A Neutron Diffraction Study of the Effect of Holdings and Heat Treatment on Residual Stresses in a Steel Weld

Residual stresses in an X-shaped weld of 32-mm-thick steel plates have been studied using neutron diffraction. The effect of pre-holding of weldments and their post-weld heat treatment on the distribution of residual stresses has been studied. The stress distribution is close to symmetric with respect to the centerline of the weld section and clearly asymmetric with respect to the middle of the weld thickness. The maximum tensile (longitudinal) stresses occur in the weld half-thickness, which was welded first. The peak value of longitudinal stresses in a fixed plate is 800 MPa (98% of the yield strength of the weld metal), which is significantly higher than that in a free plate (530 MPa). The zone of maximum compressive (transverse) stresses of –400 MPa in a fixed plate is located in the first half-thickness of the weld, while its second half occurs in the free plate. After heat treatment, the tensile and compressive stresses remained in general tensile and compressive, respectively. The maximum tensile longitudinal stresses were reduced to 270 MPa in the fixed plate and to 220 MPa in the free plate. The maximum compressive transverse stresses in both plates were reduced to ‒170 MPa.