Svetsaren 03 1999

7/30/2019 Svetsaren 03 1999

1/36

A welding review published by The Esab Group Vol. 54 No. 3 1999

Oil & Gas

7/30/2019 Svetsaren 03 1999

2/36

Svetsaren No.3 1999

Contents Vol. 54 No. 3 1999

Development of matching composition supermartensitic stainless steel welding consumables

Newly developed supermartensitic metal-cored wires produce high-quality welds withproperties which match requirements.

Linepipe welding beyond 2000

Pipeline construction continues to grow despite low oil prices and slow world economicgrowth.

Tanko know-how in double-headed tanksThe first application in a series of double-head tanks delivered to be used for low-temperature application (LNG).

Welding engineering standardisationinternational and European

A review of international and European standards for welding.

Stubends & Spatter

Product briefs.

Filler alloy selection for aluminium welding

How to choose the most suitable filler alloy for aluminium welding.

Precision laser gantry

Austrian Voest Alpine Stahl Linz GmbH gets more precise cutting and a smaller amount offinishing work with laser cutting systems from ESAB-Hancock.

Plasma welding aluminium

Plasma welding is the process for the third millennium.

Successful TIG welding of umbilicals for the oil industry

Umbilicals made of stainless steels developed by Kvaerner Oilfield Products AS in Norway.

The millennium bug or the Y2k problem

Why is it a problem and how will it affect us all?

Strip cladding replaces sheet lining

Report on an unusual application for strip cladding in the pulp and paper industry.

2

Articles in Svetsaren may be reproduced without permission but withan acknowledgement to Esab.

PublisherBertil Pekkari

EditorLennart Lundberg

Editorial committeeKlas Weman, Lars-Gran Eriksson, Johnny Sundin, Johan Elvander, Dag Jacobsen,

Bob Bitsky, Stan Ferree, Ben Altemhl, Gerd Peters, Susan Fiore

AddressESAB AB, Box 8004, S-402 77 Gteborg, Sweden

Internet addresshttp://www.esab.comE-mail: [email protected]

Printed in Sweden by Skandia-Tryckeriet, Gteborg

A welding review published by The Esab Group No. 3 1999

3

8

11

12

16

20

23

26

29

30

33

Refinery by night in Gteborg, Sweden.

Photo:Anders Kristensson, Bildbyrn i

Gteborg AB.

7/30/2019 Svetsaren 03 1999

3/36

The development ofmatching compositionsupermartensitic weld-ing consumables is pre-sented. It is shown thatthe newly developedsupermartensitic metal-cored wires OK Tubrod15.53 and OK Tubrod15.55 produce high-quality welds with prop-erties which match re-quirements when usedwith realistic fabricationwelding procedures.

Introduction

Duplex ferritic-austenitic stain-less steels have been used forsome years to combat corrosion

problems in the oil and gas in-dustry. New weldable supermar-tensitic stainless steels are, how-ever, finding increasing applica-tion as an economical option, of-fering corrosion performancebetween that of carbon steel andduplex stainless steel (refs. 1-5).These steels offer sufficient cor-rosion resistance for sweet andmildly sour environments in com-bination with high strength and

good low-temperature toughnessand are specifically designed forfield welding where the use oflong-term post-weld heat treat-ment (PWHT) is impracticable(ref. 6). The carbon content is re-

duced to extra low levels in orderto obtain the necessary propertiesin the as-welded condition andelements such as Mo and Cu areadded for improved corrosion re-sistance.

The choice of filler materialand welding procedure is largelygoverned by the need1 to match parent material

strength,2 to achieve sufficient toughness,3 to keep hardness at an accept-

able level,4 to match corrosion resistance

and5 to avoid PWHT.

Although good results havebeen obtained with soft marten-sitic 13%Cr 4%Ni + Mo alloysand duplex or superduplex con-sumables (refs. 2-4), supermarten-sitic consumables offer a numberof advantages. Not only are theweld metal strength, hardness and

corrosion resistance similar tothose of the parent material. Theweld metal and parent materialalso respond similarly to PWHTand thereby eliminate the risk ofweld metal embrittlement whichcan occur in the case of superdu-plex weld metals. A further ad-vantage is the decreased risk ofdistortion thanks to the lowerthermal expansion coefficient ofsupermartensitic weld metals as

compared to duplex weld metals.Complications related to the dilu-tion of filler metal with parentmaterial are also avoided ifsupermartensitic consumables areused.

The aim of the present study isto show that matching composi-tion supermartensitic consum-ables can be formulated and canproduce largely martensitic weldmetals. It is also demonstratedthat supermartensitic consum-ables can be used with realisticfabrication welding procedures toproduce high-quality welds withsatisfactory properties.

Chemical composition,

microstructure and

mechanical propertiesExperimental welds

In the very early stages of devel-opment, it became evident thatthe weld metal chemical composi-tion strongly influenced the mi-crostructure and mechanicalproperties. As a first step, chemi-cal compositions and mechanicalproperties for a large number of

experimental weld metals weretherefore determined and corre-lated to microstructure, transfor-mation characteristics and weld-ing procedure (see also refs. 7and 8).

An evaluation showed thatthe very low C and N content(

7/30/2019 Svetsaren 03 1999

4/36

Mechanical properties

Weld metal yield and tensilestrength were generally well abo-ve the typical values for super-martensitic parent materials (refs.3, 4 and 6).The exception wasweld metals with a large volume

fraction of retained austenite(>25%) and with a yield strengthbelow the minimum level of 550MPa required for X80 gradesteels. Both the yield and ultimatetensile strength were lower trans-verse to welds in supermartensiticplate material than along weldsand fracture always occurred inthe parent material. Elongationwas typically in the range of 15-20%, regardless of composition

and welding method.Maximum hardness correlatedwell to the C content and PWHT(5 min/620C) was effective in re-ducing hardness (cf. refs. 1, 3, 4and 6, for example). A maximumas-welded hardness of approxi-mately 350 HV10 could be ob-tained if the C content was keptbelow 0.013%C.

Significant amounts of ferritewere found to be detrimental to

impact toughness and tended toresult in an unacceptably highductile to brittle transition tem-perature. However, the most sig-nificant effect on impact tough-ness was clearly the strong effectof weld metal oxygen content. Byplotting impact toughness againstoxygen content (Fig. 1), it can be

seen that impact toughness in-creases rapidly for oxygen levelsbelow approximately 300 ppm.For example,TIG welds with anoxygen content of about 100 ppmhad a toughness of up to 150 J at40 C, whereas SAW welds withabout 600 ppm oxygen had thelowest toughness, typically 3040J at 40 C. However, a shortPWHT could be used to improvethe impact toughness of SAW

welds significantly (Fig. 1).

Microstructure

Virtually fully martensitic weldmetals could be obtained for anMo content of up to 2.5% (Fig.2). However, the compositionalrange for fully martensitic weldmetals was somewhat limited andbecame narrower as the alloyingcontent was increased.

Ferrite (Fig. 3), with a mor-

phology very similar to that ofthe ferrite found in duplex stain-less steel weld metals, was presentwhen the relative amount of fer-rite stabilising elements was toohigh.. Another ferrite morpholo-gy, similar to that of common aus-tenitic stainless steel weld metals,was found in weld metals solidify-ing as a mixture of ferrite andaustenite (Fig. 4). One complica-tion, which was dependent on

4 Svetsaren No.3 1999

40C

20C

Impactt

oughness(J)

Weld metal O-content (ppm)

Figure 1.Influence of oxygen content on Charpy-V impact toughness at 20C and

40 C in Mo-alloyed supermartensitic weld metals.

Figure 2. Fully martensitic microstruc-ture of a 2.5% Mo supermartensiticweld metal deposited with the metal-cored wire OK Tubrod 15.55.

Weld Consumables Parent material Joint/ Interpass Heat input Comments

position temp. (C) (kJ/mm)

OK Tubrod 15.53:1.5 % Mo, 1.6 mmmetal cored wire:

TIG/MIG-1.5Mo Ar/ Ar + 0.5%CO2 12Cr 4.5Ni 1.5Mo 0.5Cu/ 60V, PA

7/30/2019 Svetsaren 03 1999

5/36

the C content, was the sometimesunacceptably high amount of re-tained austenite in some of themost highly-alloyed experimentalgrades.

Supermartensitic weld metalconstitution diagram

The need for a tool capable ofpredicting weld metal microstruc-

ture from chemical compositionwas recognised at an early stage

of consumable development. Thenegative effects of ferrite, auste-nitic solidification and excessiveresidual austenite content have tobe avoided to obtain the opti-mum properties. However, no di-agram or equation covering therange of compositions studied inthe present investigation could befound in the literature.A newconstitutional diagram for super-martensitic weld metals thereforehad to be constructed.

Like earlier diagrams proposedby Balmforth and Lippold (refs. 9and 10), the new diagram wasbased on the Kaltenhauser Crand Ni equivalents (ref. 11), butthe compositional range was ex-tended and Nb and Cu were in-cluded in the compositional fac-tors. Limiting boundaries bet-ween different microstructural re-gions (Fig. 5) were defined frommicrostructural information for a

large number of experimentalwelds, plotted on the diagram.

The new diagram was found to bevery useful in defining the opti-mum consumable compositionssuitable for steels with a varyingMo content.

Representative micrographsfor weld metals belonging to themartensite (M), the martensiteand ferrite (M+F) and the mixedsolidification microstructural re-gions of the constitution diagram(Fig. 5) are shown in Figures 2, 3and 4 respectively.

Simulated production

weldsWelding conditions

Consumables producing the de-sired weld metal microstructurewere selected for welding trials inpipe and plate material using sim-ulated production welding proce-dures. Metal-cored wires with1.5%Mo (OK Tubrod 15.53) and2.5%Mo (OK Tubrod 15.55) wereused for the butt welding of 20

Svetsaren No.3 1999 5

Figure 3. Ferrite (white phase) in a

mainly martensitic 1.5% Mo weld

metal solidifying as ferrite.

