Svetsaren 02 2002

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THE ESAB WELDING AND CUTTING J OURNAL VOL. 57 NO.2 2002

Advanced

Materials

Advanced

Materials

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C ontents Vol. 57 No. 2 2002

Articles in Svetsaren may be reproduced without permission but with

an acknowledgement to ESAB.

Publisher

Bertil Pekkari

Editor

Ben Altemhl

Editorial committee

K las Weman, B jrn Torstensson, Johnny Sundin, Johan Elvander, Lars-Erik Stridh,

Lars-Gran Erik sson, U we M ayer, M anfred Funccius, Dave M eyer, D onna Terry, Tony Anderson

Address

ESA B AB , B ox 8004, SE-402 77 G teborg, Sweden

Internet address

http://www.esab.com

E-mail: info@ esab.se

Lay-out: D uco M essie, P rinted in the Netherlands

THE ESAB WELDING AND C UTT ING JO UR NAL VO L. 57 NO .2 2002

Advanced Materials

High deposition welding of Francis turbine

runners for the Three Gorges dam project.

The art icle informs abo ut the w orld's largest

hydro po wer project ever, and describes

ESA B 's involvement in the welding of the

Francis turbine runners.

Welding of copper-nickel alloys at Kvaerner

Masa-Yards.

The orb ital TIG welding o f copper-nickel

alloy pipes as an alternative to brazing.

Friction Stir Welding- progress in R&D and

new applications

The a rticle presents recent R &D results, a

new machine series, and a fascinating new

application in the welding of thick copper.

Welding of supermartensitic stainless steels.

The orbital narrow gap girth welding of pipes

and the dissimilar joining of supermartensitic

and superduplex pipes.

Chicago Bridge & Iron Company meets

challenge of stainless steel welding for

cryogenic rocket fuel tanks

The welding of cryogenic storage tanks for

the B oeing Space Launch Co mplex 37 at

Cape Canaveral Air Force Station.

Welding high strength p ipelines - fromlaboratory to field.

A survey of the developments in the mecha-

nised G MAW of pipelines in X80 type high

strength steel.

Synergic Cold Wire submerged arc welding

Results of research on the application of this

new, cost-efficient welding process to sta inless

steel.

Welding tramway rails in Bucharest

A report on the use of ESAB's enclosed weld-

ing technique for t he joining of tra mwa y rails.

The mechanised MAG welding of the Clare

natural gas line.

The use of OK 12.65 copper-free wire in the

mechanised G MAW of a new extension of

the Irish national gas grid.

Consumable development for oxidising

chloride containing process environments.

R esearch w ork a t V TT Technical R esearch

Centre in Finland.

CIMTAS, an international player in power

generation and energy storage.

The article reviews CIMTAS, a Turkish

fabricator of pow er plants and other energy

related constructions. The fabrication of two

very large LNG ta nks is highlighted.

Stubends & SpatterShort news

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Svetsaren no. 2 2002 3

High deposition welding of

Francis turbine runners for the

Three G orges da m projec tBy: Nils Thalberg, Solveig Rigdal, Leif Karlsson, John van den Broek and Herbert Kaufmann, ESAB AB

This pa per w a s originally prese nted a t the S ta inles s S teel World America 2002 C onferenc e.

The worlds largest hydroelectric project, the Three G orges dam in C hina, will

comprise 26 Francis turbines for the production of electricity. Each turbine runner

is 10m in diameter, weighs 450 tonnes and will generate 700 M W. The runners

are made of solid 410 N iM o type martensitic stainless steel (13% C r, 4% Ni, 0.5%

M o) castings. Welding is used for the assembly and repair of casting defects.ESAB is involved in the production of the runners with consumables and

equipment for SAW and G M AW.

Three G orges the w orlds la rge sthydroelectric projectIn 1994, construction work began on the massive Three

G orges dam near Y ichang (Fig. 1). This dam is expected

to help control the flooding of the Yangtze R iver valley;

in addition, river flows will make the Three G orges

complex the largest electricity generat ing facility in the

world. The negative consequences of the project includethe forced relocation of more than one million people

and t he permanent flooding of many historical sites, not

to mention the feared environmental effects.

Figure 1. Location of Three Gorges Dam.

A la ke about 650km long with an a verage width of

1.1km will form behind the dam, which is 185m high

and about 2,309m wide. The water storage capacity of

the dam will be 39.3 billion cubic metres handling 451

billion cubic metres of Yangtze River water flowing

into the reservoir every yea r. D am sponsors say that the

22.1 billion cubic metre flood control storage capacity

of the reservoir should reduce the frequency of large

downstream floods from once every 10 years to once

every 100 years.

The Yangtze River was diverted after four years in

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4 Svetsaren no. 2 2002

Figure 2. Overview of the Three Gorges dam p roject

show ing ship-loc ks (right), a spillway in the cen tre of the

dam and pow er plants on the left and right banks (3).

Table 1. Dimensions and weights of main parts of turbine

components.

Size of main turbine components

M ax. D iameter of runner 10 m

Throat diameter of runner 9.8 mM ax. outer diameter of stay ring 16 m

Height of stay ring 4 m

Spiral case outline (X-X)/(Y-Y ) 34 m/30 m

M ax. outer diameter of head cover 13.3 m

Diameter of wicket gate circle 11.6 m

Height of head cover 1.8 m

Height of guide vane 2.9 m

Diameter of main shaft ( body) 4 m

Weight of main turbine components

R unner 450 t

Stay ring 400 t

Spiral case 700 t

Head cover 380 tM ain shaft 140 t

Single guide vane 9.5 t

Total weight of turbine 3300 t

November 1997, thereby completing the first major

construction stage. Phase 2 began in 1998 and is due to

end in 2003, when the water level will rise to 156m andthe da m will sta rt generat ing electricity. There are plans

to open a permanent ship lock for navigation in the

same year. The ship lock will consist of five locks, each280m long and 35m wide, with a water depth of 5m,

capa ble of hand ling 10,000-tonne ba rges. In a ddition, a

one-stage vertical ship lift capa ble of carrying 3,000

tonne passenger or cargo vessel will be built. Rivershipping through central Ya ngtze is expected to increase

from 10 million to 50 million tonnes annually, with a

reduction in transportation costs of 30-37 percent.

Phase 3 is scheduled for completion in 2009, when fullpower genera tion w ill begin. By then, 102.6 million cubic

metres of earth and stone will have been excavated and

27.2 million cubic metres of concrete and 354,000 tonnes

of steel reinforcing bars will have been used. In thecentre of the dam, there will be a 484-metre spillway

section with 23 bottom outlets and 22 sluice gates. On

the left a nd right ha nd sides of the spillway, there w ill be

two giant power stations (Fig. 2).

Power generation

The installed tota l electricity power-generation capacity

of 18,200 megawatts, or as much as 18 large nuclear

power sta tions, will make the Three G orges number oneamong the w orlds largest hydroelectric projects:

Three G orges, China , 18,200 MW

Ita ipu, B razil and Pa ragua y, 12,600 MW

G r and C oulee, U nited St at es, 10,100 M W

G uri, Venezuela, 10,100 MWTucuruii, B ra zil, 7,500 MW

Sa yano-Shushensk, R ussia, 6,400 MW

Kra snoyarsk, R ussia, 6,100 MWCorpus-Posad as, Argentina

and Paraguay, 6,000 MW

La G rande 2, Ca nada , 5,300 MW

Churchill Falls, Cana da , 5,200 MW

The two power stations flanking the central dam

spillway will operate 26 of the worlds largest turbine

generators, ea ch with a generating capa city of 700 MW.The total electric energy of 84.7 billion kWh produced

annually is equivalent to burning 40 million tonnes of

coal in conventional f ossil fuel-heated power stations.

Design and fabrication of turbinesTwo internat ional consortia will be responsible for theconstruction and manufacture of the 14 turbine generato r

assemblies in the left-bank powerhouse to be installed

during Phase 2 of the project. G E E nergy in Norway

(previously Kvaerner Energy, Norway), as a sub-contractor, is responsible for the hydraulic design of

eight turbines contracted by Alsthom. Five of the run-ners and core components for the turbines will be pro-

duced under G E Energys management, partly in co-operation with Ha rbin Electric Machinery Company Ltd

in China with ESA B as an important supplier of equip-

ment and consumables. The three remaining runners

contracted by the first consortium will be produced tothe Kva erner design by G EC -Alstom in France. The

second consortium, including Voith in G ermany a nd

G E in Ca nada , will jointly develop the hydraulic design

of the other six turbines in the left powerhouse.The manufacture of runner blades and t he fab rication

and welding for the entire runner will be carried out ina number of countries including Romania, Brazil,

Norway, Ca nada , France and China. Typical dimen-sions and weights of the main components of the tur-

bines are given in Table 1.

The 12 turbines in the right pow erhouse will be installed

during Phase 3. A technology transfer condition in thecontracts of the international suppliers of the first 14

turbine-generator pairs requires that t hey assist C hinese

manufacturers in producing the remaining 12 units.

Welding turbine runners

The turbine runners are made of solid 410 NiMo typemartensitic stainless steel (13%Cr, 4%Ni, 0.5%Mo)

castings. The mere size (ta ble 1) and t he complex shape

of the turbine runner means that it has to be produced

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from a number of smaller (yet still impressively sized)

castings. Welding is used to join the separate castings

and repair the casting defects. A combination of

different welding techniques, including manual metal

arc welding (MMA), semi-automatic techniques such

as gas meta l arc welding (G MAW) with solid or cored

wires and fully-mechanised welding with submerged

arc weld ing (SAW), is being used . The specific choice of

method varies depending on factors such as joint

geometry, accessibility and the cost of labour,

equipment a nd consumables. D ifferent combinations

of welding techniques and consumables will thereforebe used for different turbine runners depending on

location and the responsible company.

