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Resistance spot welding under external load for evaluation of LME susceptibility of zinc coated advanced high strength steel sheets

: Frei, Julian; Biegler, Max; Rethmeier, Michael

Bleck, Wolfgang (Chairman) ; Stahl-Institut VDEh, Düsseldorf:
METEC & 4th ESTAD 2019, European Steel Technology and Application Days : Düsseldorf, Germany, CCD Congress Center Düsseldorf, 24-28 June 2019, DVD-ROM
Düsseldorf: Steel Institute VDEh, 2019
7 pp.
International Metallurgical Trade Fair with Congresses (METEC) <10, 2019, Düsseldorf>
European Steel Technology and Application Days (ESTAD) <4, 2019, Düsseldorf>
Conference Paper
Fraunhofer IPK ()
advanced high strength steel; LME; RSW; testing method; zinc coated steel

Some zinc coated advanced high strength steels (AHSS), under certain manufacturing conditions, are known to be prone to liquid metal embrittlement (LME) during resistance spot welding. LME is an undesired phenomenon, which can cause both surface and internal cracks in a spot weld, potentially influencing its strength. An effort is made to understand influencing factors of LME better, and evaluate geometry-material combinations regarding their LME susceptibility. Manufacturers benefit from such knowledge because it improves the processing security of the materials. The experimental procedure of welding under external load is performed with samples of multiple AHSS classes with strengths up to 1200 MPa, including dual phase, complex phase and TRIP steels. This way, externally applied tensile load values are determined, which cause liquid metal embrittlement in the samples to occur. In the future, finite element simulation of this procedure gives access to in-situ stress and strain values present during LME formation. The visualization improves the process understanding, while a quantification of local stresses and strains allows an assessment of specific welded geometrie