Influence of TiO₂ on Intragranular Acicular Ferrite Nucleation in Low-Carbon Steel

Oxide metallurgy technology uses inclusion to induce Intragranular acicular ferrite (IAF). The purpose is to refine the steel’s organization and improve its strength. However, the mechanism that inclusion induces IAF nucleation is still unclear. To solve this problem, we added TiO₂ into the low-carbon steel to investigate the ferrite nucleation mechanism induced by Ti inclusions by SEM, TEM, and EPMA. The results show that TiO₂ was added to the molten steel to form composite inclusions TiN–MnS–3MnO·Al₂O₃·3SiO₂–Ti₃O₅ by temperature control. These inclusions are effective in inducing IAF nucleation. It is consistent with the depletion zone mechanism and low mismatch degree mechanism. It is attributed to MnS inclusions in the composite inclusions and Mn elements in the solute poverty zone. The mismatch strain between TiN–MnS–3MnO·Al₂O₃·3SiO₂–Ti₃O₅ and IAF is less than 6%. The in-depth study of the mechanism of induced IAF nucleation by containing Ti inclusions is conducive to promoting the progress of oxide metallurgy technology.