Bending behavior of zinc-coated hot stamping steels

Christina Hofer, Manfred Stadler, Thomas Kurz, Verena Maier-Kiener, Alexander Mayerhofer, Thomas Hebesberger, Ronald Schnitzer

Research output: Contribution to journalArticleResearchpeer-review

Abstract

In the automotive industry, ultrahigh strength steels allow downgauging while, at the same time, passenger safety is increased. To expand the application fields of martensitic steels, which are frequently produced via hot stamping, cathodic corrosion protection is required. To date, zinc-coated components are mainly processed via the detour of cold forming, but a precooling step to solidify all zinc phases prior to hot stamping shows great potential to overcome this limitation. Therefore, herein, directly quenched 22MnB5 is compared with an adapted alloy (20MnB8) after quenching with a precooling step. Bendability is used to assess the crash performance. In addition to the damage evolution, investigated via interrupted bending tests, a detailed microstructural analysis of the near-surface region with respect to grain size, decaburization, inclusions, and other second phases is carried out. While 22MnB5 shows a fully martensitic microstructure, individual ferrite grains are observed within the martensitic matrix in the near-surface region of 20MnB8. Carbon redistribution from ferrite to the surrounding martensite entails large hardness differences between the constituents as determined by nanoindentation, resulting in an earlier onset of strain localization and, therefore, decreased local formability.

Original languageEnglish
Article number2100149
Pages (from-to)1-9
JournalSteel research international
Volume92
Issue number10
DOIs
Publication statusPublished - Oct 2021

Bibliographical note

Publisher Copyright:
© 2021 The Authors. Steel Research International published by Wiley-VCH GmbH

Keywords

  • bendability
  • ferrite islands
  • hot stamping
  • inclusion analyses
  • nanoindentation
  • zinc-coated steels

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