Article ID: ISIJINT-2022-123
The quality of spot welds between galvanized dual phase steels of 590 MPa (DP590Z) and Al-Si coated press-hardening steels (PHS) of 22MnB5 (PHS1500AS) are determined by welding metallurgy of both base metal and the coating. In this study, extending the dwelling time between two pulses is proposed to suppress splash in the broad process window of welding current and improve mechanical properties of spot welds. The increased welding current enlarges the fusion zone (FZ) size and consequently enhances the strength of welds in both shear and cross tensile tests. Furthermore, martensite with high carbon content and retained austenite near the fusion line was found for the first time in the spot welds in these kinds of steels. The high carbon zone alters the location of broken button and deteriorates the mechanical properties of spot welds. Down-slope pulse is proposed in this study to eliminate carbon enrichment, which improved the mechanical properties of the welds.
