Abstract: Hydrogen traps, hydrogen diffusion coefficient and hydrogen embrittlement sensitivity at the surface, quarter and half thickness of EH36 steel were investigated by means of hydrogen penetration test and slow tensile test. The results show that the microstructure of the surface and the quarter thickness is mainly bainite, the microstructure of the surface is relatively fine, and the half thickness is mainly ferrite and pearlite. The density of reversible and irreversible hydrogen traps decreases sequentially from the surface to the half thickness, and the hydrogen diffusion coefficient increases accordingly. As the hydrogen charging current density or time increases, the yield strength, tensile strength, and elongation of tensile specimens at various thicknesses decrease to varying degrees, and the hydrogen embrittlement sensitivity increases accordingly. The tensile fracture morphology gradually transitions from ductile dimples with ductile fracture characteristics to river like patterns with brittle fracture characteristics. The hydrogen embrittlement sensitivity is the smallest at the surface, and the hydrogen embrittlement sensitivity is the highest at the half thickness. Some hydrogen induced cracks are observed on the tensile fracture surface at the half thickness.

Key words: EH36 steel, hydrogen trap, hydrogen embrittlement sensitivity