Short-Pulse Welding Technique for Resistance Spot Welding of Aluminum Alloy 6016-T4
The objective of this research is to develop and characterize the use of the short-pulse welding approach for the resistance spot welding (RSW) process on aluminum alloy 6016-T4. Aluminum alloys are increasingly used in automobile body-in-white production concepts to address weight and fuel efficiency requirements. RSW remains a preferred method of joining due to speed, existing equipment, maintenance experience, low cost, and absence of an added joining element. The purpose of the short-pulse welding technique is to improve the consistency of weld quality and to reduce undesired defects including rapid degradation of the welding electrodes, poor surface appearance of the joint, and expulsion of molten material from the welding zone. Additionally, the technique provides significant energy and process time savings to enable a more efficient and flexible application in production. In this work, RSW process simulations and experimental welding tests using two medium frequency direct current (MFDC) welding systems were used to develop the approach. The effects of RSW process parameters on the size of the fusion zone were studied, and it was found that short welding times could be used with the same current and force levels to produce the same welding result. In addition, the use of sharp, rectangular shaped pulses led to more effective nugget development due to more efficient heating of the fusion zone. Further analysis evaluated the electrode wear process for short-pulse RSW of this alloy and the benefits obtained by reduction of pulse width. Finally, combined RSW simulations and experiments examined the solidification and development of fusion zone microstructure using the short-pulse welding approach.