Mechanical and technological analysis of AISI 304 butt joints welded with capacitor discharge process

In the present work, the capacitor discharge welding process (CDW) applied on AISI 304 circular bars was studied. The CDW process is essentially an electrical resistance welding technology, realized through current pulses of high intensity and discharged by large capacitors; the process allows to reduce stress concentration effects at the weld toe, obtaining thin welds and achieve good material integrity. CDW process characteristics lead to conceive the idea to investigate on the interaction between the weld technological aspects and the related mechanical properties. In this research activity, 150 cylindrical specimens with bore diameter 6 mm and different igniter dimensions were machined in AISI 304 austenitic stainless steel; a special equipment was designed to clamp specimens and to assure perfect electrical continuity. The main CDW welding parameters (energy input P, applied forces and igniter dimensions) were studied in order to optimise the welding process. The static and fatigue properties were finally analysed for the welded bars and the results were correlated to process parameters; mechanical tests give good results with respect to base metal if the proper welding parameters are used, despite the fact a brittle character was observed for the welded joints.