5. gas– shielded metal arc weldingdantn/wt/wt1-c5.pdf · gas-shielded metal arc welding 56 the...

2003

5.

Gas– Shielded Metal Arc Welding

5. Gas-Shielded Metal Arc Welding 56

The difference between gas-shielded metal arc welding (GMA) and the gas tung-

sten 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 elec-

trogas and the nar-

row gap welding

and also the gas-

shielded plasma

metal arc welding,

a combination of

both plasma weld-

ing and MIG weld-

ing, 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

strongly heated than the negative pole,

thus improving the melting characteris-

tics of the feed wire.

Figure 5.2 shows the principle of a

GMA welding installation. The weld-

ing power source is assembled using

the following assembly groups: The

transformer converts the mains volt-

age to low voltage which is subse-

quently rectified.

© 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


Apart from the torch cooling and the

shielding gas control, the process

control is the most important installa-

tion component. The process control

ensures that once set welding data

are adhered to.

A selection of common welding in-

stallation variants is depicted in Fig-

ure 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 electrode over

the contact tube. The shielding gas

nozzle is shaped to ensure a steady

gas flow in the arc space, thus protect-

ing arc and molten pool against the

atmosphere.

© 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


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


A so-called “Two-Wire-Drive” wire

feed system is of the most simple de-

sign, 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 coun-

terpressure roller generates the fric-

tional force which is needed for wire

feeding.

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 mo-

tion is the outcome of the motor rota-

tion and the angular 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 burn-

ing phase of the arc, material is molten

and accumulates at the electrode end.

The voltage drops slowly while the arc

shortens. Electrode and workpiece


Wire Feed System

1

24 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


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


make contact and a short-circuit occurs. In the short-circuit phase is the liquid elec-

trode material drawn as result of surface tension into the molten pool. The narrowing

liquid root and the

rising current lead

to a very high cur-

rent density that

causes a sudden

evaporation of the

remaining root.

The arc is reig-

nited. The short-

arc technique is

particularly suitable

for out-of-position

and 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

with a high CO2

proportion a long

arc is formed in the

upper power range,

Figure 5.9. Material

transfer is unde-

fined and occurs as

illustrated in Fig-

ures 5.13 and 5.14.

Short-circuits with

very strong spatter

formation are

Short-Circuiting Arc Metal Transfer

br-er5-07e.cdr

1 ms

1 mm

time

time

wel

ding

cur

rent

wel

ding

vol

tage

Figure 5.7

© ISF 2002

Choke Effect

br-er5-08e.cdr

timetime

wel

ding

cur

rent

wel

ding

cur

rent

choke effectlow medium

Figure 5.8


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 deposition

rate the spray arc

is used for welding

filler and cover

passes in the flat

position.

Connections be-

tween welding


Long Arc

wel

ding

vol

tage

wel

ding

cur

rent

time

time


Spray Arc

wel

ding

vol

tage

wel

ding

cur

rent

time

time

Figure 5.9 Figure 5.10

© ISF 2002

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

br-er5-11e.cdr

wel

ding

vol

tage

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: COM21: 82% Ar, 18% COM23: 92% Ar, 8% O

2

2

2

Figure 5.11


parameters, shielding gas and arc

type are shown in Figure 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 am-

perage has to be increased in order to

remain in the spray arc range. When

pure carbon dioxide is applied, the

spray arc cannot be produced. Figure

5.11 shows, moreover, that with the

increasing CO2 content the welding

voltage must also be increased in or-

der 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 conductivity of the

argon the arc core becomes very hot –

this results in a deep penetration in the

weld centre, the so-called “argon fin-

ger-type penetration”. Weld reinforce-

ment is strongly pronounced. Applica-

tion of CO2 and helium leads, due to

the better thermal conductivity of these

shielding gases, to a wide and deep

penetration.