Figure 4. Ferrite (white phase) formed

during ferritic/austenitic solidification

of a mainly martensitic 2.5%Mo weld

metal.

Figure 5. Constitution diagram for supermartensitic weld metals. Information is

provided about the solidification mode and microstructural constituents, including

the presence of significant amounts of retained austenite at two different C levels.

Weld/steel C N (ppm) Si Mn Cr Ni Mo Cu O (ppm)

Steel:

Plate: 12Cr 4.5Ni 1.5Mo 0.5Cu 0.023 112 0.19 1.96 11.5 4.5 1.3 0.48 51

Pipe: 12Cr 6.5Ni 2.5Mo 0Cu 0.010 87 0.17 0.50 12.3 6.6 2.5 0.02 63

Plate: 12Cr 6.5Ni 2.5Mo 0.5Cu 0.020 130 0.10 1.76 12.4 6.5 2.3 0.49 110

Weld:

MIG/TIG-1.5Mo 0.017 80 0.63 1.32 12.4 6.7 1.5 0.55 230

TIG/MIG-2.5Mo 0.012 90 0.33 1.97 12.5 7.0 2.3 0.50 270

SAW-2.5Mo 0.008 220 0.35 1.78 12.6 6.9 2.4 0.50 670

TIG/MIG-2.5Mo-pipe 0.009 135 0.31 2.0 12.5 7.0 2.2 0.44 284

Table 2. Chemical composition (wt.%) of steels and weld metals.

Cr =Cr+6Si+8Ti+4Mo+4Nb+2Aleq

Ni

=40(C+N)+2Mn+4Ni+Cu

eq(Cu)

F + FA solidification

> 0.02 %C < 0.01 %C

M

M+F

M+A

M+F+A

7/30/2019 Svetsaren 03 1999

6/36

mm 1.5%Mo and 2.5%Mo super-martensitic plates and for thegirth welding of a 2.5%Mo pipewith an outer diameter of 255mm and a wall thickness of 13mm.As shown in Table 1, TIGwas used for root passes in MIGwelds, whereas the SAW weldingof plate material was performedfrom both sides in an asymmetri-cal X joint.The pipe girth weldwas completed in only three pass-es, one TIG root pass and twoMIG passes (Fig. 6), with a heatinput of approximately 2.8kJ/mm.

Microstructure and chemicalcomposition

All the plate and pipe welds weredefect free and had a largely mar-

tensitic microstructure.The chem-ical compositions of weld metalsand parent materials of simulatedproduction welds are presentedin Table 2. It can be seen thatTIG/MIG welds in a high-C par-ent material have a C content ofabove 0.010%, whereas the SAWand the TIG/MIG welds in thelow-C pipe material have0.008%C and 0.009%C respec-tively.

Mechanical properties

The mechanical properties of thesimulated production welds were

in good agreement with the expe-rience acquired from the experi-mental welds. The strength wasclearly overmatched, as is evi-denced by cross-weld tensile testfractures appearing in the parentmaterial, and the ductility wassufficient to pass bending tests(Tables 3 and 4). The maximumhardness was approximately 350HV10 or below and, as expected,the impact toughness was strong-ly dependent on the oxygen con-tent (Table 2). However, a com-parison of the impact toughnessof the TIG/MIG-2.5Mo pipe weldand the TIG/MIG-2.5Mo platebutt weld produced the somewhatunexpected result that a higherheat input and larger weld beadswere beneficial (Tables 3 and 4).

This result is contrary to what hasbeen seen for experimental weldsand further studies are clearlyneeded to establish the effect ofheat input on impact toughness. Itis encouraging, however, that highproductivity welding procedurescould also offer advantages interms of improved toughness.

Corrosion resistance

The preliminary results from SSC

testing in formation water (20C,20 bar pCO2, 100,000 ppm Cl

,4 mbar or 40 mbar pH2S,4.5

7/30/2019 Svetsaren 03 1999

7/36

ready obvious that this conceptoffers a number of advantages interms of properties, productivityand the chance to perform aPWHT when desired.One furtheradvantage that is often over-looked is the fact that a marten-sitic weld metal microstructure isexpected for all levels of dilutionwith parent material when weld-ing with a supermartensitic con-sumable.This is clearly an advan-tage compared with what hap-pens when using duplex or super-duplex consumables, as the result-ing microstructure in this case isdirectly related to the degree ofdilution.

In conclusion, although the fur-ther fine tuning of matching com-position supermartensitic con-

sumables is expected, it is nowpossible to predict the micro-structure from the new supermar-tensitic weld metal constitutiondiagram and the relationship bet-ween microstructure, compositionand properties is fairly wellunderstood. It is therefore mostprobably only a matter of timebefore supermartensitic consum-ables replace duplex and super-duplex in the welding of super-

martensitic stainless steel.

Conclusions

Metal-cored wires have been de-veloped for supermartensiticsteels; OK Tubrod 15.53 with1.5%Mo is suitable for steels with01.5%Mo and OK Tubrod 15.55with 2.5%Mo is intended forsteels with an Mo content of upto 2.5%Mo.A very low C and Ncontent (

7/30/2019 Svetsaren 03 1999

8/36


Despite low oil prices and slow

world economic growth, pipe-line construction continues at arate of 2025 000 km per year.A large part of this arisesthrough the demand for natu-ral gas, spurred on by the needto reduce CO2 emissions natural gas produces 50% lessthan coal and 30% less thanoil. Pipelines vary from around15 centimetres to more than a

metre in diameter and in lengthup to thousands of kilometres.Individual pipes are normally12 m, or occasionally 18 m inlength so every kilometre of linerequires 83 or 56 welded joints.

While in many cases there aresimilar technical requirements forprocess pipework within the fac-tory fence and for linepipe out-side the fence, there is a funda-mental economic difference bet-

ween the two. Many sections ofprocess pipework can be weldedat the same time: if a faster rateof progress is needed, more weld-ers can be deployed. Line pipelaying, on the other hand, in-

volves such a large team of oper-ators and heavy equipment, notonly for welding but also fortrenching, pipe handling, NDTand so on, and such disruption ofagricultural or other activities

along the right of way, that eachsection of pipeline, in the West atleast, is laid progressively fromone end to the other.The pipecan only advance across the coun-try, or indeed the sea bed, as fastas the individual sections can bejoined together. Not only is weld-ing always on the critical path forpipe laying, but it is generally the

single rate-determining process inthe activity. This puts a high pre-

mium on speed and productivityin pipeline welding. Several com-panies of the ESAB Group havebeen involved in this activity formany years and can offer a rangeof options for pipe welding.

MMA welding

The first arc-welded pipelineswere joined using cellulosic elec-

trodes, which were developed in1929. The breakthrough in pro-duction speed came in 1933 withthe introduction of the stove-

pipe technique in which the elec-trodes were used in the down-ward direction for all passes in-cluding the root.With only minorchanges, stovepipe welding is stillused today on a wide range ofpipelines. Several characteristicsof cellulosic electrodes make

them ideal for the purpose. Thecoating is very thin and requireslittle energy to melt it, so nearlyall the electrical energy of the arcis available to melt the electrodeand parent steel. Organic materi-al in the coating produces a volu-

minous gas shield which protectsthe weld metal from the atmos-phere even when the arc lengthvaries, so the welder can use vari-ations in arc length to exercise

limited control over melting andpenetration, helped by a suitablepower source. Hydrogen ions inthe arc plasma increase penetra-tion. Slags are formulated to befast freezing so that high currents

can be used in the vertical-downposition without the slag runningahead and flooding the arc. All

these features of the first E6010cellulosic electrodes are contin-ued in todays types.

One further characteristic dis-tinguishes ESABs Pipeweld elec-

trodes. For some 45 years, cellu-losic electrodes were formulatedto run with high arc voltages inthe belief that, as in the case ofE7018 and especially E7024types, this would lead to highermetal deposition rates. When put

to the test in 1978, however, thisidea proved to be false. Bothcommercial products and elec-trodes specially formulated to runat high and low arc voltages allshowed the same core burn-offrate at a given current. Unlikeelectrodes which produce a cupof flux at the tip within which the

heat of the arc is retained, any ex-tra arc voltage in the case of cel-lulosic electrodes simply results in

more radiant heat being lost fromthe arc column.This is not to saythat all cellulosic electrodes de-posit metal at the same rate, butit is found that the real differenc-es which exist arise from varying

Linepipe welding beyond 2000by D.J.Widgery, ESAB, Waltham Cross, U.K.

7/30/2019 Svetsaren 03 1999

9/36


spatter losses rather than fromvarying burn-off rates. This isgood news for the welder, whosince the introduction of thePipeweld series in 1979 no longerhas to put up with a harsh arc inthe belief that this is the fastestway to weld pipe: a smoother, lessspattery arc is not only morecomfortable but offers productiv-ity advantages as well. For root-ing, the old-established E6011type, NuFive, achieves a similarresult with a mixed sodium andpotassium binder.

Welding engineers unfamiliarwith traditional stovepipe weldingare often alarmed to discover thatthe cellulosic electrodes give weldhydrogen contents typically in ex-cess of 50 ml/100g.This has not

prevented them from being usedwithout problems on steels up toAPI 5LX 70, since the proceduresdeveloped, especially the use of ahot pass following immediatelyafter the root pass to temper thebead and HAZ, were designed todeal with that situation. However,for higher strength steels, or wherehydrogen cracking is thought topose an unusual risk, such as inhot tapping operations, basic elec-

trodes designed to operate in thedownward direction have been de-veloped. The best known of theseis Filarc 27P, which allows a signifi-cant improvement in pipe weldingproductivity as compared withconventional E7016 or 7018 elec-trodes and has an establishedrecord over 20 years of pipe weld-ing. This has now been joined bythe higher strength 37P, which issuitable for pipe grades up to X80.

