3. Submerged Arc Welding - kau.ac.krmercury.kau.ac.kr/welding/Welding Technology I - Welding...

3.

Submerged Arc Welding

3. Submerged Arc Welding 32

2005

In submerged arc welding a mineral weld flux layer protects the welding point and the

freezing weld from the in-

fluence of the surrounding

atmosphere, Figure 3.1.

The arc burns in a cavity

filled with ionised gases

and vapours where the

droplets from the continu-

ously-fed wire electrode

are transferred into the

weld pool. Unfused flux can

be extracted from behind

the welding head and sub-

sequently recycled.

Main components of a submerged arc welding unit are:

the wire electrode reel, the wire feed motor equipped with grooved wire feed rolls which are

suitable for the demanded wire diameters, a wire straigthener as well as a torch head for cur-

rent transmission, Figure 3.2.

Flux supply is carried out via a hose from the flux container to the feeding hopper which is

mounted on the torch head. Depending on the degree of automation it is possible to install a

flux excess pickup behind

the torch. Submerged arc

welding can be operated

using either an a.c. power

source or a d.c. power

source where the electrode

is normally connected to

the positive terminal.

Welding advance is pro-

vided by the welding ma-

chine or by workpiece

movement.

© ISF 2002

Assembly of a SA Welding Equipment

br-er3-02e.cdr

AC or DC current supplywire straightenerwire feed rollsflux supplyindicatorswire reel

power sourcewelding machine holder

Figure 3.2

© ISF 2002

Process Principle of Submerged Arc Welding

br-er3-01e.cdr

base metal

weld metal

solid slag

flux

arc

weld cavitymolten poolliquid slag

electrode

contact piece

flux hopper

Figure 3.1


2005

Identification of wire electrodes for submerged arc welding is based on the average Mn-

content and is carried out in steps of 0.5%, Figure 3.3. Standardisation for welding filler mate-

rials for unalloyed steels as well as for fine-grain structural steels is contained in DIN EN 756,

for creep resistant steels in DIN pr EN 12070 (previously DIN 8575) and for stainless and

heat resistant steels in DIN pr EN 12072 (previously DIN 8556-10).

The proportions of additional alloying elements are dependent on the materials to be welded

and on the mechanical-technological demands which emerge from the prevailing operating

conditions, Figure 3.4. Connected to this, most important alloying elements are manga-

nese for strength, molybdenum for high-temperature strength and nickel for toughness.

The identification of wire electrodes for submerged arc welding is standardised in DIN EN

756, Figure 3.5.

During manufacture of fused welding fluxes the individual mineral constituents are, with

regard of their future composition, weighed and subsequently fused in a cupola or electric

furnace, Figure 3.6. In the dry granulation process, the melt is poured stresses break the

© ISF 2002

Wire Electrodes forSubmerged Arc Welding

br-er3-03e.cdr

commercial wireelectrodes

main alloying elementsMn Ni Mo Cr V

alloy type

Mn

MnMo

Ni

NiMo

NiV

NiCrMo

S1S2S3S4

0,51,01,52,0

S2MoS3MoS4Mo

1,01,52,0

0,50,50,5

S2Ni1S2Ni2

1,01,0

1,02,0

S2NiMo1S3NiMo1

1,01,5

1,01,0

0,50,5

S3NiV1 1,5 1,0 0,15

S1NiCrMo2,5S2NiCrMo1S3NiCrMo2,5

0,51,01,5

2,51,02,5

0,60,60,6

0,80,50,8

From a diameter of 3 mm upwards all wire electrodes haveto be marked with the following symbols:

S1

Si

Mo

S6:

:

:

I IIIIII_ _

Example:

S2Si:

S3Mo:

II

III

Figure 3.3

© ISF 2002

Properties and Application Areas for WireElectrodes in Submerged Arc Welding

br-er3-04e.cdr

DIN EN 756mat.-no.