A recombination (endothermic break

of the linkage in the arc space – exo-


argon helium

argon

helium

temperature

ther

mal

con

duct

ivity hydrogen

nitrogen

CO2

CO282%Ar+18%CO2

Figure 5.12


current-carryingarc core

argon carbon dioxider

argon carbon dioxide

r

tem

pera

ture

Fr

FaF

Fa F

Fr

Figure 5.13


thermal 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 elec-

trode end, Figure 5.13. This gener-

ates 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.

The pointed shape of the arc attach-

ment 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 Figure 5.15, are ac-

tive inside the arc space; however

these forces are of less importance.


wire elektrodes

current-carryingarc core

argon carbon dioxide

Figure 5.14


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


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 weld-

ing 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 multicompo-

nent gas with a he-

lium proportion,

also a high-rating

power source and a

precisely controlled

wire feed system for

high wire feed

speeds are neces-

sary.

Figure 5.17 depicts the deposition rates over the wire feed speed, as achievable with

modern high-efficiency MAG welding processes.

During the transi-

tion from the short

to the spray arc the

drop frequency rate

increases erratically

while the drop vol-

ume decreases at

the same degree.

With an increasing

CO2-content, this

“critical current

range” moves up to

higher power ranges

© ISF 2002

Deposition Rate

br-er5-17e.cdr

conventionalGMA

Ø 0,8 mm

Ø 1,0 mm

Ø 1,2 mm

wire feed speed

depo

sitio

n ra

te

m/min

kg/hhigh performanceGMA welding

25

20

15

10

5

00 5 10 15 20 25 30 35 40 45

Figure 5.17

Figure 5.16

Rotating Arc



and is, with inert gas constituents of lower than 80%, hardly achievable thereafter.

This effect facilitates the pulsed-arc welding technique, Figure 5.18.

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

corresponds with the

short arc range, the

arc length is ionised

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 magnetic

forces. Figure 5.20.

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

drop

vol

ume

num

ber

of d

ropl

ets 1/s 10 cm-4 3

critical currentrange

A


Pulsed Arc


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

wel

ding

cur

rent

ms

Um

Im

IEff

UEff

Figure 5.18 Figure 5.19

wel

ding

cur

rent 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


Figure 5.19 shows an example of pulsed arc real current path and voltage time

curve. The formula for mean current is:

∫=T

0m idt

T1

I

for energy per unit length of weld is:

∫=T

0

2eff dti

T1

I

By a sensible se-

lection of welding

parameters, the

GMA welding

technique allows a

selection of differ-

ent arc types which

are distinguished

by their metal

transfer way. Fig-

ure 5.21 shows the

setting range for a

good welding

process in the field

of conventional

GMA welding.

Figure 5.22 shows

the extended set-

ting range for the

high-efficiency

MAGM welding

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%CO2wire diameter: 1,2 mmwire type: SG 2

volta

ge [v

]

welding current

Figure 5.21

Setting Range or Welding Parameters in Dependence on Arc Type

br-er5-22e.cdr Quelle: Linde, ISF2002

10

20

30

50

V

volta

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


Some typical ap-

plications of the

different arc types

are depicted in Fig-

ure 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

welding voltage, Figure 5.24. The

weld seam shape is considerably in-

fluenced by the arc length. A long arc

produces a wide flat weld seam and, in

the case of fillet welds, generally un-

dercuts. A short arc produces a nar-

row, banked weld bead.

On the other hand, the arc length is

inversely proportional to the wire

feed speed, Figure 5.25. This has in-

fluence 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

© ISF 2002

Applications of Different Arc Types

br-er5-23e.cdr

arc typesap

plic

atio

ns

spray arc long arc short arc pulsed arcM

IGM

AG

MM

AG

Cw

eldi

ng m

etho

dsse

am ty

pe, p

ositi

ons

wor

kpie

ce th

ickn

ess

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


Wire Feed Speed

operating point:

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

lowlonglowlow

AL

mediummediummediummedium

highshorthighhigh

AM AK

weld appearance:

arc length:longmediumshort

v , ID

U

AL AM AK

Figure 5.24


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 ob-

tained.

