<p>Steel slag, rich in CaO, can mineralize with CO₂ to form CaCO₃, offering dual benefits of waste utilization and carbon reduction. The aim of this study was to introduce CO₂ for mineralization reaction during the cooling process of high-temperature ladle furnace (LF) slag, and to investigate the factors affecting CO₂ sequestration in LF slag through direct gas–solid reaction. Mineralized samples were characterized using carbon sulfur analysis, XRD, FT-IR, TGA, and SEM–EDS. The results indicate that the carbon sequestration rates obtained via the mass gain method and carbon content analysis were generally consistent, with a maximum sequestration rate of 2.85% achieved by the mass gain method. Among the influencing factors, CO₂ concentration, slag particle size, atmospheric pressure, and ambient temperature were identified as the primary factors governing carbon sequestration rate. CaCO₃ was detected in the mineralized samples, although its diffraction peaks were relatively weak, likely due to limitations imposed by reactant stability and reaction conditions. The thermal weight loss of mineralized samples was attributed to the decomposition of CaCO₃, and this thermal weight loss exhibited a trend similar to that of carbon sequestration rates. CaCO₃ was observed on the particle surfaces in smooth, angular morphologies, suggesting a possible reaction model for the direct gas–solid mineralization of LF slag. These findings provide both theoretical insights and experimental evidence to support the application of direct gas–solid mineralization of LF slag for CO₂ sequestration.</p> Graphical Abstract <p></p>