Local post-weld heat treatment (PWHT) is often used for mitigating welding-induced residual stresses in pressure vessels and piping systems. As large and ultra-large pressure vessels are increasingly used in petrochemical and power generation industries, traditional local PWHT procedures stipulated in Codes and Standards become difficult to implement for some of the ultra-large vessels due to their very large diameter and overall length. In this paper, a new method referred to as primary-secondary heating based local PWHT technique (PS-PWHT) is proposed. Both finite element residual stress modeling and experimental residual stress measurements were performed for both validating the effectiveness of the proposed technique and elucidating the underling mechanisms. The results show that the PS-PWHT method can reduce welding-induced residual stresses in a significant manner, even leading to some level of compressive residual stresses at the vessel weld region.

局部焊接后热处理（PWHT）通常用于减轻压力容器和管道系统中焊接引起的残余应力。随着大型和超大型压力容器越来越多地用于石化和发电行业，由于某些超大型容器的直径和总长度非常大，因此规范和标准中规定的传统本地PWHT程序变得难以实施。在本文中，提出了一种称为基于初次加热的局部PWHT技术（PS-PWHT）的新方法。进行了有限元残余应力建模和实验残余应力测量，以验证所提出技术的有效性并阐明其下伏机理。