5.
Gas– Shielded Metal Arc Welding
5. Gas-Shielded Metal Arc Welding
61
The difference between gas-shielded metal arc welding (GMA) and the gas tungsten arc
welding process is the consumable electrode. Essentially the process is classified as metal
inert gas welding (MIG)
gas-shielded arc
welding (SG)
and
gas-shielded metal-arc
welding (GMAW)
metal inert
gas welding
(MIG)
electrogas
welding
(MSGG)
Narrow-gap gasshielded arc
welding (MSGE)
tungsten gasshielded welding
metal
active gas
welding
plasma gas
metal arc
welding
tungsten
inert-gas
welding
tungsten
plasma
welding
hydrogen
tungsten arc
welding
(MAG)
(MSGP)
(TIG)
(WP)
(WHG)
plasma
jet
welding
plasma
arc
welding
(WPS)
(WPL)
plasma jet
plasma
arc
welding
(WPSL)
gas mixture gas metalarc CO2
metal-arc
welding
welding
(GMMA)
(MAGC)
consumable electrode
non consumable electrode
br-er5-01e.cdr
metal
active
gas
welding (MAG). Besides,
there are two more process
variants,
the
electrogas
and the narrow gap welding
and
also
the
gas-
shielded plasma metal arc
welding, a combination of
both plasma welding and
© ISF 2002
MIG welding, Figure 5.1.
Classification of Gas-Shielded
Arc Welding Processes
Figure 5.1
In contrast to TIG welding,
where
the
electrode
is
normally negative in order to avoid the melting
of the tungsten electrode, this effect is exploited in MIG welding, as the positive pole is
wire feed unit
strongly heated than the negative pole, thus
improving the melting characteristics of the
water
cooling
feed wire.
shielding gas
control device
Figure 5.2 shows the principle of a GMA weld-
control switch
ing installation. The welding power source is
assembled
using
the
following
cooling water
control
assembly
rectifier
transformer
groups: The transformer converts the mains
voltage to low voltage which is subsequently
welding power source
rectified.
Apart from the torch cooling and the shielding
br-er5-02e.cdr
© ISF 2002
gas control, the process control is the most
GMA Welding Installation
important installation component. The process
control ensures that once set welding data are
adhered to.
Figure 5.2
2005
5. Gas-Shielded Metal Arc Welding
62
A selection of common welding installation variants is depicted in Figure 5.3, where the
universal device with a separate wire feed housing is the most frequently used variant in the
industry.
compact device
3 to 5m
universal device
5, 10 or 20m
3 to 5m
mini-spool device
10, 20 or 30m
push-pull device
1 torch handle
2 torch neck
3 torch trigger
4 hose package
5 shielding gas nozzle
6 contact tube
7 contact tube fixture
8 insulator
9 wire core
10 wire guide tube
11 wire electrode
12 shielding gas supply
13 welding current supply
5 to 10m
© ISF 2002
br-er5-03e.cdr
Manual Gas-Shielded
Arc Welding Torch
Types of Welding Installations
Figure 5.3
© ISF 2002
br-er5-04e.cdr
Figure 5.4
Figure 5.4 shows in detail a manually operated inert-gas shielded torch with the common
swan-neck shape. A machine torch has no handle and its shape is straight or swan-necked.
The hose package contains the wire core and also supply lines for shielding gas, current and
cooling water, the latter for contact tube cooling. The current is transferred to the wire electrode over the contact tube. The shielding gas nozzle is shaped to ensure a steady gas flow
in the arc space, thus protecting arc and molten pool against the atmosphere.
A so-called “Two-Wire-Drive” wire feed system is of the most simple design, as shown in
Figure 5.5. The wire is pulled off a wire reel and fed into the hose package. The wire transport roller, which shows different grooves depending on the used material, is driven by an
electric motor. The counterpressure roller generates the frictional force which is needed for
wire feeding.
