Effect of Rare‐Earth Cerium on Inclusion Evolution in 25Mn‐0.45C‐0.3Al Ultra‐High‐Manganese Steel

This work focuses on 25Mn‐0.45C‐0.3Al ultra‐high‐manganese steel, aiming to reveal the evolution behavior of inclusions and the regulatory mechanism of cerium (Ce) via systematic experiments and thermodynamic calculations. Results indicate that the original inclusions in the steel are dominated by Al 2 O 3 , MnS, and Al 2 O 3 ‐MnS composite inclusions. With the increase of Ce addition, liquid inclusions undergo a sequential evolution: Al 2 O 3 → CeAlO 3 /Ce 2 O 3 → Ce 2 O 2 S/Ce 2 O 2 S‐Ce 2 O 3 → Ce 2 O 2 S/Ce 2 O 2 S‐CeS. Ce addition significantly modifies angular, harmful inclusions into thermodynamically stable, near‐spherical rare‐earth–containing inclusions; the inclusion number density decreases from 67.4 to 16.9 mm −2 . The optimal modification effect is attained at a cerium content of ~0.01 wt% and a holding time of no less than 30 min, which enables the comprehensive optimization of inclusions in steel in terms of quantity and morphology.