Comparative studies of stress-relief cracking in relaxation test specimens and in a full-scale weldment

An attempt is made to assess the susceptibility of stress-relief cracking (SRC) of simulated HAZ microstructures in heated specimens of SA508 Class 2 steel, using a notched bend relaxation test. The ability of this test to reproduce service conditions is explored by comparing cracking behaviour and the fractographic details of the cracks produced with observations made on stress-relief cracks in actual weldments of SA508 Class 2 obtained from the same manufacturer.It is shown that SRC in the relaxation test and in the weldments exhibited similar fractographic features and micromechanisms of cracking. From the test specimens, it was found that a critical value of stress-intensity factor was necessary to produce ‘severe’ cracking, and application of this value to the cracking observed in the weldments appears to be fully consistent with the details of weldment manufacture. It is proposed that a stress-intensity approach of this sort can provide a general method for the assessment of possible SRC in welded components.