Abstract
Applying an external static magnetic field to laser beam welding may lead
to a change in geometry of the weld seam. Since the most common
influence of a magnetic field acting on an electrically high
conducting fluid is the generation of a Lorentz force, the outcome of
such experiments is a strong indication for the presence of electric
current in the melt pool. Owing to the static nature of the magnetic
field, induction is restricted to the movement of the liquid metal and
therefore negligible, leaving thermoelectricity as the sole potential
source of current. The present work discloses analytically that the
current may indeed originate from a gradient of thermoelectric power.
Based on the examples iron and aluminium, key features of the current
distribution are determined numerically together with an investigation of
the dependence of the distribution on material properties. By carrying out
welding experiments in the heat conduction mode, validation is achieved
of the thermoelectric source of the current and of basic properties of
its contribution.
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