Page 390 - Failure Analysis Case Studies II
P. 390
375
__
Fig. 2. Replicated micrograph of reheat crack showing bainitic microstructure and crack path following prior austenite grain
boundaries (magnification x 100).
Fig. 3. Replicated micrograph of reheat crack showing bainitic microstructure and crack path following weld heat affected
zone (magnification x 50).
values consistent with the original weld procedure qualification record (PQR), of between 181 and
204 HB.
2.4. Discussion
A literature survey [l] reveals that reheat or stress relaxation cracking may occur in the HAZ of
welds in low-alloy steel during post-weld heat treatment or during service at elevated temperature.
The factors that contribute to reheat cracking are:
(a) a susceptible alloy composition;
(b) a susceptible HAZ microstructure;
(c) a high level of residual strain combined with some degree of triaxiality;
(d) temperature in the strain relaxation (creep) range.
