40Cr10Si2Mo钢的热变形模型及动态再结晶行为

 为了优化马氏体耐热钢40Cr10Si2Mo的热轧生产工艺参数,建立线棒材轧制数字化设计及智能化系统数据库,在Gleeble-3500热模拟机上对马氏体耐热钢40Cr10Si2Mo进行单道次热压缩试验,研究了该钢在温度为900~1 100 ℃、应变速率为0.1~20 s-1条件下的应变补偿本构方程及动态再结晶行为,为探索塑性变形行为和组织优化提供理论依据。结果表明,应力随变形温度的升高而减小,随应变速率的增加而增加。温度和应变速率对热变形抗力(真应力)的影响主要取决于在塑性变形过程中,金属内部发生的加工硬化与动态回复、再结晶等软化机制交互作用的结果。建立了双曲正弦(Arrhenius)本构模型。对比发现所建立的本构模型预测值与试验值相关系数R2为0.983 97,平均相对误差(AARE)为4.531%。采用对σ-ε曲线进行4次多项式拟合并求导的方法,分析了40Cr10Si2Mo钢的软化过程以及不同温度和应变速率下动态再结晶的临界条件。阐述了动态再结晶的临界条件与lnZ(Zener-Hollomon参数)值的关系。发现40Cr10Si2Mo钢在lnZ值小于63时,动态再结晶的临界应变随lnZ值的增大而增大。在lnZ值大于63时,动态再结晶的临界应变随lnZ值的增大变化不明显。对比了40Cr10Si2Mo钢的微观组织,发现在1 100 ℃/0.1 s-1条件下晶粒发生了相互吞食合并,部分再结晶晶粒没有长大,最终导致混晶组织出现。然而增加应变速率有助于动态再结晶晶粒的细化。

Hot deformation model and dynamic recrystallization behavior of 40Cr10Si2Mo steel

In order to optimize the hot-rolling production process parameters of the martensitic heat-resistant steel 40Cr10Si2Mo and establish digital design and intelligent system database for wire and bar rolling, the constitutive equation of the strain compensation and the dynamic recrystallization behavior of martensitic heat resistant steel 40Cr10Si2Mo at temperatures ranging from 900 to 1 100 ℃ and stain rates from 0.1 to 20 s-1were studied by single-pass compression tests carried out on Gleeble-3500 thermo-mechanical simulator,which can provide theoretical basis for the plastic deformation behavior and optimizing microstructure of 40Cr10Si2Mo steel. The results show that the stress decreases with the increase of deformation temperature and increases with the increase of strain rate. The effect of temperature and strain rate on thermal deformation resistance (true stress) is mainly determined by the interaction of work hardening, dynamic recovery, recrystallization and other softening mechanisms that occur inside the metal during the plastic deformation process. A constitutive model of Arrhenius was established. The correlation (R2) and the average relative error (AARE) are 0.983 97 and 4.531% respectively between the predicted value of the proposed model and the experimental results. The method of fourth order polynomial fitting and derivation to the σ-ε curves were used to analyse the softening process of 40Cr10Si2Mo steel and the critical conditions of dynamic recrystallization at different deformation conditions. The relationship between the critical condition of dynamic recrystallization and the value of lnZ (Zener-Hollomon parameter) was described. When the lnZ value was less than 63,the critical strain of dynamic recrystallization increased with the increase of the lnZ value. When the lnZ value was greater than 63,the critical strain of dynamic recrystallization did not change significantly with the increase of the lnZ value. Through comparing the microstructure of 40Cr10Si2Mo steel,it was found that the grains swallowed each other and merged, and some of the recrystallized grains did not grow up under the conditions of 1 100 ℃/0.1 s-1,which eventually led to the appearance of mixed crystal structure. However,increasing the strain rate was beneficial to refine the dynamic recrystallization grains.