Assessment of Magnetization Effects on Hydrogen Cracking for Thick Walled Pipelines

摘要

The experimental studies in this dissertation were on the magnetization effect on hydrogen concentration in pipeline steels, the magnetization effect on hydrogen concentration in coldworked steel samples, and the magnetization effect on hydrogen induced cracking for thick high strength pipeline steels. To evaluate how a strong magnetic flux density produced throughout recurrent pigging routines affect the hydrogen-induced cracking susceptibility of thick walled and high-strength pipeline steels, five independent variables and one dependent variable have been defined. The independent variables are pipeline steel grade, wall thickness, residual stress effect, magnetic flux density, and hydrogen charging time. The dependent variable is the absorbed hydrogen concentration. The experimental approach used three steel grades: X52, X70, and X80. The actual yield strength levels of these grades were in the range of 70-90 ksi. The wall thickness ranges from 9/32 to 5/8 inches (6.89 to 15.3 mm). Test specimens are sectioned from cold worked samples bent at different angles to induce varying levels of residual stresses. The selected magnetic flux density level is the saturation induction and the hydrogen charging time was set at different periods of time from one to six hours.