2005
5. Gas-Shielded Metal Arc Welding
63
1
4-roller drive
2
4
4
3
1
3
2
F
4
4
3
1
2
1 wire guide tube
2 drive rollers
3 counter pressure rollers
4 wire guide tube
2
planetary drive
3
direction of
rotation
5
6
1 wire reel
3 wire transport roll
2 wire guide tube
4 counter pressure roll
3
5 wire feed roll with a V-groove for steel electrodes
6 wire feed roll with a rounded groove for aluminium
br-er5-05e.cdr
1
© ISF 2002
br-er5-06e.cdr
© ISF 2002
Wire Feed System
Figure 5.5
1 wire guide tube
2 roller holding device
3 drive rollers
2
Wire Drives
Figure 5.6
More complicated but following the same operation principle is the “Four-Wire-Drive”, Figure 5.6. Here, the second pair of rollers guarantees higher feeding reliability by reducing the
risk of wheel slip. Another design among the wire feed drive systems is the planetary drive,
where the wire is fed in axial direction by the motor. A rectilinear rotation-free wire feed motion is the outcome of the
welding voltage
motor rotation and the angular offset of the drive
rollers
time
which
are
firmly
welding current
connected to the motor
shaft.
time
1 ms
1 mm
Figure
5.7
depicts
the
metal transfer in the short
arc
© ISF 2002
br-er5-07e.cdr
Short-Circuiting Arc Metal Transfer
Figure 5.7
range.
During
the
burning phase of the arc,
material is molten and ac2005
5. Gas-Shielded Metal Arc Welding
64
cumulates at the electrode end. The voltage drops slowly while the arc shortens. Electrode
and workpiece make contact and a short-circuit occurs. In the short-circuit phase is the liquid
the molten pool. The narrowing liquid root and the
welding current
result of surface tension into
welding current
electrode material drawn as
rising current lead to a very
high current density that
causes a sudden evapora-
time
time
tion of the remaining root.
The arc is reignited. The
choke effect
low
short-arc technique is par-
medium
br-er5-08e.cdr
© ISF 2002
ticularly suitable for out-ofChoke Effect
position and root passes
welding.
welding current
welding current
Figure 5.8
time
welding voltage
welding voltage
time
time
time
br-er5-09e.cdr
© ISF 2002
br-er5-10e.cdr
Long Arc
Figure 5.9
© ISF 2002
Spray Arc
Figure 5.10
2005
5. Gas-Shielded Metal Arc Welding
65
The limitation of the rate of the current rise during the short-circuit phase with a choke
leads to a pointed burn-off process which is smoother and clearly shows less spatter formation, Figures 5.8
In shielding gases with a
35
C1
shielding gas composition:
C1: CO2
M21: 82% Ar, 18% CO2
M23: 92% Ar, 8% O2
welding voltage
V
long arc
high CO2 proportion a
M21
M23
long arc is formed in the
upper power range, Figure
25
5.9. Material transfer is
20
undefined and occurs as
mixed
circuiting arc
15
short arc
contact tube distance: approx. 15 mm
150
3,5
br-er5-11e.cdr
4,5
illustrated in Figures 5.13
spray arc
and
contact tube distance: approx. 19 mm
5.14.
Short-circuits
with very strong spatter
200
welding current
250
A
300
5,5
7,0
wire feed
8,0
m/min
10,5
formation are caused by
© ISF 2002
the formation of very large
Welding Parameters in Dependence on
the Shielding Gas Mixture (SG 2, Ø1,2 mm)
droplets at the electrode
Figure 5.11
end.
If the inert gas content of the shielding gas
exceeds 80%, a spray arc forms in the upper
characterised by a non-short-circuiting and
spray-like material transfer. For its high deposition rate the spray arc is used for welding filler
thermal conductivity
power range, Figure 5.10. The spray arc is
helium
hydrogen
CO2
nitrogen
and cover passes in the flat position.
argon
Connections between welding parameters,
temperature
shielding gas and arc type are shown in Figure 5.11. When the shielding gas M23 is used,
argon 82%Ar+18%CO2
CO2
helium
the spray arc may already be produced with an
amperage of 260 A. With the decreasing argon
proportion the amperage has to be increased
br-er2-12e.cdr
© ISF 2002
in order to remain in the spray arc range. When
pure carbon dioxide is applied, the spray arc
Figure 5.12
2005
5. Gas-Shielded Metal Arc Welding
66
cannot be produced. Figure 5.11 shows, moreover, that with the increasing CO2 content the
welding voltage must also be increased in order to achieve the same deposition rate.
