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transcript
5.
Gas– Shielded Metal Arc Welding
5. Gas-Shielded Metal Arc Welding 61
2005
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)
and metal active gas
welding (MAG). Besides,
there are two more process
variants, the electrogas
and the narrow gap weld-
ing and also the gas-
shielded plasma metal arc
welding, a combination of
both plasma welding and
MIG welding, 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 ex-
ploited in MIG welding, as the positive pole is
strongly heated than the negative pole, thus
improving the melting characteristics of the
feed wire.
Figure 5.2 shows the principle of a GMA weld-
ing installation. The welding power source is
assembled using the following assembly
groups: The transformer converts the mains
voltage to low voltage which is subsequently
rectified.
Apart from the torch cooling and the shielding
gas control, the process control is the most
important installation component. The process
control ensures that once set welding data are
adhered to.
© ISF 2002
gas-shielded arc welding (SG)
Classification of Gas-ShieldedArc Welding Processes
br-er5-01e.cdr
gas-shielded metal-arc welding (GMAW)
tungsten gas-shielded welding
metal inert gas welding
(MIG)
plasma jetplasma
arcwelding(WPSL)
plasmaarc
welding
(WPL)
Narrow-gap gas-shielded arc
welding (MSGE)
electrogaswelding(MSGG)
plasma gasmetal arcwelding
(MSGP)
gas mixturemetal-arcwelding
(GMMA)
gas metal-arc COwelding
(MAGC)
2
hydrogentungsten arc
welding
(WHG)
plasmajet
welding
(WPS)
metalactive gaswelding
(MAG)
tungsteninert-gaswelding
(TIG)
tungstenplasmawelding
(WP)
consumable electrode non consumable electrode
Figure 5.1
wire feed unit
water cooling
shielding gascontrol device
control switch
cooling watercontrol
rectifier
transformer
welding power source
GMA Welding Installation
br-er5-02e.cdr © ISF 2002
Figure 5.2
5. Gas-Shielded Metal Arc Welding 62
2005
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.
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 elec-
trode 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 trans-
port 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.
© ISF 2002br-er5-04e.cdr
Manual Gas-Shielded Arc Welding Torch
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 core10 wire guide tube11 wire electrode12 shielding gas supply13 welding current supply
Figure 5.4
© ISF 2002br-er5-03e.cdr
Types of Welding Installations
compact device universal device
mini-spool device push-pull device
10, 20 or 30m 5 to 10m
3 to 5m5, 10 or 20m
3 to 5m
Figure 5.3
5. Gas-Shielded Metal Arc Welding 63
2005
More complicated but following the same operation principle is the “Four-Wire-Drive”, Fig-
ure 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 mo-
tion is the outcome of the
motor rotation and the an-
gular offset of the drive
rollers which are firmly
connected to the motor
shaft.
Figure 5.7 depicts the
metal transfer in the short
arc range. During the
burning phase of the arc,
material is molten and ac-
© ISF 2002br-er5-06e.cdr
Wire Drives
4-roller drive
1 wire guide tube2 drive rollers3 counter pressure rollers4 wire guide tube
3 4 3
3
3
1
1
1
2 2
2
1 wire guide tube2 roller holding device3 drive rollers
planetary drive
direction of rotation
Figure 5.6
© ISF 2002br-er5-05e.cdr
Wire Feed System
1
2
4 2
F
65
1 wire reel
2 wire guide tube
5 wire feed roll with a V-groove for steel electrodes
6 wire feed roll with a rounded groove for aluminium
3 wire transport roll
4 counter pressure roll
4 4 3
Figure 5.5
© ISF 2002
Short-Circuiting Arc Metal Transfer
br-er5-07e.cdr
1 ms
1 mm
time
time
weld
ing c
urr
ent
weld
ing v
oltage
Figure 5.7
5. Gas-Shielded Metal Arc Welding 64
2005
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
electrode material drawn as
result of surface tension into
the molten pool. The nar-
rowing liquid root and the
rising current lead to a very
high current density that
causes a sudden evapora-
tion of the remaining root.