Semi-automatic and

mechanised welding

The development of CO2-shiel-ded welding in the USSR in the1950s opened the way for semi-automatic pipeline welding andthe first CO2-welded cross-coun-try pipeline in the USA was laidin 1961. Two years later, a compa-ny which became part of theESAB Group was involved in thefirst UK pipelines to be weldedwith the CO2 process, the SouthWales Supergrid and the PennineSpur. By 1966 the process hadbeen greatly refined for theNorth Wales Supergrid and later

for other pipelines to distributethe newly discovered natural gasfrom the North Sea.

Although thousands of kilome-tres of pipeline were laid semi-automatically using CO2 with sol-id wire, the possibility of increas-ing speeds still further led to ef-forts to mechanise or automatethe gas-shielded process. Severalof these were successful and to-day this is the preferred methodfor offshore and long-distance on-shore pipelines.

Mechanised pipe welding sys-tems now all use on-site end bev-elling to guarantee the good fit-up that is needed to make highproduction speeds possible.Twobroad categories of rooting sys-tem are available. CRC use an

internal welding bug, while sever-al other companies use copperbacking rings of ingenious design,with all welding from the outside.Many thousands of kilometres ofpipe have been successfully laidwith both systems. For mainlinewelds, welding is in the downwarddirection for root, filling and cap-ping passes.Welding parametersare increasingly under computercontrol, so modern pipe welding

systems can legitimately be de-scribed as automatic.

In the early days of mechan-ised pipe welding, 0.9 mm (0.035in) Oxweld 65 triple-deoxidisedwire was widely used and thesame wire, now known as Spoo-larc 65, is still supplied by theESAB Group. A more recent de-velopment, Spoolarc XTi, is avail-able where improved toughness isrequired.

Tubular wire

While the advantages of tubularwire have led to its widespreadadoption in many other sectors,pipe welding has always been aconservative industry and hasbeen relatively slow to move totubular wires. That situationseems to be about to change.

One reason why semi-automa-tic pipe welding with solid wiresdid not replace MMA pipe weld-ing to any great extent was usersfear of lack-of-fusion defects. Atthe same time, the main reasonwhy tubular wires have succeededwhile solid wires have failed in

other industries such as ship-building is their lower susceptibil-ity to lack of fusion.

For semi-automatic pipe weld-ing, modern all-positional rutileflux-cored wires such as OK Tub-rod 15.17 offer a low-hydrogen,high productivity alternative to

cellulosic electrodes. Because ru-tile wires combine a very control-lable spray transfer at all currentswith a slag stiff enough and volu-minous enough to support theweld metal in welding verticallyupwards, there is less to gain bywelding downwards than there iswith MMA electrodes and mostprocedures are for upward weld-ing. Rutile wires have found aparticular place in carrying outrepairs and tie-ins, where mech-

anised welding is not always fea-sible or where ultimate speed isless important than it is in mainline welding. In the early days ofCO2-shielded pipe welding, lossof shielding when the wind blewcould be a source of weld poros-ity. Today, the tents in whichwelding is performed are so wellsealed that on one recent linethere were reports of welders suf-fering from lack of oxygen as the

tent filled up with shielding gas,so the use of argon mixtures oflower density than CO2 is pos-sible without risking loss ofshielding.

The relatively high speed withwhich it was possible to weldopen pipe roots with solid wireunder CO2 can also be achievedwith modern metal-cored wires ofthe type designed for CO2 opera-tion, such as OK Tubrod 14.12,

while the risk of defects is re-duced at the same time. If onelesson has been learnt by thewhole pipe welding industry sincethe 1960s, though, it is the advan-tage of using on-site end prepara-tion and efficient clamping to en-sure reproducible joint geometryeven when fully automatic weld-ing is not used. Only in this waycan open roots be welded at opti-mum speed.

Metal-cored tubular wires beennot been regarded as a viable re-placement for solid wires inmechanised pipe welding untilvery recently, though their use isnow starting to be seen as logical.

7/30/2019 Svetsaren 03 1999

10/36


A 1.2 mm metal-cored wire istypically used in place of a 1.0mm solid wire as the tubular typeis of lower density. Productivity isimproved by up to 20% and it ishoped that as statistical evidenceis gathered, it will be possible toreduce the defect incidence belowthe 56% regarded as acceptablefor solid wires.

For parts of the world whereshielding gas is not readily avail-able, self-shielded tubular wiresfor pipe welding have been avail-able for more than 20 years. The-se are magnificent examples ofthe consumable developers art,and it is difficult not to be im-pressed by the ingenuity whichgoes into their design. Unfortu-nately, compromises have to be

made in formulating self-shieldedwires and productivity tends tosuffer as compared with gas-shiel-ded types.As a result, the numberof lines laid with self-shieldedwire remains small, though thatcould change as the proposedpipelines across Central Asiastart to be built.

Double jointing

The rate of progress of a pipeline

across country is equal to the rateof butt welding multiplied by thelength of a pipe section.Where itis possible to double the length ofthe sections by welding them off-line, or double jointing, thespeed of the line is similarly dou-bled. The feasibility of doublejointing depends on access to thesite: if the right of way is straightand wide, even triple jointing maybe possible in some cases. Double

or triple jointing is now commonon laybarges laying offshore pipe-lines.

The advantage for the weldingengineer of welding off-line is thatthe pipe can be rotated so thatwelding is all downhand, thus al-lowing the very productive sub-merged arc process to be used. Formany years, the standard consum-ables for the job were OK Autrod12.34 with OK 10.71 flux, which

are suitable for pipe steels up toX70 grade.A more recent devel-opment is the use of tubular wiresfor the submerged arc process.

Where double jointing is car-ried out on a lay barge, the pro-

cess may be strictly off-line, but itis still required to keep up withthe fixed position welding. In thatcase, the conventional use of asingle 3 or 4 mm diameter solidwire may not be fast enough. Theuse of twin 2.4 mm solid wirescan speed up the process, but tu-bular wire also brings benefits ofup to 30% in productivity com-pared with solid wire and it toolends itself to twin arc welding.OK Tubrod 15.24, a 1% Ni wire,gives excellent results for doublejointing and is again used withOK 10.71 flux.

Welding high strength

pipe steels

Pipe steels with yield strength up

to 480 MPa (X70) are now incommon use and a full range ofMMA electrodes, solid and tubu-lar wires is available to weldthem. The first X80 pipelines witha minimum yield strength of 550MPa have been laid on land andinvestigations are under way tolook at the practicality of off-shore lines in X80 steel.

One of the questions whichhas to be answered about weld-

ing high strength steels in gener-al and pipe steels in particular iswhether the weld metal isshould overmatch the parentsteel. Most pipe welding stan-dards such as API 1104 requirethe weld metal to match thespecified minimum tensilestrength of the pipe but specifi-cally exclude any need to matchthe actual pipe strength. Giventhat in service the major stress

acts on the longitudinal weld,this may seem reasonable and itis the basis on which land lineshave so far been laid. At theX80 strength level, it is generallyconcluded that cellulosic elec-trodes will only be used for theroot and perhaps the hot pass,since it may be difficult to achie-ve the required toughness andresistance to hydrogen crackingusing them in the fill and cappasses. In the root, a degree ofundermatching is usually per-missible, even to the extent ofusing the E6011 NuFive elec-trode, provided the bulk of thejoint is filled with weld metal of

matching strength. For the fillingand capping passes, the E9018-Gelectrode Filarc 37P is used inthe vertical-down direction.Alternatively, a rutile flux-coredwire such as OK Tubrod 15.19, astronger version of 15.17, maybe used in the upward direction.

In mechanised vertical-downwelding, where a narrow jointpreparation is combined with ahigh travel speed so that weldcooling rates are extremely high,even carbon-manganese consum-ables such as Spoolarc XTi canproduce weld metals strong andtough enough to match mostspecifications for welding X80pipe.

For offshore lines in X80 pipe,some contractors may look for

weld metals which overmatch theactual rather than the nominalpipe strength in order to take ad-vantage of new ways of calculat-ing allowable defect size. Metal-cored wires such as Tubrod 14.05and 14.06 not only allow realovermatching of X80 pipe, but of-fer a significant productivity ad-vantage at the same time. For thefuture, constant development ofnew electrodes and wires in

ESABs laboratories will allowany foreseeable grades of pipe-line steel to be successfullywelded.

About the author

David Widgery is Group SpecialProjects Manager based in Walt-

ham Cross, England.After gradua-tion he joined The Welding Insti-tute, Cambridge in 1964, gaining aPh D from Cambridge Universityfor work on weld metal toughnessin 1975. In 1976 he was awardedthe American Welding SocietysJames F. Lincoln Gold medal andjoined GKN Lincoln Electric asTechnical Manager.There he wasresponsible for the development ofall types of welding consumablesand equipment. Following ESABsacquisition of GKN Welding in1982 and BOC Welding in 1983, he

moved to Waltham Cross as Devel-opment manager, Flux-CoredWire. In 1996 he took on a newrle co-ordinating developmentprojects within the Group.

7/30/2019 Svetsaren 03 1999

11/36


Tanko S.P.A. (Syracuse,Italy) is a firm specialis-ing in the manufactureof tanks which are readyfor use for the storage ofoil and gas products.The product range com-prises both traditionaltanks and cryogenic

ones for low-temperatu-re application (LNG).

Double-head tanks

Tanko has acquired a great dealof experience of manufacturingvessels for LING transportationby sea. In this application, thefirst three in a series of double-head tanks (intersecting vessels)have been already delivered to

Fincantieri to be used for LPG(NH3) at a temperature of 48 Cand a pressure of 5 bar.At pre-sent, Tanko is finishing the secondset of double-head tanks for thesame customer.

In all, the estimated workingtime totals 300,000 man-hours.

The base material in these ves-sels was 13 Mn Ni 63 (EN10028/4), a fine-grain steel, andthey were assembled, tested andinsulated at the Punta Cungoyard (Syracuse, Sicily).

After being completed, thetanks were transported on largebarges to Genoa harbour where aproper portal crane had been

constructed to lift and load thevessels onto the ship.

Each double tank was 32 me-tres long, 21 metres wide and 12metres high, with a weight of 700tonnes.