Referenceanalysisapprox.weight %

Properties and application

S11.0351

CSiMn

= 0,08= 0,09= 0,50

CSiMn

= 0,11= 0,15= 1,50

CSiMn

= 0,10= 0,30= 1,00

CSiMnMo

= 0,10= 0,15= 1,00= 0,50

CSiMnNi

= 0,09= 0,12= 1,00= 1,20

CSiMnNi

= 0,10= 0,12= 1,00= 2,20

CSiMnMoNi

= 0,12= 0,15= 1,00= 0,50= 1,00

For lower welding joint quality requirements;in:boiler and tank construction, pipe production,structural steel engineering, shipbuilding

= 0,10= 0,10= 1,00

CSiMn

S21.5035

S31.5064

S2Si1.5034

S2Mo1.5425

S2Ni1

S2Ni2

S3NiMo1

For higher welding joint quality requirements; in:pipe production, boiler and tank construction,sructural steel engineering, shipbuilding.Fine-grain structural steels up to StE 380.

For high-quality welds with mediumwall-thicknesses.Fine-grain structural steels up to StE 420.

Especially suitable for welding of pipe steels,no tendency to porosity of unkilled steels.Fine-grain structural steels up to StE 420.

For welding in boiler and tank construction andpipeline production with creep-resistant steels.Working temperatures of up 500 °C. Suitablefor higher-strength fine-grain structural steels.

For welding low-temperature fine-grainstructural steels.Non-ageing.

Especially suitable for low-temperature welds.Non-ageing.

For quenched and tempered fine-grainstructural steels.Suitable for normalising and/or re-quenchingand tempering.

Figure 3.4


2005

crust into large fragments. During water granulation the melt hardens to form small grains

with a diameter of ap-

proximately 5 mm.

As a third variant, com-

pressed air is additionally

blown into the water tank

resulting in finely blistered

grains with low bulk weight.

The fragments or grains

are subsequently ground

and screened – thus bring-

ing about the desired grain

size.

Identification of a Wire Electrodein Accordance with DIN EN 756

br-er3-05e.cdr

Wi re e le c t ro de D I N EN 75 6 - S2Mo

DIN main no.

Symbols of the chemicalcomposition:S0, S1...S4, S1Si, S2Si, S2Si2, S3Si,S4Si, S1Mo,..., S4Mo, S2Ni1, S2Ni1.5,S2Ni2, S2Ni3, S2Ni1Mo, S3Ni1.5,S3Ni1Mo, S3Ni1.5Mo

Figure 3.5

© ISF 2002

Production of FusedWelding Fluxes

br-er3-06e.cdr

lime quarz rutile bauxite magnesite

silos

balance

roasting kiln

coke

coke

air

raw material

molten metal

tapping

coal-burning stoveelectrical furnace

granulation tub

foaming air

screen

balance

cylindrical crusher

drying oven

Figure 3.6

© ISF 2002

Production of AgglomeratedWelding Fluxes

br-er3-07e.cdr

rutile Mn - ore fluorspar magnesite alloys

sintering furnace

silosball mill

balance

mixer

dish granulator

gas

drying oven

heat treatment furnace

cooling pipe

screen

balance

Figure 3.7


2005

During manufacture of agglomerated weld

fluxes the raw materials are very finely

ground, Figure 3.7. After weighing and with

the aid of a suitable binding agent (water-

glass) a pre-stage granulate is produced in the

mixer.

Manufacture of the granulate is finished on a

rotary dish granulator where the individual

grains are rolled up to their desired size and

consolidate. Water evaporation in the drying

oven hardens the grains. In the annealing fur-

nace the remaining water is subsequently re-

moved at temperatures of between 500°C and

900°C, depending on the type of flux.

The fused welding fluxes are characterised by

high homogeneity, low sensitivity to moisture,

good storing properties and high abrasion re-

sistance. An important advantage of the agglomerated fluxes is the relatively low manufactur-

ing temperature, Figure 3.8. The technological properties of the welded joint can be improved

by the addition of temperature-sensitive deoxidation and alloying constituents to the flux. Ag-

