Based on the fractal cluster-cluster agglomeration (CCA) model, two-dimensional simulations of cluster aggregation process have beencarried out by varying initial particle number, particle size and sticking probability between clusters. Particle size and amount of seed particleshave small effects on the shape of clusters. Actual alumina clusters observed in tundish show the chain-like appearance and are very similar tothe simulatedagglomerated clusters with highstickingprobability.The agglomeration process of alumina chain-like clusters aroundimmersionnozzle in the tundish and RH process are plausibly controlled by the random collision process with high sticking probabilityvalues. [doi:10.2320/matertrans.MRA2007037](Received February 15, 2007; Accepted May 18, 2007; Published July 19, 2007)Keywords: fractal, fractal dimension, inclusion, chain-like inclusion, deoxidation, cluster-cluster aggregation