Due to the dimensions, the ves-sel was not fully constructed in-doors, but a yard was set up whe-re the three sub-assembled com-ponents were joined together tocreate a single tank.

For a single double vessel,more than 150 plates were used,longitudinally and circumferen-tially welded to one anotherand to the central partitionplate.

The heads, four for each tank,consisted of sixteen sectors andone spherical plate, all of themcold formed.

Suitable working procedureswere used to keep the final toler-ances within 0.1%.

Welding

In addition to the cold forming of

the head components, the work-ing procedure included plate cut-ting, bevelling, bending and weld-ing.

The head sectors were weldedusing the SAW process, whileSAW and FCAW processes wereused for most of the total welds,where stick electrodes were usedon quite a small scale.

All the vertical joints werewelded with Filarc PZ 6125,

0.9% basic flux-cored wire andall the circumferential jointswere welded with sub-arc con-sumables and a circomatic weld-ing machine.

Inspection and rules

The tanks were designed andmanufactured to comply with themost rigorous national and inter-national rules.

All the outer shell welds and

all the butt joints were checked100% by RX, while a 100% UTinspection was carried out on thepartition plate joint to the mainshell.

The entire project complieswith EN ISO 9001.

Tanko know-how in double-head tanks

by Ben Altemhl, Filarc Welding Industries, The Netherlands

The welding consumablessupplied by ESAB Italy were:

SAW: Siderfil Ni 26(Siderotermica Brand)+ OK Flux 10.62

FCAW : Filarc PZ 6125SMAW: Filarc 75

7/30/2019 Svetsaren 03 1999

12/36

International standar-disation is organised bythe ISO and IEC. TheISO is responsible formost standardisation.The IEC is responsiblefor electrotechnical stan-

dardisation.European standardisation is or-ganised by the CEN, CENELECand ETSI.The CEN is respon-sible for most standardisation.

The CENELEC is responsible forelectrotechnical standardisation,apart from telecommunications,for which the ETSI is responsible.

International welding standar-disation within the ISO began in1947 when ISO/TC44 Weldingwas set up. European weldingstandardisation began in 1987

when CEN/TC121 Welding wascreated. The CEN had been inoperation since 1960, but it be-came far more active when theEU decided on a new method inthe mid-1980s. As a result, the de-

tailed technical rules were nolonger included in directives butin harmonised standards.

ISO/TC44 Welding and

allied processesThe set-up is shown in Figure 1.The chairman is Jean-PierreGourmelon of France. The secre-tary is Hlne Brun-Maguet,AFNOR, France.

In the Vienna Agreement,the ISO and CEN have agreedto co-operate in order to avoidthe duplication of work. When itcomes to welding, about 70% ofthe standards are the same forthe ISO and CEN. Some of thestandards are prepared withinISO/TC44, while CEN/TC121 isresponsible for the remainder.

SC3 Welding consumables wasreorganised in 1994. SC3 has sin-ce published ISO14175 (EN439)Shielding gases for arc weldingand cutting.

The International Institute ofWelding, IIW, has been acceptedby the ISO as an internationalstandardising body. IIW Com-

mission II Arc Welding is devel-oping some standards for weld-ing consumables.

There are two different sys-tems for the classification ofwelding consumablesone inEurope, the other in the PacificRim countries. The existence ofthese two systems has made itimpossible to prepare standardsfor the classification of weldingconsumables that can be accept-

ed on a worldwide basis. The so-lution that is now being tested isto prepare cohabitation stan-dards. In these standards, thereare two routes, if necessary, oneEuropean, the other Pacific


Welding engineering

standardisation

international and Europeanby Olof Dellby, Svetskommissionen, Sweden and Ulf P Karlsson, ESAB, Lax, Sweden

Welding of heat exchanger.

7/30/2019 Svetsaren 03 1999

13/36

Rim. The first cohabitationdraft will be sent out for DISvoting at the beginning of 2000.

SC4 Arc Welding Equipment,see IEC/TC26.

SC6 Resistance welding hasprepared a large number of

standards and work to revisethem has just started. Nearly allof them have become Europeanstandards.

SC7 Representation andterms has prepared standards in-cluding ISO2553 welded, brazedand soldered jointssymbolicrepresentation on drawings. Thisstandard is due for revision. The-re are two systems for weldingdesignations, ISO2553 and theUS AWS. The existence of twosystems means that there is a

risk of mistakes. Most of theSC7 standards have been accept-

ed by CEN/R121.SC8 Gas welding equipment

has prepared a large number ofstandards. Unfortunately,CEN/TC121/SC7 Gas weldingequipment has not accepted theISO standards but has preparedits own standards which deviateto some extent from the ISOstandards.

SC10 Unification of require-ment in the field of welding hasprepared standards includingISO5817 Arc welded joints insteelfusion weldingguidance

on quality levels for imperfec-tions. This standard is currentlybeing revised. Some SC10 stan-dards have been accepted byCEN/TC121. Otherwise, SC10accepts European standads.

SC5 Testing and inspection ofwelds,

SC9 Health and safety andSC11 approval requirements

for welding and allied processespersonnel run small operationsof their own. The sub-commit-tees accept European standards.

IEC/TC26 Electric

Welding

International standards for weld-ing equipment are handled byIEC TC26. The committee has aGerman secretariat, with Dr. Karl

Bhme as its secretary, and aSwedish chairman, Ulf P Karls-son.Within ISO/TC44, there is asubcommittee, SC4, entitled Arc


ISO/TC44Welding and allied

processes

Soldering and brazing

materials

Arc welding equipment

Testing and inspection of

welds

Resistance welding

Representation and

terms

Gas welding equipment

Health and safety

Unification of

requirements in the fieldof metal welding

Approval requirements

for welding and allied

processes personnels

SC12

SC11

SC

10

SC9

SC8

SC7

SC6

SC5

SC4

Welding consumablesSC3

Health and safety in

welding and allied

processes

Specification and qualifica-

tion of welding procedures

for metallic materials

Destructive tests on

welds

Approval requirements

for welding and allied

processes personnel

Welding consumables

Quality management in

the field of welding

Non-destructive

examination

Representation and

terms

Gas welding equipment,

cutting and alliedprocesses

Brazing and soldering

SC9

SC8

SC

7

SC6

SC5B

SC4

SC3

SC2

SC1

WG13

CEN/T C 121

Welding

Fig. 1. ISO/TC44 Welding and

allied processes with subcom-

mittees.

Fig. 2. CEN/TC121 Welding

with subcommittees and one

of the working groups.

Welding of ship hull.

7/30/2019 Svetsaren 03 1999

14/36

welding equipment. At the pre-sent time, there is no rivalry bet-ween the two groups.To reachglobally accepted standards, thetwo organisations have joinedforces and set up a joint workinggroup (JWG1) with the chairmanof IEC/TC26 as the convener.The aim of IEC/TC26 togetherwith ISO/TC44/SC4 is to producea series of standards covering

welding equipment and accesso-ries of all kinds.Table 1 shows the present situ-

ation in terms of published stan-dards and standards under prep-aration:

CEN/TC121 Welding

The set-up is shown in Figure 1.The chairman since the start in1987 has been Birger Hansen,Denmark.The secretary is LoneSkjerning, DS, Denmark.

TC121 prepares general stan-dards for welding. TC121 hopesthat the CEN TCs preparingproduct standards will make ref-erence to the TC121 standards in-

stead of making their own rulesfor welding.TC121 has no powerto force the product standardscommittees to use TC121 stan-dards. This is the weak point inthe CEN system.There is no cen-tral authority in the CEN respon-sible for co-ordinating the rules indifferent standards.

WG13 Destructive tests onwelds has published standards for

destructive testing, bend testingand tensile testing of welded joints.SC1 Specification and qualifi-

cation of welding procedures formetallic materials has publishedeight standards in the EN288 se-ries.These standards are nowunder revision and the prENs willbe sent out in the beginning ofyear 2000. SC1 has also pub-lished a technical report on mate-rials classification for welding.SC1 is preparing an extension of

the EN288 series with a newnumbering system, see Figure 3.

SC2 Approval requirements forwelding and allied processes per-sonnel has published EN287-1

Welder approvalSteel, EN287-2Welder approvalAluminiumand EN719 Welding co-ordina-tion. Standards for copper andnickel has also be published.EN287-1 is under revision, prENis expected in 2000.

SC3 Welding consumables

SC3 has published 19 standards.Most of them are classification

standards for consumables of var-ious types. SC3 has also pub-lished some standards on the test-ing of consumables. SC3 has pre-pared a standard on type approv-al that is now under considera-tion. This standard and a standardwith supplementary tests are in-tended to be used in a Europeansystem for the type approval ofconsumables. In addition to thestandards, the CEN membersmust agree on a voluntary systemfor the reciprocal approval ofconsumable testing, i e consum-ables approved in one CEN coun-try are approved in all other CENcountries.


Number Title Status Date Personal comment

IEC 60974-1 Arc welding equipment. Published 1989 Unfortunately, it has not yet

Part 1 Power sources Revised 1998 been published as an ISO standard

IEC 60974-1,A1 Amendment

Plasma power sources FDIS January 2000 Published 2000 at the earliest

IEC 60974-2 Liquid cooling systems CD December 1999 Published 2002 at the earliest

IEC 60974-3 Arc starting and stabilising

devices WG doc CD in March 2000

IEC 60974-4 Pulsed power sources Already implemented in 60974-1

IEC 60974-5 Wire feeders CDV January 2000 Published 2001 at the earliest

IEC 60974-6 Power sources for

manual welding with Currently it exists as a European

limited duty WG doc March 2000 standard EN 50060

IEC 60974-7 Torches. FDIS September 1999 Published 2000 at the earliest

IEC 60974-8 Plasma cutting systems Becomes part of 609741, through

Amendment 1 and part of 7, Torches.

IEC 60974-9 Graphical symbols for Requires approvalarc welding NWI of IEC TC3

IEC 60974-10 EMC requirements CDV January 2000 Currently exists as a European

standard EN 50199.