glomerated fluxes have, in

general, a lower bulk weight

(lower consumption) which

allows the use of compo-

nents which are reacting

among themselves during

the melting process. How-

ever, the higher susceptibil-

ity to moisture during stor-

age andprocessing has to

be taken intoconsideration. Different Welding Flux Types

According to DIN EN 760

br-er3-09e.cdr

MS

CS

ZS

RS

AR

AB

AS

AF

FB

Z

MnO + SiOCaO

2 min. 50%max. 15%

manganese-silicate

CaO + MgO + SiOCaO + MgO

2 min. 55%min.15%

calcium-silicate

ZrO + SiO + MnOZrO

2 2

2

min. 45%min. 15%

zirconium-silicate

TiO + SiOTiO

2 2

2

min. 50%min. 20%

rutile-silicate

Al O + TiO2 3 2 min. 40% aluminate-rutilel

Al O + CaO + MgOAl OCaF

2 3

2 3

2

Al O + SiO + ZrOCaF + MgOZrO

2 3 2 2

2

2

Al O + CaF2 3 2

CaO + MgO + CaF + MoSiOCaF

2

2

2

min. 40%min. 20%max. 22%

aluminate-basic

min. 40%min. 30%min. 5%

aluminate-silicate

min. 70% aluminate-fluoride-basic

min. 50%max. 20%min. 15%

fluoride-basic

other compositions

Figure 3.9

© ISF 2002

Properties of Fused andAgglomerated Welding Fluxes

br-er3-08e.cdr

Properties

uniformity of grainsize distribution

grain strength

homogeneity

susceptibilityto moisture

storing properties

resistance to dirt

current carrying capacity

slag removability

high-speed weldingproperties

multiple-wire weldability

flux consumption

1)assessment : -- bad, - moderate, + good, ++ very good

2)core agglomerated flux

Fused fluxes1) Agglomerated

fluxes1)

+/++

+/++

+/++

+/++

+/++

+/++

-/++

-/+

-/++

-/++

-/++

-- /++2)

+/++

+/++

+/++

+/++

+/++

--/+

-/+

-/+

-/++

+/++

Figure 3.8


2005

The SA welding fluxes are, in accordance with

their mineralogical constituents, classified into

nine groups, Figure 3.9. The composition of the

individual flux groups is to be considered as in

principle, as fluxes which belong to the same

group may differ substantially with regards to

their welding or weld metal properties.

In addition to the groups mentioned above

there is also the Z-group which allows free

compositions of the flux.

The calcium silicate fluxes are recognized by

their effective silicon pickup. A low Si pickup

has low cracking tendency and liability to rust,

on the other hand the lower current carrying

capacity of these fluxes has to be accepted.

A high Si pickup leads to a high current cur-

rying capacity up to 2500 A and a deep

penetration. Aluminate-basic fluxes have,

due to the higher Mn pickup, good mechani-

cal properties. With the application of wire

electrodes, as S1, S2 or S2Mo, a low crack-

ing tendency can be obtained.

Fluoride-basic fluxes are characterised by

good weld metal impact values and high

cracking insensitivity. Figures 3.10a and

3.10b show typical properties and applica-

tion areas for the different flux types.

© ISF 2002

Classification of Fluxes for SAWelding According to DIN EN 760 (I)

br-er3-10ae.cdr

MS - high manganese and silicon pickup- restricted toughness values- high current carrying capacity/ high weld speed- unsusceptible to pores and undercuts- unsuitable- suitable for high-speed welding and fillet welds

for thick parts

CS acidic types

basic types

- highest current carrying capacity of all fluxes- high silicon pickup- suitable for welding by the pass/ capping method of thickparts with low requirements

- low silicon pickup- suitable for multiple pass welding- current carrying capacity decreases with increaseingbasicity

ZS - high-speed welding of single-pass welds

RS - high manganese pickup/ high silicon pickup- restricted toughness values of the weld metal- suitable for single and multi wire welding- typical: welding by the pass/ capping pass method

AR - average manganese and silicon pickup- suitable for a.c. and d.c.- single and multi wire welding- application fields: thin-walled tanks, fillet welds forstructural steel construction and shipbuilding

Figure 3.10a

© ISF 2002

Classification of Fluxes for SA WeldingAccording to DIN EN 760 ( )II

br-er3-10be.cdr

AB - medium manganese pickup- good weldability- good toughness values in welding by the pass/ cappingpass method

- application field:unalloyed and low alloyed structural steels- suitable for a.c. and d.c.- applicable for multilayer welding or welding by thepass/ capping pass method

