Filtern
Dokumenttyp
- Vortrag (2) (entfernen)
Sprache
- Englisch (2)
Referierte Publikation
- nein (2)
Schlagworte
- LME (2)
- Advanced high strength steel (1)
- Cracking mechanism (1)
- Current density (1)
- RSW (1)
- Testing method (1)
- Zinc coated steel (1)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (2)
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 geometries.
Cracking mechanism is proven to be liquid metal embrittlement. Method is suitale for Determination of LME susceptibility. Formation of LME is highly dependent on temperature fields, influenced by wlding curren (high influence) and electrode wear (low influence). Hot-dip galvanized material causes highest electrode wear - potentially beneficial in combination with low welding currents (lower current density) regarding LME. Other methods to reduce current density like Change of electrode cap shape may be beneficial. Critical loadcases are between 50% and 60% of the material's yield strength (valid only for tested materials, coatings and the Parameter choices). -> Only externally applied tensile stress is known