Effects of Electro-force Control on the Microstructure and Welding Characteristic During Resistance Spot Welding

Recently, lightweight vehicle bodies are in increasing demand to satisfy exhaust gas and environmental regulations around the world. In particular, aluminum alloys are widely used to manufacture lightweight parts, because of their excellent properties including corrosion resistance and mechanical properties. After the forming process, the welding process is important for manufacturing aluminum alloy parts. Resistance welding of aluminum alloys has several problems, due to internal weld defects such as cracks, shrinkage cavity, or porosity, which can result from the Al(2)O3 oxide film on the surface of the aluminum alloy. This study investigated electrode-force type controls to improve the weldability of the aluminum alloy. It was found that a high electrode-force on squeeze time can collapse the Al(2)O3 oxide film on the surface. It can reduce defects in the nugget by about 42%, by reducing heat input energy, compared to the continuous electrode-force 4 kN (reference value). Also, with high electrode-force during the hold time, defects were reduced by about 80%, by increasing the cooling rate. The weld quality has a great influence on the electrode-force type control, and internal defects in the nugget are greatly affected by the electrode-force on hold time.