Effect of Ti and O Content on the Evolution of Inclusions in Mg‐Ti Treated Marine Steel During Homogeneous Heat Treatment

Mg‐Ti treatment is a new technique in oxide metallurgy. It increases the number density and refines the size of oxide inclusions, which leads to further refinement of the matrix structure and enhances low‐temperature impact toughness. This article investigates the influence of Ti and O content on the evolution of inclusions in Mg‐Ti treated marine steel during homogeneous heat treatment, employing a combined approach of experiments and theoretical calculations. The results show that increasing the Ti content significantly alters the composition and number density of inclusions. Specifically, the inclusion composition shifts toward Ti 3 O 5 in the MgO‐Ti 3 O 5 ‐Al 2 O 3 system, and the inclusion number density increases. Oxygen content is a key factor governing the generation and transformation of Ti‐Mg‐O inclusions. Thermodynamic analysis reveals that this transformation requires a minimum dissolved oxygen content of approximately 14.4 ppm. Consequently, when the oxygen content decreases from 22 to 8 ppm, falling below this critical threshold, the transformation reaction ceases. Two distinct inclusion transformation mechanisms are identified. The first is the modification of existing high‐MgO inclusions, a process controlled by the diffusion of Ti within the inclusions. The second is the formation of new Ti‐Mg‐O inclusions, governed by the diffusion of Mg in the austenitic matrix.