Abstract
An investigation was carried out on the effects of impurity contents and cooling time from 800°C to 500°C of weld thermal cycle on stress relief cracking susceptibility in 2 1/4 Cr-1 Mo steel synthesized HAZ. In this study, critical displacement to crack initiation (Δl'/c) and critical stress to crack initiation (σSR) obtained by constant loading test on heating in stress relief thermal cycle was adopted as a parameter to evaluate the stress relief cracking susceptibility.
The results are summerised as follows;
1) Δl'/c decreased with increasing of X=(10P+5Sb+4Sn+As)/100.
2) σSR at 600°C on heating decreased with increasing of X.
3) Δl'/c increased when the cooling time from 800°C to 500°C becomes shorter than 10 sec. and longer than 60 sec. In the former conditions austenite grain is refined and in the latter conditions upper bainite structure is formed.
