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9 Welding Process
– At the beginning of the welding process, the welding element (stud) in the welding
gun is lifted clear off the workpiece by a lifting device (solenoid). An initial switched
current triggers a pilot arc of a low current power (see figure, position 2). Then the
main arc ignites between the face area of the welding element and the workpiece.
– The main arc burns at the set current during the welding time preselected at the po-
wer unit. The selected welding energy must match the requirements of the selected
welding element. The energy of the arc melts the face of the welding element and
the workpiece (see figure, position 3).
– At the end of the preset welding time, the stud is mechanically moved to the work-
piece. On plunging into the weld pool, the two weld zones join and solidify. The
contact of stud and workpiece extinguishes the arc in a short-circuit and the main
current is switched off.
– The weld zone solidifies and cools down. The welding element is now welded to
the workpiece over its entire cross-section of the welding element (see position 4).
As soon as the weld metal is cooled down, the welding gun can be carefully with-
drawn from the welding element. When using shielding gas, the shielding gas flow
is switched off with the withdrawal of the welding gun. If a ceramic ferrule is used,
it can be removed by light hammer blows.
The welding range of drawn-arc stud welding is about 3 to 25 mm diameter when
using mild steel/stainless steel. Welding elements with rectangular cross-section
should not exceed a ratio length : width of about 5 : 1. All technical information and
adjustment values are based on the use of welding elements which correspond with
current standards.
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