热影响区元素晶界偏聚对焊接构件低周疲劳性能的影响

发布时间：2018-02-12 06:32

本文关键词： 低周疲劳焊接构件热影响区晶界偏聚硬度分布　出处：《机械工程学报》2015年14期 　论文类型：期刊论文

【摘要】：对25Cr2Ni2Mo V低压转子钢焊接模拟件进行低周疲劳性能试验,测得焊接接头应变与疲劳寿命关系式,对比分析接头不同区域低周疲劳性能,确定热影响区是接头低周疲劳性能的薄弱环节。进行焊接接头硬度分布测定、疲劳裂纹扩展路径金相分析以及热影响区原奥氏体晶界元素偏聚行为俄歇分析等一系列试验。结果表明,焊接接头热影响区存在大硬度梯度的软硬界面,在疲劳载荷作用下形成应变集中,导致焊接构件低周疲劳性能弱化;在热影响区扩展过程中,疲劳裂纹遇到原奥氏体晶界往往会沿着晶界发生偏折,并在晶界上形成一定程度的割裂;俄歇分析表明热影响区原奥氏体晶界存在明显的杂质元素S和合金元素Cr的偏聚,其共同作用致使该区抗疲劳裂纹扩展性能弱化,从而降低整个焊接构件的低周疲劳性能。
[Abstract]:The low cycle fatigue performance test of 25Cr2Ni2Mo V low pressure rotor steel is carried out. The relationship between strain and fatigue life of welded joints is obtained, and the low cycle fatigue properties in different regions of joints are compared and analyzed. Determine that the heat affected zone is the weak link of low cycle fatigue properties of joints. The hardness distribution of welded joints is measured. A series of tests, such as metallographic analysis of fatigue crack growth path and Auger analysis of segregation behavior of primary austenite grain boundary elements in HAZ, show that there is a soft and hard interface with large hardness gradient in the HAZ of welded joints. The strain concentration formed under fatigue load leads to the weakening of low cycle fatigue properties of welded members, and during the process of heat affected zone propagation, the fatigue crack often deflects along the grain boundary when it meets the original austenite grain boundary. Auger analysis shows that there is obvious segregation of impurity element S and alloying element Cr in the original austenitic grain boundary in the heat affected zone, which results in the weakening of the fatigue crack propagation property in the region, due to the effect of the segregation of the impurity element S and the alloying element Cr. In order to reduce the low cycle fatigue performance of the whole welded member.
【作者单位】：清华大学机械工程系;清华大学先进成形制造教育部重点实验室;
【基金】：上海市科学技术委员会资助项目(13DZ1101504)
【分类号】：TG405

【参考文献】