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Vol.63, No.2, 143 ~ 152, 2025
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| Title |
| Precipitation Behavior and Mechanical Properties of High-Nitrogen Austenitic Stainless Steel According to Chemical Composition and Heat Treatment Temperature |
| 권기환 Ki-hwan Kwon , 김성훈 Seong Hoon Kim , 조효행 Hyo-haeng Jo , 이진종 Jinjong Lee , 하헌영 Heon-young Ha , 이창훈 Chang-hoon Lee , 정재석 Jae-suk Jeong , 이태호 Tae-ho Lee , 강남현 Nam Hyun Kang |
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| Abstract |
| The precipitation behavior and mechanical properties of high-nitrogen austenitic stainless steels were investigated for various chemical compositions and solution treatment temperatures. For this study, Fe- 22.1Cr-12.2Ni-5.1Mn-2.1Mo alloys with three different sets of Nb, V, and N contents were prepared, and two distinct solution treatment temperatures were applied. An increase in Nb or N content resulted in finer austenite grain size, attributed to the formation of additional precipitates, such as Z-phase and (Nb,V)(C,N), at the grain boundaries. Notably, the effect of a 0.07 wt% increase in Nb content was found to be comparable to more than a 100℃ reduction in solution treatment temperature. The yield strength was observed to increase with decreasing grain size, consistent with the Hall-Petch relationship. When the grain size effect was excluded, and in the absence of Z-phase, a higher N content led to an increase in strength due to solid solution strengthening. On the other hand, an increase in Nb content resulted in reduced strength, even though there was little change in the austenite N content. Thermodynamic analysis suggested that Z-phase precipitation may replace MX particles, which could account for the observed decrease in strength. While Zphase precipitation promotes a finer grain size, coarse Z-phase particles did not contribute effectively to precipitation hardening. Therefore, to achieve higher strength in high-nitrogen austenitic stainless steels, alloy design must be optimized, particularly when Nb addition is considered.
(Received 10 October, 2024; Accepted 12 December, 2024) |
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| Key Words |
| High nitrogen austenitic steel, Precipitation, Tensile properties, Niobium, Z-phase |
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