| Title |
Effects of Nb Content on Grain Growth in High-Nitrogen Austenitic Stainless Steels |
| Authors |
전상명(Sangmyeong Jeon) ; 위영욱(Young Uk Wi) ; 정재석(Jaesuk Jeong) ; 송전영(Jeon Young Song) ; 서동우(Dong-Woo Suh) |
| DOI |
https://doi.org/10.3365/KJMM.2026.64.9.771 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Austenitic stainless steel; Z-phase; Carbonitride; Grain growth; Nb |
| Abstract |
The effects of Nb content on the austenite grain growth behavior of high-nitrogen austenitic stainless steels were investigated during isothermal annealing. Three alloys containing 0.02, 0.11, and 0.30 wt.% Nb designated 2Nb, 11Nb, and 30Nb, respectively were hot-rolled and subsequently isothermally annealed at 1100 °C for 0.5 to 96 h. In the as-hot-rolled condition, few precipitates were observed in 2Nb, whereas 11Nb and 30Nb contained fine spherical MX carbonitrides and Z-phase along with coarse rod-like Z-phase. Extraction residue ICP analysis revealed that most of the added Nb (0.07 of 0.11 wt.% in 11Nb and 0.29 of 0.30 wt.% in 30Nb) had precipitated. During annealing, 2Nb exhibited typical parabolic grain growth, reaching a mean grain size of approximately 300 μm after 96 h. In contrast, grain growth in 11Nb and 30Nb was strongly suppressed, with mean grain sizes remaining at around 50 μm even after 96 h owing to grain-boundary pinning by the fine Nb precipitates. After prolonged annealing, however, a few grains grew remarkably in 11Nb (≥ 48 h) and 30Nb (≥ 96 h), producing long-tailed grain size distributions. This abnormal coarsening was attributed to a local loss of pinning force caused by precipitate coarsening. Notably, the maximum size of these coarsened grains approached the mean grain size of 2Nb under the same annealing conditions, indicating that the locally unpinned regions grew in a manner comparable to the precipitate-free 2Nb alloy. |