合金元素对20CrMnTi钢凝固组织影响的模拟

 为了改善20CrMnTi小方坯的凝固组织，采用移动边界法先对20CrMnTi钢的温度场进行模拟，在此基础上，采用元胞自动机有限元法（CAFE法）对其凝固组织进行了数值模拟。当模拟结果与实际结果基本吻合时，进一步探讨了硅、铬、锰、钛等合金元素对20CrMnTi钢凝固组织的影响规律。模拟结果表明，在该钢号的合金元素规定范围内，适当减少硅元素的质量分数，能够提高铸坯中心等轴晶比例，使晶粒数目增加，晶粒平均半径减小。适当添加铬元素能够扩大铸坯中心等轴晶区，从而减小晶粒平均半径，增加晶粒数量。增加锰元素质量分数可以提高铸坯的中心等轴晶率。最后根据所得模拟结果对该钢种的合金元素进行调整，达到了扩大铸坯中心等轴晶区和细化晶粒的目的。

Numerical simulation of effects of alloying elements on solidification structure of 20CrMnTi billets

In order to improve the solidification structure of 20CrMnTi billet， a moving boundary method was used to simulate the temperature distribution of 20CrMnTi billets in continuous casting. On this basis， using CAFE （cellular automaton-finite element analysis） approach， the solidification structure of 20CrMnTi billets were studied by numerical simulation. When the simulation results and actual results were in a good agreement， the effects of alloying elements， such as Si， Cr， Mn and Ti， on the solidification structure of 20CrMnTi billets were further discussed. The simulation results show that within the specified range of alloying elements of the 20CrMnTi steel， with the appropriate reduction of Si， the proportion of the billet equiaxed grains in the center increased， and the number of grains increased， hence the average grain radius reduced. Properly increasing the content of Cr could enhance the ratio of equiaxed grains， reduce the average radius of grain and increase the number of grains. The increased content of Mn tended to raise the ratio of equiaxed grains. Finally， based on the simulation results， the alloy element of the 20CrMnTi steel was adjusted to expand the area of equiaxed grain in the billet center and refine the grain size.