The arc is reignited. The
short-arc technique is par-
ticularly suitable for out-of-
position and root passes
welding.
© ISF 2002
Choke Effect
br-er5-08e.cdr
timetime
weld
ing
cu
rre
nt
weld
ing
cu
rre
nt
choke effectlow medium
Figure 5.8
© ISF 2002br-er5-09e.cdr
Long Arc
we
ldin
g v
olta
ge
weld
ing
cu
rre
nt
time
time
Figure 5.9
© ISF 2002br-er5-10e.cdr
Spray Arc
weld
ing v
olta
ge
weld
ing c
urr
ent
time
time
Figure 5.10
5. Gas-Shielded Metal Arc Welding 65
2005
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 forma-
tion, Figures 5.8
In shielding gases with a
high CO2 proportion a
long arc is formed in the
upper power range, Figure
5.9. Material transfer is
undefined and occurs as
illustrated in Figures 5.13
and 5.14. Short-circuits
with very strong spatter
formation are caused by
the formation of very large
droplets at the electrode
end.
If the inert gas content of the shielding gas
exceeds 80%, a spray arc forms in the upper
power range, Figure 5.10. The spray arc is
characterised by a non-short-circuiting and
spray-like material transfer. For its high deposi-
tion rate the spray arc is used for welding filler
and cover passes in the flat position.
Connections between welding parameters,
shielding gas and arc type are shown in Fig-
ure 5.11. When the shielding gas M23 is used,
the spray arc may already be produced with an
amperage of 260 A. With the decreasing argon
proportion the amperage has to be increased
in order to remain in the spray arc range. When
pure carbon dioxide is applied, the spray arc
© ISF 2002
Welding Parameters in Dependence on the Shielding Gas Mixture (SG 2, Ø1,2 mm)
br-er5-11e.cdr
weld
ing v
oltage
150 200 250 300A
15
20
25
V
35
contact tube distance: approx. 15 mm
spray arc
long arc
short arc
contact tube distance: approx. 19 mm
mixedcircuiting arc
C1
M21
M23
welding current
wire feed 5,53,5 4,5 7,0 8,0 10,5m/min
shielding gas composition:C1: CO
M21: 82% Ar, 18% CO
M23: 92% Ar, 8% O
2
2
2
Figure 5.11
© ISF 2002br-er2-12e.cdr
argon helium
argon
helium
temperature
therm
al co
nd
uctivity
hydrogen
nitrogen
CO2
CO282%Ar+18%CO2
Figure 5.12
5. Gas-Shielded Metal Arc Welding 66
2005
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.
The different thermal conductivity of the
shielding gases has a considerable influence
on the arc configuration and weld geometry,
Figure 5.12. Caused by the low thermal con-
ductivity of the argon the arc core becomes
very hot – this results in a deep penetration in
the weld centre, the so-called “argon finger-
type penetration”. Weld reinforcement is
strongly pronounced. Application of CO2 and
helium leads, due to the better thermal conduc-
tivity of these shielding gases, to a wide and
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, Fig-
ure 5.14.
© ISF 2002br-er5-14e.cdr
wire elektrodes
current-carryingarc core
argon carbon dioxide
Figure 5.14
Figure 5.13
© ISF 2006
Influence of Shielding Gason Forces in the Arc Space
br-er5-13e.cdr
current-carryingarc core
argon carbon dioxider
argon carbon dioxide
r
tem
pe
ratu
re
Fr
FaF
Fa F
Fr
5. Gas-Shielded Metal Arc Welding 67
2005
The pointed shape of the arc attachment in
carbon dioxide produces a reverse-direction
force component, i.e., the molten metal is
pushed up until gravity has overcome that
force component and material transfer in the
form of very coarse drops appear.
