Influence of Antimony on the Oxidation Characteristics of 65Mn Steel

This study systematically investigates the dual effects of Sb on the oxidation behavior of 65Mn steel, combining laboratory experiments with industrial-scale validation. Key findings demonstrate that Sb additions significantly suppress both continuous and isothermal oxidation, with 0.03 wt% Sb reducing mass gain by 15.9% (continuous oxidation) and achieving maximal suppression of 85.2% at 800°C (isothermal oxidation), while increasing the oxidation activation energy from 184.0 kJ·mol-1 (Sb-free) to 200.7 kJ·mol-1. Notably, Sb nearly eliminates IGO at the "nose temperature" of 777.6°C, where IGO depth peaks at 18.5 μm in Sb-free specimens. However, excessive Sb (0.21 wt%) induces hot shortness due to grain boundary segregation of low-melting-point Sb-rich phases (Fe-ε(FeSb) eutectic phase), causing edge cracking during hot rolling, where industrial trials reveal local Sb enrichment exceeding 26–29 wt% at crack sites (>120× bulk content). Incomplete descaling coverage‌ at edge regions ("descaling shadow zones") combined with localized ‌undercooling‌ (ΔT ≈ 120°C) promotes Sb enrichment beyond its solid solubility limit, which elucidates why Sb-induced cracking occurs exclusively at strip edges. Mechanistically, Sb enrichment at oxide/substrate interfaces blocks Fe2-/O2- diffusion, while its volatility prevents stable oxide formation, creating a kinetic barrier. The study identifies an optimal Sb content of 0.03 wt% that balances oxidation inhibition (IGO suppression >90%) with hot shortness.