- 11 -
ing wire functions as a carrier of the arc and as the
source of additional material at the same time. Pro-
tective gas flows from the spacer who protects arc
and the whole weld against the effects of surround-
ing atmosphere (Pic. 9).
Picture 9
PROTECTIVE GASES
ADJUSTMENT OF WELDING PARAMETERS
For approximate adjustment of welding current and
voltage with MIG/MAG methods corresponds with
empirical relation
U
2
= 14 + 0.05 x I
2
. According to
this relation we can set required tension. During
adjustment of the tension, we must take into ac-
count with its decrease at loading by welding. De-
crease of tension is approximately 4.8 V to 100 A.
Adjustment of welding current is done so that for
chosen welding tension set required welding current
by increasing or decreasing of the speed of wire feed
or we tune the tension so that the welding arc is
stable. For good quality of welds and optimal ad-
justment of welding current it is necessary to reach
the distance of drawing die from material of approx-
imately 10x
welding wire (Pic. 10). Dipping of
drawing die in gas tube should not extend 2 - 3 mm.
Picture 10
WELDING ARC TYPES
a/ Short welding arc
Welding with a very short welding arc means a low
voltage level of the welding arc and current in the
lower part of the range. The surface tension of the
bath facilitates the bringing-in of the drop into the
melted metal and - because of this - the new ignition
of the arc. This cycle is repeated over and over and
this causes permanent changing between the short
circuit connection and period of welding arc burning.
The melted metal flow is relatively “cool”, which
means that this method is suitable for welding of
thin metal sheets and for welding in forced positions.
The transition from the short arc to the spray arc
depends on the welding current, wire diameter and
gas mixture (Pic. 11).
b/ Transition welding arc
If it is allowed by the dimensions of welded materi-
als, the welding operation should be conducted
under a higher consumable output (for economic
reasons), i.e. without exceeding the long or spray
arc. The transition welding arc means a slightly ex-
tended short welding arc. The material transition
takes place partly freely, partly within the short-
circuit connection. By this, the number of short-
circuit connections is reduced and the melting bath
flow is “hotter” than in the case of the so-called
short welding arc. This welding method is suitable
for middle thicknesses of materials and down-welds.
c/ Long welding arc
Large drops are formed in the long welding arc and
they penetrate the material by its weight. At this
method, accidental short-circuit connections and
consequent short-term current increases take place
causing the metal spraying after each ignition of the
welding arc. This welding method is suitable for
welding under CO
2
shield and other gas mixtures
with the high CO
2
content in the upper part of the
range. The method is not much suitable for welding
in forced positions (Pic. 11).
d/ Spray welding arc
The main feature of this welding method is the ma-
terial transition in small droplets without any con-
nection. The spray arc is to be adjusted, if welding is
to be done in inert gases or argon-rich mixtures in
the upper part of the range. The method is not suit-
able for welding in forced positions.
Long welding arc Short welding arc
Picture 11
HOLDING AND CONTROLLING THE WELDING TORCH
Protective gases
Inert gases – method MIG
Active gases – method MAG
Argon (Ar)
Helium (He)
Mixture He/Ar
Carbon dioxide
Mixed gases
Ar/CO2
AR/O2
Summary of Contents for MW2040
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