High-strength low-alloy (HSLA) steels show excellent toughness when trace amounts of transition elements are added. In steels, prior austenite grain size (PAGS), which is often determined by the number of added elements, is a critical factor in determining the mechanical properties of the material. In this study, we used two etching methods to measure and compare the PAGS of specimens with bainitic HSLA steels having different Nb contents These two methods were nital etching and picric acid etching. Both methods confirmed that the sample with high Nb content exhibited smaller PAGS than its low Nb counterpart because of Nb’s ability to hinder austenite recrystallization at high temperatures. Although both etching approaches are beneficial to PAGS estimation, the picric acid etching method has the advantage of enabling observation of the interface containing Nb precipitate. By contrast, the nital etching method has the advantage of a very short etching time (5 s) in determining the PAGS, with the picric acid etching method being considerably longer (5 h).

Abstract
1. 서 론
2. 실험 방법
3. 결과 및 고찰
4. 결 론
References

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• 성효경(경상국립대학교 나노신소재융합공학과/경상국립대학교 K-metal) | Hyo Kyung Sung (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU)/Department of Materials Engineering and Convergence Technology, Center for K-metal, Gyeongsang National University (GNU))
• 김정기(경상국립대학교 나노신소재융합공학과/경상국립대학교 K-metal) | Jung Gi Kim (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU)/Department of Materials Engineering and Convergence Technology, Center for K-metal, Gyeongsang National University (GNU))
• 설재복(경상국립대학교 나노신소재융합공학과/경상국립대학교 K-metal) | Jae Bok Seol (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU)/Department of Materials Engineering and Convergence Technology, Center for K-metal, Gyeongsang National University (GNU)) Corresponding Author