Identify the type of electric welding shown in the following figure?

AC Supply

Welding transformer

Welding spot

Metal pieces

Rolling (or) wheel type electrodes

Concept:

In seam welding, electrodes used in the form of rollers or wheels, and leak-proof joint is obtained by this.

(i) Spot welding: In resistance spot welding, two or more sheets of metal are held between electrodes through which welding current is supplied for a definite time and also force is exerted on workpieces. 

(ii) 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.

Seam welding is a continuous spot welding.