Page 97 - SSAB Welding Handbook Edition 2

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Welding handbook 15.0 Magnetic arc blow

The selection of welding parameters Measures for multiple arc welding
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The stability of the arc depends on the welding Arc blow encountered when using multiple
parameters. A short arc length and low current electrodes can be counteracted by feeding one or
value can stabilize the arc. If needed, a reduced more electrodes with A.C. In this case, the
diameter of the consumable further assists in electrode with A.C. continuously changes the
reducing the current level. However, observe that direction of its magnetic field, counteracting arc
a lowered current level promotes lowered welding blow, according to fig. 15.9.
productivity.
A beneficial technique to use during multiple arc
welding is to combine the positive aspects from
both A.C. and D.C. welding. The first electrode
is fed by a D.C. current with positive polarity in
order to attain a deeper penetration profile. The
other electrode/electrodes are supported by A.C.
When applying two electrodes connected to A.C.,
the current phase shift between them can be set
to approximately 90º for a high resistance to arc
blow.

+ A.C.

Magnetic field

Fig. 15.9: Welding performances with two electrodes using a
0combination of D.C. and A.C.

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It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.