Investigation of Liquid Metal Embrittlement during Resistance Spot Welding of Martensitic Steel with Zn Jet Vapor-Deposited Coating
Advanced high-strength steels protected by zinc coatings have contributed to a reduction in CO<sub>2</sub> emissions in the automotive industry. However, the liquid metal embrittlement (LME) of the Fe/Zn couple induced by simultaneously acting stresses and high temperatures during resist...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/aa9775966d7645ee8c8c30e6019905b6 |
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| Sumario: | Advanced high-strength steels protected by zinc coatings have contributed to a reduction in CO<sub>2</sub> emissions in the automotive industry. However, the liquid metal embrittlement (LME) of the Fe/Zn couple induced by simultaneously acting stresses and high temperatures during resistance spot welding could be the cause of unexpected failure. We investigated the possible risk of LME in spot-welded martensitic steel with Zn jet vapor-deposited coating and its influence on weld strength. The weld nugget cross-sections were analyzed (optical microscopy, SEM-EDS), and their tensile shear strengths were compared with their uncoated counterparts. LME cracks were observed in all samples meeting the process window (6, 6.5, 7 kA) located at the edge of the sheet/electrode indentation area. The frequency and length of cracks increased with current, and the occurrence of Zn within cracks indicated the LME mechanism. The shear tests showed the Zn-coated sample underwent a decrease in tensile shear strength that was most evident at a welding current of 7 kA (13.2%). However, LME was excluded as a cause of lower strength. The decrease was attributed to the smaller nugget diameter and the thin slit of Zn coating remaining in the weld notch. |
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