2020 年 45 巻 1 号 p. 5-7
In the present paper, behavior of hydrogen in a low carbon high strength steel produced by thermo-mechanical controlling process (TMCP) was investigated by means of tensile testing and silver decoration technique, which can easier visible hydrogen using Ag particles. Tensile tests were performed on the specimens with and without hydrogen charging at a strain rate of 5.6×10-6 s-1. As a result, the hydrogen-charging decreased elongation to failure. It was also clarified that this decreasing of ductility is closely related to the quasi-cleavage fracture by SEM observation of fracture surface on detail. However, the sensitivity of hydrogen embrittlement was lower than that of the as-quenched martensitic steel. After silver decoration treatment, Ag particles distributed homogeneously on the specimen surface, which indicated hydrogen evolved homogeneously from the steel. This implies that it is very complex the mechanism of the hydrogen embrittlement in this high strength steel produced by TMCP due to the fine martensitic microstructure and existence of cementites.