Optimization of multi-process parameters in secondary cooling solidification process of S30432 continuous casting billet

• A finite element model of solidification and heat transfer was established for the secondary cooling process of S30432 continuous casting billet, enabling systematic study of process parameters. • Orthogonal experiments revealed the coupling effects of casting speed, superheat, and specific water flow on solidification structure, leading to optimized process parameters. • Production verification showed that coarse niobium compound enrichment causes inner wall cracks during hot piercing, and optimized parameters mitigate Nb segregation and improve grain refinement. • The synergistic decrease of superheat and increase of specific water flow promotes equiaxed crystal zone expansion, improving billet quality and hot workability.