Stress-Strain Analysis of Creep Deterioration in Welded Joint of High Cr Ferritic Heat Resistant Steels

摘要

The study investigated the effect of stress and strain on Type Ⅳ cracking, which occurs in fine-grained heat-affected zones (FGHAZ) of welded joints of high Cr ferritic heat resistant steel at high temperature and low stress. A creep test of welded specimen was performed at 923 K and 90 MPa and the result showed that the cracking occurred in the FGHAZ. Further, a finite element (FEM) model was proposed to investigate the stress/strain distribution during creep process. Good agreement between calculated and measured results was observed. It was found that creep void distribution has similar trend as equivalent strain distribution, suggesting the important role of equivalent strain in creep void occurrence. On the other hand, it is considered that high hydrostatic pressure accelerates void coalescence and the occurrence of Type Ⅳ cracking. Simulation result showed that a narrow FGHAZ can decrease the equivalent strain in FGHAZ and consequently reduce occurrence of creep voids.