Influencia del límite elástico en la susceptibilidad a la fragilización por hidrógeno de aceros de pretensado

Influence of yielding strength on hydrogen embrittlement susceptibility of prestressing

The hydrogen embrittlement phenomena in prestressing steels plays an important role in Civil Engineering, because it is the main envoironment mechanism to damage the material. Furhermore: the stress corrosion cracking is often due to hydrogen embrittlement phenomenum, associated with all kinds of envoironments and electroquimical conditions. Its importance made the FIP stablish, in 1978, the Ammonyum Thiocynate test to measure the hydrogen embrittlement susceptibility of prestressing steels. In the present investigation the hydrogen embrittlement susceptibility of two prestressing steels with different yield stress is compared, in order to point out the difference of mechanical parameters of the material -in particular the yield stress- in the behaviour in the presence of the mentioned phenomena. the experimental programme includes frature tests in aggresive envoironment under different electro-chemical conditions (different values of pH and potential). The theoretical analysis includes the statement of a non-conventional model of hydrogen diffusion in metals, and the consideration of the compresive residual stresses distribution in the vicinity of the crack tip. The model is able to explain the different behaviour of both steels under hydrogen embrittlement.