THE ESAB WELDING AND CUTTING JOURNAL VOL. 60 NO.1 2005
MECHANISATION
&
AUTOMATION
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THE ESAB WELDING AND CUTTING JOURNAL VOL. 60 NO. 1 2005
Articles in Svetsaren may be reproduced without permission but with
an acknowledgement to Esab.
Publisher
Johan Elvander
Editor
Ben Altemühl
Editorial committee
Björn Torstensson, Johnny Sundin, Bertil Pekkari, Lars-Erik Stridh, Dave Meyer, Tony Anderson,
Peter Budai, Soeren Carlsson, Klaus Blome
Address
Svetsaren, ESAB AB, Marketing Communication
c/o P.O. Kernkade 8 3542 CH Utrecht, The Netherlands
Internet address
http://www.esab.com
E-mail: info@esab.se
Orbital TIG welding - a great way to join
pipes. See page 3 for full information on
the ESAB product range and usage.
Printed in The Netherlands by True Colours
Contents Vol. 60 No. 1 2005
3
6
7
11
13
18
Orbital TIG – a great way to join pipes.
ESAB supplies a complete range of orbital TIGequipment for the mechanised welding of tubes.
21
ESAB Welding Process Center facilities
improved with new location.
New laser-hybrid equipment installed.
23
27
31
Submerged arc welding of steels
for offshore wind towers.
Production economy makes high demands on the
deposition rates of welding processes.
OK Flux 10.72 is a new flux for submerged arc
welding with excellent weldability and good weld
metal toughness at - 50ºC.
Permanova’s seam tracking laser welding tool.
This article reviews the seam tracking feature
of the Permanova WT03 laser welding tool, an
essential component of the laser-hybrid welding
systems supplied by ESAB.
1019442_Svetsaren_01-2005.indd 2
The article looks at the different approaches to
mechanised pipeline welding and their implications
in different parts of the world.
Cutting technology in shipbuilding.
Railtrac flexible tool for Dutch
pipeline constructor NACAP.
Dutch pipeline layer NACAP B.V, in Eelde, The
Netherlands, developed a flexible method for the
welding of pipelines on land.
The upgrading of welding equipment with modern
components, can be a cost-effective alternative to
investment in new equipment.
Mechanised welding of pipelines.
Light mechanisation - easy and
cost-efficient with ESAB.
The “mechanical or cold hand” can withstand a
higher current and can move faster than the hand
of a human welder. ESAB supplies specialised
equipment and dedicated consumables.
Retrofitting of automatic welding systems.
The article describes the latest trends in cutting technology for shipbuilding. Cutting speed and bevel
quality, and their effects on fabrication are reviewed
for various cutting methods.
Improved productivity in automated
aluminium welding fabrication.
The successful use of the AlumaPak bulk drum
in the US market has led ESAB to introduce the
drum into the European and North American markets
under the ESAB brand name of Marathon Pac.
Product news.
34
•
•
•
•
9% Ni steel and Aristo SuperPulse.
ESAB versatile in robotic welding.
NOMAD finalised.
ESAB high purity consumables for
welding creep resisting steels.
• OrigoMig 405 welding package.
• OrigoMag C150/C170/C200/C250
• COMBIREX CXL-P- CNC cutting machine.
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Orbital-TIG – a great way
to join pipes
By: Juha Lukkari, ESAB Oy, Finland.
ESAB supplies a complete range of orbital TIG-equipment – including power sources
and weld monitoring programmes - for the mechanised welding of pipes.
Why mechanisation?
Although pipes have been welded using mechanised
systems since the 1960’s, the TIG-process still accounts
for a considerable amount of manual welding. Yet, there
are many good reasons to explore the use of orbital TIGwelding for applications ranging from single-run welding
of thin-walled stainless pipes to multi-run welding of
thick-walled pipes, and even narrow-gap welding:
•
•
•
•
•
Young welders are difficult to recruit.
Operator ergonomics are improved significantly.
Remote control and video control options.
Increased duty cycle - so higher productivity.
Welding procedures repeatable - resulting in a
consistent weld quality.
• Good control over heat input.
• Equipment available for use “on site”.
Stationary vs. orbital
There are two main catagories of mechanised welding
systems:
• Stationary: the welding head has a fixed position
while the pipe rotates.
• Orbital: the pipe has a fixed horizontal or vertical
position while the welding head rotates.
Orbital-TIG clamp-on welders
Clamp-on pipe welding tools are used in orbital welding
of small and medium-sized pipes, see figures 1 and 2.
The tools can also be equipped with a wire feeder. The
maximum pipe diameter that can be handled is around
200 mm. Tools bigger than this are impractical and
unwieldy. The same type of welding tool can be used to
weld pipes within a specific diameter range. The PRB/
PRC clamp-on welding tools, for example, cover the
diameter ranges 17-49 mm, 33-90 mm and 60-170 mm.
Normally, pipe standards are taken into consideration
while designing welding heads, in order to make the
Figure 1. Three PRB welding tools for pipe diameters
Ø 17-170 mm. They are compact welding heads with
a unique pincer action. The head is positioned and
secured around the pipe in seconds.
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scope of a single welding tool relatively broad.
The clamp-on tool is locked onto the pipe in the welding
position by a single movement of the hand, using the
“self-locking pliers” principle. PRC welding tools can
also be provided with the AVC function (Automatic
Voltage Control of the arc length) and with a weaving
action mechanism - both needed in the multi-run welding
of thick-walled pipes.
Clamp-on pipe welding tools can be either open (open
tools) or enclosed (closed tools). Enclosed heads cover
the entire weld area within a space filled with shielding
gas, figure 3. This is to prevent the hot weld zone from
oxydation. The weld surface is protected in the same way
as the root of a stainless pipe weld is protected by backing
gas. Enclosed tools are used in particular for welds
requiring extreme purity, such as pipes used in the
pharmaceutical industry or titanium pipes.
For pipe diameters above 170 mm, orbital welding can
Figure 2. Three PRC welding tools for pipe diameters Ø 17-170
mm. This onward development of the PRB head features weaving
and arc voltage control, providing higher productivity and better
weld quality, especially with thick-walled tubes.
Figure 4. PRD 100 carriage.
Figure 3. Three enclosed PRH welding tools for pipe diameters Ø 3-76 mm. The rotating part and the tungsten electrode
are enclosed by a gas chamber formed by the outer casing.
This water-cooled head is designed for welding thin-walled
stainless steel and titanium tubes.
be achieved by using a welding carriage that travels the
circumference of the pipe along a track, figure 4. ESAB’s
PRD 100 carriage is particularly low (75 mm), which
means that it will fit into confined spaces. Welding heads
for narrow-gap welding of thick-walled pipes are also
available (to be discussed later).
Figure 5. Pipe groove cutter MF3i for pipe diameters
Ø 25-152 mm.
Mechanisation requires accuracy
Mechanised welding requires a greater accuracy of
groove preparation and fit-up than manual welding where the welder can use his skills to “patch-up” any
shortcomings. In orbital welding, the machine only does
what it has been programmed to do, without compensating for joint irregularities. The time spent on machining a
joint preparation with adequate precision, therefore, often
exceeds the actual welding time. Efficient machining
tools are available from ESAB, figure 5.
Also narrow gap welding
Narrow-gap welding with orbital TIG welders and special
welding heads is a process adopted over recent years,
figure 6. By narrowing the cross section of the joint, the
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joint volume is reduced by a factor of 2-3, depending on
the wall thickness, figure 7. The bevel angle of a conventional U-groove is 10-20º, but in narrow-gap welding it is a
mere 2-6º. A narrow-gap weld is usually made by welding
“bead-on-bead” - so one run per layer.
Power required as well
Power sources for orbital TIG welding come in a variety
of sizes and models, figure 8. The Weldoc WMS 4000
welding monitoring system can be connected to all of
them. When using a carriage (PRD) or a welding head
(PRC) equipped with the AVC function and weaving
mechanism, Protig 450 should be the power source.
Welding monitored by camera
A small camera installed in the welding carriage enables
the operator to monitor the welding process, figure 9.
This significantly eases the task of monitoring welding
and improves management of the process and ergonomics
of the operator.
Figure 6. Narrow-gap PRB welding head for pipe wall thickness
up to Ø 80 mm. Inset shows a typical weld cross section in
stainless steel AISI 304.
Today, many industries require highly detailed verification,
reporting and documentation of mechanised welding
sequences.
This is achieved by connecting a PC with a monitoring
programme to the programmable power sources, figure
10. The welding parameters are measured at intervals
as short as 0.5 seconds and displayed in real time. The
capacity is large enough to monitor and register scores of
parameters. When the welding is completed, the measured
welding parameters are obtained as output.
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Weld sequences monitored and documented
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After welding, it is easy to compare actual values with set
values and pinpoint any deviations. The parameters can
also be allocated limit values to facilitate the monitoring
of any deviations with respect to the welding procedure
specification (WPS).
Figure 7. Comparison of cross-sectional areas of pipe welding
grooves. Groove dimensions: normal U (included angle 30°,
radius 3 mm and root face 2 mm) and narrow-gap groove
(included angle 4 degrees, radius 3 mm and root face 2 mm).
Figure 8. Power sources for TIG welding: Prowelder 160, 250 and 320 and Protig 450.
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Figure 9. Orbital narrow-gap
welding. The operator controls
the welding process via a
monitor receiving the image
from a camera mounted onto
the welding head.
Figure 10. Monitoring of welding parameters using the
Weldoc WMS 4000 computer programme.
A compact printer is also available for documentation,
for example, printing of welding current, voltage, travel
speed and wire feed speed, measured sector-specifically
and bead-specifically during the welding.
* EN 1418: Welding personnel - Approval testing of welding operators for fusion welding and resistance weld
setters for fully mechanised and automatic welding
of metallic materials.
About the author
Operators need to be qualified!
Users of mechanised welding systems must be qualified
to a special standard, EN 1418*, and not only to EN287
which is the qualification standard for manual welders. In
EN 1418, the user is referred to as the ‘operator’ - not the
‘welder’. Note that the operators standard also includes a
mandatory “theory” test to verify the operator’s knowledge
of the functioning of the welding station.
Juha Lukkari joined ESAB OY in Finland in 1974 after
graduating from the Helsinki University of Technology. He
has held several positions and is currently head of technical
customer service.
For more information contact: juha.lukkari@esab.fi
ESAB Welding Process Centre facilities
improved with new location
ESAB’s Process Center in Gothenburg
– the company’s primary center for
application research and training in
Europe – has moved to a new location
on the same premises.
The move, to a more convenient
position closer to the welding laboratories, had been long considered,
but became necessary with the
arrival of the new laser-hybrid
cell which required considerable
space. All diciplines involved in
application research and training
now enjoy short communication
lines and the new lay-out ensures a
more efficient use of the facility.
For more information contact:
larserik.stridh@esab.se
The laser-hybrid installation at the new Process Centre in Gothenburg, Sweden.
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Light mechanisation.
Easy and cost-efficient with ESAB
By: Juha Lukkari, ESAB Oy, Finland.
Light mechanisation of welding involves the use of small, easy to use, and comparatively
low-priced equipment to move the welding gun, generally making use of small tractors
and carriers on rails that can be connected directly to existing MIG/MAG power sources.
ESAB supplies a full range of equipment and consumables.
Also see page 11 for a story on the Dutch pipeline fabricator, NACAP, applying light
mechanisation on a section of Europipe.
Why light mechanisation?
The most obvious reason for light mechanisation is to
obtain a higher productivity in the form of more welded
meters per time unit. The duty cycle is higher than in
manual welding and the travel speeds and deposition
rates obtained are also greater.
A typical application is fillet welding in PB position.
A human welder will experience great difficulties in
continuously handling a welding gun at travel speeds
in excess of 50 cm/min, but a small tractor can easily
achieve 100 cm/min or more. In manual welding, the
endurable welding current limit is perhaps about 300 A,
but machines can easily withstand 300-350 A.
As a result, the deposition rate when using, for
example, metal-cored wire OK Tubrod 14.12 (AWS
E70C-6M, EN T 42 2 M M 1 H10), increases to as high
as 6-8 kg/h.
