THE INFLUENCE OF WELDING TIME ON MECHANICAL PROPERTIES OF RESISTANCE SPOT WELDED TWIP STEEL SHEETS
This paper presents an analysis of the welding time effect on the mechanical properties of resistance spot welded TWIP980 steel sheets. Optical microscopy, microhardness measurements across the welded joints, and tensile shear tests of the joints were conducted to evaluate the quality of the joints. With welding time increasing, a macro expulsion cavity occurred in the FZ. The NS increased with increasing welding time up to 300 ms, and above 300 ms it decreased. On the other hand, the indentation depth increased almost linearly with increasing welding time. The hardness values in FZ and HAZ were lower than that in the BM. The lowest hardness values were observed in the HAZ. However, higher welding time led to higher hardness in HAZ. The tensile shear load, tensile shear deformation and failure energy of the joints increased with increasing welding time, but above 300 or 350 ms, these values decreased.