Quantitative Investigation on the Evolution of Ti(C_x, N_1−x) in Ultra-high-Strength Steel Slab During TSCR Process: Precipitation and Redissolution

The second phase in the slab has a significant impact on the quality and property of the slab and the final product. It is essential to understand the ‘precipitation–redissolution’ evolution law of the second phase in the TSCR process to regulate it rationally. The ‘precipitation–redissolution’ evolution behavior of Ti(C_x, N_1−x) in slab during TSCR process of ultra-high-strength steel was investigated by simulation experiments, and its effect on austenite grain boundary pinning force and solid solution amount of microalloying elements was analyzed. The results indicate that Ti(C_x, N_1−x) shows ‘precipitation–redissolution–coarsening’ behavior during the TSCR process. Ti(C_x, N_1−x) redissolved 15.96 pct during reheating, and the maximum size of Ti(C_x, N_1−x) particles increased by 6.67 pct during the holding process. Before and after the soaking process, the maximum size of Ti(C_x, N_1−x) particles in TSCR process decreased by 42.34 pct, while it increased by 8.02 pct in the traditional process. The pinning force of Ti(C_x, N_1−x) on austenite grain boundary in TSCR process is always lower than in the traditional process, and it reaches a maximum at the end of continuous casting. The solid solution amount of Ti element in the TSCR slab before rolling is 1.26 times that of the traditional process, providing a significant solid solution advantage. The research results offer theoretical guidance for regulating the product quality and property of ultra-high-strength steel TSCR process.