Nut welding is used to describe the projection welding process used to attach threaded nuts to a metal substrate. This is a projection weld because the nuts either have a partial or full ring projection or multiple corner edges are formed into projections. This is a very common form of welding in the automotive and appliance industry. These weld nuts provide the assembly points for all of the screws and bolts used in assembly of these products. It is a reliable fast repetitive process.
Weld nut with corner projections
Reference: AWS C1.1 Recommended Practices for Resistance Welding
RWMA Manual Section 1, Chapter 3