current-carrying
arc core
The different thermal conductivity of the
shielding gases has a considerable influence
temperature
on the arc configuration and weld geometry,
Figure 5.12. Caused by the low thermal conductivity of the argon the arc core becomes
r
r
argon
carbon dioxide
Fa
F
Fr
wire elektrodes
Fr
F
argon
current-carrying
arc core
Fa
carbon dioxide
br-er5-13e.cdr
© ISF 2006
argon
Influence of Shielding Gas
on Forces in the Arc Space
carbon dioxide
Figure 5.13
very hot – this results in a deep penetration in
the weld centre, the so-called “argon fingertype
penetration”.
Weld
reinforcement
is
br-er5-14e.cdr
© ISF 2002
strongly pronounced. Application of CO2 and
helium leads, due to the better thermal conductivity of these shielding gases, to a wide and
Figure 5.14
deep penetration.
A recombination (endothermic break of the linkage in the arc space – exothermal reaction
2CO + O2 ->2CO2 in the workpiece proximity) intensifies this effect when CO2 is used.
In argon, the current-carrying arc core is wider and envelops the wire electrode end, Figure
5.13. This generates electromagnetic forces which bring about the detachment of the liquid
electrode material. This so-called “pinch effect” causes a metal transfer in small drops, Figure 5.14.
2005
5. Gas-Shielded Metal Arc Welding
67
The pointed shape of the arc attachment in
carbon dioxide produces a reverse-direction
acceleration
due to gravity
force component, i.e., the molten metal is
wire electrode
electromagnetic
force FL
(pinch effect)
pushed up until gravity has overcome that
force component and material transfer in the
form of very coarse drops appear.
viscosity
surface
tension S
droplets necking
down
backlash forces fr
of the evaporating
material
inertia
electrostatic
forces
suction forces,
plasma flow
induced
Besides the pinch effect, the inertia and the
gravitational force, other forces, shown in Figure 5.15, are active inside the arc space;
however these forces are of less importance.
If the welding voltage and the wire feed speed
are further increased, a rotating arc occurs
work piece
br-er5-15e.cdr
© ISF 2002
Forces in Arc Space
after an undefined transition zone, Figure
5.16. High-efficiency MAG welding has
been applied since the beginning of the nine-
Figure 5.15
ties; the deposition rate, when this process is
used, is twice the size as, in comparison, to spray arc welding. Apart from a multicomponent
gas with a helium proportion, also a high-rating power source and a precisely controlled wire
feed system for high wire feed speeds are necessary.
Figure
5.17
depicts
the
deposition rates over the
wire feed speed, as achievable
with
efficiency
modern
MAG
high-
welding
processes.
During the transition from
the short to the spray arc
the drop frequency rate inbr-er5-16e.cdr
creases erratically while the
© ISF 2002
Rotating Arc
drop volume decreases at
Figure 5.16
2005
5. Gas-Shielded Metal Arc Welding
68
the same degree. With an
25
deposition rate
increasing
Ø 1,2 mm
kg/h
high performance
GMA welding
20
this
“critical
current
range” moves up to higher
Ø 1,0 mm
15
power ranges and is, with
10
Ø 0,8 mm
conventional
GMA
inert gas constituents of
lower than 80%, hardly
5
0
CO2-content,
achievable thereafter. This
5
0
10
15
20
25
30
35
40
45 m/min
effect
wire feed speed
br-er5-17e.cdr
facilitates
the
pulsed-arc welding tech-
© ISF 2002
nique, Figure 5.18.
