The influence of the structural-mechanical state of the transit gas pipeline steel on the susceptibility to hydrogen embrittlement

Different modes of cathodic polarization of pipe steel specimens based on current den­sity, which determine its moderate and intense hydrogen charging, are substantiated. The hy­drogen embrittlement resistance of 17H1S steel in the as-delivered and post-opera­ted states was determined by the change in plasticity depending on the hydrogen charging intensity and the direction of cutting the specimens relative to the pipe axis. Unexploited steel is not prone to hydrogen embrittlement under moderate hydrogen charging, while exploited steel has shown this feature. The impor­tant role of non-metallic inclusions in the hydrogen embrittlement of steel, which depen­ded on its structural-mechanical and hydrogen charging conditions, was determined using metallographic and fractographic analyses. Under moderate hydrogen charging the intergranular embrittlement takes place while under in­tense transgranular embrittlement; the differences are due, obviously, to different mechanisms of transport of hydrogen absorbed by the metal.