Role of drawing-induced residual stresses and strains in the hydrogen embrittlement susceptibility of prestressing steels

Hydrogen embrittlement (HE) of prestressing steel is a major technological problem in damage tolerance and structural integrity of structures in harsh environments, it being strongly influenced by residual stresses and plastic strains after cold-drawing. This paper calculates the distributions of such variables (mechanical approach) and later the stress-and-strain assisted diffusion of hydrogen (chemical approach) in a real manufacturing process by multi-step cold drawing. Results confirm the relevant role of plastic strain in HE of prestressing steel and thus the necessity of considering it in hydrogen diffusion calculations, because stress-only assisted diffusion leads to dramatic (and non conservative) underestimation of the hydrogen content.

► Self-similitude of radial distributions of residual stresses after each drawing pass.
► Tensile residual stresses at wire skin (very dangerous for HE susceptibility).
► Very relevant role of plastic strain in H diffusion and thus in HE susceptibility.
► Stress-only assisted diffusion leads to dramatic underestimation of H content.
► Maximum H concentration at wire skin (a HE crack could appear promoting failure).