13
Principle of the MIG / MAG welding
The welding wire is fed from the wire coil to the contact tip due
to the wire-feeding rolls. The arc burns between the melting
wire electrode and the workpiece. The welding wire acts as
arc carrier and filler material. Shielding gas flows through the
gas nozzle and protects the arc against the atmospheregas.
At metal shielded gas welding both, inert and active gases are
used. The distinction is made between Metal Inert Gas (MIG)
and Metal Active Gas (MAG) welding.
Further possible classification is by the type of arc. This
means the external form of the arc, is proneness to short-
circuiting, and the way of transfer to the workpiece.
It is not possible to select the arc force to each individual
welding process. This is only limited possible for example at
the short circuiting arc. The mode of material transfer can be
selected at all types of gas shielded metal arc welding by
choosing the suitable current and the corresponding arc volt-
age, although the short circuit frequency and the size of the
drops depends from the type of shielded gas used.
Types of arc
Short circuit arc
This type of arc is specially suitable for thin materials and po-
sitional welding due to a relative cool welding pool welded
with very short arc, low arc voltage and low current. The sur-
face tension of the welding pool helps to draw the drop into
the bath and to reignite the arc. This cycle is repeated again
and again so the short circuit and the arcing period is con-
stantly alternating.
)
The transition from the short circuit to spray arc de-
pends on the wire diameter and the gas mixture.
Transitional arc
The transitional arc is especially suitable for medium thick-
ness sheet metals and for vertical-down welding. The transfer
of the electrode to the workpiece takes place partly in short
circuit and in free flight. Due to less short circuiting the weld-
ing pool is hotter than at the short circuit arc. Welding with
transitional arc provides higher electrode melt rate and is
more economic than welding at short circuit arc.
Long arc
Long arcs are typical at welding at the higher ampere range
under carbondioxid and gases with a high CO
2
content. It is
not particularly suitable for positional welding. In this type of
arc large drops are formed which falls into the welding pool
mainly by force of gravity. Due to that short circuits occasion-
ally occur, which by the increase of the current at the moment
of the short circuiting lead to spattering when the arc is reignit-
ed.
Spray arc
The spray arc is not suitable for positional welding, due to the
extremely liquid nature of the welding pool. The spraying arc
forms by welding at the higher range of ampere using inert
gas or mixtures with high argon content. The most typical
characteristic of the spray arc is the short circuit free transfer
of extremely fine droplets.
Working range at MAG welding
13 Basic of the MIG / MAG welding
process
Welding
process
Shielded gas
inert
active
MIG
Helium (He)
Argon (Ar)
Mixtures of
Ar/He
MAG-C
Carbon dioxide
100 % CO
2
MAG-M
Mixtures of
Ar/CO
2
Ar/O
2
Arc
Contact tip
Gas nozzle
Wire electrode
Wire-feed rolls
Power source
Workpiece
Shielding gas
Welding seam
Wire diameter
Long arc /
Spray arc
Transitional
arc
Short
circuit arc
mm
A
V
A
V
A
V
0.8
140…
180
23…
28
110…
150
18…
22
50…
130
14…
18
1.0
180…
250
24…
30
130…
200
18…
24
70…
160
16…
19
1.2
220…
320
25…
32
170…
250
19…
26
120…
200
17…
20
1.6
260…
320
26…
34
200…
300
22…
28
150…
200
18…
21
Favourable welding characteristic are only possible if voltage and
current are correctly adjusted.
CO
2
requires an arc voltage approx. 3 V higher than gas mixtures
with a high argon content.
Содержание MULTIMIG 400puls
Страница 2: ...2 5 5 6 10 8 9 6 7 12 15 14 11 10 ...
Страница 19: ...19 Appendix mounting torch holder ...
Страница 20: ...326601 06 05 ...