Evaluation of residual stress near the weld overlay cladding by welding and post-weld heat treatment

Abstract

AbstractAustenitic stainless steel is welded as a cladding on the inner surface of a reactor pressure vessel (RPV) made of low alloy steel. In order to assess the structural integrity of the RPV precisely, the residual stress distribution caused by weld-overlay cladding and post-weld heat treatment (PWHT) is evaluated. Since the cladding layer is very thin compared to the vessel wall, it is necessary to evaluate the residual stress distribution around the weld fusion line, which can be very steep. In this study, cladded specimens were fabricated using different welding methods. Residual stress measurements using both sectioning and deep hole drilling (DHD) methods were then performed to evaluate the residual stress distributions through the weld fusion line. Three-dimensional thermal-elastic-plastic-creep analyses based on the finite element method were also conducted to evaluate the residual stress caused by weld-overlay cladding and PWHT. It was shown that analytical results provided reasonable agreements on weld residual stress with experimental results. It was also clarified that the main cause of residual stress due to welding and PWHT was the difference of thermal expansion between weld and base metals.Keywords:: reactor pressure vesselweld-overlay claddingpost-weld heat treatmentweld residual stresssectioning methoddeep hole drilling methodfinite element methodthermal-elastic-creep analysis AcknowledgementThis report is part of a project undertaken in 2007 by the Japan Atomic Energy Agency on behalf of the Nuclear and Industrial Safety Agency of the Ministry of Economy Trade and Industry.