The three main components of a Francis turbine

runner a re the runner crown, the vanes and t he runner

band (fig. 3). In all, approximately 7-10 tonnes of

welding consumables will be used for the assembly of

each runner. Most of this is needed to join the vanes to

the crown and the band. The first sections will focus on

the SAW twin-wire solution chosen by G E Energy for

joining the vanes to the crown. P re-production tests and

experience of using semi-automatic welding with metal-

cored wires will then be discussed.

Fully-mechanised SAW of vanes to runnercrownG E E nergy in Norway (formerly K vaerner E nergy)

secured the contract for building three runners, partly

in co-operation with Harbin Electric Machinery

Company Ltd, which received the contract for two

additional turbines. Welding methods with the highest

possible deposition rates were specified to manufa cture

runners of this considerable size in a cost effective

manner. The design criteria set by Kva erner Energy

AS, Norway, were to achieve a deposition rate of noless than 16 kg/hour. Aft er eva luat ing differ ent

possibilities, SAW with two wires (twin-arc) was

considered to be t he best method ba sed on productivity

Figure 3. Main components of a Francis turbine runner.

Figure 4. New compact SAW tw in arc welding head.

Figure 5. Welding

station with m anipulator

and welding head

positioned for welding

turbine runner.

and weld metal quality criteria, as well as previous

experience from other critical applications. However,

the full productivity potentia l needs to be utilised while

the welding head precisely follows the approximately

4m long joints with complicated three-dimensional

geometry between the turbine runner vanes and the

runner cro wn/runner b and (Fig. 3). The limited a ccess

for the welding head between the vanes is another

complicating factor. A high-accuracy manipulation andcontrol system is therefore necessary to obtain all the

benefits from a fully-mechanised welding process and

achieve the required productivity.

Crown

Vanes

Band

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Welding equipment

E SAB Welding E quipment AB received a contract from

Kvaerner E nergy A/S, Norway, for the design and supply

of two complete, numerically controlled welding manip-ulators for welding the Francis turbine runners. To fulfil

the requirements, a new compact welding head ha d to be

designed (Fig. 4). The mounting permits vertical, hori-

zontal and rotating movements to allow precise adjust-

ments as the welding head moves along the joint.To make it possible to follow the 4m long joint, the wel-

ding head is mounted on a column and boom manipu-

lator, thereby permitting welding within a workingvolume of 2 x 4.3m horizonta lly and 2m in height (Fig. 5).

The manipulators can b e programmed through " teach-

in" , which means that the welding head is positioned at

various points along the weld preparation and all thenecessary data is stored in the control-box memory.

Individual weld beads can be easily programmed by

simply adding a suitable offset, thereby minimising the

amount of programming required for a multipass weld.

SAW consumables

Approximately three to four tonnes of SAW filler wire

will be used to join the vanes to the crown for eachturbine runner. The welding of ro ot runs and , wherever

necessary, the supplementary welding of filler beads

will mainly be done w ith G MAW using a metal-cored

wire, as described in a later section.In a ddition to t he equipment a nd productivity aspects,

the mechanical and metallurgical properties of the weld

metal and the ba se material in the as-welded condition,

as well as a fter P WHT, must comply with stringentreq uirements. The specified classification fo r the wire is

AWS ER 410NiMo, modified as required to fulfil

mechanical and weldability requirements. This con-

sumable will deposit a weld metal with a compositionsimilar to that of the 410 NiMo type ma rtensitic stainless

steel (13% Cr, 4% Ni , 0.5% Mo) used in the castings.

The requirements that have to be fulfilled by the

combination of flux and wire include:

A diffusible hydrogen of less than 3ml per 100g weldmetal.

A minimum flux basicity index of 2.7.

Minimum Charpy-V impact toughness of 50 J a t 0C

aft er P WHT and a minimum of 20J in the as-weldedcondition.

Accepted bend tests in the as welded condition and

aft er P WH T. Minimum yield strength of 550 MPa a nd minimum

tensile strength of 760 MPa aft er P WHT.

G ood weldability, including wetting characteristics,

slag deta chability a nd weld surface appearance for amaximum welding current o f 970A.

Aft er initial tests, the new E SAB wire/flux combi-

na tion , O K Autro d 16.79 (2x 2.4mm)/OK Flux 10.63(Table 2), was shown to deposit a weld metal fulfilling

all the a bove req uirements.

Weld tests

The final acceptance tests for the welding consumables

and welding stations included:

a) welding in 60mm thick material in a symmetrical 45X-joint a nd

b) welding on a specimen simulating a 300mm thick

vane to be welded to a 200mm thick section of the

crown in a symmetrical double J joint.

All the tests were performed on cast material of thequality to be used in production.

A preheat of 100-150C and a maximum interpasstemperature of 200C were used with welding

parameters of 970A, typically 31V and welding speeds

of 60-70 cm/min. All the test s were performed w ith two

2.4mm wires in line.

Table 2. Welding consumab les used for SAW tw in wire welding of vanes to runner crown.

Consumable Classification Flux Typical all-weld metal

basicity composition (wt. %)

C Si Mn Cr Ni MoO K Flux 10.63 EN 760 SA FB 1 55 AC H5 3.2

O K A utrod 16. 79 A WS A 5. 9 ER 410 N iM o mod. -

Table 3. Mechanical data from accep tance tests.

Weld Test condition Cross weld Impact Hardness Side bend testing

tensile strength t oughness (HV10) (180, 6xt)

(MPa) at 0C (J)

Weld metal Weld metal

60 mm X-joint As welded 824-829** 34, 31, 33 369-394 no remarks

PWHT* 728-739** 86, 88, 87 284-300 no remarks300 mm double J-joint PWHT* 838-866** 82, 86, 83 290-305 no remarks

* Post weld heat treatment: 580C / 4 h

** Fracture in base metal

0.02 0.4 0.7 12.3 4.3 0.5

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The accepta nce criteria included welda bility aspects such

as wetting characteristics, slag detachability and weld

surface appeara nce, mechanical propert ies (Table 3) andnon-destructive testing using ultrasonic and radi-

ogra phic examina tion. The test results were satisfactoryand E SAB was awa rded a contract for the delivery of

two complete welding stations with an option also to

purchase consumables.

Production experience

The thickness of the va ne varies a long the 4m long joint,

but it is mainly between 70 and 220mm. With a typicalwelding current of 700-800A and a welding speed of

70cm/min, so me 200-300 weld bea ds have to b e

deposited w ith heat inputs of a bout 2kJ/mm for eachjoint. Consistent performance and reliability are there-

fore just a s important a s deposition rates during welding.The welding stations were delivered and assembled in

Huludao in China towards the end of 2000. Non

destructive testing has confirmed the high andconsistent quality of the weld metal and welding is

proceeding as planned without major complications.

GMAW with metal-cored wiresESAB has a wide range of consumables for hydro-

turbine solutions, not only for SAW but also for G MAWand MMA. In particular, the range of meta l-cored wires

(MCW) has a long and successful track record.

Productivity and weldability

Productivity from cored wire welding, regardless of the

wire type used, is always superior to that of manualwelding with manual metal arc stick electrodes, due to

the higher duty cycle. In a ddition, deposition rates a re on

a much higher level. MCWs have little or no slag formingingredients in the fill and they also have only a small

amount of arc stabilisers. As with solid wires, weldsdisplay only small islands of de-oxidat ion products, mak-

ing them popular for productive multi-run welding with-out inter-run de-slagging. This explains their widesprea d

use for mechanised and robotic operations. The metal-

cored types for turbine applications are medium filling-rate wires suitable for manual, mechanised and robotic

operation, in all welding positions.

The advantages for turbine fabrication and repair can

be summarised as follows.

High duty cycle compared with other manual andsemi-automatic welding methods.

Low spatter operation with well wetted, f lat andfully penetrating beads, leading to significantly

reduced post weld labour.

G ood all-positional weldability, even in the low-

current range. Can be welded with conventional or pulsed arc

power sources.

Metal-cored wires for hydropower turbine

applications

FILARC PZ6166 is a MCW which has been speciallydeveloped for welding 410 NiMo type martensitic

stainless steel in the hydro power industry. The w ire isavailable with diameters of 1.2 mm and 1.6 mm and is

welded with eit her 98%Ar/2%O 2 or 98%Ar/2%CO 2.

The second of these shielding gases produces thesmallest amount of silicate on the bead surface. The

rolling manufacturing technology guarantees wireswith a weld metal hydrogen content in the " extra low"

class (H D M 760 >570 >15 50 40

Table 4. Typical all-w eld metalmechanical properties for themetal cored w ire PZ6166 afterpost w eld heat treatment at 580-600C fo r 8 hours.

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part ly with the SAW two-wire process with solid wire as

described above. FILARC PZ6166 was introduced

after a test programme was successfully completed,showing that requirements relating to mechanical

properties and hydrogen levels could be fulfilled.

However, other important aspects included weldabilityfeatures, such as good penetration, excellent wetting

and low spatter, ensuring a minimum of post weld

cleaning, grinding and repair. The consumption for the

metal-cored wire is estimated at roughly 7-10 tonnesper runner.

Another C hinese company, the D ongfang E lectric

Machine Company as a subcontractor in the Voith

consortium, has also considered metal-cored wires (incombination with solid wires) as a possible solution for

the production of turbine runners. A smaller Francis

turbine runner was therefore successfully produced,

using the FILARC PZ6166 metal-cored wire, as a pre-fabrication test to evaluate the suitability of this

consumable for the Three G orges project.