Light mechanisation holds more advantages than a
higher productivity, however, that can individually, or
together, justify an often modest investment.
• Improved work conditions and safety. The physically
strenuous work is transferred to the machine and the
welder is charged with setting and controlling the
process - enjoying ergonomically improved conditions.
• The quality of the weld is often better and more
consistent. Optimal welding parameters are maintained
throughout the entire length of the weld, and starts and
stops - always potential defect points - are avoided.
• Improved weld appearance. The appearance of, for
example, mechanised welded stainless steel welds,
can be so good that architects even utilise them as a
cosmetic feature on the outside of fancy office buildings
- actually the case in Helsinki !
Design welds with eye to mechanisation
To enable the welding to be mechanised, it must be
taken into consideration at the construction design stage.
Long straight welds without obstacles along the way are
easy to mechanise. Fillet welds are always more attractive
than butt welds from the mechanisation point of view.
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Skilled operator
Mechanisation can never be successful without the
supervision of an experienced operator. He must set the
appropriate welding parameters, recognise when they
need to be adjusted and control the overall process.
This calls for an experienced manual welder with expert
knowledge.
Selection of cored wires
Light mechanisation of MIG/MAG welding is primarily
based on the use of cored wires. The choice of type of
cored wire depends mainly on the welding position and
on the required impact strength.
Figure 1. Railtrac 1000.
Impact toughness: -20ºC
• PB-position welding:
metal-cored wire OK Tubrod 14.12 (AWS E70C-6M,
EN T 42 2 M M 1 H10).
• Vertical welding (PF):
all-positional rutile flux-cored wire OK Tubrod 15.14,
OK Tubrod15.15, FILARC PZ6113 (AWS E71T-1/EN
T 46 2 P M 2 H10).
• Horizontal-vertical welding (PC):
Either cored wire type.
Figure 2. Miggytrac 1000.
Impact toughness: -40ºC
• PB-position welding:
metal-cored wire OK Tubrod 14.05 (AWS E70C-G/
EN T 42 4 Z M M 2 H10).
• Vertical welding (PF):
all-positional rutile flux-cored wire OK Tubrod 15.17,
PZ6138 (AWS E81T1-Ni1/En T 46 3 1Ni P C 2 H5).
• Horizontal-vertical welding (PC):
Either cored wire type.
Welding
Arc
Welding
Wire
current: DC-
voltage
speed
feed
(A)
(V)
(cm/min)
(m/min)
3.5
320
32
100
16
4
330
32
90
17
5
340
33
65
18
7
340
34
35
19
a-size
(mm)
Table 1. Fillet welding in PB-position using metal-cored wire
OK Tubrod 14.12-1.2mm.
Light-mechanisation equipment
Butt weld, PF position.
ESAB equipment for light-mechanisation breaks down in
two categories:
carriers on rails:
• Railtrac 1000 W (Figure 1).
• Railtrac 1000 FW.
and small tractors:
• Miggytrac 1000 (Figure 2).
• Miggytrac 2000.
• Miggytrac 3000.
Typical applications
Fillet weld, PB position.
A typical application for a tractor is performing fillet
welds in PB-position. The productivity achieved easily
doubles that of manual welding, see table 1. Metal-cored
wire OK Tubrod 14.12 is exploited to its maximum.
A typical application for a carriage on rails is vertical
welding (PF), which can be either butt welding or fillet
welding. Roots of butt welds can be made with ceramic
weld metal support.
• Vertical welding (PF).
• Plate thickness: 14 mm.
• Groove and run sequence: 45° V-joint, root pass,
two filler layers.
• Weld metal support: Ceramic backing.
• All-positional rutile flux-cored wire: PZ6113 – 1.4mm.
• Shielding gas: 75%Ar+25%CO2.
• 1st pass: 160-180 A, 22-23 V, 10-12 cm/min.
• 2nd pass: 180-190 A, 24-25 V, 16-18 cm/min.
• 3rd pass: 210-220 A, 24-25 V, 14-15 cm/min.
• Weaving and edge stopping time: Depends on actual
groove width.
• Impact toughness (weld metal):
• -20ºC: 27, 75, 73 / av. 58 J.
• -40ºC: 60, 50, 46 / av. 52 J.
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Figure 4. Manufacturing of stainless steel facade beams for a
large office building in which the architect would most probably not have accepted manual welding. Fillet welds in PB
position. Use of Miggytrac and rutile flux-cored wire: OK
Tubrod 14.31.
Figure 3: Horizontal-vertical pipe weld.
Pipe welds
When welding large-diameter pipes, eg, natural gas pipes,
two rails bent to a specified diameter can be used in welding
by mounting them around the pipe and fastening them to
one another to form a continuous track around the pipe.
Example:
• Pipe steel: X65.
• Pipe diameter: 800 mm.
• Wall thickness: 12 mm.
• Groove and run sequence: V-joint, 60-70°.
• Shielding gas: 75%Ar+25%CO2.
• Root pass: Various options:
• Manually from top down (PG) using metal-cored wire
OK Tubrod 14.12.
• Manually using basic or cellulosic electrode.
• Fill-up run and final run: No’s 2 and 3:
• Using carrier upwards (PF), 6 -> 12 o’clock
• All-positional rutile flux-cored wire: OK Tubrod 15.14
• 1.2 mm, 180-200 A, 23-24 V, 10-20 cm/min.
Figure 5. Vertical-up welding on the inside of a debarking
drum. Railtrac and all-positional rutile flux-cored wire: OK
Tubrod 15.15.
Piles
The joint welds in pile pipes to be driven into the ground
can also be mechanised by using rails bent to match
specified diameters. Fixed steel backing is often used at
the root side.
•
•
•
•
•
•
•
•
Pipe diameter: 800 mm.
Wall thickness: 12 mm.
Backing: Fixed steel bar.
Groove and run sequence: see figure 3.
Welding position: horizontal-vertical (PC).
Metal-cored wire: OK Tubrod 14.12 – 1.2mm.
Shielding gas: 75%Ar+25%CO2.
Passes, 6–7 in number: 180-210 A, 25-30 V,
45-55 cm/min.
• Mechanisation with Railtrac.
Figure 6. Horizontal-vertical welding of the main supporter of
a gantry crane. Railtrac and metal-cored wire: PZ6105R.
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Industrial applications
The figures 4 to 9 show projects in which light mechanisation was used. They are all based on the use of cored
wire. Also refer to page 21, reviewing a recent pipeline
project in the Netherlands using Railtrac equipment and
cored wire.
Figure 8. Welding of
steel fender piles for a
suspension bridge in
Argentina. Railtrac and
basic flux-cored wire
OK Tubrod 15.27. See
Svetsaren 2/2003 for
the full story.
About the author
Juha Lukkari joined ESAB OY in Finland, in 1974, after
graduating from the Helsinki University of Technology. He
has held several positions in the company and is currently
head of Technical Customer Service.
Figure 7. Welding of the suspended roof structure of the
Benfica stadium in Lisbon. Railtrac and structural all-position
flux-cored wire PZ6113. See Svetsaren 2/2003 for the full story.
Door opening contract in China
In November 2004, ESAB in Laxå, Sweden, sold its first
flash butt chain welding machine to Zhang Jia Kou Coal
Mining Machinery Ltd Co - China’s largest and most
modern coal mining chain and equipment producer. The
company is a part of China Coal Mining Engineering
Equipment Import & Export Co.
The machine is designed for different kinds of chains;
from 30 mm to 60 mm bar diameter. The basic chains
are collector links for lifting chains and large coal mining
chains, some with one forged and one welded link in
succession.
For more information contact: juha.lukkari@esab.fi
The machine is based on the SVU - series of flash butt welding
machines, upgraded with a higher clamping force and
some additional useful functions. The machine features
an automatic setting to obtain a constant secondary voltage
with mains fluctuating +/-15%. Also, the machine adapts to
the temperature of the link (from T room up to 800° C).
PRODUCT DATA:
Upset force:
350 kN
Clamping force:
480 kN
Transformers (AC):
2x 250 kVA
Weight:
12,800 kg.
For more information contact:
sylve.antonsson@esab.se
ESAB supplies rail welding equipment to India and Croatia
ESAB in Laxå, Sweden has recently
delivered two automatic flash butt
welding machines for rails; designed
to produce long, high quality rails of
all types.
Plant in India and HZ- Infrastruktura
in Croatia. The Bhilai machine is part
of a complete rail welding factory
supplied by Geismar; the Croatian
contract is a single machine order.
The deliveries - through Geismar,
France - were to the Bhilai Steel
The ZFR 11 GC 6T machines have
built-in trimming units, and include
TECHNICAL DATA:
Clamping force:
196 Metric tons
Upset force:
96 Metric tons
Max current for standard rail (UIC 60):
70.000 Amps
Weight:
38.000 kgs
compressor-type cooling units and
exhaust systems. Other features
include PC control with forces and
speeds controlled in closed loops
via sensors and a high response
proportional valve, and full logging of all welding parameters and
the most recent 1000 alarms. The
welding process uses DC- current
which gives equal load on the three
phases.
For more information contact:
sylve.antonsson@esab.se
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Railtrac flexible tool for Dutch
pipeline constructor NACAP
By: Frits Woldinga, NACAP B.V. , The Netherlands and Sjabbe Datema, ESAB Nederland B.V.
International pipeline contractor NACAP B.V, with its head office in Eelde, The Netherlands,
developed a flexible method for the welding of pipelines on land, utilising two ESAB
Railtrac FW 1000 welding tractors and OK Tubrod 15.09 flux-cored wire. The advantages
compared with commonly used mechanised pipeline welding systems are found in a lower
investment and shorter set-up times before welding. The new method was successfully
applied on a 17 km pipeline crossing the northern part of the Netherlands.
The pipeline, for which the equipment was developed,
is in X70 grade steel with a diameter of 42 inch and a
nominal wall thickness of 14.0 mm. Sections to pass
under canals are 16.4 or 19.9 mm in thickness. Weld
metal toughness requirements are min. 40J at -40°C.
NACAP developed the system in-house and after
extensive testing official welding procedure qualifications
were made. The equipment comprises some features that
are non-standard to the ESAB equipment and the design
includes an extremely light welding tent.
The method uses two Railtrac FW 1000 tractors
simultaneously walking the pipe circumference from 6
‘o clock to 12 ‘o clock; clockwise and counter clockwise.
The diameter of pipelines in general are smaller than
the type of applications for which Railtrac has been
developed, having originated from shipbuilding practice.
The aluminium rail coming with the equipment would
require more fixtures around the pipe circumference
to avoid buckling when tension is applied. Even the
slightest unroundness in the orbit of the tractor would
have a negative effect on the weld quality. Instead of
adapting the standard ESAB rail, NACAP decided to
develop its own, more rigid rail equipped with fast
coupling gear.
The 2nd adaptation to the equipment, done by ESAB
at the request of NACAP, involved a change from one
drive wheel to two drive wheels, one on either side of the
tractor. This increased the stability of the tractor while
travelling the pipe circumference at a high speed.
The system uses two ESAB AristoMig 400w
inverter controlled power sources with Aristofeed
wire feed units.
Figure 1: Railtrac at work.
First the root pass, hot pass and two filler layers are
deposited vertically down with MMA with cellulosic
electrodes. The subsequent filling is done with Railtrac
using OK Tubrod 15.09 all-position rutile cored-wire
welded under Ar/CO2 mixed gas.
OK Tubrod 15.09 has a fast freezing slag that supports
the weld pool well in positional welding at very high
deposition rates. The slag easily releases leaving behind a
clean weld for subsequent passes. One parameter setting
could be applied for all beads in this kind of application.
NACAP preferred to use three optimised parameter
settings while travelling from 6 to 12 ‘o clock.
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Figure 2: The welding tent, including equipment, is easily
moved to the next weld, helped by its weight of just 500kg.
The EN classification of OK Tubrod 15.09, T 69 4 Z
P M 2 H5, indicates that it is a consumable for high
strength steel and that the weld metal hydrogen content
falls within the lowest EN class, H5. This allows lower
preheat temperatures than consumables with a higher
hydrogen content, such as cellulosic electrodes. This
was visible in the welding procedure for the complete
weld. During MMA welding a preheat temperature of
150 ºC was maintained, whereas 100ºC was sufficient
for FCAW.
