chapter 3 - submerged arc welding
DESCRIPTION
sawTRANSCRIPT
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
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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
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base metal
weld metal
solid slag
flux
arc
weld cavitymolten poolliquid slag
electrode
contact piece
flux hopper
Figure 3.1
3. Submerged Arc Welding 33
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
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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
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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
3. Submerged Arc Welding 34
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
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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
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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
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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
3. Submerged Arc Welding 35
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
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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
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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
3. Submerged Arc Welding 36
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)
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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
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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
3. Submerged Arc Welding 37
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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
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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
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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
3. Submerged Arc Welding 38
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
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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
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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
3. Submerged Arc Welding 39
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
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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
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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
3. Submerged Arc Welding 40
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
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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
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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
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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
3. Submerged Arc Welding 41
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
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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
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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
3. Submerged Arc Welding 42
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
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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
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GMA welding
GMA welding
SA welding
SA welding
oscillated
Figure 3.23
3. Submerged Arc Welding 43
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
3. Submerged Arc Welding 44
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
3. Submerged Arc Welding 45
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
© ISF 2002br-er3-29e.cdr
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
3. Submerged Arc Welding 46
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
© ISF 2002br-er3-31e.cdr
Figure 3.31
© ISF 2002br-er3-32e.cdr
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
© ISF 2002br-er3-33e.cdr
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
3. Submerged Arc Welding 47
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.
© ISF 2002br-er3-34e.cdr
+ +
( )_ ( )_
+ _ + ~
__ +( ) ( )_ _
elektrode
arc
workpiece
+ +
Magnetic Interaction of Arcs at SA Tandem Welding
Figure 3.34