| dc.description.abstract | Abstract. This study systematically investigated spot heating local postweld heat treatment (PWHT) for pressure vessel nozzle to cylinder butt welds through experimental and numerical analyses. A dual-stage local heat treatment methodology, i.e., primary plus secondary local PWHT (PS-PWHT), was developed specifically for nozzle to cylinder butt welds, with a systematic investigation of secondary heating parameters affecting residual stress reduction. The results demonstrate that the PS-PWHT method achieves 50–70% residual stress reduction at critical inner surface locations. Two optimized secondary heating configurations, i.e., elliptical saddle-shaped secondary heating (E-SH) and rectangular saddle-shaped secondary heating (R-SH), were established based on reverse bending moment analysis of axial/hoop heating bands. Geometric parameters were quantified with recommended secondary heating distances (WDC = 2Rt and WDS = 4Rt) and (2–3)t width range (where WDC and WDS are the primary and secondary heating distances for the hoop and axial heating bands, respectively, and t represents wall thickness). A heating temperature range of 300–450 °C was identified for secondary heating, balancing effective stress relief without material degradation and damage. The developed process control strategy demonstrates significant improvements in mitigating welding-induced residual stresses through the PS-PWHT method. | |