The deposition rate that is obtained with FCAW is
attractive. The time needed to complete one weld,
installation and de-installation included is roughly one
hour. Fast transportation to the next weld is aided by
the light weight of the welding tent; 500kg equipment
included. To NACAP, this fast task force is a welcome
asset to the automatic welding systems they utilise all
over the world, and increased usage of this system is
foreseen. An additional 11 km pipeline in the northern
part of The Netherlands is already planned.
Figure 3: Weld appearance of the cap layer showing the
typical smooth “rutile” weld metal.
About The Authors
Frits Woldinga is Welding Technologist at NACAP, The
Netherlands. Sjabbe Datema is Sales Engineer at ESAB
B.V., The Netherlands.
For more information contact: sjabbe.datema@esab.nl
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Submerged arc welding of steels
for offshore wind towers
The German renewable energy industry goes offshore
By Rolf Paschold and Dirk Dirksen, ESAB GmbH, Solingen.
Rough maritime conditions place high loads
and stresses on offshore wind turbines. For
this reason, the mechanical characteristics
of steels and weld metals are very high.
Steels with yield strength of 355 MPa are
commonly used and high wall thicknesses
result in higher weld joint volumes.
Production economy makes high demands
on the deposition rates of applicable
welding processes. ESAB has introduced,
OK Flux 10.72, a new flux for submerged
arc welding with excellent weldability and
good weld metal toughness at – 50ºC.
The results of the highly productive twin-arc
tandem welding system are discussed.
Introduction
Requirements for offshore wind turbines
Wind at sea is stronger than on land, resulting in higher
wind turbine efficiency. After erection, testing and
implementation of single offshore wind turbines, complex
offshore wind parks are now established, mainly in
Scandinavia. Several areas in the North and Baltic Seas
are also being considered. Offshore turbines up to 5 MW
are planned and the combined capacity in parks adds up
to 1,500 MW, with towers of more than 100 m high.
Before installing wind turbines, environmental issues and
risks for and from navigation are considered. These studies
are important not only for the owners and insurance
companies, but also for the manufacturers of offshore
energy equipment. Some results from the technical and
risk analysis are leading to special requirements for the
production and erection of offshore turbines. Typical
risks for foundations and towers include:
Figure 1. Examples of principles for foundations: from left to right
gravity foundation, monopile, tripod. [Source: www.sky2000.info]
Figure 2. Tension leg offshore wind
turbine [1].
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Figure 3. SAW-Tandem-twin process for longitudinal welding in wind tower production.
• Collision by ships.
• Tides, streaming and heavy swelling.
(especially on the North Sea).
• Ice drifting (especially on the Baltic Sea).
• Squalls and Hurricanes.
Monopiles typically have a diameter above 4 m and a
length of more than 30 m. They are made from 40 – 70
mm thick plates of a width of 2 – 3 m. For comparison
onshore towers have a wall thickness up to 45 mm at the
bottom and about 10 – 15 mm at the top.
Foundations for offshore wind turbines
For mild steels, the carbon equivalent (CE or CEV) usually
increases with increasing wall thickness, the greater
thickness causing higher cooling rates during welding.
For this reason, appropriate measures have to be taken to
avoid hardening of the structure in the heat affected zone
(HAZ) and cold cracking, such as [3, 4]:
Several foundation concepts are under consideration,
including monopiles, gravity solutions, tripods, jacket
foundations and others (Fig. 1). Some of them are already
in use or in test phases [2].
For single turbines and wind parks (eg, Horns Reef,
Denmark) monopiles are preferred for water depth up to
25 m. If depth and sea ground conditions allow, piles are
rammed deeply into the ground. With increasing depth,
the tripod foundation is of interest. Common to all of
these foundation options is some degree of construction
from pipe work. The production of such “pipes” is based
on the forming and welding of thick plates.
When the sea bed is too firm for piles, floating tension leg
turbines may offer the best solution (Fig.2) [1].
Requirements for steels and welded joints
If the service life time of an offshore turbine is about 20
years, this could be equivalent to about 10 9 load cycles.
The fatigue load requires welded joints to be preferably
placed in areas of low stress and to be notch-free [2].
•
•
•
•
Preheating.
Sufficient heat input.
Multi-layer welding.
Low hydrogen content of welding consumables.
According to Germanischer Lloyd [2] structural parts are
classified into main groups, depending on the type and
amount of stresses and loads:
• Special Structural Members
(Highly stressed, eg, flanges).
• Primary Structural Members
(normally stressed parts, eg, tower wall plates).
• Secondary Structural Members
(low stressed, eg, lamp holder).
S355J2G3 is the most commonly used steel for
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onshore wind towers, whereas the toughness demands
in offshore deployment necessitate fine grained steels
with higher impact toughness.
Steels for “Special Structural Members“ are to be of high
quality with low impurities of sulphur and hydrogen and
of guaranteed adequate through-thickness ductility. The
yield strength class is 275 MPa and above, good Charpy-V
values are demanded for all regions of the welded joint to
min. –40°C. Additionally CTOD-testing can be required.
The following steels according to EN 10225 [5] are
suggested as appropriate:
S355G8+M
S420G2+Q
S460G2+Q
S355G10+M
S355G8+N
S420G2+M
S460G2+M
S355G10+N
The requirements for steels for “Primary Structural
Members“ are rather similar, except the improved
through-thickness properties. The European standard
limits the carbon content to C ≤ 0.14% and the carbon
equivalent to CEV ≤ 0.43%; GL-rules contain very
similar limits. The EN-standard requires Charpy-V values
of ≥ 50 J at –40°C, GL-rules: ≥ 34 J longitudinal and
≥ 24 J transversal. The recommended steels according to
EN 10225 [5] are:
S355G7+M
S420G1+Q
S460G1+Q
S355G9+M
S355G7+N
S420G1+M
S460G1+M
S355G9+N
For lower plate thickness between 25 and 50 mm the
GL-rules allow the use of simple steels such as:
S355G6+M and S355G3+N acc. to EN 10225,
S355J2G3 acc. EN 10025 (with special certification).
of the delivered batch for meeting the requirements after
welding with or without post weld heat treatment (PWHT).
In addition, the tower producers set strict limits on tolerances
in plate thickness, surface quality and joint preparation.With
increasing strength and toughness, heat input and cooling
rates (preheat and interpass temperatures) as well as energy
per unit of length, become more important. According to the
standards and rules, suppliers and producers have to meet
several demands [2]. The fabricator should only use welding
consumables which have proven to have constantly
high CTOD-values at -10°C.
Welding fabrication is based on welding procedure
qualifications (WPQs) in accordance with EN 288-3,
including details such as:
•
•
•
•
•
•
Preheat temperature.
Maximum interpass temperature.
Welding process.
Heat input.
Welding position.
Welding consumable.
WPQs are commonly made in all cases and have to be
available for the purchaser of the wind turbine module.
Welding of a WPQ is essential, especially when welding
without PWHT, which fabricators aim for. Usually PWHT
(stress relieving) is demanded for thick walled steels
in conditions +N (normalised) and +M (temperature
controlled milling) in the offshore industry. This is valid
for steels t ≥ 40 mm according to EN 10255 and t ≥ 50
mm referring to GL-rules.
To allow welding without an expansive PWHT, factors to
be proven include:
Requirements for fabricators
According to EN 10225, the steel producer has to provide
customers with information about weldability, if the
thickness is t ≥ 40 mm. The article “18 – additional
requirements” is about certification of weldability tests
according to customer wishes, to prove the suitability
• Certified weldability of the steel.
• Mastery of welding procedures, shown by WPQ’s.
• CTOD-testing acc. to EN 10225, appendix E,
or purchasing the plates acc. to “Additional
requirements 18” acc. to EN 10225.
Figure 4. SAW-welding of the first layer with the first welding
head only (Twin-arc).
Figure 5. Tandem-Twin-welding with four wires Ø2.5 mm
(H.I. 2.7 kJ/mm, deposition rate 28 kg/h at 100% duty cycle)
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Dim.
Material
Heat
mm
C
Si
Mn
P
S
N
Al
Cu
Cr
Ni
Ti
Nb
CEV
S355G8+N
09639
50
0.14
0.20
1.47
0.014
0.004
0.003
0.042
0.07
0.05
0.19
0.003
0.025
0.41
Autrod 12.22
PV-
ø2.5
0.107
0.19
0.91
0.013
0.012
0
0.001
0.069
0.05
0.03
0.001
0.003
EN 756: S2Si
403028048
0.083
0.33
1.62
0.015
0.007
EN 10225
Weld metal
EN 756:
0.07
S 38 5 AB S2Si
Table 1: Chemical composition of the base metal, SAW-wire and the weld metal, as well as CEV acc. to EN 10225
Welding production
The tough requirements regarding the quality and mechanical properties of the welded joints seem to be in conflict
with productivity. However, submerged arc welding is
capable of combining high quality with high deposition
rates and is, therefore, the first choice for wind turbine
towers and foundations. Process variants with more than
one wire electrode become more important with increasing
thickness and joint volumes, because they offer a further
increase in deposition rate. One development is the
Tandem-Twin-process (Fig. 3) with four wire electrodes,
capable of depositing more than 30 kg/h of weld metal
(based on 100% duty cycle).
With high welding currents (more than 1600A) for high
deposition rates, the heat input has to be in focus. Meeting
the requirements for quality, the heat input and weld bead
thickness have to be limited in multi-layer technique, so
travel speed is increased to values above 100 cm/min.
This takes advantage of the tempering effects of following
beads, which has a positive influence on the mechanical
properties in all regions of the joint, especially on the
toughness at -40°C and below.
The first choice of wire is OK Autrod 12.22 (EN 756
– S2Si). A higher Si-content is of positive influence on
deoxidization and slag detachability. In addition, the wire
has very low content of impurity elements that have an
impact on toughness.
Testing Position
BM
HAZ
WM
Lowest value HV10
154
170
178
Average HV10
157
211
193
Highest value HV10
161
260
205
Heat Input
Heat input is of great importance. If it is too low, the
HAZ hardens and becomes susceptible to cold cracks.
If it is too high, the grain growth in the HAZ affects the
toughness. The heat input during test welding has been
1.9 kJ/mm for the first (Fig. 4) and 2.7 kJ/cm for the
following layers.
Welding Procedure Testing with S355G8+N
Base material
Welding tests have been carried out on plates S355G8+N
acc. to EN 10225 (similar to S355NL / EN 10113-2, but
with guaranteed through-thickness ductility). A melting
heat reaching the maximum acceptable carbon content of
C = 0.14% has been chosen, see table 1.
Wire and flux
To increase operating efficiency of the multi-wire process
and meet the tough mechanical requirements, a newly
developed flux is suggested, featuring high currentcarrying capacity, good high-speed behaviour and good
slag detachability in relatively narrow joints.
The new aluminate-basic welding flux OK Flux 10.72
(EN 760 - SA AB 1 57 AC H5) has been adapted to meet
the requirements of European wind energy producers,
producing a weld metal with toughness down to -50°C.
Figure 6: Cross
section of the
welded joint,
t = 50 mm.
To start with, the preheating temperature was 125°C, the
maximum interpass temperature was limited to 250°C.
After the fourth weld bead, the working temperature
was between 160 and 180°C. However, in production on
larger workpieces, the temperature has to be maintained
by heating.
As commonly used in wind tower production, the included
angle of the V-groove was 50+5°, the land 3–5 mm. To
start with, a backing pass was produced by MAG-welding,
placed on the back side and ground off after turning.
Including the capping passes, 31 beads have been welded
with the submerged arc process (Fig. 5, 6).
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Results of mechanical testing
Conclusions
The welded plate was not heat treated, having in mind, that
almost all producers will use the qualification procedures
by CTOD-testing at -10 degrees C instead of heat treating
later on.
The welding tests have proven that highly economical
variants of the SAW process can meet the requirements for
quality and mechanical values in the offshore wind power
industry. The limited investments for increased deposition
rates by using Tandem-Twin welding recommend this
process variant to wind turbine producers - not only in
the offshore segment.
• Hardness Values:
The hardness testing HV10 was executed on the cross
section, containing unaffected base material (BM), heat
affected zone (HAZ) and weld metal (WM).
