1 Introduction Page 3
Stud welding unit operating manual Date: July 2021
ALPHA 850 07.2021 / EN Rev.: A
1.3 Weld process
The ALPHA 850 welding device can be used to weld ordinary commercial studs
both in the short cycle drawn arc process (BH 10) as well as under the drawn arc
process (abbreviated BH 100).
The drawn arc process is for full-surface welding of studs of specific geometric
dimensions on metal workpieces that have a wall thickness of at least 1/4 of the
stud diameter.
To ensure de-oxidation of the melt bath and to improve ignition of the arc, the front
surfaces of the studs to be welded generally have a special aluminium preparation
adapted to the stud diameter.
To protect the weld pool from atmospheric influences and to centre the arc, it is
preferred that ceramic rings (CF) be used. This also prevents the melt from cooling
too fast.
For overhead welding or a horizontal welding position the ceramic ring (CF) forces a
constantly uniform shape of the weld bead and protects the user from weld
splatters.
In exceptional cases, such as when welding in tub position or reduction of the
aluminium preparation, weld pool guard can also be ensured by introducing
shielding gas (SG).
The shielding gas introduced drives the atmosphere out of the welding zone. If
welding is to be done with shielding gas, it is preferable to use studs with a conically
tapered welding tip.
The short cycle drawn arc process is a version of the drawn arc process that places
no special requirements on the stud tip design during extremely short weld times.
Other than the short weld times, the process is identical to arc welding with a drawn
arc.
With the short cycle drawn arc process. studs can even be welded to dirty, oily and
oiled workpiece surfaces, whose minimum sheet thickness must not be less than
0.6 mm.
Due to the extremely short weld times, the studs can also be easily welded without
ceramic rings. To protect the weld pool, especially during aluminium welding use of
shielding gas (SG) is recommended.
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