Upset welding

From GAWDAwiki

Upset welding is a form of resistance welding in which coalescence occurs simultaneously across the entirety of the abutting surface area, or progressively along a joint, using heat from the base metals’ resistance to the current passing through them.

Process

Upset welding differs from flash welding in that pressure is applied before heating begins and it remains for the duration of the heating process. Once a sufficient forging temperature is reached, an upsetting force is exerted and the current is stopped. The combination of high temperature and high pressure at the abutting surface causes the metals to coalesce. After the finished work cools, the force is removed and the weld is considered complete.^[1]

References

1. http://steel.keytometals.com/articles/art76.htm