Fina l comme ntsClose co-operation between ESA B and G E Energyproved fruitful when it came to finding a complete

package solution. The development of a new wire/flux

combination made it possible to comply with the

requirements relating to consumable weldability andproductivity, in combination with the stringent require-

ments imposed on the mechanical and metallurgical

properties of the weld metal. This combination proved

to be very successful and it is now the standard combi-

nation for the SAW of hydro-turbines in 410NiMomartensitic stainless steels. The development of the

new, compact welding head, which was necessary for

welding in the limited space available and is capable offollowing the complicated joint geometry, was greatly

facilitat ed by input from G E E nergy.

D epending on the preferences of t he manufacturing

facility and the selected technical solutions, differentdegrees of mechanisation and, consequently, different

choices of welding method and consumable, will

produce the optimum combination of productivity and

cost. A combination of different solutions is often

applied, as a complex object, such as a turbine runner,may be partly well suited to mechanisation, whereas

other joints can be more economically welded using

manual methods. In the Three G orges project, G MAWwelding with metal-cored wires has been chosen as

either the preferred welding method or the best

method to complement mechanised SAW welding.

AcknowledgementsThe autho rs wish to thank Trond M ultubakk (G EEnergy, Norway) for providing illustrations and for

permission to publish information relating to test

results and req uirements for the Three G orges project.

Figure 6. Section of a Francis turbine runner welded with

the metal cored w ire FILARC PZ6166.

About the authors

Nils Thalberg is G lobal Marketing Mana ger forthe Po wer G eneration segment. He is located inG othenburg.

Solveig Rigdal, MSc, EWE, joined ES AB in

1982 and has since then been working with

product development and market support within

the R & D department in G othenburg. D uring

the last years, her main focus has been sub-merged arc welding of stainless and high alloyed

steels and strip cladding.

Dr. Leif Karlsson joined ESAB's R&D depart-

ment in 1986, aft er receiving a P h.D . in materia ls

science from Cha lmers U niversity o f Technology.

He currently holds a position as Manager

Research Projects at ESAB AB in Sweden,

focussing on projects dealing with corrosion

resista nt a lloys and high strength steels.

John van den Broek is Application Engineerworking within the Shipbuilding and Offshore

G roup of ESA B Europe. He is located in

U trecht, The Netherlands.

Herbert Kaufmann, M. El. Sc. and M. Mech. Sc.,

joined E SA B in 1988 as Technical D irector at

ESAB Automation Inc., USA. He is currently

working as Project Manager within the

Engineering Department of ESAB Welding

Equipment in Lax Sweden.

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Welding of copper-nickel a lloys a t

Kva erner Ma sa -Ya rdsBy Kari Lahti and Juha Lukkari, ESAB Finland

A modern ship contains many materials that represent the most advanced technical

solutions currently available. O ne of them is copper-nickel alloys, which are used as

pipes in applications where contact with seawater or biofouling media causes problems.

The welding of copper-nickel alloys is traditionally

regarded as fairly demanding due to the thermal prop-

erties of copper. It is difficult to obtain a stable weld-pool and to weld without lack of fusion. Those prob-

lems are a thing of the past at Kvaerner Masa Yards

(KMY ) in Finland. Orbital TIG welding wa s the key toimproved quality and increased productivity in thewelding of copper-nickel piping.

To b ra ze o r not to b razeBrazing was the main joining process used at KMY in

Helsinki prior to the unprejudiced thoughts of w elding

engineer Eero Nyknen, together with Hannu Mutkalaand Kalevi Selvinen from the outfitting department.

They contacted ESAB in Finland in order to find outwhether it was possible to w eld copper-nickel instead o f

brazing. The defect ra te during bra zing was fa irly highand, in add ition, the open f lame used inside a ships hull

was considered to be a safety risk.Figure 1. Test weld ing at ESAB Oy, Finland, using a Prowelder

160 power source and PRB 33-90 welding head.

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Fric tion S tir Welding progress in R&D

a nd new a pplica tionsBy Lars Gran Eriksson and Rolf Larsson, ESAB AB, Welding Automation, Lax

In spite of its very recent introduction into industry, Friction Stir Welding is already

frequently used in production. This article presents some recent results from the

continuous research work that is in progress on the process, a new machine series

that is going to be introduced and an extremely fascinating new application in the

welding of thick copper.

Metallurgical considerations in Friction StirWeldingFriction Stir Welding is a comparatively new welding

process intro duced b y TWI in the U K in 1991. The veryfirst a pplicat ions in production w ere in t he 6000 series

aluminium alloys at SAPA in Sweden and Hydro

Marine Aluminium (shipbuilding) in Norway, followed

by the automotive industry in Australia, Sweden and

Norway, also using the 6000 series.

H igh-strength aluminium alloys in the 7000 series grades

star ted the evo lution in the aerospace industry. The FSW

process is still finding new applications in aluminium

alloys. Other materials such as copper and magnesium

alloys are ready to be introduced in production. Steel

and the joining of dissimilar ma teria ls such as copper and

aluminium are shortly expected to leave the laborato-ries, while titanium and stainless steel are waiting for

tests of tool materials to withstand the heat.

The p roc es sFSW is a solid sta te w elding process in which the weld is

completed without creating molten metal. A rotating

tool specially designed for its purpose generates heat

and deformation of a superplastic nature close to the

tool, which moves along the joint interface (Figure 1).

The tool usually has a large-diameter shoulder and a

smaller threaded pin. The rotating tool creates a thin

plasticised zone around the pin and material is

transported from the front to the rear by a solid-state

keyhole effect. The process is thus characterised by high

strain rat es and super-plasticity nea r the rot at ing tool.

The thermal cycle created by the spindle action at

different speeds is a controlling factor for the

microstructures found in the stirred zone and the heat

affected zone. A temperature gradient is superimposed

on the super-plastic deformation between the top

surface and root of the weld. When the energy input is

increased by higher rotation speed, the hardness across

the nugget zone is more equal and the grain size

increases. At very high tool rotation speeds, the nugget

properties start to deteriorate due to t he precipitationaround t he coarse grains. It is obvious that there is an

optimum speed constellation of rotating speed and the

forwa rd feed for a given material a nd thickness.

D evelopments start ed with welds from one side,

where the distance between the tool end and the root

has an important effect on the welding result.

Subsequent a pplications include tw o-sided welding with

two head s and a bobbin tool on solid material and with

two heads on hollow extrusions. With these systems, the

tolerances in material thickness are easier to cope with

and they create new opportunities in production

technology. Curved surface welding is also on the w ay.

Quality assessmentThe best wa y to determine the weld q ualities of FSW is

to compare the properties obta ined in FSW with those

produced by other welding methods. The very local

deforma tion at low heat inputs in solid stat e FSW makes

this welding method superior to o ther welding methods

such as MIG and MA G welding. Structures with

rigorous performance req uirements, such as rockets and

aircraft, and applications in which high quality is

required by codes are other areas for FSW. In the as-

welded condition, FSW has demonstrated properties

superior to those produced by other welding methods.

The welding speed and the high quality obtainedwithout any pre- or a fter-work o n the w elds will result in

the steady extension of applications. Most design and

welding codes currently accept FSW due to the high

qua lity tha t has been demonstrated w orld wide.

The FSW p lant at DanStir, Denmark.

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Increas ed w elding speed in the 6000 se riesa luminium a lloysESAB and other companies and research instituteshave done a great dea l of research o n the 6000 series ofaluminium alloys. These alloys are t he most commo nlyused in ra ilwa y wa gons, ship panels and the a utomotiveindustry and they are now also starting to attract theinterest of aircraft manufacturers. Normal welding

speeds in prod uction are 0.8-2.0 m/min. fo r 5 mm t hickwo rkpieces. As 6082 mater ial is oft en used in the T6condition (heat treated to produce higher mechanicalproperties), one task for R &D is to reduce the declinein hardness in order to ret ain as much as possible of theT6 trea tment effect. O ne solution is to weld quickly. Itis not often that a high welding speed means higherquality, but in this case it does.

In the ESAB laboratories in Lax, a great deal oftest welding has been performed with the aim ofincreasing the welding speed. A yea r a go, 3 m/min. wa sreached, but recent tests with refined procedures have

show n tha t 6 m/min. in 5 mm 6082 mater ial is possibleand that this very high speed is definitely not theultimate limit. These very promising results w ill furtherincrease the number of profitable applications forFriction Stir Welding.

Resea rch centres using ESAB S uperS tir The FSW process was invented and developed by

TWI in the U K. TWI is still leading the w ay t o newapplications and materials. With its new FSW plant ,it is well equipped for future interesting tasks.

The aerospace industry demonstrated great interestin the new process at a very early stage. The BoeingCompany at Huntington Beach, Ca, U SA developedthe process for aerospace applications, together withTWI, and it is continuously working in its laborato-ries on new tasks for aerospace, aircraft and otherapplications (Figure 2).

B oeing in St. Louis is conducting a great deal ofresearch for the aircraft industry to produce newFriction Stir Welded parts. Among other things, anew hollow profile floor section has been producedtogether with SAPA in Sweden.

Following B oeings success, other aerospace andaircraft research institutes have invested in advanced

machines for research work and test welding. EAD S inFrance, together with I nstitute Soudure, Alenia Spacioin Italy and E AD S in G ermany, are examples of theseinstitutes. Other companies have chosen to conducttheir tests at E SAB , TWI or other research centres.

For the automotive and other segments, TowerAutomotive in the USA has a well-equipped FSWcentre for research, test welding and test production.