Referring to EN 10225 (E.4) the acceptable hardness is
limited to 325 HV10.
• Tensile Test
A transverse flat tensile specimen showed a tensile
strength of 520 MPa, required strength acc. to EN 10225
is Rm = 470 – 630 MPa. The fracture occurred in the
unaffected base material.
• Impact Test
For steel grades S355, EN 10255 (E.4) requires a minimum average of 36 J and a minimum single value of 26 J
at -40°C. Test results of impact (Charpy-V) acc. to EN
875, HAZ:
V-Notch
Test-
Position
Temp.
VHT 1/2
-40°C
111
115
112
113
VHT 1/20
-40°C
56
41
58
52
VHT 1/38
-40°C
64
56
78
66
Single Values
Average
Nevertheless, the welding consumables have been
approved for -50°C, the impact values of the weld metal
produced by TandemTwin-welding are of interest:
V-Notch
Test-
Position
Temp.
VWT 0/2
-50°C
113
107
110
110
VWT 0/20
-50°C
100
75
55
77
VWT 0/38
-50°C
42
66
48
52
Single Values
Average
The weld metal does fulfil the requirements, even at
-50°C. However, there is a visible trend of increasing
values with decreasing dilution from the base metal.
The welding consumables OK Autrod 12.22 and OK Flux
10.72 have shown an outstanding welding behaviour and
excellent mechanical values. Temperature controlled
milled (M) steel grades such as S355G8+M will be the
preferred grades for welding production, recommended by
lower carbon contents and carbon equivalents to achieve a
better weldability at lower preheat temperatures.
References:
1. W. Musial and S. Butterfield: Future for Offshore Wind
Energy in the United States. Conference paper, Energy
Ocean, Palm Beach, Florida, June 29-29, 2004.
2. Dalhoff, P., u. a.: Chancen und Grenzen von Monopiles – Erste
Erkenntnisse aus dem Forschungsvorhaben Opti-Pile. 2. Tagung
Offshore WindEnergie, Hamburg 2003, www.gl-wind.com
3. SEW 088 – Schweißgeeignete Feinkornbaustähle. 4. Ausgabe,
Verlag Stahleisen mbH, Düsseldorf, Oktober 1993.
4. Merkblatt 381 – Schweißen unlegierter und niedriglegierter
Baustähle. Stahl-Informationszentrum, Düsseldorf, 1999.
5. DIN EN 10225: Schweißgeeignete Baustähle für feststehende
Offshore-Konstruktionen - Technische Lieferbedingungen;
Januar 2002.
About the authors
Dirk Dirksen (Mech. Eng./EWE) is Product & Project
Manager Automation and Engineering for Austria,
Switzerland and Germany. He joined ESAB in 1989 and is
located in Solingen, Germany.
Rolf Paschold (Mech. Eng./EWE) is Product Manager
Welding Consumables, serving the Austrian, Swiss and
German markets. He joined ESAB in 1991 and is located
in Solingen, Germany.
For more information contact rolf.paschold@esab.de
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Permanova’s seam tracking
laser welding tool
By: Niklas Wikström and Tore Salmi, Permanova Lasersystem AB, Mölndal, Sweden.
State of the art MIG equipment combined with the latest laser technology. Co-operation
between ESAB and Permanova in laser-hybrid welding brings the best of two worlds together.
This article reviews the seamtracking feature of the Permanova WT03 laser welding tool
system, an essential component of the laser-hybrid welding systems supplied by ESAB.
Overview
Weld configurations, overall dimensions and tolerances,
and the welding process itself, impose different demands
on an automated welding system. In many cases, tolerances
of the parts to be welded, including their positions, are
so precise that the weld joint can be found and followed
without a seam tracking system. Typical cases are machined
components, i.e, rotary (butt) welds for gearbox parts, with
relatively small dimensions, and the joint in a (2D) plane.
In such cases, the clamping is typically solved by pressing
together parts with press fit tolerances.
Other cases, for example in car roof welding, are more
difficult. In this typical overlap weld situation, the overall
position of the weld can vary, from car to car, by several
mm in the (3D) space. Usually, it is sufficient to locate the
beginning and/or the end of the weld trajectory with an
external optical measurement, followed by a correction of
the robot programme path position. The position sideways
of the weld is not critical, and the two plates are typically
pressed together with a pneumatically controlled force on a
roller, also securing the focus position of the laser beam.
Today, the trend in car roof welding is to use an edge
overlap weld instead, in order to get an efficient sealing
and a cosmetically pleasing weld, with less problems
from the trapping of vaporised zinc. At the same time,
a higher speed is possible without increasing the laser
power, compared with the full overlap weld situation.
Inspection of weld quality is also simplified. Typical
welding speeds are in the range of 4 to 10 m/min. The
seam tracking accuracy has to be better than +/- 0.1 mm.
Welding Tool
The standard welding tool includes a press roller with
an integrated cross jet for cover slide protection, rotating
collimation unit, and a Cover Slide Monitor (CSM).
The Permanova welding tool has a press roller, where
the pneumatic pressure can, in principle, be programmed
from a robot. The force is usually in the range 0 to 500 N.
(EPP Valve etc. not included). The collimating f 200
optics is water-cooled and has an optical swivel for
optimal access and minimal wear of the fiber. Focussing
optics is f 200 mm (optional 120-250mm).
The upper and lower position limits of the pneumatic
motion (usually ±10mm), are monitored by the seam
tracking controller and relayed to the robot. The absolute
position of the motion is also displayed in the software
and transmitted to the robot - of great assistance during
robot programming.
An integrated crossjet minimises dirt on the cover slide
glass and avoids weld spatter on the welded product.
The degree of contamination on the cover slide glass is
monitored by the Permanova CSM, mounted on the cover
glass holder. Spatter from the welding process deposited
on the cover slide surface is optically detected, and smoke
and very small particles are thermally detected. These
signals are integrated into the seam tracking software,
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Figure 1. Welding tool with seam tracking and press device.
Nr
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
giving the user the opportunity to set warning and alarm
levels. The alarms and warnings are then sent to the robot
and/or PLC.
Main features
This welding tool, Figures 1 and 2, is the result of vast
experience of high power laser beam delivery systems and
industrial installations. The result is a high performance,
versatile, compact and reliable modular tool with several
important functions, depending on the configuration:
• High power handling.
• Press roller with adjustable pressure force and
integrated crossjet.
• Protective gas supply.
• Motorised or manually adjustable (or fixed) focusing unit.
• Fiber coupling to Rofin or HAAS.
• Fiber coupling unit on rotary optical device allowing
free tilt of the tool with minimal force on the fiber
connector and cabling.
• Beam bending cube.
• Holder with quick-exchange cover slide holder/glass.
• Cover Slide Monitor CSM-OT-S.
• Wire feeder, cold wire or hot wire for arc welding (option).
• The Motorised or manual Twinspot optic (options).
• Seam tracking (option).
Seam Tracking Function
Item
Fiber Connection.
Pivoting Collimating Unit.
Cable to Electrical Control Cabinet.
Line Diode 2.
Welding Nozzle.
Process Gas Pipe.
Press Wheel.
Spatter Screen with Cross Jet.
Line Diode 1.
Cover Slide Holder.
Focusing Unit..
Beam Bending Cube.
Pneumatic Couplings.
CCD Camera.
the triangulation method. A laser line is projected on the
edge between the metal sheets to be welded at an angle of
30-45° to the normal.
This laser diode line, when observed from normal direction,
is split up in x-direction (welding direction) because
of height difference and possible air gap between both
sheets of metal. When observed from above with a
camera, the picture looks as shown in the right hand side
of Figure 4.
This picture is processed by an image processing PC,
which generates a control signal and sends it to the
servo unit, which then tilts the optical system around its
rotation axis, thereby directing the laser beam accurately
at the seam.
The seam tracking system will compensate for inaccuracies
in the robot, or the part’s fixture. The robot will follow
the nominal trajectory, ie, the trajectory that is correct
if the car fixture, car and the robot all were perfect. The
seam tracking system will then correct the deviation from
this nominal trajectory. By looking closely at the weld
spot it is possible to use a simple approach to control the
Nr
1.
2.
3.
4.
5.
6.
Item
Pivoting Collimating Unit.
Focusing Unit.
Welding Nozzle.
Cover Slide Holder.
Beam Bending Cube.
Fiber Connection.
Overview
To find an edge seam, a sensor is needed. If the seam
is measured far from the weld spot, it will be difficult
to make sure that the weld spot follows the right path.
It will be impossible to reach higher accuracies than that
achieved by the robot - which is not good enough in
demanding applications.
At the weld spot it is very hot and dirty and one of the few
sensing methods that can be used in this environment is
Figure 2. The most basic welding tool.
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Figure 4. Diode line splits due to height differences
between plates.
Figure 3. Principles of operation.
beam position. There is usually no need to account for
any delay from the measuring spot to the beam position,
so no need to rely on the accuracy of the robot, itself.
Seam Tracking Movement
On the tool there is a mechanism for moving the beam
into the desired position - a rotating motor with a ball
screw linear guide for very fast and precise movement.
This mechanism tilts the optics to move the beam. Tilting
the optics will make the movement very rigid and precise.
At start up, the unit calibrates itself to the nominal
position, found with an inductive sensor. The nominal
factory setting is 4 mm from the pressure wheel. If the
nominal position needs to be changed, the sensor can be
repositioned. The drive adjusts the beam ± 2 mm from
the nominal position. The size of this adjustment can be
increased or decreased depending on the process. The
Vision Control System will find the seam position. If
corrections are needed, the control system sends a
correction signal to the beam moving mechanism.
Robot interface
The seam tracker control cabinet communicates with
the robot/PLC preferably via a fieldbus interface like
Profibus or Interbus. A digital interface is also available
offering only the most essential control signals.
Additional features
• Logfiles of relevant weld data are recorded by the
seam tracker and saved for each weld. They are then
kept a user definable amount of time.
• Position indicator for the pneumatic motion of the tool.
• Possibility to save single pictures or entire videos of
the welding process.
• Covers Slide Monitor alarm, supervision and logging.
• Continuously adjustable diode line intensity.
• Continuously adjustable welding offset from the edge.
- Also adjustable online from the robot during welding.
• Automatic logging of the last 20 seconds (possibly
more) frames (pictures) from the welding.
- Debug possibility from the logged frames, leads to
easy calibration of the system.
• Online graphs showing measured error and regulated
position.
Figure 5. Main window of seam tracking software.
•
•
•
•
Simple and intuitive operator interface.
All measurement results are presented in mm.
Can be used as an offline measurement system.
Optional remote assistance over internet/modem.
Specifications
Welding tool:
Handles 10kW laser power
NA 0.12
Rofin or Haas fibers
Pneumatic motion ±10 mm
Focal length f160 or f200mm
Seam tracking function:
Control sampling frequency and camera speed: 105Hz
Beam position resolution:
±0.002mm
Seam measurement
±0.01mm
Control
±0.05mm
About the authors
Niklas Wikström, MSc. Engineering Physics, is
Development Engineer at Permanova, responsible for software development, control engineering and electronics.
Tore Salmi, MSc. Engineering Physics, is Marketing
Manager at Permanova. His responsibilities include the
supply of laser process tools and laser robot fibre systems
to the automotive industry and other high-tech branches.
For more information contact: tore.salmi@permanova.se
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Retrofitting of automatic
welding Systems
Cost-efficiency with state-of-the-art technology
By: Peter Kjällström and Björn W. Ohlsson, ESAB Automation, Laxå, Sweden.
Investment in new automatic welding equipment such as column and boom, gantries and
longitudinal fixtures may be costly and, often, the equipment and systems are planned for a
service life of a decade, or more. However, over such a long period, new products and
changing production targets may cause the original equipment to become quickly outdated.
In many cases, upgrading of existing equipment using modern components, is a cost-effective
alternative to investment in new equipment. ESAB offers a retrofit service to fabricators, for its
own arc and flash welding systems - and for equipment from other suppliers.
Why retrofit?