IEC 60974-11 Electrode holders Published 1992 For revision 2002

IEC 60974-12 Coupling devices for

welding cables Published 1992 For revision 2002

IEC 60974-13 Terms for arc welding Requires approval

equipment PWI of IEC TC3

Table 1. IEC/TC336 Electric welding.

7/30/2019 Svetsaren 03 1999

15/36

SC4 Quality management

in the field of welding

SC4 has a large scope. It is a miniTC121.The most important stan-dard SC4 has published is theEN729 series, EN729Quality re-quirements for weldingFusionwelding of metallic materials.The-

se standards are umbrella stan-dards for welding. They providegood support for a company usingwelding in its production to en-sure that the welding is done in acompetent manner.The use ofthese standards will considerablyreduce the problems and enhancethe quality.

The EN729 series is intendedfor arc welding. For resistancewelding, SC4 has prepared prENISO14554, which will be publishedin 2000.

Another important group ofstandards is the EN1011 series.EN1011-1 General Guidance forarc welding has been published.

EN1011-2 Ferritic steels has re-cently been sent out for a secondround of consideration in the nearfuture. It has not been possible toagree on one system for deter-mining the preheating tempera-ture.The standard has two sys-

tems, one British, which is a mod-ernised BS513, and a German sys-tem.They give different values. Aworking group is discussing vari-ous systems for determining thepreheating temperature.

EN1011-3 Stainless steels andEN1011-4 Aluminium will bepublished in 2000.

SC9 Health and safety

SC9 prepares standards for health

and safety in welding that are notprepared by other CEN commit-tees. SC9 has prepared standardsfor sampling airborne particlesand gases in the operatorsbreathing zone and laboratorymethods for particles and so on.

Other CEN committees arepreparing standards related tohealth and safety in welding andallied processes. SC9 follows thiswork.

CEN/TC240 Thermal

spraying

CEN/TC240 has published sixstandards.

TC240 is preparing a series ofstandards for quality require-ments, prEN ISO 14922-1/4,which will be published in 1999.

CENELEC TC26

European standards for weldingequipment are handled by

CENELEC TC26. The commit-tee has a German secretariat,with Dr. Karl Bhme as secre-tary, and a British chairman,Geoffrey B Melton, TWI. As theEuropean members of IEC TC26are the same as the members ofCENELEC TC26, there is nor-mally only some administrativework involved in transferring anIEC document to a CENELECdocument and obtaining a Euro-pean standard at the same timeas the international one by par-allel voting.

In 1992, the industry becameaware of the need for an EMCproduct standard for weldingequipment.A joint working groupwas set up between CISPR/B,IEC TC77, CENELEC TC210and CENELEC TC26. SecretaryGeoffrey B Melton,TWI, andconvener Ulf P Karlsson, ESAB.In December 1995, the product

standard EN 50199 Electromag-netic compatibility (EMC), Prod-uct standard for arc weldingequipment, was published.

An international EMC stan-dard has reached the CDV stage.

SC4, see under IEC TC26 Elec-tric welding

European standards for

welded products

There are standards for simple

pressure vessels, EN286. There isalso ENV 1090-1 Execution ofsteel structuresPart 1: Generalrules and rules for buildings.prEN 13445-1/7 Unfired pressurevessels and prEN 13480-1/7 Me-tallic industrial piping are beingconsidered.To some extent, thefirst one has its own rules forwelding and refers only partly toTC121 standards. The second re-fers to TC121 standards but with

some changes. As the TC121 stan-dards are general, it may happenthat a product committee wishesto reduce or step up the require-ments in a TC121 standard. Thisis naturally acceptable, but it is

not acceptable if the productcommittees write their own weld-ing rules.

Conclusion

There have been some fairly in-tensive discussions between theCEN, ISO and IIW. The author is

of the opinion that the differentroles of the organisations are nowunderstood and co-operation isgood.

In CEN, there is some uncer-tainty due to the fact that theproduct committees are not obli-ged to adopt the TC121 standardsand can draw up their own rulesfor welding.

AcronymsISO International Organisation for Stan-dardisation

IEC International Electrotechnical Com-mission

CEN European Committee for Standar-disation

CENELEC European Committee forElectrotechnical Standardisation

ETSI European Committee for Electro-technical Standardisation

CD Committee draft

CDV Committee draft for voting

DIS Draft international standard

FDIS Final draft international standard

PrEN Proposal for European standard

NWI New Work Item

PWI Preliminary Work Item

WG doc. Work Group Document


About the authors

Olof Dellby is secretary of theSwedish Welding Commission sin-ce 1975. His main responsibility isstandardisation. He is also activein IIW, ISO and CEN and secreta-ry of CEN/TC 121/SC 3 Weldingconsumables and ISO/TC 44/SC 3Welding consumables.

Ulf P. Karlsson is an electrotechni-cal engineer at the R&D Depart-ment at ESAB Welding Equip-ment in Lax, Sweden. He is activein standardisation work as chair-man of SEK TK26, Arc Weldingand internationally as chairman ofIEC TC 26 Arc Welding Equip-ment. SEK = Swedish Electrotech-nical Commission.

7/30/2019 Svetsaren 03 1999

16/36

The Stainless Steel World 99

Conference and Expo was held16th to 18th November in theHague, The Netherlands. Papersfrom major end users and suppli-ers were presented and ESABcontributed with 3 papers.

In parallel with the conference,an exhibition was organised whe-re a large variety of products as-sociated with stainless steels weredisplayed. ESAB had an interest-ing stand at which ESABs strength

in important sectors such as pulp& paper, chemical tankers andcryogenic applications wereshown.

A lot of products were on dis-play such as covered electrodes inVacPac, flux cored wires andSAW wires and flux, MIG andTIG wires and ESW/SAW stripsand fluxes for cladding.The orbi-tal TIG welding equipmentMechtig 160 and the PRB weld-

ing head for tube-to-tube weldingalso attracted great interest.The conference attracted 250

delegates from key industries andanother 3.000 people visited theexhibition.

ESAB is now introducing Eco-Mig, a non-copper-coated weldingwire which improves productivity

and helps to make the environ-ment cleaner.

A special production techniqueand the absence of copper coat-ing give the EcoMig wires uniquecharacteristics. They withstandhigh currents and produces a verystable arc with good penetrationand flow.This results in higher

deposition and improves produc-tivity compared with convention-al wire.As there is no coppercoating, there are no stoppagesresulting from copper flakeswhich block the wire feed conduitand contact tips. Our special pro-

duction technique helps to ensurereliable feed and good currenttransfer in the contact tip.

As far as the welder is con-cerned, EcoMig improves boththe working environment andwelding. The stable arc producesless spatter. The joints are uni-form and strong. The need forfinishing work with its grindingdust and distracting noise is re-

duced. The risk of cracking as aresult of copper residue in theweld metal is eliminated. Thewelding fumes are less of ahealth hazard as the copper con-tent is lower.

ESABs EcoMig wire comes intwo gradesOK Autrod 12.50 forsteel with a minimum tensile

stress of up to 420 MPa and OKAutrod 12.63 for steel with a min-imum tensile stress of up to 460

MPa. EcoMig is supplied in envi-ronmentally-sound wire-basketreels or in the Marathon Pac bulkpackage.

The octagonal Marathon Pacdrum is made of environmentally-compatible corrugated boardwith an integrated moisture barri-er.When the drum is empty, itcan be easily compressed to pro-duce a flat package, which canthen be sorted for recycling. Thewire-basket reels can also be

compacted and recycled. WhenEcoMig is introduced into theproduction process, the environ-ment experiences an overall im-provement.


Stub-ends

&Spatter

Nothing but benefits fromEcoMig

Stainless Steel

World 99

7/30/2019 Svetsaren 03 1999

17/36

The numerical control is the heartof any cutting process. The newNCE 620 is fast, precise, and loa-ded with the entire range of pro-

cess data. It controls all processparameters for any cutting pro-cess. After material type, thick-ness, process and desired cut qua-lity has been selected the NCE

620 automatically sets ideal cut-ting speed, delay times, gas pres-sures, gas mixtures and other vari-ables. The cutting database inclu-des process data for laser, plasma.oxy-fuel and water-jet cutting.

The NCE 620 utlizes themodern high-speed processor toimplement intelligent motion con-trol algorithms. This technologyallows high dynamic accuracy,improved acceleration-decelera-


ESAB MobileMaster wire fee-ders are built for harsh environ-ment such as construction sites,pipelines, shipyard, off-shore,general fabrication and mobilewelding rigs.The totally enclosed,impact-resistant case protectswelding wire from dirt, metal grit,moisture and other contaminantsand the unique rain gutter doordesign keeps water from dripping

Tough environmenteasy choice

Intelligent process controlNCE 620

ESAB plasma makes the cutWhere do you go when yourefaced with the task of dismantlinga radioactive laboratory? Thepeople at Oak Ridge Laborato-ries contacted Manufacturing Sci-ences Corporation, which in turnstudied the available processes

and equipment manufacturersand determined that ESAB Plas-marc equipment was a cut abo-ve the rest.Through in-depth timestudies and a review of the manydifferent types of cuts required,MSC determined that the ESABE SP-200 plasma system was thesmart choice.The versatility of theESP-200 is apparent in the re-quirements of both manual andmechanized cutting. Either manu-

al cutting with the PT-26 torch or

mechanized cutting with the PT-19XLS torch mounted on fixtures,the ESP-200 provides the cuttingspeeds required to fulfill the paceof this multi-year project. Majorfixturing was required to maketwo simultaneous cuts down the

length of low level radioactivepipes.The pipes range in size from2 inches (5 cm) to 3 feet (100 cm)diameter and up to 3/4 inch (19mm) thickness. Other areas re-quire hand cutting with the PT-26torch and still others require con-tour cutting with XY coordinatedrive shape cutting table.All cutswith the sixteen ESP-200 systemsare made with air in the manualor mechanized mode allowing

complete commonality of repair

tion, and faster response to dyna-mic loading while optimising ser-vo control command signals.

