Investigating the Effect of Electrode Pressure on Nugget Size, Microstructure and Tensile Shear Strength of Resistance Spot Welded Advanced High Strength Dual Phase Steel Joints

The main objective of this investigation is to study the effect of electrode pressure on nugget formation, microstructural features and tensile shear strength (TSS) properties of resistance spot welded advanced high strength steel lap joints. The tensile shear strength (TSS) properties were evaluated in straight lap (SL-TSS) and cross lap (CL-TSS) joint configuration. Results showed that TSS of joints increases with increase in electrode pressure up to 4.0 MPa. Further increase results in drastic reduction in TSS of spot joints. The DP-800 steel spot joints developed using the electrode pressure of 4.0 MPa exhibited superior SL-TSS of 830 MPa and CL-TSS of 684 MPa extending straight lap and cross lap joint efficiency upto 99.71 and 82.17%. It is attributed to the evolution of finer needle like martensitic structure in nugget zone.