Spot Welding Of Aluminum Alloy Spot Welding Electrode Wear

Resistance spot welding (RSW) is an major method in modern automobile manufacture industries, it has been widely used in sheet-metal joining for auto-body because the advantage of RSW is inherently properties of the high productivity and the efficient robotization. With the aluminum car being good for environment and the wider application of aluminum alloy, the welding experts have been focusing on electrode degradation during RSW of aluminum alloy. Electrode tip degradation has been researched by tracking the change s of the diameter change of electrode tip and the tensile strength of welding spot in RSW of aluminum alloy in the present thesis. The morphology of electrode tip and the microstructural transformation of alloying deposits on electrode tip have been investigated by several methods, i.e. scanning electron microscopy (SEM), X-ray diffraction technique (XRD) and energy dispersive X-ray spectroscopy (EDX). On this basis, the electrode failure mechanism is studied . The results show that the diameter of electrode tip increased with increasing of welding spots( from 5.2mm increased to 10.22mm); the change trend of tensile strength of welding spots is similar to that of the nugget diameter with welding spots increasing during RSW processing of aluminum alloy sheet, the change trend is decreased with increasing of welding spots (The tensile strength decreased from about 3400N to 2600N; the nugget diameter decreases from about 7.46mm to 4.9mm), the electrode tip life is about 2500 spot welds. The local welding occurs between the electrode tip surface with the weldpiece surface during RSW of aluminum alloy, the local welding is contributed to electrode pitting. The metallurgical reaction of copper with aluminum occurs on the interface during RSW process, which leads to CuAl₂ phase to bring about. Pitting and alloying are the main failure mechanisms contributing to the electrode degradation because pitting results in material loss and hence the increase in electrode tip diameter, and the increase in electrode resistance because of alloying of copper with aluminum.