Welding is a joining process that produces coalescence of materials
(typically metals or thermoplastics) by heating them to welding temperature,
with or without the application of pressure or by the application of pressure
alone, and with or without the use of filler materials.
workpieces are welded by melting both of them and adding more molten metal or
plastic to form a pool that cools to form a strong joint. The energy to form the
joint between metal workpieces most often comes from a flame (e.g.
oxy-acetylene) or an electric arc, but welding by laser beam, electron beam,
ultrasound and friction processes is well established. Energy for fusion welding
of thermoplastics typically comes from direct contact with a heated tool or a
Welding differs from soldering and brazing in that enough heat is applied to
melt the materials to be joined. Soldering uses solder, a lower-melting-point