Comparison of hydrogen embrittlement resistance of high strength steel sheets evaluated by several methods

Shusaku Takagi, Yukito Hagihara, Tomohiko Hojo, Wataru Urushihara, Kaoru Kawasaki

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Applications of ultra-high strength steel sheets to automotive bodies have expanded steadily in recent years. Various methods are used to evaluate resistance to hydrogen embrittlement (HE), which is one problem of ultra-high strength steels. In this study, the critical HE conditions obtained by the SSRT, CSRT and 4-point bending test were compared by using the same materials. The materials were two ultra-high strength steel sheets with tempered martensite microstructures, one with the SCM435 composition and the other a V- Added steel containing many hydrogen trapping precipitations. The specimens were charged with hydrogen by the cathodic charging method. The specimens used in the SSRT and CSRT were machined with notches on both sides of the parallel part. The values of the stress concentration factor (Kt) of the specimens were 4.26 and 1.76. A coupon-shaped specimen was used in the 4-point bending test. The critical HE conditions evaluated by the average applied stress and the average hydrogen content of the specimen were different depending on the test methods. The HE conditions were also evaluated by the local stress and the local accumulated diffusible hydrogen content at the fracture initiation point. The critical condition evaluated by the 4-point bending test was located in a higher stress and higher hydrogen content region compared with the critical conditions obtained by the CSRT and the SSRT.

Original languageEnglish
Pages (from-to)685-692
Number of pages8
JournalIsij International
Volume56
Issue number4
DOIs
Publication statusPublished - 2016 Jan 1
Externally publishedYes

Keywords

  • 4-point bending test
  • Conventional strain rate test
  • Delayed fracture
  • Local diffusible hydrogen content
  • Local stress
  • Slow strain rate test

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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