The influence of geometry on residual stress around repair welds

Residual stress mitigation is a key strategy in the design and manufacture of nuclear power plant components for the prevention of component failure and the extension of power plant lifetimes. Repair welds comprise significant non-steady-state features that contribute to complex residual stress profiles that must be understood, modeled and minimized to ensure the efficiency of the repair. This is of particular importance given that in-situ measurement, and post weld heat treatment of residual stress profiles in repair welds is often impractical. Previous work indicates that the highest stresses accumulate at the ends of the repair where the weld pass stops overlap. Here we present a series of neutron diffraction measurements on two three-pass slot welds with different end slope angles to determine the effect of staggering the weld pass stop locations. It is shown that significant reductions in peak stresses can be made by decreasing the steepness of the end of the slot to stagger the weld stop locations for different beads. Additionally, these are the first reported measurements of residual stress in the new SA508 grade 4N steel which has been designed for deployment in future advanced PWR systems.