Ladle bottom-blowing argon refining is essential for removing non-metallic inclusions from molten steel and improving steel cleanliness. However, in actual production, a size-selective issue still exists: inclusions larger than 150 μm can be removed quite effectively, while a portion of fine particles smaller than 50 μm always remains. To investigate this problem, 3D ladle model was built using the VOF-DPM coupled method and a size-grouped capture probability model was implemented. By referring to bubble-particle interaction theory, a scaling law that links the effective attachment factor to particle size was derived and incorporated into Fluent via UDFs. This allowed the capture behavior of six particle groups (50 μm to 300 μm) to be judged differently. The simulation shows that both bubble capture and surface retention control the removal efficiency, but their dominance varies significantly with particle size. For 50 μm particles, the bubble capture rate is 39.0% by theend of the simulation, and the surface capture rate is 44.02%; if the time is extrapolated to 2 h, the overall removal rate would reach 72.93%. For particles ≥200 μm, the removal is mainly attributed to surface retention after flotation, which accounts for over 60% of the removal, and the overall removal rate levels off within the 150 μm–200 μm size range, reaching 82.1% at 200 μm. It was also found that the inability to remain stably at the surface is the main reason why fine particles are difficult to remove: 50 μm particles can only stay at the surface for about 49.3 s on average, while particles ≥150 μm can remain for over 578 s. These results clearly reveal the transition of capture mechanisms with particle size, and they are considered to be of practical reference value for the precise adjustment of the bottom-blowing argon refining process.
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