D anStir in D enmark is one of several companiesfocusing on test welding, the production of test seriesand low series production with FSW. D anSt ir,however, has a large, flexible FSW plant well suited

to different tasks (photo page 11). The research and development of production data iscontinuously being conducted by the producers of a lu-minium structures, such as H ydro Mar ine Aluminiumin Norway and SA PA in Sweden.

Figure 1. FSW process in a

but t joint against backing bar.

At its plant in Lax, ESAB has two FSW machines forresearch work, demonstrations and test welding forcustomers (Figure 3). Its engineering division is wellequipped to comply with customers requirements forproduction solutions, including the design, manufac-ture, commissioning and service of FSW machines andcomplete production plants world wide.

New mod ula rise d ma chine s eriesIn order for manufacturers to invest in the FSW weld-ing technique in a cost-effective manner, ESAB is nowlaunching a new modularised machine series calledLE G IO , new members of the ESA B Super Stirprogramme. With the new machines, material with athickness of between 1.4 and 100 mm can be welded.The spindle power ranges from 1.5 kW to 100 kW. Themachine series consists of two main types, the S seriesfor straight welds and the U series for straight welds inthe X or Y directions, as well as in optional patterns suchas circles, squares and so on. Each series has two maindesigns, one floor mounted with vertical surfaces formounting large fixtures, circumferential welding unitsor a lower head assembly for double-sided welding andone type w ith a ta ble for mounting small fixtures.

The FSW 3 UT (Universal type w ith ta ble, 11 kW

spindle, max. capacity 10 mm in the 6000 series) will beintroduced at the E ssen Alu Fair in G ermany in 2002(Figure 4).

Welding thick co pper ma teria l with FS WD evelopments in the Friction Stir Welding (FSW) ofcopper will take a further step forward, a s the SwedishNuclear Fuel and Waste Management Co . (SKB ) isinvesting in a full-scale FSW plant a t its canisterlaborato ry in O skarshamn, Sweden. The ba ckgroundto SK B s interest in welding thick copper sections isthe Sw edish decision t o deposit high-level nuclear

wa ste in copper canisters at a d epth of 500 metres inthe bed rock. The sealing of the copper canisters needsto be of a very high quality, as it must remain intactduring the 100,000-year service life of the repository.

SKB has studied different welding methods in co-

Figure 2. Take-over test of

the FSW plant supplied by

ESAB AB, Welding

Automation to Boeing's

space rocket plant.

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Figure 3. At the test centreat ESAB Lax, FSW p rocessdevelopment and investiga-

tions of different customerapplications are made.


Figure 4. FSW 3 UT oneexample of the new modu-larised machine series fromESAB AB, Welding

Automation.

operat ion with TWI in the U K. Full-scale electronbea m weld ing tests have been performed. I n 1998-1999,a t est rig wa s built at TWI f or the Friction Stir Weldingof mock-up canisters. A fixture holds the canister androta tes it during w elding (Figure 5). The lid is presseddown with four hydraulic cylinders. The welding speedreaches 150 mm per minute. A t the beginning, the trialswere exclusively limited to welding segments, but, af ter

fine-tuning the process, a full circumferential weldcould be completed in November 2000. The FSWprocess has functioned well and SKB now feelsconfident about taking the next step in the develop-ment and has decided to install a full-scale FSWmachine at its canister laboratory in order toinvestigate the fea sibility of the process for the pro duc-tion of canisters (Figure 6). SK B has assigned the taskof designing, manufa cturing, testing and co mmissioningthe machine to ESA B AB , Welding Automation, Lax.Test welding in O skarshamn is scheduled to sta rt ea rlyin 2003. SK B can then begin the w ork of optimising thewelding parameters. This has not been possible with

the test r ig at TWI.When welding a circular seam with FSW, a hole is left

in the material when the FSW tool is retracted . This holecan be filled afterwards or simultaneously when the toolis retracted. A more simple and reliable method is to fin-ish the weld in solid materia l outside the joint (Figure 7).In the latt er case, SKB is planning to finish the weld a t thetop of the lid. However, the hole may create difficultiesfor the non-destructive testing after welding. RemainingR &D work will also focus heavily on the design of the lidand the testing methods. The testing methods that a redeveloped by SKB in co-operation with Uppsala

University at the SKB canister laboratory are digitalradiography, ultrasonic and inductive testing. Anotherimportant part of the development of the welding andtesting techniques is to determine the criteria for the sizeand form o f the weld defects that can be accepted.

ConclusionThe new findings, new machine series and newapplications presented above confirm our previousstatements that FSW will continue to expand. We areconvinced that the large automotive segment will takeoff in the near future, together with other segments thatare currently showing substantial interest in the FSWmethod. The increased productivity that results from

FSW compared with other manual or automaticwelding methods and, in many cases, the highinvestment levels require large volumes. This demandcan be met by installing FSW plants to meet severalmanufacturers needs, if their own volumes are notsufficient. H owever, the new machine series introducedby ESAB will minimise investments, thereby making itpossible for more manufacturers of aluminiumstructures to install FSW systems.

Figure 5. The SKB trial testrig at TWI.

Figure 6. A sketch of theFSW plant that shall besupplied by ESAB WeldingAutomation to SKB, Swedenduring 2002. The weldinghead rotates during the

process around the fixedcanister.

Figure 7. The picture showsthe hole from the retractingtool and how it can be placedbeside the weld joint in solidmaterial.

About the authors

Lars Gran Eriksson, MSc Electrical Engineering, joinedESA B in 1973. He ha s held different ma nagementpositions within the Automation and Engineeringdepartments, and within International Operations. He hasbeen leading ESABs development and introduction ofnew inventions such as automation of ship panelproduction, robotic arc welding, narrow gap welding ofpressure vessels, fully automatic production systems foranchor cha ins, and the FSW process.

Rolf Larsson, Mech. E ng., is Technical Mana ger for t he

marketing & sales group responsible for FSW andresista nce welding within in the business area A utoma tion& Engineering in Lax, Sweden. He holds a number ofpatent s within the Friction Stir Welding technology.

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Welding of superma rtens itic

stainless steels

Recent developments and application experience

By: Leif Karlsson, Solveig Rigdal, John van den Broek, Michael Goldschmitz and Rune Pedersen, ESAB

This pa per w a s originally prese nted a t the S ta inles s S teel World America 2002 C onferenc e.

R ecent developments in the welding of supermartensitic stainless steels and the

typical all-weld metal properties of matching-composition welding consumables are

presented. The article compromises the G M AW orbital narrow gap girth welding of

supermartensitic pipes in 5G -down position, the production of longitudinally welded

20 pipes using a combination of plasma arc and submerged arc welding, anddissimilar joining of supermartensitic and superduplex pipes.

IntroductionThe recently introduced weldable supermartensitic

stainless steels have become an economical alternative

for ma ny a pplications in the oil and gas industry. These

steels offer sufficient corrosion resistance for sweet a nd

mildly sour environments, in combination with high

strength and good low-temperature toughness (1, 2).

Supermartensitic steels are also well suited to fieldwelding where preheating and long term post-weld

heat treatment (PWHT) is impracticable.

The successful application of a material requires that

welding can be performed reliably and economically

and that the welds comply w ith requirements relating

to strength, among other things. For example, reeling

is a common o peration when laying offshore flow lines.

This opera tion involves bending pipes, introducing

significant plastic deformat ion. Local stra ining at welds

may occur when welding consumables with under-

matching strength are used. Matching composition

supermartensitic welding consumables, guaranteeing

overmatching yield strength, are therefore specified for

several current and future projects.

Significant alloy development in matching composition

consumables has taken place over the past few years

and our understanding of the relationship between

chemical composition, microstructure and properties

has improved rapidly (3-8). H owever, the d evelopment

of further optimised consumables and economical

welding procedures is still a cha llenging area of a ctivity.

The present paper presents the application of match-

ing composition welding consumables to t he G MAW

orbital narrow gap girth welding of supermartensitic

pipes in the 5G -down position and to t he production oflongitudinally welded 20" pipes. The welding proce-

dures and properties are discussed, illustrating that

supermartensitic consumables can be used with realistic

fabrication welding procedures to produce high quality

welds with satisfactory properties. Finally, some

experience from the dissimilar welding of supermarten-

sitic stainless steels to superduplex steels is presented.

The advantages and disadvantages of using different

filler materials are discussed in terms of weldability,

mechanical properties a nd corrosion resistance.

S uperma rtens itic w eld meta l prope rtiesThe first sections of this paper deal with

supermartensitic pipes welded with matching-

composition consumables. The level of dilution with

the parent material inevitably influences the properties

of t hese welds. Typical chemical compositions a nd

mechanical properties of all-weld metals, produced

with the same commercial supermartensitic metal-

cored wires (MCW), are therefore presented as

reference information in Tables 1 and 2 below. Thewires deposit a fully martensitic 13%Cr-type, Mo-

alloyed, extra-low carbon weld metal designed

primarily for welding supermart ensitic steels.

