再熱割れ感受性評価試験片が具備すべき条件

抄録

Investigating the general conditions which the specimen to evaluate the susceptibility of reheat cracking must have, a series of processes from welding to PWHT (Post Weld Heat Treatment) were modeled by 3D thermal elastic-plastic-creep analysis based on FEM for the reheat cracking test specimen used in this study.
Noting the components of the welding residual stress owing to the test bead itself, the component in the direction of weld line, σ_x, was remarkably large and another two components perpendicular to weld line, σy, and thickness direction, σz, were small. Performing the third layer of restraint beads, σ_y, on the position where the reheat cracking was anticipated was large because the bending moment in the cross section became large due to the shrinkage of the following restraint beads. After the fourth layer restraint beads, σ_y, was not changed. This is because the bending stiffness in the cross section of the specimen became large. Performing the PWHT without whole restraint beads, σ_y was largely relaxed without accumulation of creep strain because the bending moment in the cross section was released. So, the evaluation of the reheat cracking susceptibility using the specimen should be performed after the whole restraint beads was laminated. When the susceptibility of the reheat cracking caused by PWHT is evaluated by the specimen used in this study, the test bead welding should be done remained the stress concentration in coarse grained HAZ but the restraint bead welding which is performed from back side should be full penetration. The plate thickness of restraint beads side should be at least four layers, which become to be full penetration.