This work compares three aluminium sheet joining processes to determine their capability, efficiency and cost for mass production applications in automotive structures and closures. The joining processes investigated are Resistance Spot Welding (RSW), SelfPierce Riveting (SPR) and Spot Friction Joining (SFJ). Quantitative comparisons have been made on the basis of tensile strength (shear and peel), process time, equipment price and running cost.RSW is the most commonly employed joining method for steel sheet in the automotive industry. Its principle benefits are high speed and low cost operation, plus the ability to weld a wide range of joint configurations with the same gun. The main process limitations for aluminium are weld consistency and electrode-life, though recent work has shown that both of these can be largely overcome with regular electrode polishing [1,2]

Electrode pitting was investigated in resistance spot welding of 1.5-mm-thick sheet aluminum alloy 5182 using a medium-frequency direct-current welder and electrodes with a tip face curvature radius of 50 mm and tip face diameter of 10 mm. Detailed investigation of the metallurgical interactions between the copper electrode and aluminum alloy sheet was carried out using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The results indicated that electrode degradation, which eventually leads to weld failure, proceeded in four basic steps: aluminum pickup, electrode alloying with aluminum, electrode tip face pitting, and cavitation. Since pitting and cavitation result from Al pickup and alloying, periodic electrode cleaning could extend electrode tip life by limiting the buildup of Al on the tip face. This work is part of the effort to improve electrode tip life in resistance spot welding of aluminum alloys for automotive applications.

No abstract

No abstract

No abstract