Effect of solute partition coefficient and TiN precipitation on micro-segregation of 22MnB5 steel
GUO Wei1,2, LONG Mu-jun 1,2, WU Jia-lu1,2, ZHANG Hao-hao1,2, AI Song-yuan1,2, CHEN Deng-fu1,2
1. School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; 2. Chongqing Key Laboratory of Vanadium and Titanium Metallurgy and New Materials, Chongqing University, Chongqing 400044, China
Abstract：In order to improve the micro solute segregation in solidification process the accuracy of the model calculation, based on the solute distribution coefficient and the inclusion of the important influence to the solute segregation, this study quantitatively analyses the solute distribution coefficient and separation effect on solidification process of solute elements content of TiN, provide theoretical reference for the research on high strength steel solidification process of micro alloy. A solute microsegregation model coupled with TiN precipitation thermodynamic model was established for 22MnB5 steel, and the effects of temperature and solidification path on solute distribution coefficient were investigated. The results show that the phase transition has greater effects on kTi (titanium distribution coefficient) and kN (nitrogen distribution coefficient) than the temperature. When the solid phase ratio is 0.74, the phase transition from L+δ to L+γ occurs, kTi decreases from 0.26 to 0.20, and the degree of titanium segregation increases. kN increased from 0.30 to 0.46, and the degree of nitrogen segregation decreased. When the solid phase ratio fs is 0.43, TiN begins to precipitate. When the effect of TiN precipitation on microstructure segregation is not considered, the mass percent of Ti and N in the liquid phase at the end of solidification is 0.286% and 0.005 6%, respectively. When TiN precipitation is considered, the mass percent of Ti and N in the liquid phase at the end of solidification are 0.237% and 0.001 9%, which decrease by 17.2% and 66.9%, respectively. At the same time, due to the high degree of titanium segregation during solidification, the enrichment of titanium at the solidification front is enough to offset the consumption of TiN precipitation, while the mass percent of initial nitrogen in steel is low, and the trend of nitrogen segregation decreases with the solidification process, and the degree of solute nitrogen segregation is also reduced under the influence of the transformation from L+δ to L+γ phase. So the segregation of solute nitrogen at the solidification front is not enough to offset the consumption of TiN precipitation. Therefore, the mass percent of nitrogen in the liquid phase at the solidification front increases to decrease obviously due to the precipitation of TiN, while the segregation degree of titanium only weakens at the end of solidification.
郭伟, 龙木军, 吴家璐, 张浩浩, 艾松元, 陈登福. 22MnB5钢溶质分配系数及TiN析出对微观偏析的影响[J]. 钢铁, 2022, 57(3): 44-54.
GUO Wei, LONG Mu-jun , WU Jia-lu, ZHANG Hao-hao, AI Song-yuan, CHEN Deng-fu. Effect of solute partition coefficient and TiN precipitation on micro-segregation of 22MnB5 steel[J]. Iron and Steel, 2022, 57(3): 44-54.
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2022, Vol. 57 