AS - mainly neutral metallurgical behavior- manganese burnoff possible- good weld appearance and slag removability- to some degree suitable for d.c.- recommended for multi layer welds for high toughnessrequirements

- application field: high-tensile fine grain structural steels,pressure vessels, nuclear- and offshore components

- mainly neutral metallurgical behaviour- however, manganese burnoff possible- highest toughness values right down to very lowtemperatures

- limited current carrying capacity and welding speed- recommended for multi layer welds- application field: high-tensile fine-grain structural steeels

FB

AF - suitable for welding stainless steels and nickel-base alloys- neutral behaviour as regards Mn, Si and otherconstituents

Z - all other compositions

Figure 3.10b


2005

Figure 3.11 shows the identification of a welding flux according to DIN EN 760 by the ex-

ample of a fused calcium silicate flux. This type of flux is suitable for the welding of joints as

well as for overlap welds. The flux can be used for SA welding of unalloyed and low-alloy

steels, as, e.g. general structural steels, as well as for welding high-tensile and creep resis-

tant steels. The silicon

pickup is 0.1 – 0.3% (6),

while the manganese

pickup is expected to be

0.3 – 0.5% (7). Either d.c.

or a.c. can be used, as, in

principle, a.c. weldability

allows also for d.c. power

source. The hydrogen con-

tent in the clean weld

metal is lower than the

10 ml/100 g weld metal.

The flux classes 1-3 (table 1) explain the suitability of a flux for welding certain material

groups, for welding of joints and for overlap welding. The flux classes also characterise the

metallurgical material be-

haviour. In table 2 defines

the identification figure for

the pickup or burn-off be-

haviour of the respective

element. Table 4 shows

the gradation of the dif-

fusible hydrogen content

in the weld metal, Figure

3.12.

Identification of a Welding FluxAccording to DIN EN 760

br-er3-11e.cdr

we l d i ng f l ux D I N E N 76 0- S F C S 1 67 AC H 10

DIN main no.

flux/SA welding

method of manufacture F fused A agglomerated M mechanically mixed flux

flux type(figure 3.9)

flux class 1-3 (table 1)

metallurgicalbehaviour (table 2)

hydrogen content (table 4)

type of current

Figure 3.11

Parameters for Flux IdentificationAccording to DIN EN 760

br-er3-12e.cdr

unalloyed andlow-alloyed steel

generalstructural steel

high-tensile & creepresistant steels

welding of joints

hardfacing

stainless and heatresistant steelsCr- & CrNi steels

pickup of elementsas C, Cr, Mo

flux class1 2 3

table 1

table 2

metallurgialbehaviour

identificationfigure

proportion flux inall-weld metal

%

1234

over 0,70,5 up to 0,70,3 up to 0,50,1 up to 0,3

burnoff

5pickup orburnoff

0 up to 0,1

6789

0,1 up to 0,30,3 up to 0,50,5 up to 0,7over 0,7

pickup

table 4

identificationhydrogen content

ml/100g all-weld metalmax.

H5

H10

H15

5

10

15

Figure 3.12


2005

Figure 3.13 shows the identification of a wire-flux combination and the resultant weld

metal. It is a case of a combination for multipass SA welding where the weld metal shows a

minimum yield point of 460

N/mm² (46) and a minimum

metal impact value of 47 J at

–30°C (3). The flux type is

aluminate-basic (AB) and is

used with a wire of the qual-

ity S2.

The tables for the identifica-

tion of the tensile properties

as well as of the impact en-

ergy are combined in Figure

3.14.

The chemical composition of the weld metal and the structural constitution are dependent on

the different metallurgical reactions during

the welding process as well as on the used

materials, Figure 3.15. The welding flux influ-

ences the slag viscosity, the pool motion and

the bead surface. The different combinations

of filler material and welding flux cause, in di-

rect dependence on the weld parameters (cur-

rent, voltage), a different melting behaviour

and also different chemical reactions. The di-

lution with the base metal leads to various

strong weld pool reactions, this being depend-

ent on the weld parameters.

