Resistance spot welding (RSW) is a process typically used in high-volume, rapid welding applications, such as those found in the automotive, appliance and aerospace industries, to join sheet metal from foil to 0.250-in. (3mm) in thickness. Multiple sheets and dissimilar metals can also be simultaneously welded.
In spot welding, the pieces to be joined are clamped between two electrodes under high force. A large electrical current is passed from electrode to electrode to generate heat at the sheet-sheet (faying) interface. Heating of the joint may occur from both the electrical resistance across microscopic asperities at the faying interface and from the inherent bulk resistivity of the metal.
After the welding current is shut off, continued electrode force maintains pressure on the molten zone during weld nugget solidification to provide joint integrity.