Effect of structural induced stress on creep of P92 steel welded pipes

Objective During operation, additional stress will be formed in the welded joints of boiler piping system for coal-fired unit due to the coeffect of steam pressure and external structure constraint. Therefore, the aim of this paper is to investigate the effect of structural induced stress on high temperature service life of welded joints. Methods Finite element simulation method is used to simulate the evolution of creep stress and creep strain of P92 steel main steam pipe joints under internal steam pressure and external structual induced stress. Results The results show that the radial stress of P92 steel joints is minorly affected by the axial structural induced stress. However, a clear change of hoop stress is observed , especially at the FGHAZ. The creep strain of the weakest FGHAZ on the pipe inner surface of P92 steel joints is significantly aggravated by axial structural induced tension stress and axial structural induced compression stress, and the axial structural induced compression stress has a more significant effect on the aggravation of creep strain than axial structural induced tension stress. Meanwhile, the creep strain of FGHAZ on the pipe outer surface is also increased by axial structual induced compression stress, by contrast, axial structual induced tension stress has little effect on this region. Conclusion The influence of structural induced stress should be considered when evaluating the creep damage and service life of P92 steel pipe joints.