不锈钢棒材应变不均匀对两相微观结构演变的影响

The effect of uneven strain on the evolution of two phase microstructure for stainless steel bar

双相不锈钢热轧制备过程中应力应变分配不均,导致奥氏体相和铁素体相软化、相变竞争激烈,组织结构演变和性能调控复杂。以热轧2209双相不锈钢棒材为研究对象,采用有限元仿真技术对Φ43 mm棒材6道次热连轧过程进行三维热力耦合模拟,结果表明,棒材横截面上特征区域的应变与温度变化分布极不均匀;中心金属温度最高且塑性应变最大。对棒材不同特征区域的微观分析表明,在棒材表面和内部,两相体积占比不均匀且晶粒动态再结晶不协调,棒材表面δ→γ相变占据主导;然而在棒材内部区域,在高温高应变速率工况下,发生γ→δ逆相变。因此通过控制轧制工艺改善不锈钢两相协调变形行为,从而全面提升棒材力学性能。

The distribution of stress and strain is uneven during the rolling preparation of double-phase stainless steel,resulting in the intense competition of two-phase softening and phase change.This uneven phenomenon further produces the complex tissue structure evolution and performance regulation.In this paper taking the hot rolled 2209 double-phase stainless steel bar as the research object,a three-dimensional thermo-mechanical coupling process of Φ43 mm bar was simulated through the finite element.The results show that the strain and temperature distribution in the characteristic region of the bar are very uneven.Both the temperature and the plastic strain in the center of bar possess the greatest value.The microscopic analysis from the different feature areas show that the volume ratio of the two phases and the dynamic recrystallization are uneven in the surface and interior of the bar,where the main phase transition is δ→γ.However,in the internal area of the rod,the γ→δ reverse phase transition occurs under the high temperature and high strain rate.Therefore,by controlling the rolling process could improve the coordinated deformation behavior of the two phases,and comprehensively improve the mechanical properties of the bar.