drawn arc procedure
Drawn arc ignition in general:
The drawn arc welding process is suitable for studs from 2mm up to 25mm.
A wide variety of stud shapes can be welded. The most common types are threaded studs, pins, insulating pins, bayonet pins, tapped studs
bushings, concrete anchors and flat anchors made of the materials ST37, 15Mo3, 1.4301,1.4713/42/62, 1.4841 )
The drawn arc welding process requires up to 3000A and lasts up to 2
seconds. Here, a pilot arc is first generated with low current.
After a short "pre-annealing time", the main arc, which really melts the materials, is generated.
During the duration of the main
arc, the studs is lifted from the workpiece and later plunged back into the molten material of the workpiece, where
the stud bonds with the workpiece .
Short cycle procedure:
Short-cycle welding is used for stud diameters of 3-12mm. It has the particular advantage that, due to the short, shallow penetration, thinner sheets can also be welded. (1/8 x D). The welding time is5 to 100 ms at a current of up to 1500 A.
Drawn arc procedure with ferulle:
Drawn arc ignition with ceramic ring:
Since an increasingly large and unstable weld pool forms in welds with a diameter > 5mm, a ceramic ring must be used to secure the weld pool. Furthermore, it supports the welding process by stabilizing the arc, shaping the molten metal, shielding the atmosphere and slowing down cooling, which has a beneficial effect on the weld structure.
This ceramic ring is slid over the stud before welding and removed by crushing after solidification. Its main components are magnesium aluminosilicate and aluminum oxides, and it is characterized by its high temperature and thermal shock resistance.