P92钢焊缝金属高温低周疲劳行为分析

Study on high temperature low cycle fatigue behavior of P92 steel weld metal

P92钢常用于锅炉高温、高压主蒸气管道等部件,其焊接接头性能的优劣直接关系到机组的安全可靠运行.文中通过P92钢焊缝金属在630℃下的低周疲劳试验,研究了低周疲劳行为及其循环应力应变关系,采用塑性应变能密度对其低周疲劳进行了寿命预测,并根据断口形貌,分析了P92钢焊缝金属的断裂机理.结果表明,P92钢焊缝金属表现出循环软化特征;其低周疲劳寿命与应变幅值满足Coffin-Manson关系;采用塑性应变能密度的方法可以很好地预测P92钢焊缝金属低周疲劳寿命.二次裂纹密度的增加是其在高应变幅下寿命下降的主要原因.

P92 steel is often used for the high temperature and high pressure components of boiler,the performance of the welded joint is vital for the safe running of the unit.Therefore,this paper conducted the low cycle fatigue test of P92 steel weld metal under 630℃,and studied the low cycle fatigue behavior and the relationship between cycle stress and strain.Moreover,an approach of plastic strain energy density is used for predicting the low cycle fatigue life.At the same time,the mechanism of fatigue fracture for P92 steel weld metal was studied by the fracture morphology analysis.The results indicated that P92 steel weld metal performed a behavior of cyclic softening,its fatigue life and strain amplitude are satisfied with the Coffin-Manson relationship,and the way of plastic strain energy density is applied well to P92 steel weld metal.The reason for the decrease of fatigue life at high strain amplitude is the increase of the density of secondary cracks.