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