5. Gas– Shielded Metal Arc Welding

2003

5. Gas-Shielded Metal Arc Welding

56

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 gas-shielded arc welding (SG)

two more process

gas-shielded metal-arc welding (GMAW) metal inert gas welding (MIG) electrogas welding (MSGG) Narrow-gap gasshielded arc welding (MSGE)

variants, the elec-

tungsten gasshielded welding

trogas and the nar-

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

and also the gasshielded

plasma

metal arc welding, a combination of both plasma weld-

non consumable electrode

br-er5-01e.cdr

row gap welding

© ISF 2002

ing and MIG weld-

Classification of Gas-Shielded Arc Welding Processes

ing, Figure 5.1.

Figure 5.1 In contrast to TIG welding, where the electrode is normally negative in order to avoid the melting of the tungsten

wire feed unit

electrode, this effect is exploited in MIG welding, as the positive pole is

water cooling

strongly heated than the negative pole,

shielding gas control device

thus improving the melting characteris-

control switch cooling water control

tics of the feed wire. Figure 5.2 shows the principle of a

rectifier transformer

GMA welding installation. The welding power source is assembled using

welding power source

the following assembly groups: The transformer converts the mains voltage to low voltage which is subsebr-er5-02e.cdr

© ISF 2002

quently rectified. GMA Welding Installation

Figure 5.2

5. Gas-Shielded Metal Arc Welding

compact device

57 Apart from the torch cooling and the

universal device

shielding gas control, the process 5, 10 or 20m 3 to 5m 3 to 5m

control is the most important installation component. The process control ensures that once set welding data are adhered to.

mini-spool device

push-pull device

A selection of common welding installation variants is depicted in Figure 5.3, where the universal device

10, 20 or 30m

5 to 10m

with a separate wire feed housing is the most frequently

used variant in

the industry.

© ISF 2002

br-er5-03e.cdr

Types of Welding Installations

Figure 5.4 shows in detail a manually operated inert-gas shielded torch with the common swan-neck shape. A

Figure 5.3 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

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

nozzle is shaped to ensure a steady gas flow in the arc space, thus protecting arc and molten pool against the atmosphere.

© ISF 2002

br-er5-04e.cdr

Manual Gas-Shielded Arc Welding Torch

Figure 5.4

5. Gas-Shielded Metal Arc Welding

58 A so-called “Two-Wire-Drive” wire

1 2

4

feed system is of the most simple de-

2

F

sign, as shown in Figure 5.5. The wire is pulled off a wire reel and fed into the hose package. The wire transport

4

4

3

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

5

feeding.

6

1 wire reel

3 wire transport roll

2 wire guide tube

4 counter pressure roll

More complicated but following the

5 wire feed roll with a V-groove for steel electrodes

same operation principle is the “Four-

6 wire feed roll with a rounded groove for aluminium br-er5-05e.cdr

© ISF 2002

Wire Feed System

Wire-Drive”, Figure 5.6. Here, the second pair of rollers guarantees higher feeding reliability by reducing

Figure 5.5 4-roller drive 4

3

the risk of wheel slip. Another design

1

3

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 motor rota-

1

2

2

1 wire guide tube 2 drive rollers 3 counter pressure rollers 4 wire guide tube

tion and the angular offset of the drive rollers which are firmly connected to

planetary drive 3

the motor shaft. direction of rotation

Figure 5.7 depicts the metal transfer in the short arc range. During the burn-

3

ing phase of the arc, material is molten 1

and accumulates at the electrode end.

1 wire guide tube 2 roller holding device 3 drive rollers

2

br-er5-06e.cdr

The voltage drops slowly while the arc

© ISF 2002

Wire Drives

shortens. Electrode and workpiece Figure 5.6

5. Gas-Shielded Metal Arc Welding

59

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 narrowing liquid root and the welding voltage

rising current lead to a very high current time

density

that

welding current

causes a sudden evaporation of the remaining

time

1 ms 1 mm

root.

The arc is reignited. The shortarc

technique

is

particularly suitable

br-er5-07e.cdr

for

Short-Circuiting Arc Metal Transfer

and

Figure 5.7

out-of-position root

passes

welding.

