Abstract
Since the crack growth due to hydrogen embrittlement in mild steels is accompanied with a considerable plastic deformation, the application of the linear elastic fracture mechanics to this problem is not suitable. Therefore J-integral/crack extention R-curve was applied, in order to examine the effects of microstructure on crack growth due to hydrogen embrittlement in mild steels.
The results obtained are as follows;
(1) With increasing hydrogen content, criticalJ-integral (Jcr) for the initiation of crack due to hydrogen embrittlement decreases slightly, but the marked decrease of the slope of R-curve was recognized.
(2) In ferritic-pearlitic steels, the crack extended parallel to the rolling plane is much larger than that normal to it, but such a difference is quite small in tempered bainitic steels.
(3) These results can be explained in terms of the banded structure comprising ferrite and pearlite layers. It was confirmed that both the effects of elongated MnS and texture on a crack growth are quite small.
