The Research On Medium Manganese Steel Hydrogen Behavior And Resistance To Hydrogen Embrittlement

The work of this thesis was carried out integrating with the state 863 project Study and production technology development of high Mn steel plates with high strength high toughness and Ti/Steel composite plate for ocean platform. The hydrogen permeation behavior, hydrogen embrittlement and internal friction behavior of two tested steels with different composition after hydrogen charging were investigated, and the effects of the composition and the microstructures, especially reversal austenite, on the hydrogen permeation behavior, hydrogen embrittlement and internal friction behavior were analyzed, and the mechanisms were also discussed. The main conclusions are as follows:(1) The difference of the hydrogen permeation curves, permeation time and apparent diffusion coefficient between the two quenched steels are not obvious. But the permeation time of the tempered Ⅱ steel is longer than that of tempered I steel, and the apparent diffusion coefficient of the tempered II steel is less than tempered I steel, and the reason is that Ⅱ steel contains Cr, Cu and Ni elements.(2) The permeation time of two quenched steels is less than that of tempered steels, and the apparent diffusion coefficient of two quenched steels is larger than that of tempered steels. The difference of the apparent diffusion coefficient between quenched and tempered Ⅱ steels is larger than that between quenched and tempered I steels, and this is because that there is large amount of reversal austenite, and the size of martensite laths is small.(3) The strength and the tensile behavior of the two steels didn’t change after hydrogen charging, and the ductility parameters such as elongation and area reduction decreased as the hydrogen charging time increased, and this effect of hydrogen on the ductility is more obvious in the slow strain rate tensile test.(4) Among the hydrogen embrittlement index (He) of the two steels, only the HE of quenched I steel after charging 72 hour is over 15%, the HE of other samples are all less than 15%. There are small amount of quasi-cleavages in the fracture morphologies of the slow strain tensile samples with quenched state and after charging 72 hours, and all the other samples show the fractograph with dimples, and this is due to the reversal austenite in the tempered microstructures.(5) The internal friction curves of two steels show three internal friction peaks at 260K,320K and 510K, and these three peaks are y peak, Snoek peak and SKK peak, respectively. After hydrogen charging, the peak values have changed.