Besides the pinch effect, the inertia and the
gravitational force, other forces, shown in Fig-
ure 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
after an undefined transition zone, Figure
5.16. High-efficiency MAG welding has
been applied since the beginning of the nine-
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 achiev-
able with modern high-
efficiency MAG welding
processes.
During the transition from
the short to the spray arc
the drop frequency rate in-
creases erratically while the
drop volume decreases at
© ISF 2002br-er5-15e.cdr
Forces in Arc Space
work piece
electrostaticforces
surfacetension S
acceleration due to gravity
wire electrode
viscosity
droplets necking down
inertia
suction forces, plasma flowinduced
electromagnetic force F(pinch effect)
L
backlash forces fof the evaporating material
r
Figure 5.15
Figure 5.16
Rotating Arc
© ISF 2002br-er5-16e.cdr
5. Gas-Shielded Metal Arc Welding 68
2005
the same degree. With an
increasing CO2-content,
this “critical current
range” moves up to higher
power ranges and is, with
inert gas constituents of
lower than 80%, hardly
achievable thereafter. This
effect facilitates the
pulsed-arc welding tech-
nique, Figure 5.18.
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
Setting parameters:
- background current I
- pulse voltage U
- impulse time t
- background time
t or frequency f with
f = 1 / ( t + t ), resp.
- wire feed speed v
G
P
P
G
G P
D
300 300
time
200
I G I m I krit
400 600
t Gt P
200 200
100 100
0 00
dro
p v
olu
me
num
ber
of
dro
ple
ts 1/s 10 cm-4 3
critical currentrange
A
© ISF 2002br-er5-18e.cdr
Pulsed Arc
Figure 5.18
© ISF 2002br-er5-19e.cdr
500
time
arc
volta
ge
150 5 10 20 300
50
100
150
200
250
300
350
400
5
10
15
20
25
35
A
V
we
ldin
g c
urr
ent
ms
Um
Im
IEff
UEff
Figure 5.19
© ISF 2002
Deposition Rate
br-er5-17e.cdr
conventionalGMA
Ø 0,8 mm
Ø 1,0 mm
Ø 1,2 mm
wire feed speed
de
po
sitio
n r
ate
m/min
kg/hhigh performanceGMA welding
25
20
15
10
5
00 5 10 15 20 25 30 35 40 45
Figure 5.17
5. Gas-Shielded Metal Arc Welding 69
2005
and wire electrode and work
surface are preheated. Dur-
ing the pulsed phase the
material is molten and, as in
spray arc welding, super-
seded by the magnetic
forces. Figure 5.20.
Figure 5.19 shows an ex-
ample of pulsed arc real
current path and voltage
time curve. The formula for
mean current is:
∫=
T
0
midt
T
1I
for energy per unit length of weld is:
∫=
T
0
2eff dti
T
1I
By a sensible selection of welding parameters, the GMA welding technique allows a selection
of different arc types which
are distinguished by their
metal transfer way. Figure
5.21 shows the setting
range for a good welding
process in the field of con-
ventional GMA welding.
Figure 5.22 shows the ex-
tended setting range for the
high-efficiency MAGM weld-
ing process with a rotating
arc.
© ISF 2002
Parameter Setting Range in GMA Welding
br-er5-21e.cdr
optimal settinglower limitupper limit
working range welding current / arc voltage
400325
50
10
15
20
25
30
35
40
45
50 75 100 125 150 175 200 225 250 275 300 350 375
spray arc
transition arc
short arcshielding gas: 82%Ar, 18%CO2
wire diameter: 1,2 mmwire type: SG 2
vo
ltag
e [
v]
welding current
Figure 5.21
we
ldin
g c
urr
en
t
pulsed current intensity
Non-short-circuiting metal tranfer range
backround current intensity
time
Pulsed Metal Transfer
br-er5-20e.cdr © isf 2002
Figure 5.20
5. Gas-Shielded Metal Arc Welding 70
2005
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
working range is linearly
dependent on the set weld-
ing voltage, Figure 5.24.