Deposition Rate
Figure 5.17
In pulsed-arc welding, a
change-over
occurs
be-
tween a low, subcritical background current and a high, supercritical pulsed current. During
the background phase which corresponds with the short arc range, the arc length is ionised
300
300
200
200
critical current
range
100
100
UEff
3
V
arc voltage
10 cm
drop volume
number of droplets
35
-4
1/s
25
20
Um
15
10
5
500
0
0
200
A
400
tP
0
600
A
400
welding current
Ikrit
Im
- background current IG
- pulse voltage UP
- impulse time tP
- background time
tG or frequency f with
f = 1 / ( tG + tP), resp.
- wire feed speed vD
350
300
IEff
250
200
Im
150
100
50
0
time
IG
tG
Setting parameters:
0
br-er5-18e.cdr
© ISF 2002
5
br-er5-19e.cdr
10
15
time
20
ms
30
© ISF 2002
Pulsed Arc
Figure 5.18
Figure 5.19
2005
5. Gas-Shielded Metal Arc Welding
69
welding current
and wire electrode and work
surface are preheated. During the pulsed phase the
material is molten and, as in
spray arc welding, superseded
by
the
pulsed current intensity
Non-short-circuiting
metal tranfer range
backround current
intensity
magnetic
forces. Figure 5.20.
time
Figure 5.19 shows an example of pulsed arc real
© isf 2002
br-er5-20e.cdr
current path and voltage
Pulsed Metal Transfer
time curve. The formula for
Figure 5.20
mean current is:
Im =
1T
idt
T ∫0
for energy per unit length of weld is:
Ieff =
1T 2
i dt
T ∫0
By a sensible selection of welding parameters, the GMA welding technique allows a selection
of different arc types which
50
are distinguished by their
working range welding current / arc voltage
45
metal transfer way. Figure
shows
the
40
setting
range for a good welding
process in the field of conventional GMA welding.
spray arc
optimal setting
lower limit
upper limit
35
voltage [v]
5.21
30
transition arc
25
short arc
shielding gas: 82%Ar, 18%CO2
wire diameter: 1,2 mm
wire type: SG 2
20
15
Figure 5.22 shows the extended setting range for the
10
50
75
100
125
150
175 200 225 250
welding current
275
350
375
400
Parameter Setting Range
in GMA Welding
ing process with a rotating
arc.
325
© ISF 2002
br-er5-21e.cdr
high-efficiency MAGM weld-
300
Figure 5.21
2005
5. Gas-Shielded Metal Arc Welding
70
Some typical applications of the different arc types are depicted in Figure 5.23. The rotating
arc, (not mentioned in the figure), is applied in just the same way as the spray arc, however,
it is not used for the welding of copper and aluminium.
The arc length within the
filler metal: SG2 -1,2 mm
shielding gas: Ar/He/CO2/O2-65/26,5/8/0,5
working range is linearly
dependent on the set weld-
V
The weld seam shape is
30
voltage
ing voltage, Figure 5.24.
considerably influenced by
rotating
arc
50
transition zones
spray arc
high-efficiency
spray arc
20
the arc length. A long arc
high-efficiency short arc
10
produces a wide flat weld
short arc
seam and, in the case of
100
fillet welds, generally under-
200
br-er5-22e.cdr
cuts. A short arc produces a
300
welding current
400
A
600
Quelle: Linde, ISF2002
Setting Range or Welding Parameters
in Dependence on Arc Type
narrow, banked weld bead.
Figure 5.22
On the other hand, the arc length is inversely proportional to the wire feed speed, Figure
5.25. This has influence on the current over the internal adjustment with a slightly dropping
power source characteristic. This again is of considerable importance for the deposition rate,
i.e., a low wire feed speed leads to a low deposition rate, the result is flat penetration and low
base metal fusion. At a constant weld speed and a high wire feed speed a deep penetration
can be obtained.
arc types
intensity is
pendent
on
the
de-
contact
tube distance, Figure 5.26.
