应变幅对国产锻造奥氏体不锈钢环境疲劳寿命影响的试验研究

Experimental study on the effect of strain amplitude on environmental fatigue life of domestic forging austenitic stainless steel

为验证模拟压水堆核电站冷却剂服役环境对国产锻造主管道用奥氏体不锈钢疲劳寿命的影响,采用高温高压循环水疲劳测试系统对从产品锻件取样加工后的标准试样进行了低周疲劳试验,分析了试验数据与美国机械工程师学会(American Society of Mechanical Engineers,ASME)规范平均/设计疲劳曲线的关系,获得了应变幅对奥氏体不锈钢环境疲劳寿命的影响规律,并初步评价了ASME规范设计疲劳曲线和环境疲劳修正系数的适合性。

Background： Environmental assisted fatigue （EAF） is the important issue in the field of fatigue analysis, assessment and safety regulation of pressurized water reactor nuclear components. Some factors affect fatigue life of materials and related mechanisms. Purpose： The aim is to verify the influence of simulated pressurized water reactor coolant environment on the fatigue life of domestic forging main coolant pipe made of austenitic stainless steel. Methods： Fatigue tests were conducted using high-temperature and high-pressure water fatigue testing system, and standard round-bar fatigue specimen made from product forging. Results： The relationship between test data and American Society of Mechanical Engineers （ASME） code fatigue mean/design curve was analyzed. The effect of strain amplitude on fatigue life of austenitic stainless steel was investigated and the suitability of ASME code fatigue design curve and fatigue life environmental correction factor were preliminarily evaluated. Conclusion： The fatigue life of forged 316LN stainless steel in high-temperature and high-pressure water are lower than those at room temperature in air. The environmental degradation is more obvious under low strain amplitudes than that under high strain amplitudes. The best-fit curve based on the updated Argonne National Laboratory （ANL） model isrecommended for the fatigue design of domestic austenitic stainless steel. The environmental effect should be incorporated into the fatigue design of domestic austenitic stainless steel. The fatigue crack mainly initiated from the surface micro-pits and slip bands for the domestic forged austenitic stainless steel in high-temperature and high-pressure water.