The weld seam shape is
considerably influenced by
the arc length. A long arc
produces a wide flat weld
seam and, in the case of
fillet welds, generally under-
cuts. A short arc produces a
narrow, banked weld bead.
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.
At equal arc lengths, the
current intensity is de-
pendent on the contact
tube distance, Figure 5.26.
With a large contact tube
distance, the wire stickout is
longer and is therefore
characterised by a higher
ohmic resistance which
leads to a decreased current
© ISF 2002
Applications of Different Arc Types
br-er5-23e.cdr
arc types
ap
plic
atio
ns
spray arc long arc short arc pulsed arc
MIG
MA
GM
MA
GC
weld
ing m
eth
ods
seam
type, po
sitio
ns
work
pie
ce thic
kness
aluminiumcopper
aluminiumcopper
aluminium(s < 1,5 mm)
steel unalloyed, low-alloy, high-alloy
steel unalloyed, low-alloy
steel unalloyed, low-alloy
steel unalloyed,low-alloy
steel unalloyed, low-alloy,high-alloy
steel low-alloy, high-alloy
-
-
-
fillet welds or butt welds at thin sheets, all positions
root layers of butt welds
all positions
inner passes and cover passes of fillet or butt welds in position PC, PD, PE, PF, PG (out-of-position)
at medium-thick or thickcomponents,
fillet welds or innerpasses and cover passes of thin and medium-thick components, all positions
root layer welds only conditionally possible
fillet welds or inner passes and cover passes of butt welds at medium-thick or thickcomponents in positionPA, PB
fillet welds or inner passes and cover passes of butt welds at medium-thick or thickcomponents in positionPA, PB
welding of root layers in position PA
Figure 5.23
Setting Range or Welding Parameters in Dependence on Arc Type
br-er5-22e.cdr Quelle: Linde, ISF2002
10
20
30
50
Vvo
lta
ge
high-efficiency spray arc
rotating arc
transition zones
short arc
high-efficiency short arc
100 200 300 400 600A
filler metal: SG2 -1,2 mmshielding gas: Ar/He/CO /O -65/26,5/8/0,52 2
welding current
spray arc
Figure 5.22
5. Gas-Shielded Metal Arc Welding 71
2005
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
considered.
The torch position has considerable influ-
ence on weld formation and welding proc-
ess, Figure 5.27. When welding with the torch
pointed in forward direction of the weld, a part
of the weld pool is moved in front of the arc.
This results in process instability. However, it
ha s the advantage of a flat smooth weld sur-
face with good gap bridging. When welding
with the torch pointed in reversing direction of
the weld, the weld process is more stable and
the penetration deeper, as base metal fusion
© ISF 2002br-er5-25e.cdr
Welding Voltage
weld appearancebutt weld
weld appearancefillet weld
operating point:welding voltage:arc length:
highlong
mediummedium
lowshort
arc length:longmediumshort
U
v , ID
AL
AM
AK
AL AM AK
Figure 5.24
© ISF 2002br-er5-24e.cdr
Wire Feed Speed
operating point:
wire feed speed:
arc length:
welding current:
deposition efficiency:
low
long
low
low
AL
medium
medium
medium
medium
high
short
high
high
AM AK
weld appearance:
arc length:
long
medium
short
v , ID
U
ALAM
AK
Figure 5.25
© ISF 2002br-er5-26e.cdr
Contact Tube-to-Work Distance
lk1 lk2 lk3
wire electrode:
shielding gas:
arc voltage:
wire feed speed:
welding speed:
1,2 mm diameter
82% Ar + 18% CO
29 V
8,8 m/min
58 cm/min
2
conta
ct
tub
e-t
o-w
ork
dis
tance l
k
mm
current
30
20
10
0200 250 A300 350
3
2
1
operating rule:
l = 10 to 12 dk D
Figure 5.26
5. Gas-Shielded Metal Arc Welding 72
2005
by the arc is better, although the weld bead
surface is irregular and banked.