A major reason for the retrofitting
of welding equipment is to avoid the
situation where spare parts can no
longer be purchased. Suppliers tend
to maintain stocks of spare parts for a
certain period after the equipment has
been taken out of production (ESAB,
for ten years) but, unavoidably, the
moment comes that vital parts are no
longer available. Timely replacement
can prevent this and extend the life
cycle of the equipment.
Generally, however, fabricators want
to increase the productivity of welding
systems by upgrading using the latest
technology. Column and boom installations for submerged arc welding with
single wire heads, for example, can be
equipped with twin-wire heads, tandem
heads, or a combination of these, for a
relatively low level of investment that is
soon paid back by increased productivity.
With extreme material thickness, an
upgrade with narrow gap submerged
arc equipment may be advantageous.
Changing products and material thickness may also require to retrofit with a
different process, for instance, replacing MAG welding with SAW.
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Increased quality
By replacing old control boxes and power sources with
the latest models, during the retrofit, fabricators gain the
ability to store optimum welding parameters settings,
benefit from improved start and stop characteristics, and
obtain consistent weld positioning from joint tracking
systems. The result is improved weld quality and a userfriendly system.
SAW flux dryers and heaters, in combination with an
upgraded flux supply system, are another example. By
keeping flux dry and hot, weld porosity from moisture
is prevented and rejects avoided.
Retrofit project provides Kvaerner with
40% higher welding productivity.
Kvaerner Kamfab AB, in Karlstad Sweden, a member of
the Norwegian Aker Kvaerner Group, specialises in the
manufacture of equipment for the chemical pulp industry;
from single machines to complete production lines. The
company employs some 235 personnel and has a turnover
of around 400 MSEK.
ESAB has a long relationship with Kvaerner Kamfab as
a supplier of welding equipment and consumables. Over
recent years, ESAB has seen increasing demand from
Kvaerner for new equipment and retrofitting of existing
installations – mainly due to the overwhelming success
of Kvaerner’s latest pulp washer, the Compact Press.
This high efficiency, high capacity washer, developed by
parent company Kvaerner Pulping AB, was introduced
in 2000 and, since then, some 50 installations have been
delivered world-wide.
With increasing orders and customer demand for shorter
delivery times, Kvaerner made further investment in
machinery, including the retrofitting, by ESAB, of
two giant column and boom (CaB) installations for the
welding of cylindrical pressure tanks. The tanks, have a
diameter of 3m and a length of 18m, and are submerged
arc welded both from the inside and from the outside.
The welding covers various qualities of stainless steel
with 10-15mm wall thickness. The objective was to
increase the capacity of the installations. The project
was completed during 2003.
Each CaB installation was stripped from its old welding
equipment. The remaining framework was reconditioned,
painted and equipped with new welding heads, flux unit,
power sources and cabling (see photo). New equipment
included:
• LAF 1250 power source.
• A6S welding head with motor slides and twin
wire equipment.
• PEH control box.
• GMD joint tracking system.
• Flux feeding and recovery system with TPC
pressure tank.
• General overhaul of the system, including new
cable chains.
Kvaerner calculations indicate that the retrofit has resulted
in a 40% increase in productivity, mainly due to:
• higher deposition rate due to changing over to twin arc
welding.
• less post weld labour due to a n improved weld quality.
• reduced downtime.
Kvaerner Kamfab, last year, won their most prestigious
order ever; a complete production line for the biggest
pulp mill in China, located in Jian Lin and having a
capacity of 3000 tons of pulp a day.
About the authors
Peter Kjällström is After Sales Manager and Björn W.
Ohlsson is Sales and Marketing Manager Automation at
ESAB Automation, Laxå, Sweden.
For more information contact: peter.kjallstrom@esab.se
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Mechanised welding of pipelines
By: D.J. Widgery, ESAB Group LTD., United Kingdom.
This article looks at the different approaches to mechanised pipeline welding and their
implications in different parts of the world.
Systems for the mechanised welding of pipelines have
been available for more than 40 years and have long been
in exclusive use for offshore pipelines. Yet until recently,
they were seen on only a few land pipelines. Now, however,
the difficulty and expense of finding sufficiently skilled
manual and semi-automatic pipeline welders has led to a
rapid growth of mechanised welding onshore. This article
looks at the different approaches to mechanised pipeline
welding and their implications in different parts of the
world.
Early systems
Almost as soon as CO2-shielded welding was developed,
torches were mounted on carriages for mechanised
circumferential welding of pipelines. The first crosscountry
pipeline to be welded semi-automatically with the CO2
process was laid in the US in 1961, when there were already
five mechanised GMAW systems under development [1],
with the first field trial taking place in the same year.
Inevitably, Darwinian natural selection took its toll on
the early machines, but it is remarkable how soon the
distinctive features of today’s systems began to crystallise.
Development started to diverge along two lines. In one,
the welding heads or “bugs” were mounted on bands or
chains clamped to the pipe. This became the model for
subsequent onshore systems. The other approach used
an external frame, inside which the welding heads were
mounted, and this subsequently found its main application
on lay barges. Designed for the wide, open spaces of the
USA and USSR, the first machines produced in the 1960s
did not have lightness or compactness as a priority and
it is perhaps not surprising that they were not adopted in
countries with narrower rights of way and more crossings.
It was soon discovered that for semi-automatic welding,
choosing the right size and type of consumable was the
key to success. There was an initial assumption that the
smaller the wire diameter, the more controllable the arc
would be, and a number of users tried 0.8 mm diameter
wires. However, in side-by side tests, welders preferred
a 0.9 mm type. It appeared that the lower electrical
resistance in the electrode extension (stickout), and hence
lower resistive heating, meant that wire burnt off more
slowly at a given current and more heat was available
1.
2.
3.
4.
Drive motor
Welding wire spool
Welding head
Chain
5. Guide roll
6. Wire feeder
7. Wire feeder
Figure 1. Tandem mechanised pipe welding system by
Falkewitsch, 1961 [1].
to melt the parent material and avoid the dreaded “cold
laps” or lack of fusion. Another discovery was that the
inclusion of a small amount of titanium in the wire
reduced the burn-off rate further and again increased the
welder’s comfort and reduced the defect rate. Comparing
a 0.8 mm titanium-free wire with a 0.9 mm titanium
-containing one at 200A, 25V it was found that the respecSvetsaren no. 1 • 2005 •
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A machine which was to influence a generation of others
was the PASSO (Progetto Arcos Saipem di Saldatura
Orbitale) equipment. This was particularly light and
compact, and was used from the outset for both onshore
and offshore construction. Its successors finally achieved
a breakthrough in Europe when mechanised pipe welding
displaced manual welding on the trunklines, even in
mountainous regions where the pipe runs through galleries
with restricted clearance. Mechanised welding was
accepted early in Canada. In the USA, the home of the
process, acceptance took longer but this was for social as
much as for technical reasons.
1.
2.
3.
4.
5.
Pipe
Track
Welding carriage
Feeding mechanism
Cassette with wire
6. Flux-cored wire
7. Forming stide
Figure 2. The Styk welding apparatus.
tive burn-off rates were 4.10 and 2.99 kg/h. In the first
case, 33% of the available heat was used to melt the wire;
in the second, 24%. Over the next 40 years, thousands of
kilometres of pipeline were laid with 0.9 mm, titanium
-bearing wires and they are still very popular today.
The job of a pipeline welder is not an easy one and
any measure which reduces the extreme concentration
required and results in fewer repairs cannot be ignored.
However, the great majority of gas-shielded welding on
pipelines has been with mechanised systems and it is not
at all clear that they benefit from the lower burn-off rate
of titanium-alloyed wires. There used to be an advantage
arising from the help titanium provided in nucleating
acicular ferrite, but modern steels and wires are so low
in impurities that high toughness can be achieved over a
range of microstructures. In today’s mechanised pipeline
welding, both titanium-bearing and titanium-free wires
are in successful use and welding manufacturers have
come to accept the right of users to make their own
choice. ESAB offers Spoolarc XTi with titanium and a
OK Autrod 12.66 as a titanium-free type.
Developments in gas-shielded systems
During the 1970s and 1980s, mechanised systems for gas
metal-arc welding proliferated, becoming well established
and reliable. The line can only move forward as fast
as successive weld roots can be completed, so CRC’s
innovation in mounting multiple welding heads on an
internal clamp to weld the root was a major step forward.
By using four heads simultaneously, an effective joining
speed approaching 2 m/min can be achieved, which
explains why newer welding processes have found it so
hard to gain acceptance. Other systems have used internal
copper backing rings, with fewer bugs but faster welding
speeds to achieve similar closing rates.
From the outset, the possibility of mounting two welding
torches on one head was seen as a possibility, as shown
by the Russian example from 1961 in Fig 1. This system
has been in regular use, for example by Serimer-Dasa,
from the 1990s. More recently, it was realised that the
two wires could be moved much closer together so that
they shared a gas shroud, though not their contact tips,
which remained electrically insulated. For this to be
practicable without the arcs interfering with each other,
the wires are fed alternately with pulses of current. The
method allows high welding speeds, so that although both
wires feed into the same weld pool, the heat input is not
excessive and there should be no serious implications for
the consumables.
In a further development, it has been proposed to replace
the two torches of a system such as that in Figure 1 with
tandem torches, creating the so-called “Dual-Tandem”
process [2]. This will allow another increase in productivity,
but the high total amount of heat going into the pipe
may have an effect on the mechanical properties of the
joint, especially then very high strength steels such as
X80 and above are used. Manufacturers are now working
on optimising the alloying for welding wires for this
application.
Uphill welding
All the mechanised pipe welding systems and applications
so far described have been aimed at maximising the
welding speed, which means welding downhill in narrow
weld preparations. This generally means that the pipe ends
must be rebevelled on site, using a machine which can
cost many times as much as a welding system. For smaller
contractors, especially in developing countries, this can
be a disincentive to mechanisation.
In many highly developed countries such as the UK,
another problem is the large number of road, rail and river
crossings which have to be laid separately and subsequently
tied in to the main line: in that case, re-bevelling and the
use of internal clamps may not be possible. In both these
situations, a solution may be to use a mechanised system
operating in the uphill direction.
In order to run uphill, some support for the weld pool
is needed and this is best provided by a rather stiff slag,
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such as that from a rutile flux-cored wire. This allows
the use of a standard API bevel, with a 60° included
angle, which pipe mills are happy to supply. Contractors
equipped with relatively inexpensive welding equipment
can then confidently tackle tie-ins and even mainline
joints where the fit-up would not be good enough for
mechanised downhill welding. If no internal access is
available, cellulose electrodes are likely to be the fastest
option for rooting, though new semiautomatic systems
are being improved all the time.
In downhill pipe welding, the task of selecting welding
consumables is made easier by the fact that the fast cooling
rate generates microstructures that are strong and tough,
so that even simple carbon-manganese consumables
can match the strength of X80 pipe steels.
A welding system which did successfully use self-shielded
flux-cored wire was partly a victim of the break-up of the
Soviet Union. This was the “Styk” process, effectively a
circumferential electrogas process without gas shielding.
Copper shoes or “forming slides” held the weld metal
in place as the head travelled round the pipe, Figure 2,
allowing wall thicknesses up to 16mm to be welded in two
passes and up to 25mm in four passes. Good weld metal
toughness down to –40° and even –60°C was claimed,
together with repair rates below 1.5% [4]. Unfortunately,
when Russia, where the equipment was mainly used,
separated from the Ukraine, where it and the consumables
were made, the process fell into disuse and the resources
were never again available for its continued development.
The opposite is the case when welding uphill. Heat inputs are
higher and cooling rates lower than those generally used by
consumable manufacturers in certifying the product, so
users should be aware that they may need to specify
a consumable with a catalogue strength higher than
that of the pipe. With this proviso, new wires such as
OK Tubrod 15.09, specially developed for this application,
have proved very successful [3].
Specially designed self-shielded wires have actually
been available for semi-automatic pipe welding for many
years, but they have made little impact on mechanised
welding. ESAB has recently taken a fresh look at the
subject and concluded that the slow burn-off rates which
give existing wires their appeal to manual welders have
militated against their adoption for mechanised welding,
since their productivity struggles to match that of stick
electrodes. New wires now being tested achieve high
productivity and may help to change this situation.
