应力状态对316LN钢高温塑性的影响

Influence of Stress State on Plasticity of 316LN Steel at Elevated Temperature

对316LN钢在Gleeble-1500D热模拟实验机上做高温拉伸实验,试样尺寸为○/10.0 mm×121.5 mm,缺口半径分别为0.5、1.0、2.0、4.0 mm和∞(光滑试样),温度为950℃!1200℃,应变速率为0.5 s-1,得到不同变形条件下试样的断面收缩率变化规律;通过数值模拟,得到开始拉伸时不同缺口拉伸试样最小横截面部位的应力三轴度分布.对比实验与数值模拟结果表明:316LN钢的高温塑性与应力三轴度和晶粒尺寸有关.如果晶粒尺寸相差不明显,应力三轴度起主导作用,应力三轴度越小,断面收缩率越大,塑性越好;如果晶粒尺寸相差明显,晶粒尺寸起主导作用,应力三轴度越小,断面收缩率越小,塑性越差.

The tensile experiments at elevated were carried out on Gleeble-1500D thermo-mechanical simulator for 316LN steel. The notched radius of specimens with the dimensions of Ф 10.0 mm x 121.5 mm were 0.5, 1.0, 2.0, 4.0 mm and ∞ （ smooth specimen）. The temperature was 950℃ - 1200 ℃ and strain rate was 0.5 s-1. The variation law of area reduction of specimens was obtained under different deformation conditions. The distribution of stress triaxiality in minimum cross section was obtained by numerical simulation when specimens were started to tension. The experiments were compared with numerical simulation results. Results show that： the plasticity of 316LN steel at elevated temperature depends on not only stress triaxiality, but also grain size. If the difference of grain size is not obvious, the stress triaxiality plays a leading role. The smaller the stress triaxiality, the bigger the area reduction, and the better the plasticity. If the difference of grain size is obvious, the grain size plays a leading role. The smaller the stress triaxiality, the smaller the area reduction, and the lower the plasticity.