RSW or resistance spot welding is a process where contacting metal surface points are joined by using heat from resistance to electric current. This is a type of electric resistance welding
The pieces are held together under the pressure created by the electrodes. These sheets may vary in thickness range of 0.5mm to 3mm. Two shaped copper alloy electrodes are used to concentrate the welding current to a single spot and to simultaneously clamp the sheets together. Once a large current passes through the metal it will melt and form a weld. This process only takes approximately 10 – 100 milliseconds. This means that the welding can be accomplished without excessive heating throughout the sheets.
The amount of heat delivered to a certain spot is determined by the resistance between electrodes and the duration and magnitude of the current. The amount of energy is then made to match the sheet’s properties, the thickness, and the types of electrodes. If the applied energy is too little the metal will not melt and create a poor weld. If the applied energy is too much will melt too much metal and create a whole rather than a weld.
In seam welding overlapping sheets are gripped between two wheels or roller disc electrodes and current is passed to obtain either the continuous seam i.e. overlapping weld nuggets or intermittent seam i.e. weld nuggets are equally spaced. Welding current may be continuous or in pulses.