While extensive research has focused on the agglomeration of AlO inclusions in low‐carbon, Al‐killed steels, the behavior of non‐AlO inclusions in Si‐ and Si/Mn‐killed steels remains poorly understood—despite their widespread industrial use and importance for steel cleanliness. This study investigates the in situ agglomeration of semisolid Al–silicate inclusions in Si‐killed steel using high‐temperature confocal scanning laser microscopy. Particle velocity, acceleration, and attractive forces at the steel/argon interface were measured directly. A modified capillary interaction model, based on the Kralchevsky–Paunov framework, was applied to calculate interparticle forces and showed good agreement with experimental results. Compared to AlO inclusions in Al‐killed steel, Al–silicate inclusions exhibited significantly weaker attractive forces (10 to 10 N) and a shorter interaction range (∼34 µm), indicating a lower tendency to agglomerate. These findings highlight key differences in inclusion behavior between steel types and confirm the model's applicability to semisolid systems.

This study investigates the growth and evolution of SiO₂-based inclusions in Si-killed steel under stagnant conditions and varying oxygen levels. Deoxidation experiments were conducted in a high-temperature furnace using commercial FeSi, with systematic variations in holding time and total oxygen content. Automated SEM–EDS analysis was employed to quantify inclusion size, number density, and chemical composition. Under stagnant conditions, SiO₂ inclusions were observed to grow and coarsen in the absence of melt agitation, following a t^1/3 scaling law. In high-oxygen melts, rapid inclusion growth was dominated by Stokes collision mechanisms, resulting in the formation of inclusions in the size range of 1–5 μm, which were subsequently removed by flotation. In contrast, low-oxygen melts exhibited slower growth kinetics governed primarily by Brownian motion and Ostwald ripening, producing smaller inclusions with characteristic sizes of 1–2 μm. These results demonstrate that the initial oxygen content plays a decisive role in controlling the dominant growth mechanisms and the extent of inclusion coarsening in non-agitated steel.