Welding is a
fabrication or
sculptural process that joins materials, usually
metals or
thermoplastics, by causing
fusion, which is distinct from lower temperature metal-joining techniques such as
brazing and
soldering, which do not
melt the base metal. In addition to melting the base metal, a filler material is often added to the joint to form a pool of molten material (the
weld pool) that cools to form a joint that can be as strong as the base material.
Pressure may also be used in conjunction with
heat, or by itself, to produce a weld.