저온 템퍼링을 이용한 1.2 GPa급 페라이트계 경량철강 개발

• Published in: 대한금속·재료학회지, 59(10) Vol. 59; no. 10; pp. 683 - 691
• Main Authors: 배효주, Hyo Ju Bae, 고광규, Kwang Kyu Ko, 박형석, Hyoung Seok Park, 정재석, Jae Seok Jeong, 김정기, Jung Gi Kim, 성효경, Hyokyung Sung, 설재복, Jae Bok Seol
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.10.2021; 대한금속·재료학회
• Subjects: dislocation movement; ferrite-based lightweight steels; size-dependent partitioning; tempering; 재료공학
• ISSN: 1738-8228; 2288-8241

Previously reported low-Mn ferritic-based lightweight steels are potential candidates for industrial applications, however, they typically exhibit lower strength, with < 1 GPa and lower strength-ductility balance, than medium- and high-Mn austenitic lightweight steels. Herein, we introduce a low-temperature tempering-induced partitioning (LTP) treatment that avoids the strength-ductility dilemma of low-Mn ferritic-based steels. When the LTP process was performed at 330 ℃ for 665 s, the strength of typical ferritic base Fe-2.8Mn5.7Al0.3C (wt%) steel with heterogeneously sized metastable austenite grains embedded in a ferrite matrix, exceeded 1.1 GPa. Notably, the increased strength-ductility balance of the LTP-processed ferritic steel was comparable to that of the high-Mn based austenitic lightweight steel series. Using microscale to nearatomic scale characterization we found that the simultaneous improvement in strength and total elongation could be attributed to size-dependent dislocation movement, and controlled deformation-induced martensitic transformation. (Received May 14 2021; Accepted July 5, 2021)