Quantitative Study on Hydrogen Concentration-Hydrogen Embrittlement Sensitivity of X80 Pipeline Steel Based on Hydrogen Permeation Kinetics

The hydrogen concentration in steel is directly related to the hydrogen embrittlement (HE) sensitivity of the steel. This study combined electrochemical hydrogen charging, the slow strain rate test (SSRT), and hydrogen permeation experiments to investigate the variation in the hydrogen concentration in pipeline steel with the electrochemical hydrogen-charging time. The influence of the hydrogen concentration in steel on the mechanical properties of X80 pipeline steel was obtained, and ultimately, a quantitative relationship between the hydrogen concentration in steel and the hydrogen embrittlement sensitivity was established. The results show that the hydrogen concentration in the steel gradually increased with the time of hydrogen charging, and the quantitative relationship formula can be given as CH = 5.35 - 4.2 exp (-0.26t); the HE index of X80 steel increased with the hydrogen concentration. Additionally, once the hydrogen concentration in steel reaches 5.08 x 10-6 mol/cm3, even the slightest alteration in the hydrogen content will precipitate a dramatic decrease in plasticity. The quantitative relationship formula between the hydrogen concentration and the HE index (FH) in X80 steel can be given as FH=0.029 exp (1.5CH) - 0.029. When the hydrogen concentration in steel is at a maximum, the FH of X80 steel reaches 88.6%. This study provides a reference for analyzing the quantitative relationship between the hydrogen concentration and the HE index in steel after electrochemical hydrogen charging.