The high-speed processorallows new levels of motion con-

trol accuracy, resulting in higherquality parts at lower total cost.This high precision motion con-trol can increase the life of thecutting equipment by reducingwear on servos and gearboxes.

The NCE 620 can be connectedto hosts, network, the Internet andIntranet, thus improving commu-nication with production planningand process control systems.

part throughout. In addition tothe sixteen ESP-200 systems, oneESP-100 system with the PT-20AM torch was put into serviceto cut thinner product as re-quired. This system also uses airas the plasma gas.

Operators making the cuts withthis equipment are required towear full protective suits and arelimited to the time they can spendin the cutting chambers. Due tothe very harsh environment whe-re these units are operating, MSCchose ESAB Plasmarc systemsbecause of their proven reliabilityand ability to make the cut at therequired speed and cut quality.

into wire compartment. Frontcontrols are located on a recessedpanel to protect dials and swit-ches. The rear handle makesMobileMaster easy to manoeuvre

into tight spots and the weight isonly 12 kg. The built-in torch hol-der has composite insulator

MobileMaster wire feedersoperate with reverse polarity(wire DC+) or straight polarity

(wire DC-). Wire spools with 21to 31 cm diameter and 20 kgweight for wires 0.6 mm2.00 mmdiameter can be used.

Safety features for these wirefeeders include insulated case,low voltage torch trigger circuitand overload protection and it isdesigned to meet the most rigidstandards including IEC-974-1specification.

7/30/2019 Svetsaren 03 1999

18/36

ESAB Welding & Cutting Prod-ucts, USA recently introduced the350mpi, an inverter-based weld-

ing power source designed forMIG, DC TIG, carbon-arc goug-ing and stick welding.

The ESAB 350mpi operatesfrom a 230/460 volt primary,either single- or three-phase. Theunit is designed to be self-protec-ting. In the event that the ESAB350mpi is accidentally attached toa higher primary voltage, thepower supply will not be dam-aged.

The ESAB 350mpi is rated350 amps at a 60 percent dutycycle with three-phase input and225 amps at a 60 percent dutycycle with single-phase primarypower.

A five-position switch allows

operators to set the unit for MIG,TIG, CV hot, touch TIG or stickwelding. No external control orpendant box is needed for any ofthese processes. The ESAB350mpi is compatible with all US-produced ESAB MIG wire feed-ers including: 28A, 35, 2E, 4HDand the 5XL Mongoose.

The controls are easy to usewhen MIG welding. There is aneight-position selector knob that

an operator sets for the weldingmaterial: stainless, aluminum,steel with CO2, steel with argon-based gas shielding, flux-coredwire or metal cored wire. Thelogic of the machine will selectthe correct slope and induc-tance, and give the operator ausable range of arc trim/forcesuitable for the material beingwelded.

For TIG welding, operators

have two options, TIG or touchTIG. The TIG position consists ofa normal DC scratch-start. Whilein the touch TIG mode, the ma-

chine senses contact between theelectrode and the base metal, soit can produce a ramp-up of cur-rent as the operator lifts the torchoff the base metal.

To stick weld with the ESAB350mpi, an operator selects thestick position on the five-positionswitch. Automatically, the ma-chine output changes to constantcurrent, and the output is hot.

The LAW 420 and 520 are twonew, robust rectifiers for MIG/MAG welding of the ESAB Pow-er Mig range. They are equipped

with large wheels, sturdy liftingeyelets and an undercarriage spe-cifically designed for transport us-ing a forklift truck. They have alow centre of gravity, even withthe feeder on top. It goes withoutsaying that the units conformwith IEC 974-1.

The LAW 420 and 520 powersources offer a wide currentrange and work well with bothCO2 and mixed shielding gases.They can run both solid andcored wires including basic flux-cored wires, which calls for high

performance.The LAW 420 canbe loaded to 400 amps at a 45%duty cycle and the LAW 520 to500 amps at a 60% duty cycle.The LAW power sources are equ-ipped with two inductance outlets

for optimised performance. Well-proven, reliable components en-sure a minimum of service andmaintenance.

The LAW 420 and 520 areavailable with or without watercooling and in reconnectable ver-sions.A wide range of optionalequipment in the Power Mig sys-tem ensures a fine choice of

workshop layouts. The MEK 4and MEK 4S feeder units are spe-

cially designed for use togetherwith these power sources.


ESAB launches new multi-process power source

Now released:

The FILARC cored wire CD!The first edition of the digitalinternational FILARC cored-wire catalogue on CD-ROM.

This digital version in English

is interactive. Practical links fromthe product data pages and othercatalogue pages lead to weldingprocedures, welder guides, appli-cation stories and overhead pres-entations.

The CD-ROM has been devel-oped for use with Acrobat Read-er 3.0 software. This software hasbeen incorporated on the CD-ROM.

Power Mig420 and 520

7/30/2019 Svetsaren 03 1999

19/36

EcoPac is a box-free bulk packag-ing intended for high volume us-

ers of flux-and metal cored wires.Since there are no boxes to bediscarded, it simplifies the use ofcomplete pallets in the workshopclose to the welding sites. Use ofEcoPac is often regarded more

efficient than the standard rou-tine of distributing single boxesfrom the warehouse, especially bylarger fabricators.

One EcoPac pallet contains 48layer-wound 16 kg basket spools,stacked in 6 layers of 8 spools.The spools are individually pack-ed in a polyethylene bag, contain-ing a sheet of corrosion inhibiting

paper, and are firmly fixed on apallet by means of cardboard pla-tes and a PE wrapping. The net

weight is 768 kg.EcoPac is available for ESAB

and FILARC brand cored wires.

Filarc 27P was one of the firstlow-hydrogen electrodes to be

specially developed for welding

pipes in the vertical-down posi-tion. The reason was quite natu-rally concern about crackingwhen welding material of higherstrength, i.e. pipe steels aboveAPI 5LX 60, but also to increaseproductivity in comparison withcellulose electrodes.

Filarc 27P is suitable for steelsup to API 5LX70. Filarc 108MPwas developed for even higherstrength steels. It is suitable for

welding API 5LX80.

Since the strength and impactproperties are difficult to combi-

ne, Filarc 37P is developed to

optimise the properties for API5LX75 and when overmatchingrequirements are specified forAPI 5LX70.

In addition to its good mecha-nical properties, Filarc 37P alsoprovides much improved produc-tivity compared with celluloseelectrodes because of its higherrecovery, lower spatter and highercurrent ability.


EcoPac

The boxfree bulk

packaging forcored wires

Filarc 37Pa new electrodefor welding pipelines

All weld metal

Yield strength Tensile strength Elongation Impact C

MPa MPa % 30 40 50

560 640 30 150J 120J 80J

Typical properties are:

New ESAB portable wirefeeder

The MEK20/MEK 20CYardfeeder is a new, en-capsulated wire feedunit, weighing only12,5 kg.The MEK 20model is used with

ESABs well-known A10system of MIG/MAGequipment. The MEK20 C is designed for theAristo 2000 system withits digital CAN bus con-trol system.

This wire feeder has arobust but compact de-

sign and can be carried into con-fined working areas. In combina-tion with an intermediate feederthe working range can be extend-ed from 40 metres to no less 64metres from the power source.

The MEK 20/20C gives excel-lent and trouble-free feeding withall types of wire including cored

wire. Extension cables permit anyproduction layout and quick-locking connections make the set-up time very short.The MEK20/20C features 2/4-stroke func-tions with pre and post flow ofgas. It is also equipped with ad-

justable backburn and crater fill-ing timers.

7/30/2019 Svetsaren 03 1999

20/36


The selection of the correct fill-er alloy is a major factor in thesuccessful welding of alumi-num, and essential for the de-velopment and qualification ofsuitable welding procedurespecifications. The most reli-able method of choosing analuminum filler alloy is by us-ing the AlcoTec filler alloy se-lection chart. Each filler alloycan produce unique character-istics in the finished weld, andthe filler alloy chart will helpyou make the most appropriatechoice. The filler alloy chartcan be found in the AlcoTecTechnical Brochure and theESAB Aluminum Solid Wireand Rod Products Brochure. In

order to successfully use thefiller alloy selection chart, it isimportant to understand thenumerous variables which gov-ern the most suitable filler al-loy for a specific application.

Unlike steel, where a filler alloyis usually matched with the ten-sile strength of the base alloy alo-ne, typically it is possible to weldmany of the aluminum base al-

loys with any one of a number offiller alloys.There are usually anumber of filler alloys which willmeet or exceed the tensilestrength of the base material inthe as-welded condition. Howev-er, the selection of filler alloy istypically not only based on thetensile strength of the completedweld.

There are a number of vari-ables which need to be consid-ered during the selection of themost suitable filler alloy for aparticular base alloy and compo-nent operating condition.Whenchoosing the optimum filler alloy,both base alloy and desired per-

formance of the weldment mustbe of prime consideration. Whatis the weld subjected to, and whatis it expected to do? We shall ex-amine each of the variables whichwe need to consider prior to thefinal selection of the most suit-able filler alloy for a particularapplication.

1. Ease of weldingThis is basedon the filler alloy/base alloy com-bination and its relative crack sen-sitivity. We shall look at the cracksensitivity curves which are usedto assess hot cracking sensitivityfor the different filler alloy/basealloy chemistry combinations.2. Strength of the weldWe shallexamine tensile strength of groo-ve welds, and shear strength of fil-let welds, and consider the filleralloy effect on these properties.3. Weld DuctilityWe shall ex-amine the effect of filler alloys onthe ductility of the completedweld, its influence on weld per-formance, and testing methodsused for welding procedure qual-ifications.4. Service TemperatureWeshall consider the importance offiller alloy selection for compo-nents used at temperatures above150 F, and the consequences of

the incorrect selection of filler al-loys for these service conditions.5. Corrosion ResistanceThe ef-fect of filler alloy on the corro-sion properties of the weld.6. Color MatchThis may be amajor consideration for anodizedaluminum used in cosmetic appli-cations.7. Post Weld Heat Treatment

Filler alloy selection can be sig-nificantly influenced with the re-

quirement for thermal post weldheat treatment.The need for afiller alloy which will respond toheat treatment may be the onlyway to obtain required mechani-cal properties.

