The effect of welding current on nugget geometry, microstructure and mechanical properties of TWIP steels in resistance spot welding

In this study, two twinning induced plasticity (TWIP) steels with different chemical compositions were produced by casting-hot rolling-cold rolling processes. A total of four groups of samples were formed by obtaining cold-rolled and heat-treated samples giving optimum mechanical properties. Welding parameters of resistance spot welding (RSW) of all samples were determined, and weldability at different welding current values was examined. Button shapes, microstructures, microhardness, and tensile shearing tests of welded joints were investigated. In addition, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses of broken samples were examined as a result of tensile testing. It has been concluded that non-heat-treated samples have higher tensile strength than heat-treated samples. In heat-treated steels; a marked increase in ductility was observed. It has been observed that RSWs of non-heat-treated steels have higher tensile load bearing capacity (TLBC) value.