With a large contact tube
distance, the wire stickout is
longer
and
is
therefore
applications
current
seam type, positions
workpiece thickness
At equal arc lengths, the
welding methods
MAGC MAGM MIG
spray arc
long arc
-
aluminium
copper
steel unalloyed, lowalloy, high-alloy
fillet welds or inner
passes and cover
passes of butt welds
at medium-thick or thick
components in position
PA, PB
welding of root layers in
position PA
characterised by a higher
short arc
aluminium
(s < 1,5 mm)
steel unalloyed,
low-alloy
steel unalloyed, low-alloy, steel low-alloy,
high-alloy
high-alloy
steel unalloyed,
low-alloy
steel unalloyed,
low-alloy
fillet welds or inner
passes and cover
passes of butt welds
at medium-thick or thick
components in position
PA, PB
fillet welds or butt welds
fillet welds or inner
at thin sheets, all positions passes and cover
passes of thin and
root layers of butt welds
medium-thick
at medium-thick or thick
components, all
components, all positions positions
inner passes and cover
passes of fillet or butt
welds in position
PC, PD, PE, PF, PG
(out-of-position)
br-er5-23e.cdr
ohmic
resistance
pulsed arc
aluminium
copper
-
root layer welds only
conditionally possible
© ISF 2002
which
Applications of Different Arc Types
leads to a decreased current
Figure 5.23
2005
5. Gas-Shielded Metal Arc Welding
71
arc length:
long
medium
short
U
AL
AM
AK
U
AL
AM
AK
arc length:
long
medium
short
vD, I
vD, I
operating point:
welding voltage:
arc length:
AL
AM
AK
high
long
medium
medium
low
short
operating point:
wire feed speed:
arc length:
welding current:
deposition efficiency:
weld appearance
butt weld
AL
AM
AK
low
long
low
low
medium
medium
medium
medium
high
short
high
high
weld appearance:
weld appearance
fillet weld
br-er5-25e.cdr
© ISF 2002
br-er5-24e.cdr
© ISF 2002
Wire Feed Speed
Welding Voltage
Figure 5.24
Figure 5.25
intensity. For the adjustment of the contact
tube distance, as a thumb rule, ten to twelve
times the size of the wire diameter should be
contact tube-to-work distance lk
lk1
lk2
lk3
The torch position has considerable influ-
3
30
considered.
ence on weld formation and welding proc-
mm
2
20
operating rule:
lk = 10 to 12 dD
pointed in forward direction of the weld, a part
1
10
ess, Figure 5.27. When welding with the torch
of the weld pool is moved in front of the arc.
0
200
250
300 A
This results in process instability. However, it
350
current
wire electrode:
1,2 mm diameter
shielding gas:
82% Ar + 18% CO2
arc voltage:
29 V
wire feed speed:
8,8 m/min
welding speed:
58 cm/min
br-er5-26e.cdr
ha s the advantage of a flat smooth weld surface with good gap bridging. When welding
with the torch pointed in reversing direction of
© ISF 2002
the weld, the weld process is more stable and
Contact Tube-to-Work Distance
Figure 5.26
the penetration deeper, as base metal fusion
2005
5. Gas-Shielded Metal Arc Welding
72
by the arc is better, although the weld bead
advance direction
surface is irregular and banked.
Figure 5.28 shows a selection of different application areas for the GMA technique and the
appropriate shielding gases.
penetration:
shallow
average
deep
gap
bridging:
good
average
bad
arc
stability:
bad
average
good
spatter formation: strong
average
low
weld width:
average
narrow
average
rippled
The welding current may be produced by different welding power sources. In d.c. welding
the transformer must be equipped with downstream rectifier assemblies, Figure 5.29. An
additional ripple-filter choke suppresses the
wide
residual ripple of the rectified current and has
weld appearance: smooth
br-er5-27e.cdr
also a process-stabilising effect.
With the development of efficient transistors
© ISF 2002
the design of transistor analogue power
Torch Position
sources became possible, Figure 5.29. The
Figure 5.27
operating principle of a transistor analogue
power source follows the principle of an audio frequency amplifier which amplifies a low-level
to a high level input signal, possibly distortion-free. The transistor power source is, as conventional power sources, also equipped with a three-phase transformer, with generally only
one secondary tap. The secondary voltage is rectified by silicon diodes into full wave opera-
transistor
cascade.