Ease of welding or

relative crack sensitivity

Hot cracking is typically a result ofa metallurgical weakness of theweld metal as it solidifies and trans-verse stress across the weld. Themetallurgical weakness may resultfrom the wrong filler alloy/basealloy mixture, and the transverse

stress from shrinkage during solid-ification of the weld.These cracksare called hot cracks because theyoccur at temperatures close to thesolidification temperature.

Here we take a look at some ofthe general guidelines to be con-sidered during filler alloy selec-tion in order to minimize the riskof hot cracking.We have two is-sues; the reduction of transversestresses across the weld and the

avoidance of critical chemistryranges in the weld.

The reduction of stresses

Lower melting & solidificationpointfor base alloys with a highsusceptibility to hot cracking suchas many of the 2xxx series alloys,we may choose a 4xxx series fillersuch as 4145 which has an ex-tremely low solidification temper-ature (970 Deg F). This low solid-

ification temperature of the filleralloy ensures that the 4145 weldis the last area to solidify andthereby allows the base materialto completely solidify and reachits maximum strength beforestresses are applied to it by thesolidification/shrinkage stressesof the weld.

Smaller freezing zoneByusing filler alloy such as 4047,which has a freezing zone ofaround 10 Deg F welds can bemade which solidify quickly. Thisprovides less time for liquid met-al to be subjected to shrinkagestresses during the solidificationprocess.

Filler alloy selection for

aluminum weldingBy Tony Anderson, Technical Services Manager AlcoTec Wire Corporation, USA.

7/30/2019 Svetsaren 03 1999

21/36


Critical chemistry ranges

This issue is best addressed byuse of the relative crack sensitiv-ity curves as seen in Fig 1.

The chart shows the crack sen-sitivity curves for the most com-mon weld metal chemistries de-veloped during the welding of thestructural base alloy materials.

1. The aluminum, silicon alloys(4xxx series) are found as non-heat treatable, and heat treatablealloys with 4.5 to 13% silicon areused predominately for filleralloys. Silicon in an aluminum fill-er alloy / base alloy mixture, ofbetween 0.5 to 2.0 % produces aweld metal composition which iscrack sensitive. A weld with thischemistry will usually crackduring solidification. Care mustbe exercised if welding a 1xxx se-ries (pure Al) base alloy with a4xxx series (Al-Si) filler alloy, toprevent a weld metal chemistrywithin this crack sensitive range.

2. The aluminum, copper alloys(2xxx series) are heat treatablehigh-strength materials oftenused in specialized applications.As can be seen from the chart,they exhibit a wide range of cracksensitivity. Some of these base al-loys are considered poor for arc

welding because of their sensitiv-ity to hot cracking, but others areeasily welded using the correctfiller alloy and procedure.

3. The aluminum, magnesiumalloys (5xxx series) have the high-est strengths of the non-heattreatable aluminum alloys, and forthis reason are very important forstructural applications. Magne-sium in an aluminum weld, from0.5 up to 3.0%, produces a weld

metal composition which is cracksensitive. Another issue relating tothese base alloys, which is not di-rectly related to the crack sensi-tivity chart but is a very importantfactor for filler alloy selection,

must be addressed.As a rule the Al-Mgbase alloys with lessthan 2.8% Mg can bewelded with eitherAl-Si (4xxx series) orthe Al-Mg (5xxxseries) filler alloysdependent on weldperformance require-ments. The Al-Mg

base alloys with more than 2.8%Mg typically cannot be successfullywelded with the Al-Si (4xxx seri-es) filler alloys. This is due to aeutectic problem associated withexcessive amounts of magnesiumsilicide Mg2Si developing in theweld structure, decreasing ductili-ty and increasing crack sensitivity.

4. The aluminum, magnesium,

silicon alloys (6xxx series) areheat treatable. The 6xxx seriesbase alloys, typically containingaround 1.0% magnesium silicideMg2Si, cannot be welded success-fully without filler alloy. These al-loys can be welded with 4xxx se-ries (Al-Si) or 5xxx series (Al-Mg) filler alloys dependent onweld performance requirements.The main consideration is to ade-quately dilute the Mg2Si percent-age in the base material with suf-

ficient filler alloy to reduce weldmetal crack sensitivity.

Weld strengthGroove Weld Tensile StrengthTypically the HAZ of the grooveweld dictates the strength of thejoint and often many filler alloyscan satisfy this strength require-ment. However, there are twofactors to consider when develop-ing welding procedures for thenon-heat treatable and the heat

treatable alloys.1. For non-heat treatable

alloys, the area adjacent to theweld will be completely annealed.These alloys are annealed by heat-ing to 600700 Deg F, and the re-quired time at this temperature isshort.The welding procedure willhave little effect upon the trans-verse ultimate tensile strength ofthe groove weld, as the annealedHAZ will typically be the weakest

area of the joint.Welding proce-dure qualification for these alloysis based on the minimum tensilestrength of the base alloy in its an-nealed condition.

2. The heat treatable alloys re-

quire longer times at temperatureto fully reduce their strength. Thisdoes not typically occur duringwelding and the strength of theHAZ will only be partially re-duced.The amount of strengthloss is both time and temperaturerelated in these alloys.The fasterthe welding process and heat dis-

sipation from the weld area, theless the heat effect and higher theas welded strength. Excessivepreheating, lack of interpass cool-ing, and excessive heat input fromslow, weaving weld passes all in-crease peak temperature andtime at temperature. These fac-tors by themselves, as well as theuse of too small a specimen toprovide adequate heat sink, cancreate sufficient overheating so

that minimum strength values re-quired to pass procedure qualifi-cation tests are not met.

Fillet weld shear strengthUnlike groove welds, fillet weldstrength is largely dependent onthe composition of the filler alloyused to weld the joint.The jointstrength of fillet welds is based onshear strength which can be af-fected considerably by filler alloyselection. In structural applica-

tions the selection between 5xxxseries filler or a 4xxx series fillermay not be so significant with re-gard to tensile strength of groovewelds. However, this may not bethe case when considering theshear strength of fillet welds.

Typically the 4xxx series filleralloys have lower ductility andprovide less shear strength in fil-let welded joints. The 5xxx seriesfillers typically have more ductil-ity and can provide close to twice

the shear strength of a 4xxx seriesfiller alloy in some circumstances.Tests have shown that a requiredshear strength value in a filletweld in 6061 base alloy required a1/4 inch fillet weld with 5556 fillercompared to a 7/16 fillet with4043 filler alloy to meet the samerequired shear strength. This canmean the difference between aone run fillet and a three run fil-let to achieve the same strength.

DuctilityDuctility is a property that de-scribes the ability of a material toplastically flow before fracturing.Fracture characteristics are de-

Fig 1.

7/30/2019 Svetsaren 03 1999

22/36


scribed in terms of ability toundergo elastic stretching andplastic deformation in the pres-ence of stress raisers (weld dis-continuities). Increased ductilityratings for a filler alloy, indicategreater ability to deform plasti-cally and to redistribute load, andthereby decrease the crack propa-gation sensitivity.

Ductility may be a considera-tion if forming is to be performedafter welding or if the weld is go-ing to be subjected to impactloading.Also ductility is consid-ered when conducting bend testsduring procedure qualifications.The 4xxx series filler alloys haverelatively low ductility, this is ad-dressed with special requirementswithin the code or standard relat-

ing to test sample thickness,bending radius, and/or materialcondition.

Corrosion resistance

The use of SMAW electrodeswith their flux coating gave con-cern for possible corrosion prob-lems relating to entrapped fluxwithin the welded joint. Today al-most all aluminum welding is per-formed using the GMAW (MIG)or the GTAW (TIG) welding pro-cesses, and flux entrapment is notan issue.

One filler alloy, developed pri-marily for use within a specificcorrosive environment, is filleralloy 5654 developed to weld stor-age tanks to hold hydrogen per-oxide. This filler alloy has a highpurity with low copper and man-ganese content which is requiredfor this very active chemical.

Most unprotected aluminum

base alloy filler alloy combina-tions are quite satisfactory forgeneral exposure to the atmo-sphere. In cases where a dissimi-lar aluminum alloy combinationof base and filler is used, andelectrolyte is present, it is pos-sible to set up a galvanic actionbetween the dissimilar composi-tions. The difference in alloy per-formance can vary based uponthe type of exposure. Filler alloycharts ratings are typically basedon fresh and salt water only. Cor-rosion resistance can be a com-plex subject when looking at ser-vice in specialized high corrosiveenvironments, and may necessi-

tate consultation with engineersfrom within this specialized field.

Service temperatureStress corrosion cracking is anundesirable condition which canresult in premature failure of awelded component. One condi-tion which can assist in the

development of this phenomenais Magnesium segregation at thegrain boundaries of the material.This condition can be developedin the Mg alloys of over 3 %through the exposure to elevatedtemperature.

When considering service attemperatures above 150 Deg F,we must consider the use of filleralloys which can operate at thesetemperatures without any unde-sirable effects to the welded joint.Filler alloys 5356, 5183, 5654 and5556 all contain in excess of 3 %Mg, typically around 5%. There-fore, they are not suitable fortemperature service.Alloy 5554has less than 3 % Mg and was de-veloped for high temperatureapplications. Alloy 5554 is usedfor welding of 5454 base alloywhich is also used for these hightemp applications. The AlSi(4xxx series) filler alloys may be

used for some service tempera-ture applications dependent onweld performance requirements.