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 welding current

welding current

with a high CO2 proportion a long arc is formed in the upper power range, Figure 5.9. Material time

time

transfer

is

unde-

fined and occurs as illustrated in Figlow

choke effect

br-er5-08e.cdr

medium

ures 5.13 and 5.14.

© ISF 2002

Short-circuits Choke Effect

Figure 5.8

with

very strong spatter formation

are

5. Gas-Shielded Metal Arc Welding

60

welding current

welding current

caused by the formation of very large droplets at the electrode end.

time

welding voltage

welding voltage

time

time

time br-er5-09e.cdr

© ISF 2002

br-er5-10e.cdr

© ISF 2002

Long Arc

Spray Arc

Figure 5.9

Figure 5.10

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-shortcircuiting 35

C1 shielding gas composition: C1: CO2 M21: 82% Ar, 18% CO2 M23: 92% Ar, 8% O2

welding voltage

V

long arc

and

spray-like material

M21 M23

transfer. high

For

its

deposition

25

rate the spray arc 20

is used for welding mixed circuiting arc

15

short arc contact tube distance: approx. 15 mm 150 3,5 br-er5-11e.cdr

4,5

filler

spray arc

contact tube distance: approx. 19 mm

Figure 5.11

cover

passes in the flat position.

200 welding current

250

A

300

5,5 7,0 wire feed

8,0

m/min

10,5

Welding Parameters in Dependence on the Shielding Gas Mixture (SG 2, Ø1,2 mm)

and

© ISF 2002

Connections tween

be-

welding

5. Gas-Shielded Metal Arc Welding

61 parameters, shielding gas and arc type are shown in Figure 5.11. When the shielding gas M23 is used, the

thermal conductivity

helium

spray arc may already be produced hydrogen

with an amperage of 260 A. With the decreasing argon proportion the am-

CO2

perage has to be increased in order to

nitrogen

remain in the spray arc range. When pure carbon dioxide is applied, the

argon

spray arc cannot be produced. Figure

temperature

5.11 shows, moreover, that with the argon 82%Ar+18%CO2

CO2

increasing CO2 content the welding

helium

voltage must also be increased in order to achieve the same deposition br-er2-12e.cdr

© ISF 2002

rate.

The different thermal conductivity of Figure 5.12 current-carrying arc core

the shielding gases has a considerable influence on the arc configuration and

by the low thermal conductivity of the argon the arc core becomes very hot –

temperature

weld geometry, Figure 5.12. Caused

this results in a deep penetration in the

r

r

argon

weld centre, the so-called “argon finger-type penetration”. Weld reinforce-

carbon dioxide

Fa

F

ment is strongly pronounced. ApplicaFr

tion of CO2 and helium leads, due to

Fr

the better thermal conductivity of these F

shielding gases, to a wide and deep

Fa

penetration. argon br-er5-13e.cdr

A recombination (endothermic break of the linkage in the arc space – exoFigure 5.13

carbon dioxide © ISF 2002

5. Gas-Shielded Metal Arc Welding

62 thermal reaction 2CO + O2 ->2CO2 in the workpiece proximity) intensifies

wire elektrodes

this effect when CO2 is used. In argon, the current-carrying arc core

current-carrying arc core

is wider and envelops the wire electrode end, Figure 5.13. This generates electromagnetic forces which

argon

bring about the detachment of the

carbon dioxide

liquid electrode material. This socalled “pinch effect” causes a metal transfer in small drops, Figure 5.14.

The pointed shape of the arc attachbr-er5-14e.cdr

© ISF 2002

ment in carbon dioxide produces a reverse-direction

force

component,

i.e., the molten metal is pushed up Figure 5.14

until gravity has overcome that force component and material transfer in the form of very coarse drops appear.

acceleration due to gravity wire electrode

electromagnetic force FL (pinch effect)

Besides the pinch effect, the inertia and

the

gravitational

force,

other

forces, shown in Figure 5.15, are ac-

viscosity surface tension S

droplets necking down

tive inside the arc space; however these forces are of less importance.

backlash forces fr of the evaporating material

inertia electrostatic forces

suction forces, plasma flow induced work piece br-er5-15e.cdr

© ISF 2002

Forces in Arc Space

Figure 5.15

5. Gas-Shielded Metal Arc Welding

63

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 nineties; 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.

br-er5-16e.cdr

© ISF 2002

Rotating Arc

Figure 5.16

Figure 5.17 depicts the deposition rates over the wire feed speed, as achievable with modern high-efficiency MAG welding processes.

