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Application of self-piercing nuts during hot forming of 22MNB5

  • Sebastian MeyerEmail author
  • Gerson Meschut
  • Hendrik Vogt
  • Bernd-Arno Behrens
  • Sven Hübner
  • André Neumann
Research Paper
  • 33 Downloads

Abstract

The increasing use of hot-formed steels for structural components in lightweight construction requires solutions to create mounting points into the thin blank of high-strength steel. Compared to welding nuts, self-piercing nuts are often used due to advantages for the mechanical properties. The problems of setting these elements in hot-formed steels like 22MnB5 are high process forces and often limited undercuts, which are produced during the joining process. In this regard, the application of the self-piercing nut during the hot forming process of 22MnB5 is the focus of the investigation. The particular challenge is to find out the desired process parameter in a defined temperature window. Thus, the ductile austenitized 22MnB5 is exploited, while the local shape of the deformed blank in contact with the self-piercing nut is realized. A newly developed process enables insertion of the self-piercing nuts by different joining conditions. In order to evaluate the efficiency of the new process, various aspects are recorded. To achieve a successful hot forming process by a complete martensitic microstructure transformation, a minimum cooling rate of 27 K/s is provided. Furthermore, it has to be assured, that there is no thermal influence on the nut element, while the blank and the self-piercing nut are strongly heated. Otherwise, this can lead to a change in the strength class of the nut. For this purpose, hardness measurement is used to analyze the microstructure development. The mechanical behavior is described by torsion- and pull-out tests.

Keywords

Hot forming 22MnB5 Mechanical joining Self-piercing nuts 

Notes

Funding information

In this paper, selected results of the funded research projects IGF No.: 18483N (EFB No.: 01/114) were presented. The IGF project IGF No.: 18483N (EFB No.: 01/114) of the Europäischen Forschungsgesellschaft für Blechverarbeitung e. V. was promoted through the AiF under the program for the promotion of joint industrial research and development (IGF) by the Federal Ministry of Economics and Energy due to a resolution of the German Bundestag.

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Copyright information

© International Institute of Welding 2018

Authors and Affiliations

  1. 1.Laboratory for Material and Joining Technology (LWF®)Paderborn UniversityPaderbornGermany
  2. 2.Institute of Forming Technology and MachinesLeibniz Universität HannoverHanoverGermany

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