为揭示贝氏体轨道钢凝固过程中的溶质再分配规律，本工作综合考虑钢液凝固过程中δ/γ相变和枝晶粗化的影响，建立了贝氏体轨道钢凝固过程中溶质元素微观偏析模型，分析了冷却速率、C含量、Mn含量、S含量、P含量对钢液凝固过程中枝晶间溶质元素微观偏析行为、零强度温度(ZST)和零塑性温度(ZDT)的影响。结果表明，枝晶间S、P元素偏析严重；在不同固相率时，冷却速率对溶质元素微观偏析的影响存在一定差异。C含量主要影响钢的凝固方式，进而影响凝固过程钢中溶质元素的微观偏析行为；Mn、P、S含量对其余溶质元素微观偏析影响不大。C、Mn含量的增加导致ZST和ZDT均降低；随冷却速率、S和P含量增加，ZST变化不大，ZDT明显降低。

With the rapid development of high-speed and heavy-haul railways, the reliability of railway track service performance is becoming increasingly important. Bainite rail steel is widely known for its excellent properties, but solute microsegregation during solidification of molten steel affects the quality of continuous casting bloom, which can damage bainite rail steel components during service. Therefore, studying solute microsegregation of bainite rail steel during the continuous casting process is necessary. Solute microsegregation in steel occurs when solute redistributes between solid and liquid phases during solidification of molten steel. The factors that influence solute microsegregation include the equilibrium distribution coefficient of solute elements at the solid-liquid interface, cooling rate, reverse diffusion strength of solute elements in the solid phase, and dendrite coarsening. Among them, the reverse diffusion strength of solute elements in the solid phase and dendrite coarsening are two important factors that cannot be ignored. In this study, a model of solute microsegregation is established, which takes into consideration both δ/γ phase transformation and dendrite coarsening during the solidification process of bainite rail steel. The effects of cooling rate and C, Mn, S, and P contents on interdendritic solute microsegregation, zero strength temperature (ZST), and zero ductility temperature (ZDT) of steel are analyzed. The results show that S and P are more likely to segregate between dendrites compared to other elements in bainite rail steel. The effect of cooling rate on the microsegregation of solute elements varies with solid fractions. When the solid fraction is 0.99, the segregations of Si, Mn, Cr, Ni, Mo, P, and S increase differently with the increase of cooling rate. C content mainly affects the solidification mode of steel, which then affects the segregation behavior of other elements during solidification. C content has a more significant effect on the microsegregation of S and P compared to other elements in bainite rail steel. In contrast, the contents of Mn, P, and, S have little effect on the microsegregation of other solute elements. The increase in C and Mn contents result in a decrease in ZST and ZDT. However, with an increase in cooling rate and S and P contents, ZST has little change, and ZDT decreases significantly.