The superheating system steam header is one of the most important components of the thermal power unit which is related closely with the safe and stable operation for the power plant during the life extended period. The deterioration of material properties caused by the aging of microstructure is the primary cause for the early failure of high-temperature bearing components and their welding parts. In this paper, the residual service life of a 220MW boiler's steam header is comprehensively analyzed based on nondestructive test, hardness test, metallographic structure and creep-fatigue damage analysis after 30-years-service. To calculate the creep-fatigue damage, both the modified elastic based method according to ASME-III-NH and the FEM simulation according to the Bailey-Norton constitutive are implied to assess the high temperature fatigue-creep life of the steam header. To calculate the fatigue strain range, the elastic strain range is modified by introducing the multi-axial stress factor and the Poisson's ratio adjustment factor, and the creep strain modified by the creep adjustment factor is added into the fatigue strain range. The results show that there still is 8.2 years' residual life for the steam header, if the thermal power unit continues to operate on the same conditions as the past 29 years.

过热系统蒸汽总箱是火电机组最重要的部件之一，关系到电厂在延寿期内的安全稳定运行。微观结构老化引起的材料性能劣化是高温轴承部件及其焊接件早期失效的主要原因。本文通过使用无损检测、硬度检测、金相组织和蠕变疲劳损伤分析，综合分析了某220MW锅炉蒸汽总箱使用30年后的剩余使用寿命。为了计算蠕变疲劳损伤，根据 ASME-III-NH 的修正的基于弹性的方法和根据 Bailey-Norton 本构的 FEM 模拟都暗示了评估蒸汽集管的高温疲劳蠕变寿命。为计算疲劳应变范围，引入多轴应力因子和泊松比调整因子修正弹性应变范围，并将经蠕变调整因子修正的蠕变应变加入疲劳应变范围。结果表明，如果火电机组在与过去29年相同的条件下继续运行，蒸汽总箱仍有8.2年的剩余寿命。将经蠕变调整系数修正的蠕变应变加入疲劳应变范围。结果表明，如果火电机组在与过去29年相同的条件下继续运行，蒸汽总箱仍有8.2年的剩余寿命。将经蠕变调整系数修正的蠕变应变加入疲劳应变范围。结果表明，如果火电机组在与过去29年相同的条件下继续运行，蒸汽总箱仍有8.2年的剩余寿命。