The diagram of the characteristics for 3 dif-

ferent welding fluxes assists, in dependence

of the used wire electrodes, to determine the

pickup and burn-off behaviour of the element

Identification of a Wire-Flux CombinationAccording to DIN EN 756

br-er 3-13e.cdr

chemicalcomposition of the wire electrode

wi re - f l ux c om bi na t i onD I N EN 756 - S 4 6 3 AB S2

standard no.

wire electrode and/orwire-flux combinationfor submerged arcwelding

strength andfracture strain

(table1 and 2)

impact energy(table 3)

type of flux(figure 3.10)

Figure 3.13

© ISF 2002

Parameter for Weld Metal IdentificationAccording to DIN EN 756

br-er3-14e.cdr

table 2

identifi-cation

minimum base metalyield strength

N/mm2

minimum tensilestrengthN/mm2

2T

3T

4T

5T

275

355

420

500

370

470

520

600

Identification for strength properties of welding by thepass/ capping pass method welded joints

identification minimum yield pointn/mm2

tensile strengthN/mm2

minimum fracture strain%

440 up to 570

470 up to 600

500 up to 640

530 up to 680

560 up to 720

355

380

420

460

500

35

38

42

46

50

22

20

20

20

18

table 1 Identification for strength properties of multipass weld joints

table 3Identification for the impact energy of clean all-weld metal or of welding bythe pass/ capping pass method welded joints

Z

nodemands

A 0 2 3 4 5 6 7 8

-80-70-60-50-40-30-200+20

identification

temp. for minimumimpact energy 47J

°C

Figure 3.14


2005

manganese, Figure 3.16.

For example: A welding

flux with the mean charac-

teristic and when a wire

electrode S3 is used, has a

neutral point where neither

pickup nor burn-off occur.

The pickup and burn-off

behaviour is, besides the

filler material and the weld-

ing flux, also directly de-

pendent on the welding

amperage and welding

voltage, Figure 3.17. By the example of the selected flux a higher welding voltage causes a

more steeply descending manganese characteristic at a constant neutral point. Silicon pickup

increases with the increased voltage. The influence of current and voltage on the carbon con-

tent is, as a rule, negligible.

Inversely proportional to the voltage is the rising characteristic as regards manganese in de-

pendence on the welding

current, Figure 3.18.

Higher currents cause the

characteristic curve to flat-

ten. As the welding volt-

age, the welding current

also has practically no in-

fluence on the location of

the neutral point. Silicon

pickup decreases with in-

creasing current intensity. Manganese-Pickup and Manganese-BurnoffDuring Submerged Arc Welding

br-er 3-16e.cdr

S1

1,0% 3,0% Mn in wire2,0%

Mn-burnoff

Mn-pickup

S2 S3 S4 S5 S6

Figure 3.16

Metallurgical Reactions DuringSubmerged Arc Welding

br-er 3-15e.cdr

droplet reaction

dilution

weld pool reaction

welding flux welding filler metal

slag

weld metal

base metal

welding data

welding data

welding data

Figure 3.15


2005

The Mn-content of the weld metal can be de-

termined by means of a welding flux dia-

gram, Figure 3.19.

In this example, the two points on the axis

which determine the flux characteristic are

defined for the parameters 580A welding cur-

rent and 29V welding voltage, with the aid of

the auxiliary straight line and the neutral point

curve (MnNP). In this case, the two points are

positioned at 0.6% ∆Mn and 1.25% MnSZ.

Dependent on the manganese content of the

used filler material, the pickup or burn-off

contents can be recognized by the reflection

with respect to the characteristic line (0.38%

Figure 3.19

Figure 3.17 Figure 3.18

© ISF 2006

Pickup and Burnoff Behaviour in Dependenceon Welding Voltage and Wire Electrode

br-er3-17e.cdr

weld flux LW 280 current intensity 580 Awelding speed 55 cm/min

(DIN EN 760 SF CS 1 76 AC H 10)

neutral point

% Mn wire

% Si wire

% C wire

pic

ku

p/

bu

rno

ff

X in

we

igh

t %

�

33 V 36 V

25 V

0,5 1,0 2,0 2,5

27 V

29 V

25 V

36 V

0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45

0,05 0,15 0,20 0,25

25 - 36 V

0,6

% Mn

0,2

0

-0,2

-0,4

-0,6

0,6

% Si

0,2

0

-0,2

-0,4

0,05

0

-0,05

-0,10

-0,15

© ISF 2006

Pickup and Burnoff Behaviour in Dependenceon Welding Current and Wire Electrode

br-er3-18e.cdr

weld flux LW 280 arc voltage 29 Vwelding speed 55 cm/min

(DIN EN 760 SF CS 1 76 AC H 10)

