Abstract
In this paper, the mechanical behavior on SR (stress relief annealing) for the purpose of removing the residual stress produced by repair welding of thick plate is clarified. The obtained main result is as follows:
From the results of three-dimensional thermal elasto-plastic stress and creep analyses:
1) At the early stage during SR-treatment, the creep strain tends to easily accumulate in HAZ (Heat Affected Zone) and weld metal in which has been existed larger welding residual stress than the base metal, so that the stress relaxation is remarkable in HAZ and weld metal. After the stresses in HAZ and weld metal reached to be almost same magnitude of those of base metal, the stress relaxation progresses same amount all over the plate.
2) The configuration of stress distribution is not changed during SR-treatment regardless of heating and holding stage, and then the plastic strain is not produced during SR-treatment.
3) If the stress relaxation characteristic is poor in the base metal, the creep strain can easily accumulate in the weld metal and HAZ.
Comparing the results of three-dimensional thermal elasto-plastic creep analysis with that of two-dimensional plane-deformation one and one-dimensional approximate analysis:
4) The choosing of SR condition, i.e. heating rate, holding temperature and holding time etc., can be predicted by the results of one-dimensional approximate analysis.
5) In the case of replacing three-dimensional problem with two-dimensional plane-deformation problem for analyzing of the welding residual stress and SR, the accuracy of the creep strain and stress during and after SR depends upon how to actually represent the severity of mechanical conditions including the magnitude of welding residual stresses.
