Weld Nugget

In resistance spot welding, “the welding of overlapping pieces of metal at small points by application of pressure and electric current” creates a pool of molten metal that quickly cools and solidifies into a round joint known as a “nugget.”  Also see resistance spot welding.

Similarly in laser welding, the laser light is absorbed by the material causing a “keyhole effect” as the focused beam drills into, vaporizes, and melts some of the metal. As the pulse ends, the liquefied metal around the keyhole flows back in, solidifying and creating a small spot weld or ‘nugget.’  The entire process just a few milliseconds.  For more information, see laser spot welding.