Residual Stress Relief in Post-Weld Heat Treatment
This paper focuses on analysis of weld residual stress relief process during furnace-based uniform post-weld heat treatment (PWHT). Two classes of pressure vessel steels: 2-1/4CrMo and carbon steel are considered in seam weld configurations. It is found that the dominant mechanism for residual stress relief is the creep relaxation that occurs much earlier during a PWHT cycle than typically expected. This phenomenon is further confirmed by experimental data. After a large number of parametric analyses of various PWHT parameters, a simple form of relationship is proposed for relating residuals stress relief to a set of PWHT parameters for the two classes of steels. These parameters include PWHT ramp-up heating time, PWHT holding time, PWHT holding temperature, and weldment thickness.