Evolvement of residual stresses in dissimilar steel surfacing layers during the process of post-weld heat treatment
Residual stress relaxation during local post-weld heat treatment (PWHT) is a thermodynamic process, affected not only by the soaking temperature and holding time, but also by the residual stress state side overlay of the turbine rotor. In this paper, both as-welded residual stresses and heat-treated residual stresses were measured with blind-hole method. Results reveal that as-welded residual stresses are compressive in the surface weld, and tensile side the overlay both in axial and hoop direction; but after PWHT, the residual stress state reverses. With the measured stress relaxation parameters of the turbine rotor material, the stress relaxation was calculated using a power law relaxation () and time-hardening flow rule. Finite element (FE) simulation shows that the residual stress level decreases after long soaking due to stress relaxation behavior at high temperature, and the higher soaking temperature and the longer holding time, the lower of the residual stress level after soaking. While, in the cooling stage of PWHT, residual stresses increase because the elastic modulus of the weld metal recover gradually with temperature lowering. Even, the residual stress state may change if there were greatly difference in mechanical properties between welding wire and base metal. Further study reveals that different coefficient of expansion between welding wire and base metal is the main factors that stress state changes.
Turbine rotor residual stress post-weld heat treatment stress relaxation
Kaiyun Wang Hao Lu Li Gong
School of Material Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China Shanghai Electric Power Equipment Co. Ltd, Shanghai 200240, China
国际会议
济南
英文
1-9
2012-08-24（万方平台首次上网日期，不代表论文的发表时间）