应变强化对S30408奥氏体不锈钢低温冲击性能的影响

Effects of Strain-strengthening on Impact Property of S30408 Austenitic Stainless Steel at Cryogenic Temperature

室温应变强化技术可大幅提高奥氏体不锈钢的屈服强度,显著减薄容器壁厚,已广泛应用于奥氏体不锈钢深冷容器制造。采用金相显微镜、X射线衍射仪(XRD)、透射电子显微镜(TEM)和摆锤式冲击试验机研究应变强化对S30408奥氏体不锈钢低温冲击性能的影响。结果表明:材料在应变强化过程中发生应变诱发相变,相变产物为α'和ε马氏体,深冷低温对应变强化材料的相组成和含量影响不大。随着应变量的增加和温度的降低,材料冲击吸收能量KV2降低,其中裂纹扩展能EP基本不变,裂纹形成能Ei显示与总冲击吸收能量相似的变化趋势。当温度低于77 K,冲击吸收能量下降趋于平缓,呈现出"平台"现象,且应变强化对材料低温冲击性能的影响要大于温度对其的影响。即使经过15%应变量,材料仍表现出较好的低温冲击韧性。

The yield strength of austenitic stainless steel could be increased by strain-strengthening at room temperature. Stain-stretching technique can reduce the wall thickness of ,Tessel, and has been widely used in austenitic stainless steel cryogenic vessel. The effect of strain-strengthening on impact property of S30408 austenitic stainless steel was investigated by using optical microscopy, X-ray diffraction,transmission electron microscope and pendulum impact testing machine. The results show that α＇ - and ε- martensite phase were strain-induced during the strain-strengthening. The effect of microstructure and volume percent of phase on materials after stain-stretching was small. The impact absorbed energy （ KV= ） decreased with increasing deformation and temperature drop. The crack propagation energy Ep is almost unchanged,but its crack initiation energy Ei showed a similar trend with the total KV2. When the temperature was lower than 77 K,the decreasing of impact absorbed energy tended to be smooth, and showed a ＂platform＂ phenomenon. The effect of strain strengthening on cryogenic impact property of materials is greater than the effect of cryogenic temperature. Even after strained 15% ,the material was still showing a greater low temperature impact toughness.