圧力容器用2・1/4Cr-1Mo鋼の水素ぜい化割れき裂進展特性評価
1998 年 47 巻 8 号 p. 858-863
詳細
1998 年 47 巻 8 号 p. 858-863
The hydrogen-assisted crack propagation behavior of 2·1/4Cr-1Mo steel for a petroleum reactor was examined using a rising CMOD test which used a direct current potential difference (dcPD) method to measure crack extension. The initial hydrogen content in the specimens was about 5ppm when treated with thermal hydrogen charging. The equation to calibrate dcPD, defined in ASTM E647 for fatigue crack growth, gave a shorter crack extension than the actual hydrogen-assisted crack measured on fracture surfaces. A calibration curve for hydrogen cracking was derived from the relation between the actual crack extension and dcPD. The stress intensity factor at the hydrogenassisted crack initiation, KIH, was 23 to 28MPa√m and depended on the loading rate, dK/dt. Crack extension near the side surfaces was less than inside and the crack front was curved. The apparent stress intensity factor at the hydrogen-assisted crack arrest, KTH, calculated using ASTM E813 was 52 to 67MPa√m. The KTH on deepest crack front was estimated using FEM, and found to be smaller than the apparent KTH.
