Numerical Prediction of Shrinkage Cavity Location at the Tail End of Ф800 mm Large Section Round Billets During Continuous Casting With Different Submerged Entry Nozzle Port Structures

A three‐dimensional coupled model was developed to simulate flow, heat transfer, and solidification during the tail‐end stage of Φ800 mm round billet casting with a five‐port submerged entry nozzle (SEN). The computed temperature profiles agree well with in‐plant infrared measurements. Comparative analysis of single‐port, four‐port, and five‐port structures shows that multi‐port SEN designs enhance vortical flow and recirculation. The five‐port structures lower peak surface velocity from 0.036 m·s ⁻¹ (four‐port) to 0.028 m·s ⁻¹ , reducing jet impingement. Based on a modified Niyama criterion, predicted shrinkage cavity lengths are 4.2 m (single‐port), 3.4 m (four‐port), and 3.8 m (five‐port), with initial widths of 1 mm that later increase to 3, 5, and 4 mm, respectively. The five‐port design shortens the cavity by 0.4 m relative to the single‐port case, balancing flow uniformity and defect control. The simulated cavity length (3.8 m) matches industrial trial data. This work confirms that the optimized five‐port structures can significantly reduce the defective tail length, improving the metal yield and providing a reliable solution for quality‐efficient production of large‐section round billets.