At equal arc lengths, the current in-

tensity is dependent 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 resis-

tance which leads to a decreased cur-

rent 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 consid-

ered.

The torch position has considerable

influence on weld formation and

welding process, Figure 5.27. When

welding with the torch pointed in for-

ward 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 surface 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


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

cont

act t

ube-

to-w

ork

dist

ance

l k

mm

current

30

20

10

0200 250 A300 350

3

2

1

operating rule:

l = 10 to 12 dk D


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 5.25

Figure 5.26


base metal fusion by the arc is better,

although the weld bead surface is ir-

regular and banked.

Figure 5.28 shows a selection of dif-

ferent application areas for the GMA

technique and the appropriate shield-

ing gases.

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 re-

sidual ripple of the rectified current

and has also a process-stabilising

effect.

With the develop-

ment of efficient

transistors the de-

sign of transistor

analogue power

sources became

possible, Figure

5.29. The operating

principle of a tran-

sistor analogue

power source fol-

lows the principle of

an audio frequency

amplifier which am-

plifies 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


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

.6A

rgon

4.8

Hel

ium

4.6

Ar/H

e-m

ixtu

reA

r + 5

% H

or 7

,5%

H99

% A

r + 1

% O

or

97%

Ar +

3%

O97

,5%

Ar +

2,5

% C

O83

% A

r + 1

5% H

e +

2% C

O90

% A

r + 5

% O

+ 5

% C

O80

% A

r + 5

% O

+ 1

5% C

O92

% A

r + 8

% O

88%

Ar +

12%

O82

% A

r + 1

8% C

O92

% A

r + 8

% C

Ofo

rmin

g ga

s (N

-H-m

ixtu

re)

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

industrial sections shie

ldin

g ga

ses

application examples

Figure 5.28


transformer, with generally only one secondary tap. The secondary voltage is recti-

fied 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 volt-

age 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 ana-

logue or digital control sets the reference 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 vary-

ing 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 of analogue

sources. The effi-

ciency factor is

approx. 75 – 95%.

The reaction times

of these clocked

units are within of

300 – 500 µs

clearly longer than

those of analogue

power sources.

© 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


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 controlla-

ble transistor and thyristor switches. The alternating voltage is then transformer re-

duced to welding voltage levels and fed into the welding process through a secon-

dary 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 Hz trans-

former, considera-

bly 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 comparable to

the corresponding

values of switching-

type power sources.

© ISF 2002

GMA Welding Power Source,Electronically Controlled, Secondary Chopped

br-er5-30e.cdr

weldingcurrent

mains supply

Uist

Iist

3-phasetransformer

reference inputvalues


currentpickup

transistorswitch

protectivereactor

energy store

3-phasebridgerectifier

U . . U1 n

Figure 5.30

© ISF 2002

GMA Welding Power Source, ElectronicallyControlled, Primary Chopped, Inverter

br-er5-31e.cdr

weldingcurrent

mainssupply

Uist

Iist

filter

reference input values


current pickup

transistorinverter

energystorage

3-phasebridgerectifier rectifier

U . . U1 n

mediumfrequency

transformer

Figure 5.31


All welding power sources are fitted with a rating plate, Figure 5.32. Here the per-

formance capability and the properties of the power source are listed. The S in capital

letter (former K) in

the middle shows

that the power

source is suitable

for welding opera-

tions under haz-

ardous situations,

i.e., the secondary

no-load voltage is

lower than 48 Volt

and therefore not

dangerous to the

welder.

Besides the famil-

iar 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.

© 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) cosj

min. and max. no-load voltage

Figure 5.32

© 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


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 atmos-

phere 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 differ-

ent types of filler

wire.

© 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 M2M filling: metal powder S and M C and M2V rutile- or fluoride-basic S withoutW fluoride basic,

slowly slagsoldifyingS 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

5. gas– shielded metal arc weldingdantn/wt/wt1-c5.pdf · gas-shielded metal arc welding 56 the...

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