Figure 5.28 shows a selection of different ap-
plication areas for the GMA technique and the
appropriate shielding gases.
The welding current may be produced by dif-
ferent welding power sources. In d.c. welding
the transformer must be equipped with down-
stream rectifier assemblies, Figure 5.29. An
additional ripple-filter choke suppresses the
residual ripple of the rectified current and has
also a process-stabilising effect.
With the development of efficient transistors
the design of transistor analogue power
sources became possible, Figure 5.29. The
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 con-
ventional 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-
tion, smoothed by capacitors
and fed to the arc through a
transistor cascade. The
welding voltage is steplessly
adjustable until no-load volt-
age is reached. The differ-
ence between source volt-
age and welding voltage
reduces at the transistor
cascade and produces a
comparatively high stray
power which, in general,
© ISF 2002br-er5-27e.cdr
Torch Position
penetration:
gap bridging:
arc stability:
spatter formation:
weld width:
weld appearance:
shallow average
average
average
average
average
average
bad
bad
good
good
low
smooth rippled
narrowwide
deep
strong
advance direction
Figure 5.27
© ISF 2002
Fields of Application ofDifferent Shielding Gases
br-er5-28e.cdr
Arg
on 4
.6
Arg
on 4
.8
Heliu
m 4
.6
Ar/
He-m
ixtu
re
Ar
+ 5
% H
or
7,5
% H
99%
Ar
+ 1
% O
or
97%
Ar
+ 3
% O
97,5
%A
r +
2,5
% C
O
83%
Ar
+ 1
5%
He +
2%
CO
90%
Ar
+ 5
% O
+ 5
% C
O
80%
Ar
+ 5
% O
+ 1
5%
CO
92%
Ar
+ 8
% O
88%
Ar
+ 1
2%
O
82%
Ar
+ 1
8%
CO
92%
Ar
+ 8
% C
O
form
ing g
as (
N-H
-mix
ture
)
22
2 2
2
2
22
22
2
2
2
2
22
autoclaves, vessels, mixers, cylinderspanelling, window frames, gates, gridsstainless steel pipes, flanges, bendsspherical holders, bridges, vehicles, dump bodiesreactors, fuel rods, control devicesrocket, launch platforms, satellitesvalves, sliders, control systemsstator packages, transformer boxespassenger cars, trucksradiators, shock absorbers, exhaustscranes, conveyor roads, excavators (crawlers)shelves (chains), switch boxesbraces, railings, stock boxesmud guards, side parts, tops, engine bonnetsattachments to flame nozzles, blast pipes, rollersvessels, tanks, containers, pipe linesstanchions, stands, frames, cagesbeams, bracings, cranewaysharvester-threshers, tractors, narrows, ploughswaggons, locomotives, lorries
chemical-apparatus engineeringshopwindow constructionpipe productionaluminium-working industrynuclear engineeringaerospace engineeringfittings productionelectrical engineering industryautomotive industrymotor car accessoriesmaterials-handling technologysheet metal workingcraftsmotor car repairsteel productionboiler and tank constructionmachine engineeringstructural steel engineeringagricultural machine industryrail car production
industrial sections shie
ldin
g g
ases
application examples
Figure 5.28
5. Gas-Shielded Metal Arc Welding 73
2005
makes water-cooling necessary. The efficiency factor is between 50 and 75%. This disad-
vantage is, however, accepted as those power sources are characterised by very short reac-
tion times (30 to 50 µs). Along with the development of transistor analogue power sources,
the consequent separation
of the power section (trans-
former and rectifier) and
electronic control took
place. The analogue or
digital control sets the ref-
erence values and also
controls the welding proc-
ess. The power section
operates exclusively as an
amplifier for the signals
coming from the control.