The
welding voltage is steplessly
industrial sections
adjustable until no-load voltage is reached. The difference between source voltage and welding voltage
reduces at the transistor
cascade and produces a
shielding gases
and fed to the arc through a
chemical-apparatus engineering
shopwindow construction
pipe production
aluminium-working industry
nuclear engineering
aerospace engineering
fittings production
electrical engineering industry
automotive industry
motor car accessories
materials-handling technology
sheet metal working
crafts
motor car repair
steel production
boiler and tank construction
machine engineering
structural steel engineering
agricultural machine industry
rail car production
Argon 4.6
Argon 4.8
Helium 4.6
Ar/He-mixture
Ar + 5% H2 or 7,5% H2
99% Ar + 1% O2 or
97% Ar + 3% O2
97,5% Ar + 2,5% CO2
83% Ar + 15% He + 2% CO2
90% Ar + 5% O2 + 5% CO2
80% Ar + 5% O2 + 15% CO2
92% Ar + 8% O2
88% Ar + 12% O2
82% Ar + 18% CO2
92% Ar + 8% CO2
forming gas (N2-H2-mixture)
tion, smoothed by capacitors
application examples
autoclaves, vessels, mixers, cylinders
panelling, window frames, gates, grids
stainless steel pipes, flanges, bends
spherical holders, bridges, vehicles, dump bodies
reactors, fuel rods, control devices
rocket, launch platforms, satellites
valves, sliders, control systems
stator packages, transformer boxes
passenger cars, trucks
radiators, shock absorbers, exhausts
cranes, conveyor roads, excavators (crawlers)
shelves (chains), switch boxes
braces, railings, stock boxes
mud guards, side parts, tops, engine bonnets
attachments to flame nozzles, blast pipes, rollers
vessels, tanks, containers, pipe lines
stanchions, stands, frames, cages
beams, bracings, craneways
harvester-threshers, tractors, narrows, ploughs
waggons, locomotives, lorries
br-er5-28e.cdr
comparatively
high
stray
© ISF 2002
Fields of Application of
Different Shielding Gases
power which, in general,
Figure 5.28
2005
5. Gas-Shielded Metal Arc Welding
73
makes water-cooling necessary. The efficiency factor is between 50 and 75%. This disadvantage is, however, accepted as those power sources are characterised by very short reaction times (30 to 50 µs). Along with the development of transistor analogue power sources,
the consequent separation
of the power section (transthree-phase
transformer
fully-controlled
three-phase
bridge rectifier
energy
store
former and rectifier) and
transistor
power section
mains
supply
electronic
welding current
control
took
place. The analogue or
digital control sets the refuist
u1 . . un
erence values and also
iist
controls the welding procreference input
values
signal processor
(analog-to-digital)
current
pickup
ess. The power section
operates exclusively as an
© isf 2002
br-er5-29e.cdr
amplifier for the signals
GMA Welding Power Source,
Electronically Controlled, Analogue
coming from the control.
Figure 5.29
The output stage may also
be carried out by clocked cycle. A secondary clocked transistor power source features just
as the analogue power sources, a transformer and a rectifier, Figure 5.30. The transistor unit
functions as an on-off switch. By varying the on-off period, i.e., of the pulse duty factor, the
average voltage at the output of the transistor stage may be varied. The arc voltage achieves
small ripples, which are of a limited amplitude, in the switching frequency of, in general, 20
kHz; whereas the welding
current shows to be strongly
smoothed during the high
pulse frequencies caused by
3-phase
transformer
3-phase
bridge
rectifier
energy
store
transistor
switch
protective
reactor
welding
current
mains
supply
inductivities. As the transistor unit has only a switching
function, the stray power is
Uist
U1 . . Un
lower than that of analogue
sources.