During Ø 1,2 mm

kg/h

deposition rate

transi-

tion from the short

25

to the spray arc the

high performance GMA welding

20

Ø 1,0 mm

15

drop frequency rate increases erratically

10

Ø 0,8 mm

conventional GMA

while the drop volume

5

the 0

the

0

5

10

15

20

25

30

35

40

45 m/min

wire feed speed br-er5-17e.cdr

decreases same

degree.

With an increasing CO2-content,

this

© ISF 2002

“critical Deposition Rate

Figure 5.17

at

current

range” moves up to higher power ranges

5. Gas-Shielded Metal Arc Welding

64

and is, with inert gas constituents of lower than 80%, hardly achievable thereafter. This effect facilitates the pulsed-arc welding technique, Figure 5.18. 300

300

200

100

100

V arc voltage

200 critical current range

UEff

3

10 cm

drop volume

number of droplets

35 -4

1/s

25 20 Um

15 10 5

0

500

0 0

A

400

tP

200

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

time

IG

tG

Setting parameters:

350 300 IEff

250 200

Im

150 100 50 0 5

0

br-er5-18e.cdr

© ISF 2002

10

15 time

20

ms

br-er5-19e.cdr

30 © ISF 2002

Pulsed Arc

Figure 5.18

Figure 5.19

In pulsed-arc welding, a change-over occurs between a low, subcritical background current and a high, supercritical pulsed current. During the background phase which

welding current

corresponds with the pulsed current intensity

short arc range, the

Non-short-circuiting metal tranfer range

arc length is ionised and

backround current intensity

wire

electrode

and work surface are preheated. During the time

pulsed material

phase is

the

molten

and, as in spray arc welding,

superseded

© isf 2002

br-er5-20e.cdr

by

the

magnetic

Pulsed Metal Transfer

forces. Figure 5.20. Figure 5.20

5. Gas-Shielded Metal Arc Welding

65

Figure 5.19 shows an example of pulsed arc real current path and voltage time curve. The formula for mean current is:

Im =

1T idt T ∫0

for energy per unit length of weld is:

1T 2 i dt T ∫0

Ieff =

By a sensible se-

50 working range welding current / arc voltage

lection of welding

45

parameters,

40 optimal setting lower limit upper limit

35 voltage [v]

spray arc

GMA

the

welding

technique allows a

30 transition arc

selection of differ-

25 short arc shielding gas: 82%Ar, 18%CO2 wire diameter: 1,2 mm wire type: SG 2

20 15 10 50

75

100

125

150

175 200 225 250 welding current

275

300

325

350

375

are

distinguished

by

their

metal

400

transfer way. Fig-

© ISF 2002

br-er5-21e.cdr

ent arc types which

ure 5.21 shows the

Parameter Setting Range in GMA Welding

setting range for a

Figure 5.21

good

welding

process in the field filler metal: SG2 -1,2 mm shielding gas: Ar/He/CO2/O2-65/26,5/8/0,5

conventional

GMA welding.

transition zones spray arc

V

voltage

of

rotating arc

50

Figure 5.22 shows

30 high-efficiency spray arc

the extended set-

20

ting range for the

high-efficiency short arc

10

short arc

high-efficiency MAGM

100 br-er5-22e.cdr

200

300 welding current

400

A Quelle: Linde, ISF2002

Setting Range or Welding Parameters in Dependence on Arc Type

Figure 5.22

welding

600

process

with

rotating arc.

a

5. Gas-Shielded Metal Arc Welding

66 Some typical ap-

arc types welding methods MAGC MAGM MIG seam type, positions workpiece thickness

applications

spray arc

short 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

aluminium copper

different arc types

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

welding of root layers in position PA

plications of the

pulsed arc

aluminium (s < 1,5 mm)

are depicted in Fig-

-

inner passes and cover passes of fillet or butt welds in position PC, PD, PE, PF, PG (out-of-position)

ure

5.23.