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
inductivities. As the transis-
tor unit has only a switching
function, the stray power is
lower than that of analogue
sources. The efficiency
factor is approx. 75 – 95%.
The reaction times of these
clocked units are within of
© isf 2002
GMA Welding Power Source,Electronically Controlled, Analogue
br-er5-29e.cdr
welding currentmainssupply
uist
u . . u1 n iist
three-phasetransformer
reference inputvalues
signal processor(analog-to-digital)
current pickup
transistorpower section
energystore
fully-controlledthree-phase
bridge rectifier
Figure 5.29
© ISF 2002
GMA Welding Power Source,Electronically Controlled, Secondary Chopped
br-er5-30e.cdr
weldingcurrent
mains supply
Uist
Iist
3-phasetransformer
reference inputvalues
signal processor(analog-to-digital)
currentpickup
transistorswitch
protectivereactor
energy store
3-phasebridgerectifier
U . . U1 n
Figure 5.30
5. Gas-Shielded Metal Arc Welding 74
2005
300 – 500 µs clearly longer
than those of analogue
power sources.
Series regulator power
sources, the so-called “in-
verter power sources”, dif-
fer widely from the afore-
mentioned welding ma-
chines, Figure 5.31. The
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 effi-
ciency factor are compa-
rable to the corresponding
values of switching-type
power sources.
All welding power sources
are fitted with a rating
plate, Figure 5.32. Here
the performance capability
and the properties of the
power source are listed.
© ISF 2002
GMA Welding Power Source, ElectronicallyControlled, Primary Chopped, Inverter
br-er5-31e.cdr
weldingcurrent
mainssupply
Uist
Iist
filter
reference input values
signal processor(analog-to-digital)
current pickup
transistorinverter
energystorage
3-phasebridgerectifier rectifier
U . . U1 n
mediumfrequency
transformer
Figure 5.31
© ISF 2002
Rating Plate
br-er5-32e.cdr
Spower range
power capacity
in dependence
of current flow
power supply
manufacturer
rotary current welding rectifier
VDE 0542
typeproduction
numberswitchgearnumber
protective system
DIN 40 050
F F
IP21
35A/13V - 220A/25V
220
25
60%
15380
26
6,6 0,72
220 17
10
100%
15 - 38 23
170
insulations class
cooling type
~_
X
I2
U2
I1U1
U1
U1
U1
I1
I1
I1
U0 V
EDED
A
A A
AV
V
V
V
A
A A
A A
A
V V
welding
MIG/MAG
input
3~50Hz
kVA (DB) cos�
min. and max. no-load voltage
Figure 5.32
5. Gas-Shielded Metal Arc Welding 75
2005
The S in capital letter (for-
mer K) in the middle shows
that the power source is
suitable for welding opera-
tions under hazardous
situations, i.e., the secon-
dary no-load voltage is
lower than 48 Volt and
therefore not dangerous to
the welder.
Besides the familiar solid
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
very good mechanical
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
manual electrode welding
(see chapter 2). Figure
5.34 shows a list of the
different types of filler wire.
© ISF 2002
Cross-Sections of Flux-Cored Wire Electrodes
br-er5-33e.cdr
a b c
form-enclosed flux-cored wire electrode
seamless flux-coredwire electrode
Figure 5.33
© ISF 2002
Type Symbols of Flux-Cored Wire Electrodes According to DIN EN 12535
br-er5-34e.cdr
symbol slag characteristicscustomary application* shielding gas **
R rutile base, slowly soldifying slag
S and M C and M2
P S and M C and M2
B basic S and M C and M2
M filling: metal powder S and M C and M2
V rutile- or fluoride-basic S without
W fluoride basic, slowly slagsoldifying
S and M without
S and M withoutY
S other types
*) S: single pass welding - M: multi pass welding**) C: CO - M2: mixed gas M2 according to DIN EN 4392
rutile base, rapidly soldifying slag
fluoride basic, slowly slagsoldifying
Figure 5.34