de chapas grossas, aumentam o risco de recristalização durante a fase de acabamento da laminação controlada, já que o encruamento da austenita se torna significativo e a interação entre precipitação e recristalização é cada vez mais atrasada. O objetivo desse estudo consistiu em analisar a evolução da resistência média à deformação durante a fase de acabamento da laminação controlada nestes aços com baixo Mn e alto Nb para se entender melhor os mecanismos metalúrgicos que atuam durante esse processo.

Palavras-chave

Laminação controlada; Aços microligados com baixo Mn e alto Nb; Recristalização da austenita; Precipitação de NbCN.

References

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Submitted date:
11/15/2019

Accepted date:
12/08/2019