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Wire C N Si Mn Cr Ni Mo Cu

1.5 % Mo, metal cored wires:

O K Tubrod 15.53* 351 700-850 950-1050 >52 < 3503 SA W

2.5 % Mo, metal- cored wires:

O K Tubrod 15.55/Ar >100 >110 700-850 950-1050 >15 < 3503 GTAW

O K Tubrod 15.55/

Ar+30% He >401 >501 700-850 950-1050 >102 < 3503 G M A W

O K Tubrod 15.53S/

O K Flux 10.93 >301 >351 700-850 950-1050 >52 < 3503 SA W

1 P WHTa t 580-620C w ill, d epending o n time (5-30 min.), typically increa se impa ct toughnes s 20-100%.

2 Dega ss ing a t 250C/16 h or PWHTa t 580-620C w ill increas e elonga tion to >15%.

3 P WHTa t 580-620C will, de pending on time (5-30 min.), typically d ecreas e ha rdnes s 20-50 HV10.

OK Tubro d 15.53 & 15.53S are recommended f or steelswit h up to 1.5%Mo , whereas O K Tubrod 15.55 & 15.55Sshould be used for steels with higher Mo contents. Theweld metal is designed for use in the as welded,tempered or quenched and tempered condition depend-ing on the to ughness and ha rdness requirements.

R ecommended shielding gases for G MAW areAr+ 30%H e or Ar+ 0.5%CO 2. G ases with a higher CO 2

content can be used, but they will increase the weldmetal C and O content, which will result in a higherweld metal hardness. Pure Ar or Ar+ H e mixturesshould be used fo r G TAW.

Orbital narrow ga p pipe w eldingThe term orbital pipe welding generally refers to theequipment that is used when an application calls forpipes to be welded in a fixed position. However, theterm is misleading w hen using the G MAW/FCAWprocesses. If the pipe is in the horizontal position,welding is performed using either a double-up (6 to 12

oclock clockwise, followed by 6 to 12 oclock anti-clockwise) or a double-dow n technique (12 to 6 oclockclockwise, followed by 12 to 6 oclock anti-clockwise).MCWs only form small isolated silicate islands on the

solidified weld bea d. They can be removed by brushingbetween passes or they can simply be welded over, asthey will re-melt and float to the weld pool surface.MCWs are therefore well suited for welding double upas well as double down. For all-position welding, apulsing power source is preferred in order to obt ain theappropriate d roplet transfer and w eld pool control.With the right kind of joint design, double-down

welding can be performed using relatively high travelspeeds in t he 38-75 cm/min ra nge. O ne techniq ue toprovide better weld pool control at these high speedsdownhill is to use a narrow J-groove geometry. Thejoint geometry is narrow enough to a llow each pass tobridge from wa ll to wa ll without oscillation, apart fro mthe capping layer where slight weaving is necessary tocomplete the last layer.

Welding trialsFour companies undertook a collaborative project toevaluate the performance of the new wires with

supermartensitic pipe material and to demonstrateacceptability for orbital pipeline welding (9, 10). Anarrow J-groove was selected for use without a root gap(Fig. 1). An expanding clamp with copper backing


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Pass Position Amperage Arc Voltage Wire feed Welding speed

(A) (V) (m/min) (cm/min)

R oot 12-4 oclock 210 18.8 9.3 70

Fill 2,3,4 12-4 oclock 215 21.5 9.0 50

C ap* 12-6 oclock 140 18 3.0 18

R oot 4-6 oclock 178 17.5 6.0 22

Fill 2,3 4-6 oclock 175 17.5 6.0 22C ap* 12-6 oclock 140 18 3.0 18

*Slight weaving

Figure 1. The appliednarrow gap J- joint has a

small land.

Figure 2. Close up of t heorbital weld seam in thesupermartensitic pipelinematerial.

Figure 3. Cross section ofnarrow gap girth weldillustrating the excellentside wall fusion. A slightweaving is only necessaryfor capping. The totalwelding time for the 12 "(wall thickness 14.6 mm )pipe is app roximately 14minutes.

shoes was used to ensure precise pipe alignment anduniform root bead penetration.

The Pipeliner System, manufactured by Magnatech,interfaced with an ESAB Aristo LUD320W powersource, was used for the trials. The ESAB AristoLU D 320W is a synergic-type pow er source, which meansthat there is a pre-programmed relationship between thepulsing para meters/power output a nd wire feed speed. A

new synergic line was programmed for the MCW (OKTubro d 15.55 with a d iameter of 1.2 mm). Samples of 322mm (12" ) NKK-CR 13WS2.5 (13Cr-6.5Ni-2.5Mo) pipewith a wall thickness of 14.6 mm were supplied by NKKfor the t rials.Test welds were made and used to develop a weldingprocedure (Table 3 and Ref. 11). Figures 2 and 3 illus-trate the smooth bead appearance of the weld cap andthe excellent side w all fusion. For t he filling layers, therewa s no need for wea ving in order to o bta in reliable sidewall fusion, thereby permitting increased travel speedand higher productivity while maintaining a low defectrate. It was clearly demonstrated that, with the proper

equipment, welds could be performed reliably andeffectively with MCWs in a narro w J -groove geometry.

Weld properties

The weld metal toughness and strength were deter-mined in house by preparing a tensile bar and five ISO -V Charpy specimens transverse to the weld (11). Thetensile bar (21.1x12.9mm) broke in the pipe material at900 MPa, showing that the weld metal clearlyovermatched the pipe material. Impact t oughness wa stested at 40C in the as-welded condition and after ashort PWHT at 600C. The heat treatment was per-

formed in a G leeble weld simulato r (electricalresista nce heating) with rapid heat ing, a holding time offive minutes, followed by air cooling. Individual Cha rpyvalues were 44, 41 and 42 J in the as-welded conditionand 50 and 52 J af ter P WH T, illustrat ing the benef icialeffect of a short PWH T.

The weld meta l oxygen content was measured, as it isknown to ha ve a drama tic effect on the impact toughnessof supermartensitic weld metals (12). The measuredrange of 285-350 ppm correlates well with the observedimpact toughness, according to earlier studies (12),suggesting that there is potential to increase toughnessstill further by improving the gas shielding. This ispossible using a special nozzle in combination with asmall, designed gas cup or the use of a 100% inert ga s.

The results of additional tests performed at TWI(13) were in line with the above findings. Cross weld

tensile testing resulted in fracture in the parent steel.The all-weld met al yield strength w as 680 MP a a nd thetensile strength 923 MPa aft er P WHT at 637C for five

minutes. Impact to ughness was measured as a n a verageof 47 J at -46C after PWHT at 651-661C for fiveminutes. Four-point bended sulphide stress corrosioncracking (SSC C) testing for 30 days in slightly sour (10mbar H 2S) formation water and condensed waterindicated no susceptibility t o SS CC .

Longitudinal pipe weldingThe production of large-diameter supermartensiticpipes in the ra nge of 18" (475 mm) to 30" (760 mm)with a wall thickness of up to 30 mm involveslongitudinal seam welding. Currently, the inside andoutside seams are welded by SAW, as a result of whichthe back-gouging of the root pass is necessary toeliminate the risk of flaws in the root pass.

Plasma arc welding is a high energy density weldingprocess capable of producing high quality welds using

Table 3. Typical weldingparameters: Shielding gas99.5% Ar/0.5% CO2; No

backing gas (welding againstcop per backing). Totalwelding time 14 minutes.

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Figure 4. Cross section of longitud inal pipe weld (wallthickness 20 mm).

Figure 5. Microstruc ture of

longitudinal pipe weld.

a) Parent material.

b) Fusion boundary region.

c) Weld metal.

the keyhole technique and it is therefore suitable forroot runs on thick pipe sections. In the present study,the combination of a plasma arc root pa ss welded withan inert ga s backing and SAW for the fill and cap lay erswas tested. The aim was to avoid the need for backgouging, thereby increasing productivity and conse-quently reducing costs.

Welding detailsA 20 mm thick plate of 12Cr 4.5Ni 1.5Mo material wasused to prod uce a length of a 20" (508 mm outerdiameter) pipe at EEW (Erndtebrcker Eisenwerk,G mbH & Co . KG ). Machining, forming and weldingpresented no problems, although magnetism was moreevident than in the butt welding of plates. However,when the correct precautions were taken, thispresented no difficulties. Welding was done in an X-joint preparation using plasma arc welding with 1.2mm OK Tubro d 15.53 for t he roo t pa ss. Fill passes weredeposited from the outside and inside with SAW using

a 2.4 mm O K Tubro d 15.53S/ OK F lux 10.93wire/flux combina tion (F igure 4). The hea t input was inthe ra nge o f 1.0-1.7 kJ /mm f or SAW, where as asomewhat higher heat input was used for the plasmaarc welding. A maximum interpass temperature of150C was used and a 30 minute PWHT at 630C,followed by a ir cooling, was a pplied after w elding.

Microstructure and properties

The microstructure of the welded joint, including theweld metal, HAZ and parent material, consisted afterPWHT of tempered martensite as illustrated in Figure 5.

Weld metal hardness and toughness were

compara ble to those of the HAZ (Tab les 4 and 5). Forexample, the maximum weld metal hardness was 278HV10 and the maximum hardness at the fusionbounda ry wa s 280 H V10. The Cha rpy-V impact to ugh-ness was lowest in the weld metal in the high-dilutionregion at mid-thickness, averaging 62 J at 40C. Theweld metal toughness was somewhat higher (70 J at40C) when loca ting the specimen at the o uter surface,similar to the 77-79 J measured in the HAZ in thefusion boundary region. The weld metal strength washighest in the high-dilution region at mid-thickness andsomewhat lower, but still overmatching, closer to the

outer surface (Table 6).The strength and toughness of the weld meta l are in

very good a greement with previous all-weld meta l testsafter PWHT for 30 minutes at 620C (8). Therecommendations in Table 2 suggest 580-620C as theoptimum PWHT temperatures based on testsindicating the format ion of new martensite on coolingfrom PWHT temperatures of 640C and above.However, the present test suggests that a somewhathigher temperature could be beneficial for the 1.5%Momaterial in order to maximise toughness. Precisetemperature control is recommended, however, asprevious studies have shown a rapid drop in yieldstrength, toughness and elongation once too muchuntempered martensite and retained austenite ispresent in the microstructure (8).

