Mechanical properties of friction stir welded 11Cr-ferritic/martensitic steel

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

The applicability of friction-stir welding (FSW) which was already put into practical use with nonferrous-metal materials was examined to the 11Cr-ferrite/martensite steel (PNC-FMS) wrapper material in order to improve the welding performance of fast reactor core materials. In this research, the effect of FSW on mechanical and microstructural properties of the Stir Zone (SZ) was investigated. From the experimental results, there was no remarkable decrease in tensile property of the SZ as compared with the base material even though the hardness of the SZ increased due to the influence of very fine grains. This suggests that a post weld heat treatment which was required on the conventional fusion welding might be unnecessary. This study is the result of "Friction stir welding of the wrapper tube materials for Na fast reactors" carried out under the Strategic Promotion Program for Basic Nuclear Research by the Ministry of Education, Culture, Sports, Science and Technology of Japan.