Dependency of Flow Pattern in the Mold on the Distribution of Inclusions Along the Thickness of Continuous Casting Slabs

In the current study, the transition of the flow pattern in a 1000 mm × 237 mm continuous casting mold with the injected argon gas was measured using nail boards and the effect of flow pattern on the distribution of non-metallic inclusions along slab thickness was analyzed using an automatic SEM. The flow pattern in the mold transformed from double roll to complex flow and single roll as the argon flow rate increased from 16 to 20 and 30 NL/min. The surface level fluctuation increased with the increasing argon flow rate. The gas flow rate for the mold with the current dimension and a 1.7 m/min casting speed should be less than 16 NL/min to achieve a double roll flow pattern in the mold. Along slab thickness, there were accumulation bands both at the loose side and the fixed side when the flow in the mold was a double roll flow pattern. Only one accumulation band of inclusions near the fixed side was observed when the flow was a single roll in the mold, while inclusions were uniform along the thickness of the slab when the flow was a complex flow in the mold. As the argon flow rate increased from 8 to 20 and 30 NL/min, the number density of 5 μm inclusions gradually decreased along the thickness of the slab. In addition, the area of exposed eyes at the flux layer of the mold and the probability of slag entrainment increased with the increasing of argon flow rate.