Dissimilar joiningD issimilar joints are not uncommon in oil and gasprocess equipment, as the temperature andcorrosiveness of the process media vary and differentmaterials therefore need to be used for differentcomponents. One interesting dissimilar combinationinvolves joining supermartensitic and superduplexpipes of different wa ll thickness. The follow ing section

will briefly describe two recent examples fromNorwegian offshore projects where Ni-base andsuperduplex consumables were used.

Welding procedures

Supermartensitic pipes (K-X80-CR13WS2, outerdia meter 324 mm/wa ll thickness 16 mm) w ere joined tosuperduplex pipes (U NS 32760, outer dia meter 335mm/wa ll thickness 22 mm) using t he G TAW method.The welding was done at Arctos Industrier AS inSandefjord (Norway), using either Alloy 59 type Niba sed (SG -Ni Cr23Mo16, 2 mm) or superduplex (EN

12072 G /W 25 9 4 N L , 2 mm a n 2.4 mm)consumables. The compositions of the parent and fillermaterials are given in Table 7.

Welding was performed with the pipes fixed in thehorizonta l position. A 60 V-joint prepara tion w as usedwith a 2 mm root gap for the Ni-base consumables anda 3-4 mm gap when using superduplex filler material.Pure Ar was used as the shielding and purging gas inboth cases. A somewhat higher interpass temperature(ma x 150C ) and heat input (0.9-1.2 kJ /mm) w aspermitted for the superduplex consumables comparedwith the Ni-base welds, where the interpasstemperature was kept below 100C and the heat was0.9-1.1 kJ/mm. A pproxima tely 45 bea ds w ere requiredto complete the Ni-base consumable weld as comparedto 35 beads w hen using superduplex consumables.


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Table 7. Chem ical composition (wt.% ) of pipe materials and filler wires used for dissimilar joints.

C N Si Mn Cr Ni Mo W Cu Fe

Supermartensitic pipe 0.015 0.012 0.2 0.17 12.3 5.9 2.2 - 0.05 rest

Superduplex pipe 0.017 0.23 0.36 0.68 25.6 7.4 3.5 0.6 0.6 rest

O K T igrod 19.81 0.003 - 0.05 0.2 22.8 rest 15.4 - - 0.4

O K T igrod 16.88*

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All-weld longitudinal tensile properties Cross weld tensile strength

Consumable T Rp0.2 (MPa) Rm (MPa) A5 (%) Rm (MPa) Locat ion of fracture

Ni-base +20C 589 818 37 864 Supermartensitic pipe

+115C 510 726 - 780 Supermartensitic pipe

Superduplex +20C 744 879 25 843 Supermartensitic or

superduplex pipe*

+115C 608 763 - 738 Supermartensitic pipe

* 3 specimens fractured in supermartensitic pipe material and 1 specimen in superduplex pipe.

Table 8. Tensile prop erties of d issimilar welds.

Table 9. Charpy-V impact toughness (J at -46C) of dissimilar weld s betw een supermartensiticand superduplex steels.

Consumable Specimen Notch posit ionposition

Weld Supermartensitic pipe Superduplex pipemetal FL FL FL FL FL FL

+ 2mm + 5mm + 2mm + 5mm

Ni-base C ap 112 192 207 233 94 104 92R oot 141 208 - - 87 - -

Superduplex C ap 196 224 200 220 124 157 118R oot 114 235 - - 114 - -

load specimens to 90% of yield strength and they weretested for a period of 30 days.The result was very similar for bo th welds. No cracks were

found on any of the specimens in either of the two

environments. The conclusion was therefore that all the

specimens passed the sulphide stress corrosion cracking

test. Some localised corrosion wa s, however, found on the

end face of the supermartensitic side of specimens tested

in formation water. One localised attack was also found

on the side edge of a four-point bending specimen from

the Ni-base weld, tested in formation water. This attack

also took place in the supermartensitic pipe material.

Co ncluding rema rksAs exemplified above, matching-composition super-martensitic consumables are well suited both to the pro-duction of longitudinally-welded pipes and to girth weld-ing. There a re different options for the dissimilar joiningof supermartensitic and superduplex material and the

preferred choice will depend on the specific application.

Supermartensitic welding consumables

The development of matching-composition super-martensitic welding consumables and welding proce-dures is still in progress. H owever, it is obvious that thisconcept offers a number of advantages in terms ofproperties, productivity and the possibility to perform aPWHT when required. Anot her frequently overlookedadvantage, compared with duplex or superduplex con-sumables, is that a martensitic weld metal microstruc-ture is expected fo r all levels of d ilution with the pa rent

material.The parent ma terial delivery condition strength can vary,depending on the exact composition and heat treatment

cycle. Experience has shown that superduplex consum-ables usually produce overmatching or closely-matchingweld metal strength at room temperature. However, atan operating temperature of above 100C, the situationis frequently reversed, as the yield of the super-martensitic material increases, whereas the duplex mate-rial strength level typically decreases by 10-15% (8, 14).

For a number of reasons, it is therefore most probablyonly a matter of time until supermartensitic consum-ables become the preferred choice in the welding ofsupermartensitic sta inless steel.

Dissimilar welding consumables

The study revealed that both Ni-base and superduplexconsumables can be used successfully for the d issimilarjoining of supermartensitic and superduplex pipematerial. It is well known, however, that Nb-alloyed,Ni-ba se consumables are less suitab le due to the risk ofbrittle Nb-and N-rich phases forming next the fusion

bounda ry in the duplex material. Nb-free consumables,such as Alloy 59 used in this study, are therefore to bepreferred t o A lloy 625, for example.

The use of superduplex consumables is morestraightforward in the sense that no problems areanticipated on the superduplex side of the joint andbecause duplex and superduplex consumables havebeen used extensively to weld supermartensiticmaterial. However, depending on the relativedimensions of the pipes to be joined and the operatingtemperature, the lower drop in the yield of the Ni-baseweld metal with increasing temperature might bebeneficial. Problems have also been encountered withhydrogen cracking in the HAZ of supermartensiticpipes welded with superduplex consumables (15).


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Similar problems are not expected with a Ni-base con-sumable due to the high solubility and slow diffusion ofhydrogen in an austenitic microstructure.In conclusion, both Ni-base and superduplex consum-ables are suitable for the dissimilar joining of super-martensitic and superduplex material and the choiceshould be based on factors such as joint geometry andoperating conditions.

AcknowledgementsSome of the results presented in this document wereproduced within the joint European project JOTSUP(D evelopment of Ad vanced J oining Technologies forSupermartensitic Stainless Steel Line Pipes, ProjectNo: G R D 1 1999 10278).The authors wo uld like to extend their gratitude to NK KEurope Ltd, Weldtech and Valk IPS for their valuablecontributions to the successful application of super-martensitic consumables to narrow gap girth w elding.We are also most grateful to W. Schfer and J. Heather

at E EW (Erndtebrcker Eisenwerk, G mbh & Co. K G )for the production of the longitudinally-welded pipe,testing and permission to publish the results.Arcto s Industrier AS in Sandefjord, Norwa y, is grateful-ly acknowledged for its skilful welding of the dissimilarjoints and for permission to publish test results.

References1. J.J. Dufrane, " Characterisation of a new family of

martensitic-supermartensitic plate material for gastransport and processing" . Pro c. Eurocorr 98,September 1998, U trecht, the Netherland s.

2. Proceedings Supermartensitic Stainless Steels 99,Ma y 1999, B russels, B elgium.

3. L. Ka rlsson, W. B ruins, C. G illenius, S. R igdal andM. G oldschmitz, " Matching compositionsupermartensitic stainless steel weldingconsumables." Pro c. Supermartensitic Sta inlessSteels 99, Ma y 1999, B russels, B elgium, pp 172-179.

4. L. Ka rlsson, W. B ruins, S. Rigdal and M.G oldschmitz, " Welding supermartensitic stainlesssteels with matching composition consumables" .Proc. Sta inless Steel 99 - Science and M arket , June1999, Chia Laguna, Sardinia, Italy.

5. L. Karlsson, S. R igdal, W. Bruins and M.

G oldschmitz, " E fficient welding of supermartensiticstainless steels with matching consumables" , P roc.Stainless Steel World 99, November 1999, theHague, the Netherlands, pp 341-354.

6. A.W. Marshall and J .C.M.Farrar, " Welding offerritic and mart ensitic 11-14%Cr steels" . II WD oc. IX 1975-00.

7. O.M. Akselsen, G . Rrvik, C. Van der Eijk andP.E. K vaale, " Mechanical properties ofexperimental 13% Cr sta inless steel weld deposits" .Proc. Nord iska Svetsmtet (NSM) 2000,September 2000, R eykjavik, Iceland.

8. L. Karlsson, S. R igdal, A. D hooge, E. Deleu, M.G oldschmitz and J. Van den B roek, " Mechanicalproperties and a geing response of w eld metals" ,P roc. Stainless Steel World 2001, November 2001,the H ague, the Netherlands.

9. J. Van den B roek, M. G oldschmitz, L. Karlssonand S. Rigdal, " E fficient welding ofsupermartensitic pipes with matching metal coredwires" , Svetsa ren, Vol. 56, No. 2-3, 2001, pp 42-46.

10. John E mmerson, " Orb ital narrow gap MCW pipewelding" , Welding & Meta l Fabricat ion, September2000.

11. W. Bruins, " Intermediat e report on pipe welding

trials, 13%Cr supermartensitic steel" , E SAB reportMarch 27 2000.