Self-shielded welding
Non-arc welding processes
Pipelines are often laid in remote areas where it is difficult
to obtain supplies locally, so it might be thought that welding
them with self-shielded wire needing no shielding gas
would be an attractive proposition.
For 40 years, every pipe welding conference has had
papers on novel welding processes for pipelines: on
friction and electron beam welding from the 1960s;
flash butt, MIAB (Magnetically Impelled Arc Butt) and
Figure 3. Flash butt welder from the Paton Institute welding a sample of a 42” pipe.
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explosive welding from the 1970s; laser welding from
the 1980s and hybrid laser and homopolar welding
from the 1990s, among others. Several of these offer the
possibility of “one shot” welding, in which the whole
wall thickness and circumference of the pipe is welded
at the same time. This is indeed a tempting prospect for
pipeline constructors, appearing at first sight to offer the
possibility of revolutionising the productivity of pipe
laying. It is not surprising, therefore, that very large
amounts of money have been spent in building prototypes
of these systems. Of all these processes, however, only
flash butt welding has laid significant lengths of line.
Developed at the Paton Institute in Kiev, a series of flash
butt welders were produced for welding pipes of up to 42
inch diameter. The manual for one of the smaller models,
capable of welding 325 x 14 mm pipe, showed that it
operated at 16,000 A and required an input power of
180 kVA. The machine was said to complete 15 welds per
hour. The larger machine shown in Figure 3 was somewhat
slower, but nevertheless still highly competitive on
speed alone. Although the technology was licensed to
an American company and subsequently accepted for
inclusion in the American pipe welding standard API
1104, it has not been used outside the former USSR. This
is partly because of questions over the reliability of joint
properties, but above all because of the surprising ability
of mechanised GMAW welding to keep matching, in the
field, all the productivity advances claimed by the newer
processes.
The future of mechanised pipeline welding
At any given moment, an observer unfamiliar with the
history of pipeline welding might conclude, on reading
papers from the most recent conference, that new welding
processes were about to revolutionise the business of
laying lines. It is certainly true that there is some way
to go, worldwide, in raising the average speed of laying
to match that of the best contractors – in some parts of
the world significant use is still made of low hydrogen
electrodes used in the uphill direction. In these areas, it is
likely that the obvious next step of moving to stovepipe
or semi-automatic welding will be by-passed by the new
democratisation of mechanised welding with affordable
systems, often still employing standard API bevels applied
at the pipe mill.
For those with resources to spend on the ultimate in speed
and productivity, however, it seems likely than for the next
few years at least, downhill gas metal-arc welding will be
the process of choice. New rooting systems are claimed
to allow travel speeds of up to 1.5 m/min on unbacked
roots [5], while the Dual Tandem system for filling and
capping can potentially reduce the number of welding
stations on a 48 inch x 19 mm pipe from 14 to 5. Faced
with this incremental improvement in an established
method, contractors will not easily be persuaded to invest
in untried technology that does not seem to offer much
greater performance.
Of course, even incremental changes need great efforts to
achieve the reliability we have come to expect, especially
as it seems that the other means to overall cost reduction,
the introduction of X80 and X100 steels, will happen at
the same time. This is already putting pressure on welding
manufacturers to produce robust consumables that will
perform in the field as well as in the laboratory. They will
have an important part to play in the continuing improvement
of the economics of pipeline welding.
References
1. Günther, H., “Gegenwärtige Stand des Maschinellen
Zwangslagenschweißens von Rohrrundnähten auf der
Baustelle”, Schweissen und Schneiden 1962, 14 (10) 2-8.
2. Blackman, S.A., Dorling, D.V. and Howard, R. High-speed
tandem GMAW for pipeline welding, International Pipeline
Conference 2002, Calgary, October 2003, Paper IPC02-27295.
3. Widgery, D.J., “From laboratory to field”, World Pipelines,
2003 3 (5) 45-47.
4. Paton, B.E., Pokhodnya I.K. et al., Automatic position butt
welding of large diameter pipes with self-shielded flux-cored
wire by using ‘Styk’ complex, International Pipeline Conference
1980, Calgary, October 1980, Supplementary Paper, Session 4.
5. Blackman S A and Yapp D, Recent Developments in High
Productivity Pipeline Welding, IIW Document XII-1786-04.
About the author
David Widgery, MSc, PhD Metallurgy, joined ESAB in
1983 as Development Manager Flux-cored wires. As from
1996, he has worked as Special Projects Manager for the
ESAB Group.
For more information contact: david.widgery@esab.uk
26 • Svetsaren no. 1 • 2005
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Cutting technology in shipbuilding
By: ESAB Cutting Systems GmbH, Karben, Germany.
This article describes the latest trends in cutting technology for shipbuilding. Cutting
speed and bevel quality, and their effects on fabrication are reviewed for various cutting
methods.
Introduction
International competition dictates that all shipyards must
manufacture their products cost-effectively. For this reason,
there is considerable investment in precision manufacturing
- from block assembly up to grand section assembly. As
cutting of individual plates is the first stage of manufacturing
in shipbuilding, any repairs due to cutting inaccuracies
will be very costly. In short, the accuracy of the cut plate
is crucial.
The objective is to improve accuracy in manufacture by
reducing thermal deformation. Subsequent alignment and
fitting, and the total assembly procedure, will also be easier.
Figure 1. HDW, Container Ship NORASIA.
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Nowadays, shipyards worldwide almost exclusively use
the plasma cutting procedure to cut shipbuilding plate in
the thickness range, 8-20 mm. Plasma cutting provides a
five-times higher cutting speed than oxy-fuel cutting, and
thermal deformation is much lower, guaranteeing better
dimensional accuracy of cut parts.
Laser cutting has also been introduced into shipbuilding.
The process is characterised by the lowest heat input and
almost rectangular cuts that need no post-weld-machining.
As a result, the weld cross-section and the related heat input
from subsequent welding is lower.
Today, guiding machines for thermal cutting processes are
exclusively CNC controlled. The control consists of a process
computer, which not only controls the path movement of
the torches, but also calls-up the cutting programmes as
well as the machine’s monitoring devices.
Figure 2. plasma bevel unit.
Cutting tools are interrogated for their wear; information is
transferred to the operating panel and/or to the manufacturing supervision. In this way, a fully automatic cutting process is achieved. The objective is to achieve a continuous
quality of cut parts even if the used plates are of different
grades of material.
Analysis of a container ship with regard to
cutting and welding performance.
An investigation of a containership with a total length
of 220 m showed the following cutting and welding
characteristics (Figure 1):
•
•
•
•
Ship weight: 7500 tons.
27000 cut parts.
27000 profile parts (stiffener elements).
350 km welded joints.
The plate thickness breaks down as:
8 – 18 mm: 75 %.
30 – 40 mm: 25 %.
This means that 75 % of the plate thickness range is ideally
suited for plasma cutting, justifying the almost exclusive
use of plasma cutting in shipbuilding. To increase plate
turnover in manufacturing, one must observe (in addition
to set-up times):
•
•
•
•
•
•
Figure 3. Laser cutting device Thyssen Nordseewerke Emden.
Comparison of cutting speeds Plasma vs. Laser.
Crane availability.
Plate supply.
Charging plates.
Removing cut parts.
Cutting programme availability.
Cutting and marking speeds.
Today one assumes that in cutting, the cut length and
marking length are roughly the same. Today, up to 20 m/min
marking speed is reached.
Plate thickness (mm)
Figure 4. Cutting speed plasma/laser.
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Status of plasma cutting.
In the quest for increased speeds in plasma cutting, plasma
cutting with oxygen has consistently been further developed,
because it guarantees the best results with regard to the
quality of the bevel and the absence of slag. Currents
as high as 400A are now achieved which results in a
considerable increase in cutting speed.
However, with a higher current at the cutting nozzle, heat
input also increases, resulting in a more oblique cutting
edge. A possible remedy is to use a torch with bevel units,
which position the torches at a slight incline (Figure 2).
Naturally, cuts for weld edge preparation are carried out
with these machines; V and Y bevels with plasma torches,
additionally K bevels using oxy-fuel torches.
In plasma cutting, the consumption of wear parts
(electrodes and tubes) is a cost factor which should not be
underestimated. Nowadays considerable life cycles have
been achieved by consistent research and development.
For example, the life cycle with oxygen cutting used to
be considerably shorter than with nitrogen cutting, at the
initial development stage. New developments, eg, a silver
coating on the hafnium electrodes, have considerably
increased the life cycle of wear parts. Modern electronics
have also brought about considerable progress, ie, a
controlled increase and decrease of welding current at the
start and the end of the cutting sequence, respectively.
Today, the life cycle of modern electrodes can exceed
4 hours arc time.
It is well known that plasma cutting generates airborne
particles, such as dust, IR and UV light, as well as high
noise levels. For this reason, in Europe, it was mostly
performed under water. Water muffles the noise, binds
dust, and protects sufficiently from radiation. There are
disadvantages, however. Filling the water tables takes
time, in comparison with dry tables. In addition, wet
plates cannot be welded without loss of quality. Rust may
occur on the bevel edge faces, and cutting particles must
be cleaned from cut parts after water drainage. This is
carried out with high pressure water pumps, installed on
the cutting machine.
There is a tendency, in Europe, for users to return to dry
cutting, as this technique offers considerable advantages
for productivity, cut quality, charging – discharging.
However, noise level is a major problem. Noise protection
cabins are provided for operating personnel and,
sometimes, machines are encapsulated (modern cutting
machines can operate fully automatically).
Status of laser cutting
As mentioned above, laser systems have been introduced
into shipbuilding, in shipbuilding nations such as the
USA, Korea, Italy, and Germany (Figure 3). However,
the cutting speed is still lower and investment costs are
considerably higher than those of a comparable plasma
Figure 5. Ink jet marking.
Figure 6. Operator calling system.
systems. On the other hand, wear costs are clearly lower;
a precise cost comparison evaluation is not yet available,
although in progress (Figure 4).
Some arguments in favour of using a laser should not be
underestimated:
• Cut faces can be used without further post-machining.
• Noise level of a laser cutting machine remains inside
permissible limits.
• Dry cut.
• A laser system can be operated without personnel, as
wear part consumption is very low (approx. 40 hours
without operator activities).
• Based on laser power of 5 or 6 kW (currently used
for cutting), cutting speeds can be achieved which are
regarded as acceptable.
• Due to horizontal cutting edges, plates on both sides of
the cut can be used immediately, reducing the cutting
length and partly balancing the lower cutting speed
compared with plasma cutting.
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• Lower heat input causes a lower distortion of the parts.
• The narrow joint generates less airborne particles and,
additionally, there are material savings.
the CNC control can be connected to the manufacturer’s
development systems via the Internet, to log the machine’s
proceedings. With these Internet connections, trouble
shooting is carried out successfully over long distances.
Marking
Marking is an important process needed to draw bending
lines, lines for stiffening elements and registration codes.
Marking time is often calculated to be as long as cutting
time. Ink marking, similar to an ink jet printer, is most
commonly used as it can draw lines of various width, and
letters, at a speed of up to 20 m/min (Figure 5). Powder
marking has been almost completely replaced by plasma
marking, which is more dependable.
Quality of the cut
Within the long chain of actions needed to build a ship,
cutting is the first manufacturing step. If the required
accuracy is not achieved in this first stage, all subsequent
manufacturing stages will be negatively affected. These
precision cuts must meet accuracy requirements within
millimeters.
Modern guiding machines with servo drives having low
dimensional tolerances and precision guides match these
requirements. Also, the plasma torches and their wear parts
(nozzle, electrode, gas diffuser) must be accurately manufactured. To eliminate the typically inclined plasma cut,
bevel machines are used which adjust the torch by some
degrees, and which are guided tangentially to the contour.
As a result, a perfectly horizontal edge is achieved.
Summary
Plasma cutting is widely used in shipbuilding, alongside
oxy-fuel cutting for 25mm plate thickness and upwards
- especially for multi-torch operation. Also laser cutting
with its specific quality advantages has been introduced.
To meet the requirements of highest component precision,
optimum cut quality and lowest cutting costs, cutting
systems with numerous additional tools are available,
extending the application range of the systems. The
trend is still directed to shorter process times, ie, higher
cutting performance together with a higher quality. Cut
parts must immediately pass on to the next fabrication
step - without post cutting labour. Down times must be
minimised. Diagnostic devices and monitoring systems
define the time of a wear part replacement to avoid
malfunctions. The objective is a constant quality of cut
parts, even with changing material grades.
