Because of its high energy density, plasma arc welding is suitable for welding thicker
cross-sections. One variation is the keyhole plasma arc welding. The plasma arc pierces
through the welding parts and pushes the weld pool to the sides. By proper choice of
process parameters, it is possible to form a weld pool which holds itself by its own
surface tension. The molten metal behind the keyhole flows together and solidifies again
(Figure 4201.03.06).