Spot Welding - Principles and Characteristics
1. Principles and Characteristics
Spot welding is a type of electric resistance welding that also uses pressure. Two or more metal plates are held under pressure between two electrodes. When an electric current is applied, the heat occurring from the electrical resistance fuses a small areas of the parts together. The processes are as follows:

Spot Welding Processes:
1.
Pinching (Tight Holding)
Allows the current concentration in the welding area, the work pieces are held tight by electrode pressure.
2.
Electricity Fusion
While the work pieces are pinched together, a high current is applied to melt the and join contact surfaces of the metal layers under the electrodes.
3.
Pressure Holding
After applying the current, pressure is held until the melted surfaces cool down to reinforce the welded area (nugget).
4.
Release
Releasing the pressure moves electrode tips away from the joint area.

Characteristics of Spot Welding:
Welding time is short and heat in localized, minimizing distortion.
Best suited for thin sheet steel.
Required skills or technical expertise is lower than other weld types.
Difficult to visually inspect weld quality as the welded parts are layered on top of each other.