Literature
1. Jansen, H. Carlsson S., Decker K.
Thermal Cutting in Shipbuilding, State of the Art
International Welding Conference, Hannover 2002.
2. Decker, K. and Jansen, H.
Performance of Thermal Cutting Procedure in Shipbuilding.
DVS Reports, Vol. 162, (1994).
For more information contact: info@esab-cutting.de
Process optimisation
One expects a constant cutting quality from modern cutting
machines. To realize this requirement, it is necessary to
design both the power sources and the cutting tools in
such a way that all cutting parameters can be programmed
to adapt the machine to different cutting processes.
On the guiding machines, actuators are installed to provide
the necessary gas under the conditions required for an
optimum cut. These control mechanisms guarantee high,
repeatability accuracy.
Process monitoring and control
Modern, CNC controlled cutting machines allow an
operator to control several cutting machines. Laser
machines often operate without personnel. In the case of
malfunction, however, absence of personnel may lead to
considerable damage. To avoid such risks, machines are
equipped with monitoring devices that pass information
to the CNC control, in the case of failures. Via modems,
messages can be send to PC’s, fax, or mobile phones to
alert maintenance personnel (Figure 6).
Another problem can be infrequent errors, eg, once a day
or several times a week. To carry out an error analysis,
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Improved productivity
in automated aluminium
welding fabrication
By Tony Anderson, ESAB North America.
AlcoTec Wire Corporation Inc, a subsidiary of the ESAB Group, is a fully integrated
aluminum welding and brazing wire producer located in Traverse City Michigan USA
AlcoTec has developed and introduced the AlumaPak bulk drum to the aluminum
welding industry. This article reports the successful use of the
AlumaPak by automated welding fabricators.
The success of the AlumaPak in the USA market has led ESAB
to introduce the drum into the European and North American
markets under the ESAB brand name of Marathon Pac.
One thing that everyone in the welding fabrication industry
should be constantly in search of is improved productivity.
By accomplishing this goal, without compromising quality,
we have the ultimate achievement. Every manufacturing
engineer, quality engineer, and welding engineer, should
be on the lookout for methods that can help to improve
performance and reduce manufacturing costs. Some of
the common methods of increasing productivity are faster
processing times through increased welding speeds, or
innovative design that can reduce the amount of welding
required in any specific structure. This article, however, is
about recognizing the opportunity to improve productivity
through the reduction of non-productive labour costs.
For many years, ESAB has successfully produced steel wire
in a drum pack (Marathon Pac); however such packaging
for aluminum has historically been somewhat questionable
in terms of both quality and consistency of performance.
AlcoTec Wire Corporation, the world’s largest producer
of aluminum welding wire, had, on numerous occasions,
evaluated the possibility of producing aluminum welding
wire in such a package. For a number of years, however,
they chose not to release such a product onto the market.
AlcoTec’s concerns at the time were based on their belief
that the technology for producing such a product that
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would be capable of meeting their high performance
requirements was not yet available. The possibility of
compromise by producing a product of inferior operating
characteristics, coupled with the potential for damaging
their exceptional reputation within the aluminum welding
industry internationally, was totally out of the question.
This situation changed abruptly, in 2001, when Yorozu
America Corporation approached AlcoTec with a request to
help them improve their productivity with the introduction
of a reliable aluminum wire drum pack. Yorozu is an
extremely large international automotive parts supplier
that designs and manufactures innovative new products.
At the time Yorozu, at their Morrison, Tennessee plant,
had just embarked on a major conversion from steel to
aluminum fabrication. They were, and are still, using
large amounts of the ESAB Marathon Pac for their steel
welding and taking full advantage of this package’s ability
to reduce spool changing time. The specific question
from Yorozu to AlcoTec was, “We need aluminum in a
bulk drum pack. Can you supply it?”
This request promoted the evaluation of new technology
and an extensive research and development programme
by AlcoTec, the end result being the AlumaPak (figure 1).
After many prototypes and numerous modifications to both
manufacturing techniques and packaging design, AlcoTec
had developed an extremely reliable bulk drum pack
for aluminum welding wire. This package was capable
of holding 300 plus pounds (141 kg) of aluminum
welding wire and delivering it reliably through a robotized
MIG welding system. At the starting point of this
project, Yorozu had 40 robots allocated to their aluminum
fabrication, all of which were equipped with the new
AlumaPak. This has since increased to over 100 robots.
Enormous savings could be realized from reducing
downtime associated with spool changing. The transition
to aluminum welding, and the introduction of the
AlumaPak into Yorozu, was conducted with very little
interruption of manufacturing. The reason for such a
successful transition can only be attributed to Yorozu’s
forward thinking commitment to training and recognition
of new technology. Prior to the introduction of aluminum welding at their plant, Yorozu sent a number of their
engineering staff to the AlcoTec School for aluminum
welding technology. During the introduction of aluminum
welding into their plant, they contracted AlcoTec
engineers and technicians to perform extensive in-house
training of their welders and welding inspectors.
Another story, quite typical of an innovative manufacturer
who recognized the potential is that of Dee Zee, Inc, based
in Des Moines, Iowa. Dee Zee recently celebrated over 25
years as a leading supplier of aftermarket truck accessories.
Dee Zee announced their initial arrival into this market
with the introduction of 12 custom fit extruded aluminum
running board applications, in 1977. Over the years, Dee
Zee has expanded the initial offering of 12 boards to over
120 running boards and many other truck accessories.
Figure 1. Aluminum Engine Cradle and AlcoTec AlumaPak on
the Yorozu robotic welding line. The AlumaPak has 300 plus
pounds (141Kg) of tangle-free aluminum welding wire that
feeds easily and ensures accurate wire placement on the
weld joint during MIG welding, these features being particularly attractive for robotic welding.
Figure 2. A Dee Zee aluminum fabricated toolbox lid welded
with aluminum welding wire supplied in the AlcoTec AlumaPak.
Dee Zee is also a key manufacturer of aluminum toolboxes.
The box bodies are typically pressed from a single sheet
of aluminum and have continuous MIG seam-welded
sides that provide an extremely robust structure proven to
perform exceptionally well in service.
An engineer from Dee Zee, visiting AlcoTec Wire
Corporation at their display booth during the American
Welding Society (AWS) trade show in Chicago, saw the
AlumaPak on display. The engineer, being aware that the
most significant cost associated with production welding is
often the labour cost, and appreciating the fact that welding
equipment is best utilized when it is welding, immediately
saw the AlumaPak as a potential for significant savings.
His idea was quite simple; at that time Dee Zee was
using the aluminum welding wire packaged on 1-pound
(0.5 Kg) spools for their manual welding stations and
32 • Svetsaren no. 1 • 2005
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A C E N T U R Y O F I N N O V AT I O N
16-pound (7 Kg) spools for their robot applications. The
concept was based on the fact that every time a spool
of wire had to be changed, there was a period when the
welding equipment was not welding, so reduce the spool
changes and convert nonproductive down time used to
change spools into productive welding time used to make
product.
MIG with the appearance of TIG.
Graphic simulation of precision
layering with Aristo SuperPulseTM
Determined to succeed in this project, one of the first
steps for Dee Zee was to attend a four-day training
programme which was conducted by AlcoTec Wire
Corporation in Traverse City, MI. The decision to attend
this training programme would provide an invaluable
opportunity to obtain additional training in aluminum
welding technology.
Dee Zee has calculated that their decision to move to
the AlumaPak has saved them on their manual welding
stations alone 13 hours of labour time for every AlumaPak
that they run. Additional savings were also found on their
robotic stations of 1.8 hours labour for each AlumaPak
used. Since the initial introduction of the AlumaPak at
Yorozu, its concept has become increasingly popular
with many aluminum welding fabricators who have
recognized it as an opportunity for improved productivity.
For obvious reasons, large numbers of robotic aluminum
welding fabricators in North America have moved to this
product and, more recently, an increase in its popularity is
being seen in many other areas of the world.
About the author
Tony Anderson MSc CEng SenMWeldI - Is the Corporate
Technical Training Manager for ESAB North America and
past Technical Director of AlcoTec Wire Corporation. He is
Chairman of the American Aluminum Association Technical
Advisory Committee for welding and joining and holds
numerous positions including Chairman, Vice Chairman and
Member of various AWS technical committees.
New! Aristo
SuperPulseTM
Heat critical.
Weld perfect
New Aristo SuperPulseTM maximises welding productivity in
thin and thick section stainless and aluminium alloys.
Precise heat control combined with pulse action eliminates
distortion and produces a perfect finish. Aristo SuperPulseTM
delivers pulse/pulse, pulse/short arc and spray arc/pulse
options, plus MIG brazing of ultra thin sheet
material.
–
Easier positional welding
–
Uniform heat transfer and penetration
–
Less sensitive to joint gap variations
–
Suitable for automated and robotic
systems
–
Extends the working range for larger
diameter wires
Revolutionise your welding productivity with
Aristo SuperPulseTM.
Find out more at www.esab.com/superpulse
Svetsaren no. 1 • 2005 •
33
Welding and cutting
1019442_Svetsaren_01-2005.indd 33
24-03-2005 16:21:42
Product News
9% Ni steel and Aristo SuperPulse
Last year, ESAB Aristo SuperPulse
was tested for the welding of 9%
Ni-steel for low-temperature service
as part of a larger project to develop
WPS’s with more processes. These
steels are normally welded with SAW
or SMAW. Solid wire MAG welding
has never been successful and there
are very few flux-cored wires on the
market with good weldability and sufficient mechanical properties.
because of the high viscosity making
the weld pool act like chewing gum.
The welder has to move the arc
very actively in order to get any
wetting. It is really difficult to get
a good bead geometry and the
transition from weld metal to the base
material is often very sharp, resulting
in poor fatigue properties.
with an AristoMig 500w inverter
power source.
Initial tests with Aristo SuperPulse
and solid wire had been promising
and, therefore, it was decided to include
this method in the test program.
ESAB Aristo SuperPulse is a further
development of the pulse/pulse
concept giving full control over the
heat input (see Svetsaren 2/2003 p. 42)
with two new arc modes; short arc/
pulse arc and spray arc/pulse arc.
OK Autrod 19.82, a Ni-base solid
wire (ERNiCrMo-3/SG NiCr21Mo9Nb),
was used as the consumable in the
tests together with a 3-component
shielding gas mixture. The short arc/
pulse arc mode was used for positional welding and the spray arc/
pulse arc mode for downhand use.
Altogether, 24 successful PQR’s in all
positions were produced, including
butt welds welded one-sided without
ceramic backing. They all received
third party approval.
Welders know that welding with
Ni-based consumables is a challenge -
It is a software solution included in the
U8 control box used in combination
For more information contact:
larserik.stridh@esab.se
ESAB versatility in robotic welding
With the introduction of the AristoMig
robot package, ESAB is now able to
provide robot suppliers and integrators with a complete welding solution that is easy to install and use.
The AristoMig robot package offers
a choice of AristoMig inverter-based
power sources, encapsulated and
non-encapsulated, robot-mounted
wire feeders and the Aristo Pendant
U8 control box.
The Aristo Pendant U8 control box
software includes a vast library of
synergic lines for practically any
application, as well as the advanced
Aristo SuperPulse technology, which
provides greater opportunities for the
welding of aluminium, stainless steel
and for MAG-brazing.
sheet welding, typically for the
automotive industry, up to big plate
thicknesses such as in mobile
machinery. Services range from
the retrofit of existing robots
to the supply of new industrial
installations in co-operation with our
robot partners and local integrators.
The ESAB AristoMig robot package includes configurations for thin
For more information contact:
christophe.gregoir@esab.be
All ranges of welding wires are robot
quality, manufactured and supplied
in the famous ESAB Marathon Pac™
bulk drums.
The standard version of the
AristoMig robot package is available
for DeviceNet communication. It can
also be adapted to communicate with
most types of robot controller.
34 • Svetsaren no. 1 • 2005
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NOMAD finalised
Figure 1. The bridge part welded in the
production cell.