The
reference input
values
efficiency
Iist
signal processor
(analog-to-digital)
current
pickup
factor is approx. 75 – 95%.
br-er5-30e.cdr
The reaction times of these
© ISF 2002
GMA Welding Power Source,
Electronically Controlled, Secondary Chopped
clocked units are within of
Figure 5.30
2005
5. Gas-Shielded Metal Arc Welding
74
300 – 500 µs clearly longer
than those of analogue
3-phase
bridge
rectifier
filter
energy
storage
transistor
inverter
medium
frequency
transformer
power sources.
rectifier
welding
current
mains
supply
Series
regulator
power
sources, the so-called “inverter power sources”, dif-
Uist
U1 . . Un
Iist
reference input
values
fer widely from the afore-
signal processor
(analog-to-digital)
current
pickup
mentioned
welding
ma-
chines, Figure 5.31. The
© ISF 2002
br-er5-31e.cdr
GMA Welding Power Source, Electronically
Controlled, Primary Chopped, Inverter
Figure 5.31
alternating voltage coming
from the mains (50 Hz) is
initially rectified, smoothed
and converted into a me-
dium frequency alternating voltage (approx. 25-50 kHz) with the help of controllable transistor
and thyristor switches. The alternating voltage is then transformer reduced to welding voltage
levels and fed into the welding process through a secondary rectifier, where the alternating
voltage also shows switching frequency related ripples. The advantage of inverter power
sources is their low weight. A transformer that transforms voltage with frequency of 20 kHz,
has, compared with a 50 Hz transformer, considerably lower magnetic losses, that is to say,
its size may accordingly be smaller and its weight is just 10% of that of a 50 Hz transformer.
Reaction time and efficiency factor are compa-
manufacturer
insulations
class
rotary current welding rectifier
~
type
_
protective
IP21
system
VDE 0542
production
number
welding
MIG/MAG
U0 15 - 38 V
input
3~50Hz
6,6 kVA (DB) cos 0,72
F
cooling
type
F
rable to the corresponding
DIN 40 050
values
switchgear
number
S
35A/13V - 220A/25V
power range
X 60% ED 100% ED
170 A
I2 220 A
power capacity
in dependence
of current flow
U2 25 V
23 V
U1 220 V
I1 26 A
U1 380 V
I1 15 A
17 A
10 A
U1
V
I1
A
A
U1
V
I1
A
A
power supply
power sources.
All welding power sources
plate, Figure 5.32. Here
the performance capability
© ISF 2002
Rating Plate
switching-type
are fitted with a rating
min. and max. no-load voltage
br-er5-32e.cdr
of
and the properties of the
power source are listed.
Figure 5.32
2005
5. Gas-Shielded Metal Arc Welding
75
The S in capital letter (former K) in the middle shows
that the power source is
suitable for welding operations
under
hazardous
situations, i.e., the secona
seamless flux-cored
wire electrode
b
c
dary no-load voltage is
lower than 48 Volt and
form-enclosed flux-cored
wire electrode
therefore not dangerous to
the welder.
br-er5-33e.cdr
© ISF 2002
Cross-Sections of Flux-Cored
Wire Electrodes
Besides the familiar solid
Figure 5.33
wires also filler wires are
used
for
gas-shielded
metal arc welding. They consist of a metallic tube and a flux core filling. Figure 5.33 depicts
common cross-sectional shapes.
Filler wires contain arc stabilisators, slag-forming and also alloying elements which support a
stable welding process, help to protect the solidifying weld from the atmosphere and, more
often than not, guarantee
symbol
R
slag characteristics
rutile base,
slowly soldifying slag
rutile base,
rapidly soldifying slag
basic
filling: metal powder
P
B
M
V
W
rutile- or fluoride-basic
fluoride basic,
slowly soldifying slag
fluoride basic,
slowly soldifying slag
other types
Y
S
customary
application*
S and M
shielding gas **
very
good
mechanical
C and M2
S and M
C and M2
S and M
S and M
S
S and M
C and M2
C and M2
without
without
S and M
without
properties.
An
important
distinctive
criteria is the type of the
filling. The influence of the
filling is very similar to that
of the electrode covering in
*) S: single pass welding - M: multi pass welding
**) C: CO2 - M2: mixed gas M2 according to DIN EN 439
manual electrode welding
(see chapter 2). Figure
br-er5-34e.cdr
© ISF 2002
Type Symbols of Flux-Cored Wire
Electrodes According to DIN EN 12535
5.34 shows a list of the
different types of filler wire.
Figure 5.34
2005