<p>The variation in deformation of oxide inclusions was attributed to their inherent properties, which were intricately linked to their chemical compositions. The current work provided a fundamental study of the evolution and deformation of inclusions with varying compositions. These inclusions were generated through the melting and subsequent hot rolling of steels containing different total aluminum (T.Al) contents. The raw materials, specifically tire-cord steels, demonstrated a heightened sensitivity to the T.Al content. As the T.Al content increased from 7 to 78 ppm, the deoxidation process shifted from Si–Mn deoxidation to Al deoxidation. Simultaneously, the dominant inclusion types within the steel underwent a compositional shift from the CaO–MnO–Al₂O₃–SiO₂ system to the CaO–Al₂O₃ system. Inclusion deformability decreased as the average Al₂O₃ content increased. This composition-dependent deformability was attributed to the rising liquidus temperature and heightened viscosity resulting from an enhanced crystallization ability. The crystallization ability was effectively characterized by the viscosity at the liquidus temperature, denoted as <i>η</i>_m. As the T.Al content increased from 7 to 31 ppm, the average <i>η</i>_m varied from 10.39 to −&#xa0;2.79 ln(Pa·s). Meanwhile, the inclusions predominantly precipitated CaAl₁₂O₁₉ (CA₆) and Al₂O₃ crystals, both exhibiting high Young’s moduli values of 382.23 and 363.12 GPa, respectively. In contrast to the calcium aluminate silicate, the Young’s modulus of SiO₂ increased with rising temperature. This characteristic, coupled with the high liquidus temperature and viscosity, further elucidated the non-deformable behavior of SiO₂ during the hot-rolling process.</p>