Residual Stress Variation by Isothermal and Isochronal Annealing in Cold Rolled Alloy 600

In order to understand why annealing at 480°C for several hour prevents the initiation of PWSCC, the residual stress variation with isothermal annealing at 480°C and isochronal annealing between 480 and 800°C in cold rolled Alloy 600 was investigated by the XRD method. The isothermal annealing decreased residual stress slightly in the rolling direction but not in the transverse direction, whereas the isochronal annealing for two hours increased residual stress. It seemed that the decrease in residual stress by isothermal annealing was due to lattice contraction by an ordering reaction because the isothermal annealing increased hardness. The effects of the isochronal annealing could be interpreted as the influence of thermal expansion and a disordering reaction.