pic

ku

p/

bu

rno

ff

X in

we

igh

t %

�

neutral point

% Mn wire

% Si wire

% C wire

% XSZ

0,6

% Mn

0,2

0

-0,2

-0,4

-0,6

0,6

% Si

0,2

0

-0,2

-0,4

0,05

0

-0,05

-0,10

-0,15

450 A

650 A 580 A

700 A

0,5 1,0 2,0 2,5

800 A

450 A

800 A

800 A

0,15 0,20 0,25

450 A

0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45

© ISF 2002

Welding Flux Diagramm for Determinationof the Mn Content in the Weld Metal

br-er3-19e.cdr

flux diagramm LW 280

manganese(DIN EN 760 SF CS 1 76 AC H 10),

wire electrode 4 mm acc. to Prof. Thier

= 580 A U = 29 V Mn = 0.48 % Mn Mn = 1.69 % Mn

example: I

SZ1

SZ2

Ø


2005

Mn-pickup with a wire containing 0.5%Mn, 0.2% Mn-burnoff with a wire containing 1.75%Mn).

The structure of the characteristic line for the

determination of the silicon pickup con-

tent, is, in principle, exactly the same as de-

scribed above, Figure 3.20. As silicon has

only pickup properties and therefore no neu-

tral point exists, the second auxiliary straight

line must be considered for the determination

of the second characteristic line point.

Weld preparations for multipass fabrication

are dependent on the thickness of the plates

to be welded, Figure 3.21. If no root is

planned during weld preparation and also no

support of the weld pool is made, the root

pass must be welded using low energy input.

When welding very thick plates which are accessible

from both sides, the dou-

ble-U butt weld may be

applied, Figure 3.22. Be-

fore the opposite side is

welded, the root must be

milled out (goug-

ing/sanding). This type of

weld cannot be produced

by flame cutting and is, as

milling is necessary, more

expensive, although exact

weld preparation and cor-

rect selection of the weld-

ing parameters lead to a

high weld quality.

Welding Procedure Sheets for Single-V Butt Welds, Single-YButt Welds with Broad Root Faces and Double-V Butt Welds

br-er 3-21e.cdr

preparation geometry weld buildup

manual metal arc welding

manual metal arc weldingmanual metal arc welding

andSASA

SASASASA

SASASASA

Figure 3.21

Figure 3.20

© ISF 2006

Welding Flux Diagram for Determinationof the Si Content in the Weld Metal

br-er3-20e.cdr

flux diagramm LW 280

silicon(DIN EN 760 SF CS 1 76 AC H 10),

wire electrode 4 mm acc. to Prof. Thier

= 580 A U = 29 V Si = 0.16 % Si

example: I

SZ

Ø

auxiliary

straight line

auxiliary

straight line


2005

Another variation of heavy-

plate welded joints is the

so-called „steep single-V

butt weld”, Figure 3.23.

The very steep edges keep

the welding volume at a

very low level. This tech-

nique, however, requires

the application of special

narrow-gap torches. The

geometry during slag de-

tachment and also during

reworking weld-related de-

fects may cause problems. Here, high demands are made on torch manipulation and process

control. Special narrow-gap welding fluxes facilitate slag removal.

The most important weld-

ing parameters as regards

weld bead formation are

welding current, voltage

and speed, Figure 3.24. A

higher welding current

causes higher deposition

rates and energy input,

which leads to reinforced

beads and a deeper pene-

tration. The weld width re-

mains roughly constant.

The increased welding volt-

age leads to a longer arc

which also causes the bead to be wider. The change in welding speed causes - on both sides

of an optimum - a decrease of the penetration depth. At lower weld speeds, the weld pool

running ahead of the welding arc acts as a buffer between arc and base metal. At high

speeds, the energy per unit length decreases which leads, besides lower penetration, also to

narrower beads.

