Investigation on effect of thermal aging embrittlement on residual stresses of austenitic stainless steel repair welds in nuclear components subject to seismic loads

摘要

This paper presents investigation results on effect of thermal aging embrittlement on residual stresses of austenitic stainless steel repair welds in nuclear components subject to seismic loads. First, the welds on austenitic stainless steel 316L plates were manufactured consisting of the austenitic stainless steel weld metal with the delta-ferrite content sensitive to the thermal aging embrittlement. One of the welds was embrittled via conducting thermal aging acceleration test. Second, validity of finite element weld residual stress analysis was verified by performing finite element residual stress analysis and holedrilling method for the unrepaired welds. Third, effect of the thermal aging embrittlement on the residual stresses of the repair welds was evaluated by comparing the residual stresses according to whether the original welds were thermally embrittled. Last, effect of seismic loads was reviewed for the case where the repair welding was performed on the original welds being thermally embrittled. As a result, it is found that the effect of the thermal aging embrittlement on the residual stresses of the unrepaired welds is insignificant whereas tensile residual stresses of the repair welds increase in proportion to the increase in yield strength at room temperature due to the thermal aging embrittlement. In addition, the residual stresses are significantly mitigated after the seismic loads.