A welding arc is formed when a
fairly high current (10 to 2000 A)
is forced to flow across a gap
between two electrodes at
relatively low voltage (10 to 50
V). A welding arc is intensely hot
with temperatures exceeding
3000°C (see Figure 1.2) and
forms a concentrated heat source
suitable for melting most metals
rapidly. The intense heat of the
welding arc causes the filler
metal to melt and when added to
the locally hot melted workpiece,
it forms the weld fusion zone. Its
subsequent freezing
(solidification) produces the bond
(weld) between the workpieces.
Arc welding processes do not
require application of pressure to
cause fusion.