12. L. K arlsson, S. Rigda l, W. B ruins and M.G oldschmitz, " D evelopment of matchingcomposition supermartensitic stainless steel weldingconsumables" , Svet saren No.3, 1999, pp 3-7.

13. P. Woollin, " Test results from a utoma tic G MAwelds in NK -CR 13W2.5 sour gra de 12" pipe" , TWIR eport 12726/1/00, No v. 2000.

14. T. Ro gne, H.I . La nge, M. Svenning, S. lstedt, J.K .Solberg, E. La danova, R. How ard and R . E.Leturno, " E levated temperature corrosion/cracking

of large diameter weldab le 13%Cr linepipe" , P roc.E urocorr 2001, Riva del G arda, It aly, Sept-Oct2001.

15. G . R rvik, P.E. K vaale and O.M. A kselsen," Sources and levels of hydrogen in TIG welding of13%Cr mar tensitic sta inless steels" , Pro c.Supermartensitic Stainless Steels 99, May 1999,B russels, B elgium, pp 196-203.

About the authors

Dr. Leif Karlssonjoined E SAB 's R &D department in 1986,after receiving a Ph.D . in materials science from C halmersU niversity of Technology. He currently holds a position a sManager of Research Projects at ESAB AB in Sweden,focussing on projects dealing with corrosion resistant alloysand high strength steels.

Solveig Rigdal, MSc, E WE, joined ESA B in 1982 and ha ssince then worked with product development and marketsupport within the R & D department in G othenburg.D uring the last years, her main focus has been submergedarc welding of stainless and high alloyed steels and stripcladding.

John van den Broekis Application Engineer workingwithin the Shipbuilding and Offshore G roup of ESA BE urope. He is locat ed in U trecht, The Netherlands.

Michael Goldschmitz, B .SC. Meta llurgy, is R&D Mana gerfor ESAB B.V. in The Netherlands. He was nominatedSenior Expert by ESAB in 1995, for his achievements asDevelopment Engineer Cored Wires.

Rune Pedersen EWE , joined ESAB in 1985 and is cur-rently Product Manager C onsumables for ESAB Norway .

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C hica go B ridge &Iron Compa ny Meets

C ha llenge of S ta inles s S teel Welding

for C ryogenic Rocket Fuel Ta nksWelding stainless steel can be a demanding task. The task becomes even greater

when the job involves welding large cryogenic storage tanks such as those for the

Boeing Space Launch C omplex 37 at Cape Canaveral A ir Force Station, Florida.

C hicago Bridge & Iron Company (C B& I) discovered this first-hand recently when

they were hired by Raytheon, Inc., to design and build the storage tanks that hold

the liquid hydrogen and liquid oxygen used to fuel the Boeing Delta IV rocket.

Jim Smith, CB&Is project manager for the job,

describes the tanks as " large thermos bottles." The

tanks are double-walled spheres consisting of an innerwall of stainless steel and an outer wall of carbon steel

with insulation in between. The liquid hydrogen tankhas a n inner diamet er of 61 feet (18.6m), with a n outer

diameter of 67 feet (20.4m). The smaller tank for the

liquid oxygen has a n inner d iameter of 41 feet (12.5m)and an outer diameter of 47 feet (14.3m). Anyway you

look at it, there was a lot of welding to do.B ut big w elding jobs are C B &Is specialty. The

world-renown engineering and construction firmspecializes in design and building steel plate structures.

The 112 year-old compa ny sta rted out building bridges

but soon turned to other steel applications and built itsreputation on its ability to design innovative storage

facilities and erect t hem in the field. Toda y, the compa -ny is best know n for its ability to engineer and construct

flat bottom tanks, spherical storage vessels, elevated

water tanks, refrigerated storage and process systems,vacuum chambers for t he space industry, and industria l

process vessels (see ww w.chicagob ridge.com).The Cape Canaveral project was somewhat unique

in the rigors of its specifications. The tanks are required

to hold temperatures of 424F (-253C) for the hydro-gen and 320F (-196C) for the oxygen. In addition to

the size and temperature challenges, the welders soondiscovered an additional challenge resulting from the

windy cond itions of the ocean side site. The welding sur-face had to be protected by a shield gas to ensure the

integrity of the weld.

According to Smith, they needed a homogenousweld that would offer excellent strength and meet the

requirements of AMSE Co de, Section 8, D ivision 1.CB&I also wanted to use a semi-automatic welding

process to cut dow n on labor t ime and improve produc-

tivity. They found their answer in ESABs Cryo-Shield308L flux-cored wire. Cryo-Shield 308L is an all-pos-

ition wire designed fo r cryogenic applications requiringgood weld metal strength. It offers tensile strength of

80,000 psi (550MPa) and yield strength of 60,000 psi

(410MPa) with CVN toughness of 25 ft.-lbs. (34 J) at

320F (196C). U se o f an a rgon/CO 2 shield gasprotected the weld from the elements.

Part of ESABs Shield-Bright family of flux coredwires for stainless steel welding, Cryo-Shield deposits

welds at substantially higher welding currents than the

other stainless steel electrodes that were considered,resulting in a higher deposition rate. In this case, the

use of Cryo -Shield helped CB &I complete their projectwith just 10 months in the field and pass all X-ray

qualifications tests with ease. It also offered a self-peeling slag fo r fa st, easy clean-up.

CB &I ha s used E SAB filler metals for 30 years, but

this was their first experience with this relatively newproduct. They found Cryo-Shield to be extremely user-

friendly, productive and capable of meeting the moststringent specifications. ESABs excellent on-time

delivery and customer support were also top-notch,

according to Smith.Chicago B ridge & Iron is known as an innovative

company, always looking for unique and better ways tosolve their clients problems. Working with vendors such

as E SAB Welding and C utting Products, CB &I was able

to deliver on-time and within the specifications to keep

this space project on schedule for countdown.


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Welding high s treng th pipelines :

from laboratory to fieldBy: D.J .Widgery, ESAB Group (UK) Ltd

This a rtic le w a s firs t pub lished in the S eptemb er/Octob er is sue o f World P ipelines .

Although the first X80 pipelines were laid in the 1980s, it was only around the

turn of the century that the next major programmes were started by Transco

and TransC anada P ipelines. Both the welding technology and the require-

ments placed on the joints have moved on since the 1980s, and contractors

and welding manufacturers have had to come to terms with this.

Field welding showed up a lack of robustness in proce-

dures developed in the lab orat ory, but new welding con-

sumables were developed and perfo rmed well in the field.

More w ork will be needed to ensure tha t X 100 pipes can

be reliably welded, but much has already been done and

manufa cturers will be ready w hen the pipe arrives.

High s treng th p ipelinesIn 1999, Transco announced a programme of pipeline

construction in X80 steel. This was not the first X80 inE urope: a few kilometres were laid in G ermany in the

1980s and 250 km by R uhrgas in 1992-3, using ma nua l

metal-arc welding. At about the same time, Nova

Corporation in Canada started laying X80 pipe usingmechanised welding. Steels of similar strength had been

used for many years in naval applications, so no major

problems were envisaged when procedure testing

started in the U K in the spring of 2000. In t he event,lines were successfully laid in 2000 and 2001, but

contra ctors had to learn some costly lessons first.

The use of X80 pipe offshore has not yet begun, but

the experience of onshore lines should help in this moredemanding application. Still higher grades of pipeline

steel will certainly be used in the f uture and steelmakers

and consumable manufacturers are working to makethe welding of these as straightforward as possible.

X80 P ipe lines ma inline w eldingP ipeline welding may be divided into ma inline welding,

where speed is critical and there is access for backing

systems; tie-in and repa ir welding, where speed ma y be

less important and there is no internal access, anddouble jointing, where it is possible to ro ll the pipe and

to weld in the flat position. Although mechanised

welding systems have been available for many years

and are a lmost exclusively used off shore, the turn of the

century marked a w atershed which saw the first large-scale application of mechanised systems in the UK and

the U SA. I n mainline welding, these systems allow the

use of a na rrow joint prepara tion.

By welding downhill in a narrow compound bevel,

productivity benefits in two ways. The sidewalls helpsupport the weld metal at relatively high currents and

deposition ra tes, while the reduced joint volume req uires

less metal to fill it. The narrow joint has another effect:

the rapid extraction of hea t from the weld gives coolingrates well above those normally found in structural

welding. As a result, the weld metal strength is higherthan that found in a typical all-weld metal test such as

those used for classifying consumables.When mechanised welding was first used on X80

pipes in Canada, a carbon-manganese solid wire was

found to give adequate strength: the mean weld metal

yield strength w as a bove 630 MPa . The mean pipe yieldstrength was around 600 MPa, so most welds showed

real overmatching. Transco, in the UK, required the

weld metal yield strength to overmatch the pipes

specified minimum yield stress by 5%, giving aminimum of 578 MPa. This is easily achieved by

carbon-manganese consumables using single torchequipment, though with some twin torch systems the

results are close to the minimum and higher alloyingmay be preferred.

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In the 1960s, when semi-automatic gas shielded

welding was first used in the UK and USA on trans-

mission pipelines, it was found that wires containing asmall amount o f tita nium gave the best results. The burn-

off rat e of the wire wa s reduced, so the proportion of thearc energy available to melt the edges of the weld

preparation was correspondingly increased. This led to a

reduction in lack of fusion defects, the most serious pro-

blem in semi-automatic pipe welding. The titanium con-taining wires also gave good weld toughness, and weregenerally adopted when mechanised welding systems

were developed to replace semi-automatic welding.Today, many users have realised that modern mech-

anised or fully automatic pipe welding systems eliminate

defects through engineering rather than through wirechemistry, so carbon manganese wires without titanium

are gaining in popularity. B oth types are now capable ofproducing excellent toughness, Table 1.

