圧力容器用低合金鋼の高温高圧水中における低サイクル疲労挙動
1989 年 75 巻 10 号 p. 1928-1935
詳細
1989 年 75 巻 10 号 p. 1928-1935
Low cycle fatigue behaviour of low alloy steels JIS SFVQ1A (equivalent to ASTM A508 cl. 3) and SQV2A (A533B cl. 1) for reactor pressure vessel was investigated in high temperature pressurized water environment. Total strain range, strain rate and dissolved oxygen (DO) concentration were varied from 0.5% to 2.2%, 0.1%/s to 0.001%/s and 10 ppb to 8 000 ppb, respectively. Fatigue tests in ambient air and 561K air were also conducted for comparison.
Reduction of fatigue life in high temperature water environment was observed. It decreased with decreasing total strain range and rather longer fatigue lives than those in air were observed at lower total strain range. SQV2A steel showed a distinct strain rate dependence of fatigue life compared to SFVQ1A steel, while both steels showed a similar DO concentration dependence. It was found that fatigue cracks initiated at surface corrosion pits due to MnS inclusion and the low cycle fatigue behaviour of both steels depended on their sulphur contents.
It can be conclusively remarked that the materials tested possess a plenty of safety margin in high temperature water environment by judging from the fact that the present data fell on the points far above the design fatigue curve in the ASME Code Sec.III.
