The effect of welding current on nugget sizes in resistance spot welding of SPA-C steel sheets used in railway vehicles

Abstract

This paper presents an experimental study on resistance spot welding of SPA-C steel sheets used in side wall and roof in rail vehicles. SPA-C steel sheets having 2.3 mm thicknesses were joined by using resistance spot welding as lap joint. A timer and current controlled resistance spot welding machine having 120 kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 10, 15, 20, 25 and 30 periods and also welding currents were increased from 6 kA up to 11.5 kA by rise of 0.5 kA. The electrode force was kept constant at 6 kN. The nugget sizes of prepared welding specimens were calculated by means of an optical microscope and the obtained results were supported by diagrams and, finally, appropriate welding parameters were advised to the users.