The susceptibility to hydrogen embrittlement of a dual-phase steel DP600 with ferritic-martensitic microstructure was studied on previously hydrogenated samples by slow strain rate tensile tests (SSRT). The samples were subjected to electrolytic hydrogen charging in 0.05M sulfuric acid solution with the addition of KSCN at a current density of 1 and 5 mAcm-2 during 4, 8 and 24 hours. Due to the presence of hydrogen in the steel microstructure, a decrease of elongation at fracture from 24 % to 15 % was observed. Index of hydrogen embrittlement describing the relative change of elongation at fracture due to hydrogen was calculated as 38 % for the following hydrogen charging conditions: current density 1 mAcm-2 and time 8 hours. The index of hydrogen embrittlement decreased with increasing the hydrogenation time and the current density likely due to the formation of a corrosion layer that prevented further penetration of hydrogen into the steel. Changes of yield strength and tensile strength at a low current density were not observed, but at higher current densities, the yield strength increased by more than 40 MPa. Fracture surfaces of the tensile test bars were subjected to fractographic analysis. Transgranular ductile fracture was a predominant kind of fracture for all testing conditions, even for hydrogenated tensile bars. The proportion of quasi-cleavage fracture typical of hydrogen embrittlement was very low.Keywords: hydrogen embrittlement, dual-phase steel, slow strain rate test (SSRT)
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