Microstructure and Mechanical Performance of Resistance Spot Welded Martensitic Advanced High Strength Steel

Resistance spot welded 1.2 mm (t)-thick 1400 MPa martensitic steel (MS1400) samples are fabricated and their microstructure, mechanical properties investigated thoroughly. The performance failure modes exhibit a strong dependence on weld-nugget size. pull-out mode for MS1400 resistance welds does not follow the conventional size recommendation criteria of 4t0.5. Significant softening was observed due to dual phase microstructure ferrite martensite in inter-critical heat affected zone (HAZ) tempered (TM) structure sub-critical HAZ. However, upper-critical HAZ exhibits obvious higher hardness than nugget (NZ). In addition, show that cross-tension strength (CTS) is about one quarter tension-shear (TSS) weld joints, whilst absorbed energy almost identical.