Mechanical properties and microstructure of dissimilar friction stir welds of 11Cr-ferritic/martensitic steel to 316 stainless steel

摩擦攪拌接合による11Crフェライト/マルテンサイト鋼と316鋼の異材接合の強度特性と組織について

佐藤 裕*; 粉川 博之*; 藤井 啓道*; 矢野 康英  ; 関尾 佳弘  

Sato, Yutaka*; Kokawa, Hiroyuki*; Fujii, Hiromichi*; Yano, Yasuhide; Sekio, Yoshihiro

PNC-FMSとSUS316鋼の異材接合に摩擦攪拌接合(Friction stir welding)を適用し、系統的に強度と組織の評価を実施した。その結果、接合欠陥の生じない健全な継手を得ることができた。なお、本研究の一部は、文部科学省原子力基礎基盤戦略研究イニシアチブにより実施された「摩擦攪拌接合によるNa高速炉心材料の新たな接合技術に関する研究」の成果である。

Dissimilar friction stir welding (FSW) of an 11% Cr ferritic/martensitic stee (PNC-FMS) to 316-grade austenitic stainless steel was attempted with a view to its potential application to the wrapper tubes of next-generation fast reactors. The mechanical properties and microstructure of the resulting welds were systematically examined, which revealed that FSW produces a defect-free stir zone in which material intermixing is notably absent. That is, both steels are separately distributed along a zigzagging interface in the stir zone when PNC-FMS is placed on the retreating side, with the tool plunging at the butt line. This interface did not act as a fracture site during small-sized tensile testing of the stir zone. Furthermore, the microstructure of the stir zone was refined in both the PNC-FMS and 316 stainless steel sides, resulting in improved mechanical properties over the respective base material regions.