Hydrogen Embrittlement Property of a 1.5 GPa Dual-Phase Steel Evaluated Using U-bending Test: A Comparison with Tempered Martensitic Steel with Identical Tensile Strength

Abstract

The hydrogen embrittlement susceptibilities of 1.5 GPa-class dual-phase (DP) and tempered martensitic steels were comparatively evaluated using U-bending test. The U-bending tests showed no differences in hydrogen embrittlement susceptibility between the two steels. The martensitic and DP steels exhibited intergranular and quasi-cleavage fractures, respectively. The crack initiation site reached the outer surface of the specimen with increasing bolt-tightening displacement. Although qualitative trends were observed between the positions of the maximum principal stress peak and the crack initiation site, the two positions significantly differed, particularly in the DP steel. This difference could arise from premature hydrogen diffusion and the plastic strain effect.