seam welding

The continuous line welding , A form of electrical resistance welding in which small metal wheels are used as the electrodes. These wheels roll over the metal, and the current is conducted through the metal from the wheel on one side to the wheel on the other side. Heat caused by the current flowing through the resistance of the metal softens the metal, and pressure between the wheels forces the softened metal in the two pieces to flow together. Seam welding is similar to spot welding, except that the weld is a continuous line, rather than individual spots. Fuel tanks are usually seam welded, rather than spot welded.