The

rotating arc, (not mentioned in the figure), is applied

root layer welds only conditionally possible

in just the same way as the spray

br-er5-23e.cdr

© ISF 2002

arc, however, it is

Applications of Different Arc Types

not used for the Figure 5.23

welding of copper and aluminium.

The arc length within the working range is linearly dependent on the set

U

welding voltage, Figure 5.24. The AL

weld seam shape is considerably in-

AM

AK

arc length: long medium short

fluenced by the arc length. A long arc produces a wide flat weld seam and, in the case of fillet welds, generally undercuts. A short arc produces a narrow, banked weld bead.

On the other hand, the arc length is inversely proportional to the wire

vD, I

operating point: wire feed speed: arc length: welding current: deposition efficiency:

AL

AM

AK

low long low low

medium medium medium medium

high short high high

weld appearance:

feed speed, Figure 5.25. This has influence on the current over the internal adjustment with a slightly dropping power

source

characteristic.

br-er5-24e.cdr

This

Wire Feed Speed

again is of considerable importance for the deposition rate, i.e., a low wire feed speed leads to a low deposition

© ISF 2002

Figure 5.24

5. Gas-Shielded Metal Arc Welding

67 rate, the result is flat penetration and

arc length: long medium short

U AL AM AK

low base metal fusion. At a constant weld speed and a high wire feed speed a deep penetration can be obtained.

vD, I

operating point: welding voltage: arc length:

AL

AM

high long

medium medium

AK low short

At equal arc lengths, the current intensity is dependent on the contact tube distance, Figure 5.26. With a large contact tube distance, the wire

weld appearance butt weld

stickout is longer and is therefore characterised by a higher ohmic resisweld appearance fillet weld

tance which leads to a decreased current intensity. For the adjustment of

br-er5-25e.cdr

© ISF 2002

Welding Voltage

the contact tube distance, as a thumb rule, ten to twelve times the size of

Figure 5.25 the wire diameter should be considered. lk1

lk2

lk3

influence on weld formation and welding process, 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.

contact tube-to-work distance lk

The torch position has considerable 3

30 mm

2

20

lk = 10 to 12 dD 1

10

0 200

250

However, it ha s the advantage of a flat smooth weld surface with good gap bridging. When welding with the torch pointed in reversing direction of

operating rule:

300 A

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

the weld, the weld process is more

© ISF 2002

Contact Tube-to-Work Distance

stable and the penetration deeper, as Figure 5.26

5. Gas-Shielded Metal Arc Welding

68 base metal fusion by the arc is better,

advance direction

although the weld bead surface is irregular and banked.

Figure 5.28 shows a selection of different application areas for the GMA technique and the appropriate shieldpenetration:

shallow

average

deep

gap bridging:

good

average

bad

arc stability:

bad

average

good

spatter formation: strong

average

low

weld width:

average

narrow

average

rippled

ing gases.

The welding current may be produced by different welding power sources. In d.c. welding the transformer must be wide

equipped with downstream rectifier weld appearance: smooth

br-er5-27e.cdr

assemblies, Figure 5.29. An additional

© ISF 2002

ripple-filter choke suppresses the residual ripple of the rectified current

Torch Position

and has also a process-stabilising Figure 5.27

effect.

power

sources

became

possible,

Figure

92% Ar + 8% CO2 forming gas (N2-H2-mixture)

88% Ar + 12% O2 82% Ar + 18% CO2

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

5.29. The operating principle of a transistor

80% Ar + 5% O2 + 15% CO2 92% Ar + 8% O2

industrial sections

analogue

83% Ar + 15% He + 2% CO2 90% Ar + 5% O2 + 5% CO2

sign of transistor

99% Ar + 1% O2 or 97% Ar + 3% O2 97,5% Ar + 2,5% CO2

transistors the de-

Argon 4.8 Helium 4.6

efficient Argon 4.6

of

shielding gases

ment

Ar/He-mixture Ar + 5% H2 or 7,5% H2

With the develop-

analogue br-er5-28e.cdr

power source fol-

Fields of Application of Different Shielding Gases

lows the principle of an audio frequency

© ISF 2002

Figure 5.28

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

5. Gas-Shielded Metal Arc Welding

69

transformer, with generally only one secondary tap. The secondary voltage is rectified by silicon diodes into full wave operation, smoothed by capacitors and fed to the arc through a transistor cascade. The welding voltage is steplessly adjustable until no-load voltage is reached. The difference between source voltage and welding voltage reduces at the transistor cascade and produces a comparatively high stray power which, in general, 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 (transformer and rectifier) and electronic control took place. The analogue or digital control sets the reference values and also controls the welding process. 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 transistor unit has only a switching function, the stray power is lower than that three-phase transformer

