大型轧辊Cr5合金钢热压缩过程微观组织演变元胞自动机模拟

Simulation of microstructure evolution of Cr5 alloy steel for large roller during hot compression process using cellular automaton method

为研究大型轧辊Cr5合金钢在热变形时的微观组织演变规律,采用Gleeble-1500D热模拟试验机对Cr5合金钢在变形温度为900～1200℃、应变速率为0.005～5 s-1条件下进行了热压缩实验。基于热压缩实验得到的数据,建立了Cr5钢的动态再结晶元胞自动机（CA）模型,并开发了相应的CA程序。利用该CA程序计算得到的流变应力曲线与实验数据较为吻合,验证了Cr5合金钢动态再结晶CA模型的准确性。通过有限元软件FORGE模拟了Cr5钢的热压缩过程,并将采集到的宏观场量导入所建立的CA程序中,以变形温度为1125℃、应变速率为0.1 s-1为例,采用该CA程序模拟了压缩试样不同变形区域的微观组织演变行为。结果表明,Cr5钢在热压缩过程中产生了明显的变形不均匀性,大变形区发生了完全动态再结晶,平均晶粒尺寸达到30.16μm,自由变形区再结晶百分数达到64%,平均晶粒尺寸为40.24μm,难变形区还未达到再结晶临界应变,仍保有初始组织,仿真结果与实际金相照片吻合。

To study the microstructure evolution law of Cr5 alloy steel for large roller during hot forming process,the hot compression test of Cr5 steel was carried out on Gleeble-1500 D thermal simulation test machine under the temperature of 900-1200 ℃ and strain rate of 0. 005-5 s-1. A dynamic recrystallization cellular automaton（ CA） model for Cr5 steel was established based on the data obtained by thermal compression test,and the corresponding cellular automaton program was developed. The flow stress curves calculated by the CA program were in good agreement with the experimental data,which verified the accuracy of the dynamic recrystallization CA model of Cr5 alloy steel. The thermal compression process of Cr5 steel was simulated by the finite element software FORGE,and the macroscopic field quantities were introduced into the established CA program. Taking the deformation temperature of 1125 ℃ and the strain rate of 0. 1 s-1 as an example,the microstructure evolution behavior of the compression sample in different deformation areas was simulated by the CA program. The results show that Cr5 steel shows obvious deformation inhomogeneity during hot compression process,complete dynamic recrystallization occurs in the large deformation zone with an average grain size of 30. 16 μm,and the recrystallization fraction in free deformation zone reaches 64% with an average grain size of 40. 24 μm,while the hard deformation zone does not reach the critical strain of recrystallization,still retains the initial structure,and the simulation results agree well with the actual metallographic photos.