![]() ![]() For the X70 grade high-strength, acid-resistant submarine pipeline steel, an optimal Mg addition amount is 0.003% (mass fraction). On the one hand, this kind of inclusions can trap more hydrogen and reduce the diffusion coefficient of hydrogen in steel on the other hand, the internal rigid core of Al-Mg-Ti-O and external soft shell of MnS not only play a role in stress shielding but also hinder the initiation and expansion of stress cracks. ![]() The results suggested that micro/nanocomposite inclusions with "core-shell" structures obtained via Mg treatment have a greater activation energy of hydrogen desorption. The hydrogen diffusion and trapping behaviour in the tested steels treated with different Mg content was analysed by electrochemical hydrogen permeation testing and thermal desorption spectroscopy (TDS). ![]() The hydrogen embrittlement (HE) susceptibility of X70 grade, Acid-resistant, submarine pipeline steel with Mg treatment was studied via constant loading and slow strain rate tension (SSRT). Our group 20 previously theoretically calculated the critical crack nucleation size (the minimum size of inclusions leading to hydrogen-induced crack nucleation) of typical oxide inclusions such as MgAl 2 O 4, MgO and TiO, which is approximately 0.10.4 m, while MnS is approximately 2.5 m. ![]()
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