© ISF 2002

Welding Procedure Sheetfor Double-U Butt Welds

br-er3-22e.cdr

preparation geometry weld buildup

manual metal arc weldingturning and sandingmanual metal arc welding

turn

turn

turn

side 1

side 2

SASA

SASA

SASA

SASA

Figure 3.22

© ISF 2002

Welding Procedure Sheetfor Square-Edge Welds

br-er3-23e.cdr

GMA welding

GMA welding

SA welding

SA welding

oscillated

Figure 3.23


2005

Weld flux consumption is dependent on the selected weld type, Figure 3.25. Due to geo-

metrical shape, the flux consumption of a fillet weld is significantly lower than that of a butt

weld. Because of their lower bulk weight, the specific consumption of agglomerated fluxes is

lower than that of fused

fluxes.

Two different control con-

cepts allow the regulation

of the arc length (the prin-

ciple is shown in Figure

3.26). The application of

the appropriate control sys-

tem is dependent on the

available power source

characteristics.

© ISF 2002

Control of the Arc Length

br-er3-26e.cdr

1 2 3

direction of welding

L1

L2

L3

Figure 3.26

© ISF 2002

Welding Flux Consumption in Dependenceon Current Intensity and Seam Shape

br-er3-25e.cdr

2,4

2,2

2,0

1,8

1,6

1,6

1,4

1,4

1,2

1,2

1,0

1,0

0,8

0,8

0,6

0,6

0,4

0,4

0,2

0,2

0

400

400

0500

500

600

600

700

700

800

800

900

900

1000

1000

1100

1100

consum

ption k

g flu

x / k

g w

ire

consum

ption k

g flu

x/ kg w

ire

A) flat weld - I square butt joint

current intensity (A)

current intensity (A)

B) fillet weld

fused composition fluxes

fused composition fluxes

agglomerated fluxes

agglomerated fluxes

Figure 3.25

© ISF 2002

Influence of the Weld Parameterson Penetration Depth and Weld Width

br-er3-24e.cdr

constant:

plate thickness:wire electrode:flux:

welding current ( )I

constant:

arc voltage (U)

constant:

welding speed (v)

penetr

ation d

epth

tin

mm

p

weld

wid

th w

in m

m

w

tp

I

w

tp

I

w

te

12

10

8

6

4

2

0

12

10

8

6

4

2

0

12

10

8

6

4

2

0

30

20

10

30

20

10

400 500 600 700 800 Amp.

28 30 32 34 36 38 40 Volt

30 40 50 60 70 80 90 100 110 cm/min

U = 32 Voltv = 60 cm/min

I = 600 Amp.v = 60 cm/min

I = 600 Amp.U = 32 Volt

25 mm4 mm

MS-Typ

Figure 3.24


2005

The external regulation of the arc length by

the control of the wire feed speed requires a

power source with a steeply descending char-

acteristic, Figure 3.27. In this case, the short-

ening of the arc caused by some

process disturbance, entails a strong voltage

drop at a low current rise. As a regulated quan-

tity, this voltage drop reduces the wire feed

speed. Thus, the initial arc length can be regu-

lated at an almost constant deposition rate. In

contrast, the internal regulation effects, when

the arc is reduced, a strong current rise at a

low voltage drop (slightly descending charac-

teristic). At a constant wire feed speed the ini-

tial arc length is independently regulated by the

increased burn-off rate which again is a conse-

quence of the high current.

The reaction of the internal regulation to

process disturbance is very fast. This process

is self regulating and does not require any

machine expenditure.

In submerged arc welding of butt joints, it is,

depending on the weld preparation, neces-

sary to support the liquid weld pool with a

backing, Figure 3.28. This is normally done

with either a ceramic or copper backing with a

flux layer or by a backing flux. Dependent on

the shape of the backing bar, direct formation

of the underside seam can be achieved.

