A presentation given by Hassan Ghassemi-Armaki, at the February 2020 Car Body Joining Conference.
3rd Gen advanced high-strength steel (AHSS) are extensively considered for usage in Body-In-White (BIW) with lower thickness to reduce the vehicle weight and increase fuel efficiency. To improve strength and ductility in 3rd Gen. AHSS, the materials design concept can be different from Gen 1 and Gen 2 AHSS. Hence, it is necessary for the automotive industry to evaluate these materials properly for manufacturing. Resistance spot welding (RSW) continues to be a major joining process in BIW, and that is common for 3rd Gen AHSS as well.
Liquid metal embrittlement (LME) has been recognized as one of phenomena sometimes observed during welding. However, LME depends on several factors, but not only materials design but also welding condition and industrial noise factor. In Auto/Steel Partnership (A/SP), it has been aimed to understand LME behavior using Gleeble to find the proper temperature and deformation is required to form LME. A/SP has conducted a deep investigation to develop a procedure Gleeble procedure and analyzing of data for LME susceptibility level. In continuity of this effort, A/SP has developed a more lab based RSW protocol for LME evaluation which can be used for LME level evaluation of 3rd Gen AHSS. In meantime, to minimizing LME through welding parameters, the effect of different welding parameters is investigated.
To complete the loop for fully understanding the post-weld performance of 3rd Gen. AHSS in design, A/SP also investigate on weld performance during quasi-static and dynamic, through different type of mechanical tests, and a short overview will be presented.