Delayed Fracture Evaluation of High-strength Steel Sheets Using the                        Hydrogen Permeability

Kitahara Gaku, Tsuji Aya, Asada Takashi, Suzuki Tomohiro

doi:10.2355/tetsutohagane.tetsu-2021-001

<p>The application of high-strength steel sheets in automobiles has been increased to achieve low bodyweight and simultaneously enhance crashworthiness. High-strength steel sheets are susceptible to hydrogen embrittlement and it is essential to evaluate their delayed fracture resistance for appropriate use. Delayed fracture resistance is typically evaluated using the relationship between the amount of diffusible hydrogen and fracture strength obtained from a constant load test and the slow strain rate technique (SSRT). It is difficult to monitor the amount of diffusible hydrogen invading from the environment; the thermal desorption analysis is not a non-destructive analysis to obtain the amount of diffusible hydrogen and diffusible hydrogen is easily desorbed from the specimens. The hydrogen permeation test easily monitors the invasion of diffusible hydrogen. In this study, we evaluated the delayed fracture resistance of high-strength steel sheets using the hydrogen permeability obtained from the hydrogen permeation test. As a result, relationships between hydrogen permeability, mechanical properties obtained from SSRT, and the brittle fracture surface ratio were found to be consistent among various hydrogen invasion conditions, such as under hydrogen charging and corrosive environments. Furthermore, little diffusible hydrogen was detected using the hydrogen permeation test. Thus, delayed fracture resistance obtained from the relationship between hydrogen permeability and its mechanical properties proves the effectiveness of this method.</p>

Delayed Fracture Evaluation of High-strength Steel Sheets Using the Hydrogen Permeability

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