Analysis of TiN precipitation during solidification of Ti-containing micro-alloy steel
CHEN Bo-tao1, ZHANG Ze-feng2, XING Li-dong2, WANG Min2, ZENG Fan-zheng1, BAO Yan-ping2
1. Quality Department Xiangtan Iron and Steel Co., Ltd., Hunan Valin, Xiangtan 411101, Hunan, China; 2. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083,China
Abstract：Effects of separation crystallization on the precipitation of TiN inclusions during the solidification process of low carbon Titanium micro-alloy steel were studied from the aspects of thermodynamics and kinetics respectively. Thermodynamic analysis showed that TiN could not precipitate out above liquidus temperature. Due to the enrichment of TiN in the solidification front during the solidification process, when the solidification fraction reaches 0.377, TiN begins to precipitate out from the solid phase in the solidification front. At the end of solidification, the enrichment degree of Ti and N further increases, and TiN is precipitated in both solid and liquid phases. The dynamic analysis showed that the size of TiN inclusion during solidification increased significantly with the decrease of cooling rate, When the cooling rate was higher than 50 K/s, the theoretical radius of TiN was 5.5 μm. when the cooling rate was lower than 5 K/s, the theoretical radius of TiN was above 17.5 μm. TiN precipitation in solid phase is nano-level. TiN precipitates mainly ranged from 1 to 5 μm in the billet, and large size inclusions mainly precipitated at 1/4 and center of the billet, indicating that large size inclusions were precipitated during solidification.
2021, Vol. 40 
