|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Friction Stir Welding and Processing IX
||Influence of Underwater Operation on Friction Stir Welding of Medium Carbon Steel
||Tomoko Miyamori, Yutaka S Sato, Hiroyuki Kokawa
|On-Site Speaker (Planned)
To secure the safety during decommissioning of nuclear power plant, the temporary repairing of the defective steel structures placed in water is required. Friction stir welding (FSW) would be effective as an underwater repairing process because the solid-state stirring of FSW can eliminate the defects through underwater operation. However, there are few systematic studies on effect of underwater FSW on microstructure and properties of steels. In this study, underwater and conventional FSWs were applied to 0.45wt% medium carbon steel at various welding parameters, and then the microstructure and hardness of the welds were examined. Underwater FSW exhibited the higher torque and Z axial load than conventional one. Underwater FSW produced defect-free stir zone consisting of bainite with ferrite and pearlite, resulting in the higher hardness than conventional process. The microstructure evolution during FSW could be explained by the cooling rate measured during welding and the continuous cooling transformation diagram.
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