Stress corrosion cracking susceptibility of a reduced-activation martensitic steel F82H

低放射化マルテンサイト鋼F82Hの応力腐食割れ感受性

三輪 幸夫; 實川 資朗; 塚田 隆 

Miwa, Yukio; Jitsukawa, Shiro; Tsukada, Takashi

低放射化マルテンサイト鋼F82Hの応力腐食割れ感受性を調べるため、さまざまな試験温度条件かつ溶存酸素及び溶存水素を添加した条件で、低ひずみ速度試験を行った。F82H鋼の試験片にもまた、さまざまな温度での熱処理,異なるレベルの冷間加工,応力集中のためのノッチ、及び中性子照射による弾き出し損傷を与えた。中性子照射は220Cで3.4dpaまで行った。試験の結果から、非照射材では粒界型応力腐食割れが焼きならしまま材に生じること、粒内型応力腐食割れが23%以上の冷間加工を与えさらにノッチを与えた試験片で生じることがわかった。また、通常の焼きならし焼き戻し材ではSCCが起こらないことがわかった。中性子照射材では、平滑試験片に粒内型応力腐食割れが水素添加環境中(300C,溶存水素濃度1ppm)で起こることと、粒内型応力腐食割れが酸素添加環境中(300C,溶存酸素濃度10ppm)でノッチ付き試験片のノッチの背面に生じることがわかった。

In order to examine the stress corrosion cracking (SCC) susceptibility of reduced activation ferritic/martensitic steel, F82H, slow strain rate test (SSRT) was performed at various temperature in oxygenated or hydrogenated water. Test specimens of F82H were heat-treated at various temperature conditions, or were cold-worked to imitate radiation hardening and machined to make single edge notch, or were neutron-irradiated at 493 K to 3.4 dpa. It was found that in unirradiated specimen, IGSCC occurred when specimen was normalized only, and TGSCC occurred when cold-worked (over 23%) and notched specimen was tested by SSRT at 573 K in oxygenated water. In irradiated specimen, TGSCC occurred, when SSRT was conducted at 573 K in hydrogenated (DH = 1 ppm) water or when the notched specimen was tested by SSRT at 573 K in oxygenated (DO = 10 ppm) water.