Investigation of fabrication technologies for Japanese ITER test blanket module

ITER-テストブランケットモジュール第一壁構造製作のための製管・接合技術の調査

廣瀬 貴規; 野本 恭信; 榎枝 幹男; 秋場 真人

Hirose, Takanori; Nomoto, Yasunobu; Enoeda, Mikio; Akiba, Masato

ITER-TBM製作技術開発の一環としてF82H鋼を用いて161.5mm3500mmの円管及び11mm1.5mm3500mmの矩形管を冷間延伸法により試作した。これら試作管の長さはTBM実機に対して十分大きく、また表面粗さが1m以下の精密管である。したがって、TBM冷却水流路内に溶接継手を含まず、固相拡散接合時に別途表面仕上をする必要がない管の製作方法についての見通しを得た。固相拡散接合技術開発の一環として、接合界面の特性が継手特性に及ぼす影響を調査した結果、継手特性は表面酸化物の影響を受けやすいこと、この表面酸化物の分解には熱時効が有効であることを得た。

161.5mm3500mm cylindrical tubes and 11mm1.5mm3500mm square tubes were successfully fabricated from F82H bullet by cold rolling. The tube is long enough to fabricate the first wall without any joint in the cooling path. The surface roughness (Rz) is less than 1m and it is smooth enough to HIP bonding without further surface finish. As for the HIP pretreatment, the degassing conditions and surface roughness were investigated as parameters of pretreatment conditions in this work. F82H was HIPped with the conditions of 1373K, 150MPa and 2h holding time. Normalizing at 1233K for 0.5h and tempering at 1023K were performed as post-HIP heat treatment. Although tensile property of the HIP joint was not affected by the surface roughness and degassing conditions, the impact property was significantly degraded by lack of degassing. The degradation in impact property was caused by the micro dispersed oxide on the bonding surface. The oxide was decomposed by thermal aging at 1313K and the aging recovered the impact property. Therefore, to complete HIP bonding, degassing conditions must be strictly controlled to avoid the oxidation of bonding surface. And the inappropriately degassed joint should be followed by thermal aging to decompose the oxides.