Post weld heat treatmentTypically, the common heat treat-able base alloys, such as 6061-T6,lose a substantial proportion oftheir mechanical strength afterwelding. Alloy 6061-T6 has typi-cally 45,000 psi tensile strengthprior to welding and typically27,000 psi in the as-welded condi-

tion. Consequently, on occasion itis desirable to perform post weldheat treatment to return the me-chanical strength to the manufac-tured component. If post weldheat treatment is the option, it isnecessary to evaluate the filleralloy used with regards to its abilityto respond to the heat treatment.Most of the commonly used filleralloys will not respond to postweld heat treatment without sub-

stantial dilution with the heattreatable base alloy. This is notalways easy to achieve and can bedifficult to control consistently.For this reason, there are somespecial filler alloys which have

been developed to provide a heattreatable filler alloy which guar-antees that the weld will respondto the heat treatment. Filler alloy4643 was developed for weldingthe 6xxx series base alloys anddeveloping high mechanical prop-erties in the post weld heat treat-ed condition.This filler alloy was

developed by taking the well-known alloy 4043 and reducingthe silicon and adding .10 to .30% magnesium.This chemistry in-troduces Mg2Si into the weldmetal and provides a weld whichwill respond to heat treatment.

Filler alloy 5180 was developedfor welding the 7xxx series basealloys. It falls within the Al-Zn-Mg alloy family and responds topost weld thermal treatments. It

provides very high weld mechani-cal properties in the post weldheat treated condition. This alloyis used to weld 7005 bicycle fram-es and will respond to heat treat-ment without dilution of the thinwalled tubing used for this highperformance application. Otherheat treatable filler alloys havebeen developed including 2319,4009, 4010, 4145, 206.0,A356.0,A357.0, C355.0 and 357.0 for thewelding of heat treatable wroughtand cast aluminum alloys.

It must be concluded that finaldetermination of the most suit-able filler alloy can only be madeafter a full analysis of the weldedcomponents performance re-quirements. Filler alloy selectionfor welding aluminum is an essen-tial part of the development andqualification of a successful weld-ing procedure qualification.

About the author

Tony AndersonTechnical Servic-es ManagerAlcoTec, holds aBachelor of Science in WeldingEngineering and a Master ofScience Degree in Industrial Engi-neering Management & QualityAssurance. Tony was previouslyemployed for 15 years in SouthernAfrica, involved with Quality and

Welding Engineering projects.Prior to work in Africa he had 13years service with Vickers Ship-building England, primarily in-volved with welding activities onnuclear submarine projects

7/30/2019 Svetsaren 03 1999

23/36


Voest Alpine Stahl LinzGmbH has investedaround DEM 2 millionin its new laser cuttingcentre. Here plough-

shares are cut from spe-cial multi-layer sheetsthat are 8 m long and3 m wide using theALPHAREX cuttingsystem from ESABCUTTING SYSTEMS.Although the cuttingsystem has only justgone into production,

there are already signsof success. The companyusing it, Voest Alpine, isalready considering in-stalling a third set in or-der to exploit the stronggrowth in potential de-mand for customisedprecision sheet cutting.

Voest Alpine Stahl Linz GmbH,an Austrian company, has a repu-tation as a steel manufacturer. Itsproduction processes include pro-ducing steel sheets in rolling millsand further processing sheets tomake semi-finished products. Its60 or so employees turn approxi-mately 1,000 tonnes of steelsheets per year into customisedsemi-finished products, and themajority of the steel sheets that

are cut are up to 25 mm thick.Previously, sheets were cut exclu-sively using gas cutting equip-

ment, the majority of which wasfinished and supplied by ESAB-HANCOCK.

One client requiring custom-ised sheets is a company manu-facturing agricultural machinery,the French firm Kuhn, in Cha-teaubriand, which orders sheetsfor ploughshares. These special

sheets for ploughshares are 7 mmthick and are made out of Altrixmulti-layer black steel sheets,combined through the rollingprocess, each with specific prop-erties.The geometric shape ofthe flat ploughshare is irregular,meaning that flexible thermal cut-ting is the only suitable systemfor the cutting process. Further-more, the client is particularly de-pendent upon the dimension andplan conformity of the plough-share sheets, which has recentlyraised the question of whether itwould be better to replace the gas

cutting system with a laser cutting

system.

Quality, cutting perfor-

mance and safety

In 1997 a firm grasp was taken on

planning. When considering re-placing the plasma oxygen cuttingsystem with laser cutting, the firstpoint to consider was the cuttingperformance. Engineer HaraldFischerlehner, from the capital in-vestment planning department ofVoest Alpine Stahl Linz, had this

to say on the matter First of all,using laser cutting equipment is

twice as slow as the existing gascutting equipment. However, thisis more than compensated for bymore precise cutting, and a small-er amount of finishing work, forexample, the greatly reducedamount of processing requiredfor the edges and the eliminationof thermal distortion.

At the project identificationstage, proposals from several la-ser cutting system suppliers wereexamined. With such a large in-

vestment we naturally had to stu-dy the market supply in detailand look at appropriate equip-ment. In addition we also carriedout test cuts, says Fischerlehner.

Precision laser gantrySpecial multi-layer sheets are best processed

using laser cutting systems

by Dipl.-Ing Wolfgang Klinker, b-Quadrat Verlags GmbH, Kaufering, Austria

Fig 1. The ESAB Alpharex laser cutting system with the ProLas1safety mechanism

at Voest in Linz,Austria.

7/30/2019 Svetsaren 03 1999

24/36


Terms were then agreed withESAB CUTTING SYSTEMSwho already have a considerable

number of gas cutting machinesin operation in Linz, and whoprovide service that the people ofLinz are very happy with.Wewere convinced by the cuttingperformance and precision de-spite large working surfaces, Fis-cherlehner explains, as in theend the results were decisive andthe cutting quality of ESAB wasfar superior.

Special consideration had to be

given to the safety of the lasercutting equipment, with particularregard to avoiding stray radiationif the laser cutting equipmentshould malfunction.Here inAustria, says Fischerlehner, the

safety regulations for laser equip-ment are strictly observed. Spe-cifically, this means that for safetytechniques there must be an offi-cial safety certificate for protec-tive design.At the time ESABCUTTING SYSTEMS was the

only supplier of design-tested la-ser cutting equipment with safetyfeatures.

Co-operation for laser

safety

ESAB uses the active and passivemultichamber system, developedand patented by GELA GmbH,for shielding the working areaand the sphere of action of theALPHAREX laser cutting sys-

tems from the AXB and AXCranges. The accompanying Class1 shielding is built-in directly onthe machine and reduces the po-tential risk from Class 4 to Class1, therefore providing reliableprotection from leakage radia-tion. It is currently the only lasercutting device of its kind that ful-fils all the stringent requirementsand provides the operator withcomplete 30,000 sec. automatic

operation, in accordance withDIN 60825-1 and 60825-4.The trade association testing

and certification centre has testedthe equipment design and issuedan appropriate certificate con-

firming conformity with the ma-chine guideline and the appli-cable standards. As laser equip-ment has to be registered withthe Industrial Inspection Boardand the trade association beforebeing used, the existence of thisdocumentation is imperative forsafely commencing production.

Compact laser unit and

flying optics

The cutting system was orderedat the beginning of September1998, just a few weeks beforeESAB CUTTING SYSTEMSexhibited the ALPHAREX lasercutting system with the ProLas 1

safety mechanism at Euro-BLECH in Hannover. The ma-

chine design of the cutting systemwas specially developed for work-pieces that make the highest de-mands on the guiding machine asa result of their extremely largeworking surfaces. The very rigidmachine gantry is equipped withlongitudinal and transverse gui-des on each side. Low-play plane-tary gear and servo drives allowon the one hand a high position-ing speed of up to 25 m/min, andon the other, with the help of the

guides, precision positioning overthe entire working surface. Onthe x-axis the gantry moves thelaser set along with the guide ve-hicle, which as the y-axis positionsthe flying optics. The machine de-sign provides a high degree ofguiding and positioning accuracy(0.3 mm in 2 m 2 m accordingto VDI 3441).

The ALPHAREX laser cuttingsystem allows a maximum work-

ing width of up to 5 m and aworking length up to 25 m.Theworking surface of the equipmentat Voest Alpine, however, is 3 m

8 m. The CO2 laser is a 4 kWlaser from TRUMPF laser tech-nologys TLF range. The beamcontrol from the resonator to thecutter head uses flying opticswith high laser beam quality. Forthis, the laser beam issuing fromthe output mirror is first expand-ed in a beam telescope using aconvex mirror and then launchedthrough a concave mirror into thefront tilted mirror of the beamguidance device covering thewhole width of the machine.At

Fig 2. The Alpharex laser cutting system is equipped with the new numerical controlsystem NCE 620 which provides safe and easy operation.

Fig 3. The cutting performance and

precision is superior despite the large

working surfaces.

7/30/2019 Svetsaren 03 1999

25/36


its external end the beam is inturn diverted into the beam guid-ing arm which moves in parallel.At this end there is another di-

version into the z-axis for focus-sing devices in the cutter head.Only then is the laser beam con-centrated on the working surface.This type of beam guidance up tobeam issuing provides a consis-tent cutting quality across the en-tire working surface up to maxi-mum cutting widths of 25 mm ofstructural steel.The Precitec ex-changeable cutting heads that areused at Voest Alpine are mainlydesigned for steel sheets up to 6mm thick and for steel sheets bet-ween 7 mm and 25 mm thick. If

necessary a non-contact capaci-tive interval regulator will ensure

the optimum spacing and positionof the laser cutting head.

Modern control tech-

niques with technology

databases

ALPHAREX laser cutting sys-tems are equipped with the newnumerical control system NCE620, providing safe and easy oper-ation. The operator can access ex-tensive databases, ensuring thebest cutting quality and enablingrepetition. In addition, the appli-cation-specific data can be loadedinto the database and retrieved asrequired.This additional applica-

tion-specific data particularly in-cludes the processing parametersfor the special multi-layer blacksheets for ploughshares.

The laser cutting system atVoest Alpine is equipped with anew pallet-changing system table.

Pallet changing takes place as fol-lows: the pallet in the workingarea of the cutting device ismoved out of the machine andunder the second pallet table. Thelatter is moved into the machinealong with the steel sheet that isto be freshly

Svetsaren 03 1999

Documents

Transcript of Svetsaren 03 1999