fully-controlled three-phase bridge rectifier

energy store

of

analogue

sources. The effi-

transistor power section

mains supply

welding current

ciency factor is approx. 75 – 95%. The reaction times of

uist u1 . . un

reference input values

iist

signal processor (analog-to-digital)

these

clocked

units are within of current pickup

300

–

500

µs

clearly longer than © isf 2002

br-er5-29e.cdr

GMA Welding Power Source, Electronically Controlled, Analogue

Figure 5.29

those of analogue power sources.

5. Gas-Shielded Metal Arc Welding

70

Series regulator power sources, the so-called “inverter power sources”, differ widely from the afore-mentioned welding machines, Figure 5.31. The alternating voltage coming from the mains (50 Hz) is initially rectified, smoothed and converted into a medium 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

fre-

quency of 20 kHz, has, compared with a

50

former,

Hz

3-phase transformer

3-phase bridge rectifier

energy store

transistor switch

protective reactor welding current

mains supply

trans-

considera-

bly lower magnetic

Uist U1 . . Un

losses, that is to

reference input values

say, its size may accordingly

be

smaller

its

Iist

signal processor (analog-to-digital)

br-er5-30e.cdr

and

© ISF 2002

GMA Welding Power Source, Electronically Controlled, Secondary Chopped

weight is just 10% of that of a 50 Hz

current pickup

Figure 5.30

transformer.

Reaction time and efficiency

factor

are comparable to the

filter

3-phase bridge rectifier

energy storage

transistor inverter

medium frequency transformer

rectifier welding current

mains supply

corresponding

values of switchingUist

type power sources.

U1 . . Un

reference input values

br-er5-31e.cdr

Iist

signal processor (analog-to-digital)

current pickup

© ISF 2002

GMA Welding Power Source, Electronically Controlled, Primary Chopped, Inverter

Figure 5.31

5. Gas-Shielded Metal Arc Welding

71

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. The S in capital letter (former K) in manufacturer insulations class

rotary current welding rectifier

~

_

protective IP21 system

VDE 0542 production number

type welding MIG/MAG

U0 15 - 38 V

F

cooling type

the middle shows F

that

DIN 40 050

input 3~50Hz 6,6 kVA (DB) cosj 0,72

power

source is suitable

switchgear number

S

the

35A/13V - 220A/25V

power range

X 60% ED 100% ED 170 A I2 220 A 23 V U2 25 V

power capacity in dependence of current flow

17 A 10 A

U1 220 V

I1 26 A

U1 380 V

I1

15 A

U1

V

I1

A

A

U1

V

I1

A

A

power supply

for welding operations

under

ardous

haz-

situations,

i.e., the secondary no-load voltage is lower than 48 Volt

min. and max. no-load voltage © ISF 2002

br-er5-32e.cdr

and therefore not Rating Plate

dangerous to the welder.

Figure 5.32

Besides the familiar solid wires also filler wires are used for

gas-shielded

metal arc welding. They consist of a a

seamless flux-cored wire electrode

b

c

metallic tube and a flux

form-enclosed flux-cored wire electrode

core

Figure 5.33 depicts common

br-er5-33e.cdr

cross-

© ISF 2002

Cross-Sections of Flux-Cored Wire Electrodes

Figure 5.33

filling.

sectional shapes.

5. Gas-Shielded Metal Arc Welding

72

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 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

very similar to that shielding gas ** 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

Figure 5.34

electrode

covering in manual electrode (see

welding

chapter

2).

Figure 5.34 shows a list of the differ-

wire. © ISF 2002

Type Symbols of Flux-Cored Wire Electrodes According to DIN EN 12535

the

ent types of filler

*) S: single pass welding - M: multi pass welding **) C: CO2 - M2: mixed gas M2 according to DIN EN 439 br-er5-34e.cdr

of