The final design of the Robot Transport Vehicle (RTV).
As reported in previous issues of
Svetsaren, NOMAD is a project to
develop autonomous manufacture of
large steel fabrications. It is within
the EU Commission Framework 5
growth programme and has been in
progress for 42 months. The project is
now finished, the final demonstration
being held in Gosselies, Belgium, on
17th November 2004.
The aim of the project was to perform
welding on an large object, placed in a
production cell, using an autonomous
robot. It requires different systems
to communicate and to co-operate
in a friction free way. On the Robot
Transport Vehicle (RTV) there is
another internal communication link
that has to operate simultaneously.
Since the object to be welded is placed
on the floor of the production cell,
welding has to be performed in all positions, and in the most effective way.
The components in this project are very
different - a bridge part and the ”stick”
of an excavator (Figures 1 and 2).
The photographs show that they are
large constructions. In the case of
the excavator part, the plate thickness
ranges from 8 mm up to 35 mm, so
there are some multi-bead joints to be
welded. Since the vision system, the
joints and the positions all demand
different features from the consumable,
metal-cored wire is the best choice.
Standard wires were not effective
because they were fine-tuned to give
the best properties in the downhand
position. ESAB, as a partner in this
project, developed a 1.2 mm size
prototype wire with tailor-made
properties. In addition to dependable
feedability - guaranteed by a robot
quality surface treatment - it was
necessary to adapt the fluidity of the
weld pool and, very importantly, to
reduce the amount of silicon-oxides
on the bead surface. Since it is a fully
automated process where the system,
unlike a human welder, can’t see the
condition of the surface, it could be
that the wire tries to start on an oxide
island on the surface of a multi-bead
joint. A non-start would be the undesirable result.
Figure 2. The excavator stick that was
welded within the project.
Figure 3. Cross section
of a multirun fillet weld
made in the overhead
position.
The wire was successfully applied in
both the WPS development and the
final demonstration where the two
earlier mentioned parts were welded.
For more information contact:
larserik.stridh@esab.se
Figure 4. Weld surface with an
extremely small amount of oxides.
Svetsaren no. 1 • 2005 •
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35
24-03-2005 16:21:48
ESAB high purity consumables for
welding creep resisting steels
ESAB has added two low-hydrogen
electrodes to its range of consumables
for creep resisting steels; OK 76.16 for
1.2Cr – 0.5Mo types and OK 76.26
for 2.25Cr – 1.0Mo.
supplied in hermetically sealed VacPac
aluminium foil.
THE ESAB RANGE OF CREEP RESISTANT CONSUMABLES
for 1.2Cr – 0.5 Mo grades
Impurity elements, such as Sn, As, P
and Sb, are strictly controlled - leading
to a guaranteed Bruscato factor of
X <15ppm. Both fulfill step cooling
requirements, have a low moisture
absorption (LMA) coating and are
For additional information contact:
rune.pedersen@esab.no.
for 2.25 Cr – 1Mo grades
(SA-387 Grade 11 /A 335 P11 or similar) (SA –387 Grade 22 / A335 Grade P22 or similar)
MMA OK 76.16
OK 76.26
SAW
OK Flux 10.63/ OK Autrod 13.10 SC
OK Flux 10.63/ OK Autrod 13.20 SC
MAG
OK Autrod 13.16
OK Autrod 13.17
TIG
OK Tigrod 13.16
OK Tigrod 13.17
OrigoMig 405 welding package,
a new member of the Origo family
The OrigoMig 405 welding package
is ideal for welding applications
within general steel fabrication, the
vehicle industry and household and
furniture manufacturers. The package
consists of the OrigoMig 405 power
source, OrigoFeed 30-2 or 30-4 wire
feed units, a connection set (1.7, 5 or
10 m) and the PSF torch.
Reliable and easy to use.
OrigoMig 405 and 405w are stepcontrolled power sources for MIG/
MAG welding. Fourty voltage steps
provide accurate settings for even
the most critical applications.
purge and burnback time settings are
clearly indicated on the front panel
of the feeder. Voltage setting and
inductance adjustments are made on
the power source.
Available accessories
The easy to install plastic bobbin
option protects the wire spool from
dirt and dust. Extra versatility is
provided by three wire feed mounting
options; counterbalance and mast,
wheel kit or a suspension bracket.
As an option, the OrigoMig 405
can also be fitted with a V/A digital
meter and transformer for CO2 heater.
OrigoMig 405 and OrigoFeed are
designed with sturdy galvanised metal
casing. Electronically controlled
feeding gives accurate and stable arc.
The 4-wheel feed mechanism has
grooves in the feed roller and idle
pressure roller with ball bearing, to
provide positive and stable feeding
combined with low wear on the
wire. The 2-wheel feeder mechanism
is a cost-efficient solution for wire
dimension up to 1.2 mm.
With safety in mind
The OrigoFeed is designed to meet
the highest safety standard IEC/EN
60974-5 with low voltage (42 V/AC)
operations complete with an overload
device ensuring the best possible
protection.
The feeders are available with Ø30
mm feed rollers for wires up to Ø1.2
mm (30-2) and Ø1.6 mm (30-4).
• 40 voltage steps,
optimum settings for each
application.
• 2/4 stroke,
simplifies welding.
• Adjustable burnback timer
gives correct stick-out.
Easy settings
Wire feed speed, 2/4 stroke, creep
start, spot welding, inching, gas
Service and support
ESAB’s large network of distributors
and authorised service workshops
are available at www.esab.com.
• Creep start, (30-4) gradual feed
of wire for ultimate starts.
• Spot welding
(30-4) for easy operation with
pre-setting of the timer and equal
lengths of the spots.
• Gas Purge and Inching
(30-4) no wastage wire or gas
when initially setting up the
equipment for welding or
changing the wire spool.
• Two inductance outlets
- easy to optimise settings for
different applications.
• IP 23
- fit for safe out of doors
applications.
• Easy-to-use control panel
for quick set up.
For more information contact:
info@esab.se
36 • Svetsaren no. 1 • 2005
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OrigoMag C150/C170/C200/C250
A recent addition to the Origo family
OrigoMag is the ideal welding
machine for everyone who wants
good equipment to do less complex
welding jobs of high quality.
OrigoMag C150, C170, C200 and
C250 are step-regulated power
sources for MIG/MAG welding.
They are designed for light-duty
applications. A built-in wire feeder,
and the low weight of the units,
make them perfect, practical solutions
for farmers, repair shops and light
production users.
are equipped with multi-step voltage
switches and potentiometers for wire
speed adjusting to enable easy setting
of welding parameters. It is possible
to adjust burn-back time and to set
spot welding time in C170/C200/
C250. The units are fan-cooled and
equipped with thermal overload
protection. As an option, OrigoMag
C170/200/250 can be equipped with
V/A digital meter and transformer
for CO2 heater.
MIG/MAG welding.
OrigoMag can be used with both
solid wire and self-shielding cored
wire. It is designed for welding of
steel, stainless steel and aluminium.
Wire diameters from 0.6 mm up to
1.2 mm can be used depending on
the type of machine.
Power Smoothing Device™
Although OrigoMag C150/C170/
C200/C250 are 1-ph units, Power
Smoothing Device™ gives them
excellent welding performance
in CO2 and gas mixtures. Power
Smoothing Device™ provides as
smooth a welding current as for a
3-phase machines.
Easy to use
The Power Smoothing Device™
improves welding when CO2 or Ar/
CO2 gas mixture is used. The units
Torch included
Each machine is equipped with a
gas-cooled ESAB MX Torch (MXL
150v, MXL 200, MXL 270), and
each has ergonomic handles. They
have spring loaded contact pins in
the central Connector - except for
ESAB MXL 150v which is delivered
with 2.5 m and is connected directly
to the power source.
Optimum cooling of the torches
gives extended lifetime of the swan
necks and the wear parts. Gas nozzles
are available in three different
versions - standard, straight and
conical. This provide maximum
flexibility and optimum lifetime.
• Power Smoothing Device™
- excellent welding performance
for single phase machines.
• Easy change of polarity
- it may be used with both
conventional solid wire and
self-shielding cored wire.
• Easy setting of welding parameters
- welding machines for everyone.
• ESAB MX Torches™
- designed to provide the ultimate
in convenience and versatility.
Svetsaren no. 1 • 2005 •
1019442_Svetsaren_01-2005.indd 37
37
24-03-2005 16:21:50
COMBIREX CXL-P- CNC controlled
portal cutting machine
Accurate, efficient, safe.
The Combirex CXL-P is a modular
CNC controlled portal cutting machine
that can be equipped with high-speed
plasma cutting and/or oxy-fuel cutting
- making it a highly flexible production
tool. It can be configured in three sizes
to meet exact plate width requirements
of 2000 mm, 2500 mm or 3000 mm,
and equipped with up to four cutting
tools. The modular design ensures that
the machine can be easily upgraded
with extra cutting tools if requirements
change in the future.
The Combirex CXL-P has a powerful
3-axis drive system that delivers speeds
up to 20,000 mm/min. The transverse
master drive carriage is guided by a
linear guiding rail and driven by a rack
and pinion planetary AC drive. This
design ensures:
• Smooth machine movement for
higher part tolerance.
• Reduced maintenance and longer
mechanical lifetime.
• High acceleration giving excellent
cornering performance and reduction
in the overall cutting cycle.
The machine can be fitted with alternative plasma systems that deliver high
quality, precise and high speed cutting
on parts from 1 to 30 mm thick in mild
steel, stainless steel and aluminium.
The plasma cutting process is controlled
automatically from the CNC control,
ensuring the correct speed, height and
kerf compensation for a particular
part. The machine motion and set up
ensures good performance throughout
the plasma cutting speed range with an
automatic cutting cycle.
The plasma process is automatic with
both initial height sensing and arc voltage height control during cutting. The
initial height sensing gives the correct
piercing height ensuring maximum
consumable lifetime. The arc voltage
cutting height control ensures the best
cut quality available.
ESAB’s unique anti-collision plasma torch
system has the following advantages:
• Immediate stop of the machine after
collision.
• Quick and accurate alignment sensor
that guarantees correct alignment of
the torch after a collision.
Automatic Oxyfuel Cutting
The Combirex CXL-P can be fitted with
up to four oxy-fuel gas cutting torches to
cut mild steel up to 150 mm thickness.
It delivers high productivity and
quality through an automatic cutting
cycle made possible by:
• The automatic high-pressure preheating system, which boosts the
pre-heat gasses to minimise the preheating time from pre-set values.
• Automatic hole piercing by three
solenoid valves.
• Automatic torch lifting during
piercing. Automatic torch height
control by capacitance ring.
• Individual solenoid valves.
The machine meets and exceeds all
current safety regulations.
For more information contact:
info@esab-cutting.de
38 • Svetsaren no. 1 • 2005
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! # % . 4 5 2 9 / & ) . . / 6!4 ) / .
!UTOMATEDWELDING
SOLUTIONSFORWINDTOWERS
%XPERTISEEQUIPMENTANDCONSUMABLESFROMAGLOBALLEADER
%3!"ISAWORLDLEADERININTEGRATEDWELDINGAUTOMATIONANDCUTTINGSYSTEMSFOR
WINDTOWERPRODUCTION
!SAKEYSUPPLIERTOTHEWINDENERGYINDUSTRY%3!"SGLOBALEXPERIENCEBRINGS
YOUPROVENLEADINGEDGETECHNOLOGYFORADVANCEDPRODUCTIVITYSOLUTIONS
%3!"HASALSODEVELOPEDSPECIlCWIREANDmUXCOMBINATIONSTHATGIVESUPERIOR
PERFORMANCEINSUBARCWELDINGAPPLICATIONSFORWINDTOWERSANDWHICHARE
AVAILABLEWORLDWIDE
#ONTACTYOURLOCAL%3!"EXPERTATESABCOM
7ELDINGANDCUTTING
1019442_Svetsaren_01-2005.indd 39
24-03-2005 16:21:58
ESAB AB
Box 8004 S-402 77 Gothenburg, Sweden
Tel. +46 31 50 90 00. Fax. +46 31 50 93 90
www.esab.com
1019442_Svetsaren_01-2005.indd 40
24-03-2005 16:22:02