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Welding in the World

, Volume 62, Issue 5, pp 1031–1037 | Cite as

Susceptibility of electrolytically galvanized dual-phase steel sheets to liquid metal embrittlement during resistance spot welding

  • Julian Frei
  • Michael Rethmeier
Research Paper
  • 179 Downloads

Abstract

Modern advanced high-strength steel sheets for automotive applications are mostly zinc coated for corrosion resistance. However, the presence of zinc can—besides its positive effects—increase the material’s susceptibility to liquid metal embrittlement (LME) during resistance spot welding (RSW). Zinc and its eutectics are, due to their low melting point, present in liquid state during the welding process. This fact can, in combination with other factors like tensile strains or stresses, lead to the formation of brittle, intergranular cracks in the weld, and heat-affected zone. This phenomenon is commonly called liquid metal embrittlement. In order to understand the process from a practical perspective, one must learn what factors facilitate it. In this study, industry-relevant parameters are investigated regarding their influence on the occurrence of LME, embodied by the formation of surface cracks. It was found that electrode wear has less of an influence on the cracking susceptibility than welding current or tensile stresses. Finite element analysis is believed to provide a powerful tool in order to gain insights on the formation process. Modeling of the process shows promising initial results, revealing the underlying local stress and strain fields, unmeasurable with common techniques.

Keywords

High-strength steel sheets Zinc Resistance spot welding Liquid metal embrittlement Surface cracks 

Notes

Acknowledgements

The authors want to thank the voestalpine Steel Division for provision of testing materials and fruitful discussions.

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Copyright information

© International Institute of Welding 2018

Authors and Affiliations

  1. 1.Fraunhofer Institute for Production Systems and Design TechnologyBerlinGermany
  2. 2.Federal Institute for Materials Research and Testing (BAM)BerlinGermany

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