Hydrogen embrittlement characteristics of hot-stamped 22MnB5 steel

Mitsuhiro Okayasu, Takafumi Fujiwara

Research output: Contribution to journalArticlepeer-review

Abstract

Hydrogen embrittlement (HE) characteristics of 22MnB5 steel (U-bent specimen) manufactured using hot-stamping process at various temperatures were experimentally and numerically investigated. Steel resistance to HE was examined through delayed failure tests under static and cyclic loading during hydrogen charging. First, the low cyclic loading caused severe HE, in which a clear difference in the extent of HE was obtained depending on the hot-stamped sample, which directly affected the microstructural characteristics and stress–strain distribution. The hot-stamped samples with large martensite phase showed low resistance to HE compared with those with small martensite phase because of the high concentration of hydrogen trapped in the phase boundaries. Moreover, the dual phase (ferrite and martensite) of the hot-stamped samples reduced their resistance to HE, which is caused by the hydrogen trapped in the laminar-shaped pearlite phase. The resistance to HE was improved by low-temperature heating at 200 °C for 1 h because of the generation of ε-carbides as trap sites as they render the hydrogen non-diffusible. Furthermore, the internal strain in the U-bent sample could accelerate HE because of the high concentration of hydrogen. These results were verified by experimental and numerical analyses. Thus, the hydrogen trapping mechanism was proposed as a valid mechanism for HE in 22MnB5.

Original languageEnglish
JournalInternational Journal of Hydrogen Energy
DOIs
Publication statusAccepted/In press - 2021

Keywords

  • 22MnB5
  • Hot stamping
  • Hydrogen embrittlement
  • Hydrogen trapping
  • Martensite

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Condensed Matter Physics
  • Energy Engineering and Power Technology

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