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Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

 
: Böhne, Christoph; Meschut, Gerson; Biegler, Max; Frei, Julian; Rethmeier, Michael

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Science and technology of welding and joining 25 (2020), No.4, pp.303-310
ISSN: 1362-1718
English
Journal Article
Fraunhofer IPK ()
liquid metal embrittlement; advanced high strength steels; resistance spot welding; electrode geometry; weld time

Abstract
Advanced high strength steels are usually coated by a zinc layer for an increased resistance against corrosion. During the resistance spot welding of zinc coated steel grades, liquid metal embrittlement (LME) may occur. As a result, cracking inside and around the spot weld indentation is observable. The extent of LME cracks is influenced by a variety of different factors. In this study, the impact of the used electrode geometry is investigated over a stepwise varied weld time. A spot welding finite element simulation is used to analyse and explain the observed effects. Results show significant differences especially for highly increased weld times. Based on identical overall dimensions, electrode geometries with a larger working plane allow for longer weld times, while still preventing LME within the investigated material and maintaining accessibility.

: http://publica.fraunhofer.de/documents/N-575312.html