Even with mechanised welding systems, produc-

tivity continues to be an issue and contractors havestarted to look at the use of metal-cored wires as a

direct substitute for solid wires in mechanised downhillwelding. P roductivity improvements o f up to 20% seem

to be possible and because the wires are formulated

with small amounts of material to improve the arccharacteristics and the wetting of the joint by the pool,

process tolerance is improved. To help in this, wires a redesigned with a higher oxygen content than is found in

solid wires, so a small nickel addition may be made tocounteract any adverse effect on weld toughness. The

first production pipeline welds with metal-cored wire

were made in the year 2000, and Table 2 shows aprocedure fo r welding X80 pipe with a 0.8% Ni metal-

cored wire.The degree of strength overmatching here is fully

Welding proced ure

Pipe 48 X80, 31.8 mm w.t.

Welding consumable O K Autrod 12.66, 1.0 mm

Welding process mechanised G M AW

Preheat temperature 108C

Interpass temperature 110-135C

Welding direction downwards

Shielding gas root: C O 2

fill & cap: 30% Ar, 70% C O 2

Polarity electrode positive

Root C opper backing, 240-295A, 25-27V, 0.9m/min, 0.39-0.48 kJ/mm

Fill runs 1-10 210-260A , 24-28V, 0.36-0.53m/min, 0.49-0.85 kJ/mm, weave 1.5-6 mm at 1.8-5.8 Hz

C ap runs 8, 9 180-215A , 20-23V, 0.32m/min, 0.63-0.87 k J/mm weave 8.6 mm at 0.6H z

MECHANICAL PROPERTIES

Tensile properties Charpy toughness,

J at -30C

PS (M Pa) TS (M Pa) El %

Longitudinal 693 806 20 root: 110Transverse 665-678 Broke outside weld cap: 84

C TO D at -30C , mm 0.25, 0.39, 0.25, 0.80, 0.80, 0.84

Table 1. Welding procedure for X80 pipe using carbon-manganese solid w ire.

acceptable, but in earlier work it was found that on

different X80 pipe materials, transverse tensile tests

failed in weld meta l at strengths up to 768 MPa . A 1.5%Ni, 0.3% Mo wire could be used if real o vermatching is

specified for such pipe. Up to no w, however, the view inthe UK has been that that would not be necessary for

onshore pipe. This has not been put to the test yet

because the pipe delivered so far has not shown such

extreme strength.

X80 P ipe lines repa ir a nd tie-in w eldingU nlike mainline welds, repair and t ie-in welds have to be

made with no backing systems or internal welders. Nor is

it often possible to re-bevel on site to produce anaccura te compound bevel. This leads typically to t he use

of cellulosic electrodes for the root : these may be of thesofter E6010 type for greater ductility and crack

resista nce. Increa singly, flux-cored w ire is used for the fill

and cap, being suitable for a wider joint such as the 60included angle API bevel. The wires are of the all-

positional rutile type and a re used in the uphill direction.At the outset of the current campaign of X80 pipe

laying in the U K, it w as envisaged that there would be

few problems with tie-in procedures, since steel ofequivalent strength had long been welded with rutile

flux-cored wires in submarines, cranes and earthmoving equipment. Unfortunately in pipe welding,

where welding is always on the critical path forconstruction, the slow, careful procedures and strict

control of heat input and interpass temperatures which

have led to success in military applications are not

popular. It immediately became clear that welding withstringer beads would not be acceptable, and that thehigher interpass temperatures and wider weaves that

would be used would require more highly alloyed weld


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Welding proced ure

Welding consumable Tubrod 15.07, 1.2 mm Tubrod 15.09, 1.2 mm

Welding process mechanised FC AW

Preheat , C 100 min

Interpass temp, C 150 max

Shielding gas 80Ar-20C O 2

Polarity electrode positive

R oot E6011, DC -

Hot pass E9010, DC + E8010, DC +

Fill, runs 3-5 170A, 23V, 0.24 m/min, 220A, 25V, 0.24 m/min,

0.98k J/mm, full weave 1.38k J/mm, full weave

C ap 170A, 23V, 0.24 m/min, 190A, 25V, 0.24 m/min, 1.19kJ/mm,

0.98kJ/mm, 2 runs, split weave 1 run, full weave

MECHANICAL PROPERTIES

Tensile p roperties

PS (M Pa) TS (M Pa) PS (M Pa) TS (M Pa)

Longitudinal 721 765 670 721

El % R of A % El % R of A %

17 63 21 67

Transverse tensile strength 641 M P a, brok e outside weld 641 M P a TS , brok e outside weld

Charpy toughness

J at -40C 118, 108, 116, A v 114 82, 84, 84, A v 83

WELD METAL CHEMISTRY

C 0.053 0.042Si 0.32 0.34

M n 1.43 1.17

Ni 2.06 2.56

M o 0.04 0.25

Table 3. Procedures for tie-in welding o f X80 with flux-cored wire

H ydrogen-induced cold cracking (HIC C) is likely to be

the greatest problem encountered in welding very high

strength pipelines, and a major programme to look at

this is being run by VTT in Helsinki, with the co-

operation of E uropean a nd J apa nese industry. Weldingconsumables with very low hydrogen contents will be

needed and weld microstructures will assume greater

importance. Ma nufacturers and research institutes are

collaborating on the next generation of welding

procedures and will be ready to work with clients and

contra ctors to ensure their success.

Fig 2. Mechanised uphill welding with rutile flux-cored

wire on the X80 Hatton- Silk Willoughby line

Photo courtesy of Gridweld Ltd .


About the author

D avid Widgery, MSc, PhD Meta llurgy, joined ESA B in1983 as D evelopment Ma nager Flux-cored w ires. As from

1996, he has worked as Special Projects Manager for the

ESAB Group.

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S ynerg ic C old Wire (S C W )

S ubmerged Arc Welding

Application of a new cost efficient welding technique tos ta inles s s teels

By: Solveig Rigdal, Leif Karlsson and Lars stgren ESAB AB, P.O. Box 8004, SE-402 77 Gteborg, Sweden

This pa per wa s o rig ina lly prese nted a t the S ta inles s S tee l World America 2002 Co nferenc e.

The Synergic Cold Wire (SC W ) process is a recent development of submerged arc

welding (SAW) in which a cold wire is fed in synergy with the wire electrode into the

weld pool. In the present study, SCW has been applied for the first time to the wel-

ding of 22% C r duplex stainless steel. Experimental welds with good mechanical prop-

erties and good corrosion properties were produced in a highly productive manner.

IntroductionSubmerged arc welding (SAW) is currently a well estab-lished method for welding most grades of the more

widely used sta inless steels. Offering high productivity in

combination with good weld quality and environmentaladvantages, SAW is an attractive method, especiallywhen it comes to welding thicker materials like those in

large pipes and vessels, for example.

The Synergic Cold Wire (SCW) process is a recent

development which was invented in 1998 (1) and offersthe chance to increase the deposition rate in submerged

arc welding by more than 50%. In SCW-SAW, a cold wire

is fed in synergy with the a rc wire into the weld pool where

it melts (2, 3). Consequently, the arc and cold-wire depo-sition ratio always remains constant once the wire

diameters have been fixed. The cold wire can be either

trailing or leading, depending on penetration versus build-up requirements. The weld metal chemistry and depo-sition ra te a re thereby easily controlled a nd pre-selected.

The SCW process is preferably used for welding

materia l thicknesses above a pproximately 8 mm, where

several passes are required. SCW welding can be usedwith a n endless variety of combina tions of solid a nd/or

cored wires for single-, twin- (the Synergic Cold Wire

Twin [SCWT ] process), ta ndem- and multiple-wire

applications. As no arc emanates from the cold wire, itis also possible to incorporate hard to weld alloys in

cored wires. Further advantages include less distortion

due to a lower effective heat input, a reduced number

of weld beads and lower flux consumption incomparison with conventional SAW. SCW welding is

also very operator friendly as no add itional control unit

or separate feeding device is needed.

In just a short time, SCW welding has proven its adva n-tages when applied to the welding of C -Mn steels (4). This

paper presents the first results relat ing to t he SC W wel-

ding of duplex stainless steels, illustrating the benefitsand po tential of this new technique. The effect of welding

procedure on weld metal composition and properties will

be discussed and it will be demonstrated that excellent

weld meta l properties can be a chieved in a reliable, cost-

effective and productive manner. It will also be shown

that lowering the effective heat input, compared with

conventional SAW, makes the method particularly well

suited to the welding of steel grades where productivity is

hampered by heat input restrictions.

Experimenta l proc ed ureWelds were produced in EN 1.4462 standard duplexstainless steel plate material using the SCW techniqueand were subjected to X-ray inspection, metallographic

studies, corrosion testing and mechanical testing. In

addition, a number of welds were produced in 20 mm

mild steel with conventiona l single-wire SAW and w ithSCW in order to compare deposition rates.

Duplex SCW welds

Three SCW welds were produced in duplex stainlesssteel plate material with a thickness of 14-22 mm using

a wire electrode with a diameter of 3.2 mm in

combination with a cold wire with a diameter of 2.4

mm. D etails of joint preparation a nd weldingparameters are presented in Table 1 and the weld set-

up is shown in Figures 1 and 2.

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Weld V-22 V-14 X-20

Parent material EN 10088 / X2 C rNiM oN 22-5-3

Plate thickness (mm) 22 14 20

Joint preparation Vjoint Vjo

Documents

Svetsaren 02 2002