Model and Analysis of Solute Microsegregation in Bainite Rail Steel During Continuous Casting Process
GAO Xinliang1, BA Wenyue1, ZHANG Zheng1, XI Shiping2, XU Dong3, YANG Zhinan1(), ZHANG Fucheng4
1 National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, China 2 Luoyang Bearing Research Institute Co. Ltd., Luoyang 471039, China 3 Technology Innovation Center for High Quality Cold Heading Steel of Hebei Province, Hebei University of Engineering, Handan 056038, China 4 College of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063210, China
Cite this article:
GAO Xinliang, BA Wenyue, ZHANG Zheng, XI Shiping, XU Dong, YANG Zhinan, ZHANG Fucheng. Model and Analysis of Solute Microsegregation in Bainite Rail Steel During Continuous Casting Process. Acta Metall Sin, 2024, 60(7): 990-1000.
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.
Fund: National Key Research and Development Program of China(2021YFB3703500);National Natural Science Foundation of China(52122410);National Natural Science Foundation of China(51604241)
Corresponding Authors:
YANG Zhinan, professor, Tel: 15033513870, E-mail: zhinanyang@ysu.edu.cn
Table 1 Equilibrium partition coefficients, diffusion coefficients, and slopes of liquidus of elements[26]
Fig.1 Comparisons between calculated and measured[30,31] results for P (a) and Mn (b) segregations (fS—solid fraction, CR—cooling rate, RMSE—root mean square error)
Fig.2 Comparisons between calculated and measured[32-35] results for zero strength temperature (ZST) (a) and zero ductility temperature (ZDT) (b)
Fig.3 Changes of solid-liquid interface temperature (a) and segregation degree of solute elements (b) during solidification (Inset in Fig.3b shows the locally enlared curves)
Fig.4 Effects of C content on the microsegregation degree of C and Si (a), Mn and Cr (b), Ni and Mo (c), P and S (d) at different fS
Fig.5 Effects of Mn content on the microsegregation degree of C and P (a), Mn and Cr (b), Ni and Mo (c), Si and S (d) at different fS
Fig.6 Effects of S content on the microsegregation degree of C and P (a), Mn and Cr (b), Ni and Mo (c), Si and S (d) at different fS
Fig.7 Effects of P content on the microsegregation degree of C and P (a), Mn and Cr (b), Ni and Mo (c), Si and S (d) at different fS
Fig.8 Effects of cooling rate on the microsegregation degree of C and Si (a), Mn and Cr (b), Ni and Mo (c), P and S (d) at different fS
Fig.9 Effects of C content (a), Mn content (b), S content (c), P content (d), and cooling rate (e) on solidification characteristic temperatures
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