Numerical and experimental study of the effect of short-term and long-term creep modeling in stress relaxation of a multi-pass welded austenitic stainless steel pipe

This paper presents numerical and experimental study of multi-pass welding and post-weld heat treatment (PWHT) of a pipe specimen. 3D finite element models have been developed to simulate the welding process and the subsequent heat treatment, using uncoupled thermal mechanical analysis, and the stress results have been validated by experimental measurements using hole-drilling strain-gauge method. The austenitic stainless steel of type 304 has been selected as the base metal, because the knowledge of residual stress distribution after PWHT can be much helpful in the determination of heat treatment parameters to avoid intergranular corrosion (IGC) and consequently, intergranular stress corrosion cracking (IGSCC), while achieving enough relaxation. Short-term creep tests have been conducted to reach to the required creep properties. In order to verify the reliability of the extracted coefficients, a relaxation test has been conducted and simulated using the creep data, which implied that the data was quite reliable. Finally, good agreement was observed among the predicted and measured results. Moreover, it was revealed that long-term creep data induce considerable error in the prediction of residual stresses after PWHT.