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Delayed cracking in hot stamping with hot trimming for ultra-high strength steel components

  • Yuki NakagawaEmail author
  • Ken-ichiro Mori
  • Tomoyoshi Maeno
  • Ryo Umemiya
ORIGINAL ARTICLE
  • 51 Downloads

Abstract

Hydrogen-induced delayed cracking in hot stamping with hot trimming for ultra-high strength steel components at various trimming temperatures was investigated. The trimming temperature of a heated quenchable sheet was adjusted by rapid cooling with the upper punch and die, and then, the sheet was trimmed and die-quenched. A cathode hydrogen charging test was performed to examine the occurrence of delayed cracking at trimmed edges, and then, tensile strength and total elongation of the hydrogen-charged specimen were measured from the tensile test. Below, a martensite transformation start temperature of 420 °C, the fracture surface and the tensile residual stress became large, and delayed cracking was caused on the fracture surfaces of the sheared edges. Although no delayed cracking of the hydrogen-charged specimen occurred above 420 °C, the tensile strength and total elongation were reduced by hydrogen embrittlement. The critical temperature of delayed cracking for a thin sheet having 1.0 mm in thickness rose to 600 °C.

Keywords

Hot trimming Delayed cracking Residual stress Surface quality 22MnB5 

Notes

Funding information

This work was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research (B) of Number JP18H01749.

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Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Mechanical Engineering, School of EngineeringTokyo Institute of TechnologyTokyoJapan
  2. 2.Department of Mechanical EngineeringToyohashi University of TechnologyToyohashiJapan
  3. 3.Division of Systems Research, Faculty of EngineeringYokohama National UniversityYokohamaJapan

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