1.3.3 Magnetic Field Associated with a Welding Arc
When an electric current passes
through a conductor, a magnetic field is
created that surrounds the conductor
(Figure 1.6). Unless this magnetic
field is balanced in all directions, the
welding arc will tend to be deflected
from its normal axial orientation in line
with the electrode. This phenomenon
is called arc blow. It is more likely to
be present during welding of magnetic
materials (steels) and can cause
incomplete fusion types of flaws in
welds.
Some degree of imbalance in the
magnetic field is always present. The
path of the magnetic flux in the
workpiece is continuous behind the arc
and discontinuous ahead, due to the
change in the direction of the current
as it goes from workpiece to electrode
(Figure 1.7). Since a shorter arc is
stiffer, it is also less susceptible to arc
blow.
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Figure