焊后热处理对16MND5钢焊接组织结构与残余应力的影响

16MND5钢广泛应用于核岛承压容器构件，其焊接接头不可避免地会引入高的残余应力，而焊后热处理可有效消减焊接残余应力以克服应力腐蚀裂纹的影响。本工作利用轮廓法和中子衍射技术研究了焊后热处理对16MND5钢焊接残余应力的影响。结果表明，轮廓法与中子衍射测试结果在趋势和数值上取得了较好的一致性，焊后热处理使焊接态的残余应力峰值从约420 MPa降低至约210 MPa。同时，利用金相法和SEM研究了焊后热处理对焊缝区域组织结构的影响。结果表明，焊后热处理主要表现为贝氏体和少量自回火马氏体的焊缝中心组织转变为回火贝氏体和回火马氏体，热处理后的焊缝区晶粒明显长大。

Effect of Post Weld Heat Treatment on Microstructure and Residual Stress in 16MND5 Steel Welded Joint

16MND5 steels are widely used as components of nuclear pressure vessel. Inevitably high residual stresses are introduced in their welding joints, which could be reduced by post weld heat treatment (PWHT) to overcome the effect of stress corrosion cracking. In this paper residual stresses were determined in the welded and PWHT specimens using the contour method and neutron diffraction. The results show that the residual stresses obtained by the two techniques achieve good agreement in both trend and magnitude. The peak residual stress reduces from 420 MPa in the welded specimen to 210 MPa in the PWHT specimen. The microstructure was characterized by metallographic examination and SEM. The results show that the microstructure in weld center changes from primary bainite and a little self-tempering martensite in the welded specimen to primary tempering bainite and tempering martensite in the PWHT specimen. The grains in the weld center grow obviously during the heat treatment.