What is Spot Welding?
Spot welding (also known as resistance spot welding) is a resistance welding process. This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area.
It works by contacting copper alloy electrodes to the sheet surfaces, whereby pressure and electric current are applied and heat is generated by the passage of current through resistive materials such as low carbon steels.
How Does Spot Welding Work?
A form of resistance welding, spot welding is one of the oldest welding processes whereby two or more sheets of metal are welded together without the use of any filler material.
The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces. The material melts, fusing the parts together at which point the current is turned off, pressure from the electrodes is maintained and the molten “nugget” solidifies to form the joint.
Schematic diagram of resistance spot welding
The welding heat is generated by the electric current, which is transferred to the workpiece through copper alloy electrodes. Copper is used for the electrodes as it has a high thermal conductivity and low electrical resistance compared to most other metals, ensuring that the heat is generated preferentially in the work pieces rather than the electrodes.