Evaluation of liquid metal embrittlement-free weld by micro-plasma arc welding of Zn-coated interstitial free steel

The liquid metal embrittlement (LME) severity is a significant concern in the fusion welding of Zn-coated steel. The LME severity in galvannealed (GA) interstitial free (IF) steel processed through microplasma arc welding (MPAW) is investigated. The weld geometry, microstructure and mechanical properties of the 0.8 mm thin butt-welded structure are evaluated to check the welding quality. Optical microscopy and field emission scanning electron microscopy (FESEM) of the weld surface are considered to observe any LME cracks. The high-temperature tensile test is executed on GA-IF steel to simulate external stress-free MPAW conditions. The ultimate tensile strength of the welded joint is more than that of the base material, and it is LME-free, which signifies that the current MPAW system can be successfully used for joining GA-IF steel. The microstructure of the weld zone is having large grain structure and much more hardness than the base material. Even the high-temperature tension test does not show any LME cracks. Approximately, one-third of yield strength is reduced as the temperature rises from 600 °C to 700 °C. Overall, the parametric domain for MPAW of GA IF steel is successfully evaluated, which can produce any LME-free weld.