When welding circumferential tubes, the in-

clination angle of the electrode has a direct

br-er3-28e.cdr

Examples of WeldPool Backups

backing flux

ceramic backing bar

flux copper backing

Figure 3.28

© ISF 2002

Control System forConstant Length of Arc

br-er3-27e.cdr

A

A´

I

I

I´

I´

U

U

U0

U0

US

US

ID

ID

IS

IS IK I

I

external regulation D U-regulation)(

AA´

UD

UD

internal self regulation D I-regulation)(

Figure 3.27


2005

influence onto the formation of the weld bead,

Figure 3.29. For external as well as for internal

tube welds, the best weld shapes may be ob-

tained with an adjusted angular position of the

torch. If the advance is too low, the molten

bath runs ahead and produces a narrow weld

with a medium-sized ridge, too high an ad-

vance causes the flowback of the molten bath

and a wide seam with a formed trough in the

centre. The processes described here for ex-

ternal tube welds are, the other way round,

also applicable to internal tube welds.

To increase the efficiency of submerged

arc welding, different process variations are

applied, Figure 3.30. In multiwire welding,

where up to 6 wires are used, each welding

torch is operated from a separate power

source. In twin wire welding, two wire electrodes are connected in one torch and supplied

from one power source. Dependent on the application, the wires can be arranged in a parallel

or in a tandem.

In submerged arc welding

with iron powder addition

can the deposition rate be

substantially increased at

constant electrical parame-

ters, Figure 3.31. The in-

creased deposition rate is

realised by either the addi-

tion of a currentless wire

(cold wire) or of a pre-

heated filler wire (hot wire).

The use of a rectangular

Process Variations ofSubmerged-Arc Welding

single wire tandem

parallel twinwire

tandem, twinwire

© ISF 2002br-er3-30e.cdr

Figure 3.30


b2 b3b1

t 1 t 2 t 3

a3

a2

a1= 0°

0° - 30°

inclusion

Wire Position in SA-Welding

for Circumferential Tube Welds

Figure 3.29


2005

strip instead of a wire elec-

trode allows a higher cur-

rent carrying capacity and

opens the SA method also

for the wide application

range of surfacing.

However, the mentioned

process variations can be

combined over wide

ranges, where the elec-

trode distances and posi-

tions have to be appropri-

ately optimised, Figure

3.32. Current type, polarity, geometrical co-ordination of the individual weld heads and the

selected weld parameters also have substantial influence on the weld result.

Process Variations ofSubmerged-Arc Welding

iron powder/chopped wire

hot wire

cold wire

strip


Figure 3.31


tandem welding

three-wire welding

three-wire, hot wirewelding

four-wire welding

1. WH

1. WH

1. WH

2. WH

2. WH 3. WHHW

=

=

=

~

~

~~~~

3. WH

~

~

2. WH

~

65°

65°

12..16

12..1635

10 101535 12..16

75°80°

1215 18

Position of Wire Electrode inSubmerged-Arc Multi-Wire Welding

Figure 3.32


0 500 1000 1500 2000 2500 A 35000

10

20

30

40

50

60

70

80

kg/h

100

de

po

sitio

n r

ate

current intensity

we

ld m

eta

l voltage = 30 V

speed = 40 cm/min

wire protrusion = 10dlength

current intensity

Æ3,0 mm

Æ 4,0 mm

Æ5,0 mm

12

9

6

30

300 400 500 600 A 800

~~

kg/h

single wire+ metal powder

single wire+ hot wire

double wire

single wiretandem

three-wire

four-wire

Application Fields forSubmerged-Arc Process Variants

Figure 3.33


2005

The description of these individual process variations of submerged arc welding shows that

this method can be applied sensibly and economically over a very wide operating range, Fi-

gure 3.33. It is a high-efficiency welding process with a deposition rate of up to 100 kg/h.

Due to large molten pools and flux application positional welding is not possible.

When more than one wire

is used in order to obtain a

high deposition rate, arc

interactions occur due to

magnetic arc blow, Fig-

ure 3.34. Therefore, the

selection of the current

type (d.c. or a.c.) and also

sensible phase displace-

ments between the indi-

vidual welding torches are

very important.


+ +

( )_ ( )_

+ _ + ~

__ +( ) ( )_ _

elektrode

arc

workpiece

+ +

Magnetic Interaction of Arcs at SA Tandem Welding

Figure 3.34

3. Submerged Arc Welding - kau.ac.krmercury.kau.ac.kr/welding/Welding Technology I - Welding...

Documents

Transcript of 3. Submerged Arc Welding - kau.ac.krmercury.kau.ac.kr/welding/Welding Technology I - Welding...