duplex mcenerney

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Stainless Steel World©2001 KCI Publishing BV 1

AbstractAlloy 19D (UNS S32001) is arecently commercialized leanduplex (ferritic-austenitic) stainlesssteel. Comparing the compositionof alloy 19D to conventional duplexand super duplex stainless steels,the chromium content is reduced,manganese is substituted for mostof the nickel, and molybdenum isessentially eliminated. It offers thehigher strength associated withduplex stainless steel combinedwith lower cost and relativefreedom from detrimentalintermetallic phase formation.Eleven production heats of coldrolled alloy 19D strip, supplied byAK Steel, were converted to longcoils of seam welded tubing.Greater than 3.5 million feet oftubing have been produced andsubsequently used to manufactureumbilicals for several subseainstallations in the Gulf of Mexico.For subsea umbilical applicationsalloy 19D tubing is currently usedwith an externally extruded zincsheath. However, other externalprotection systems are beingconsidered. The coils of seamwelded tubing contained strip

splice, longitudinal seam andorbital welds. Each of the weldtypes was tested and evaluated.The coils were manufactured inaccordance with ASTM A 789 plusadditional acceptance criteria. Adetailed description of theacceptance criteria and associatedtesting is provided. Standardtesting of the three weld types fromall of the production heatsdemonstrated desirabledimensional, microstructural andmechanical properties. Themicrostructural characterizationconsisted of an assessment of theferrite content. The mechanicalproperties assessment consisted oftensile, hardness and burst testing.Extensive rotational fatigue andother additional tests wereperformed on samples from one ofthe production heats. Thisadditional testing was performedon samples containing each of thethree weld types. Seam weldedalloy 19D tubing enables theproduction of long coils withdesirable properties and a greatlyreduced number of girth welds(strip splice or orbital) whencompared to seamless tubing.

Experience manufacturing alloy 19D (UNS S32001)seam welded lean duplex stainless steel tubing forsubsea umbilical applications

Authors:Joseph W. McEnerneyGibson Tube Inc, USA

Keywords:Alloy 19D, lean duplex stainless steel,seam welded tubing, longitudinalseam weld, strip splice weld, orbitalweld, intermetallic phases, physicalproperties data, dimensional data,ferrite point count data, tensile testdata, hardness test data, surfaceroughness test data, burst test data,rotational fatigue test data, subseaumbilical tubing.

1. Introduction

Alloy 19D (UNS S32001) is a leanduplex (ferritic-austenitic) stainlesssteel that was developed andpatented by AK Steel and registeredas the trademark Nitronic 19D [ref.1]. Comparing the composition ofalloy 19D to conventional duplex andsuper duplex stainless steels, thechromium content is reduced,manganese is substituted for most ofthe nickel, and molybdenum isessentially eliminated. Gibson Tube,AK Steel, and SeaCAT Corporationconducted a joint developmentprogram to produce seam weldedalloy 19D tubing. A summary of thedevelopment work and initialproduction of tubing has previouslybeen reported [ref. 2]. Seam weldedalloy 19D tubing was firstmanufactured for production ordersduring the summer of 2000.

1.1 Characteristics ofAlloy 19D

Alloy 19D has several significantcharacteristics. The mechanicalstrength is higher than that foraustenitic stainless steels. Physicalproperties such as lower coefficient ofthermal expansion and higher thermalconductivity also offer designadvantages over austenitic stainlesssteels. Alloy 19D has relative freedomfrom the formation of detrimentalintermetallic phases compared to theconventional or super duplexstainless steels. A summary ofGibson Tube and AK Steelevaluations regarding intermetallicphase formation has previously been

reported [ref. 2]. Because of its leancomposition, alloy 19D has a lowercost than the conventional and superduplex stainless steels.

Alloy 19D is less corrosion resistantthan either the conventional duplex(2205) or super duplex (2507)stainless steels. For applications suchas subsea umbilical tubing wherealloy 19D is compatible with theinternal but not the external serviceenvironment, a continuous zinc anodehas been extruded on the outsidesurface. Other external protectionsystems are being considered. Thesesystems could include multi-layercoatings, with or without cathodicprotection.

Because of its duplex structure, alloy19D offers improved resistance tochloride stress corrosion cracking(SCC) compared to austeniticstainless steel alloys such as grades304L and 316L. For example, AKSteel reports data [ref. 1] showingSCC of alloy 304 in 127 hours, but nocracking of alloy 19D after 720 hours

of exposure to 25% boiling sodiumchloride with the pH = 1.5 (adjustedwith phosphoric acid).

Although an alloy’s compatibility withany service environments mustalways be carefully evaluated, alloy19D may be considered for someapplications where welded type 304Laustenitic stainless steel tubing iscurrently used. However, because ofits higher strength and leancomposition, alloy 19D welded tubingoffers design and cost advantagesover type 304L.

1.2 Subsea umbilical tubingapplications

A recent paper presented at theOffshore Technology Conferencesummarizes the evolution of subseaumbilical design for applications in theGulf of Mexico [ref. 3]. Umbilicalsprovide the electrical power,communications, chemical injectionand hydraulic fluid power necessaryto control and operate subsea wells.

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The cross-section has grown largerand ever more complex as theelectric cables and tubing have beenintegrated into a single umbilical withmore than twenty tubes. The papernotes several driving forces behindthe evolution of subsea umbilicaltubing. These driving forces include:application to oil wells, dynamicconnections to floating hosts,movement into the deeper waters ofthe Gulf of Mexico, and lengthsgreater than twenty miles (32 km).

Early subsea umbilicals utilizedthermoplastic hose. However, theincreasing water depth, higheroperating pressure and aggressivenature of the fluids resulted in the useof super duplex stainless steel(SDSS) tubing. Seamless alloy 2507SDSS tubing has been commonlyused for subsea umbilicals. However,as a result of using seamless tubing,the lengths available have beenlimited. In order to make long coils,straight lengths and/or short coils ofseamless tubing must be joined usinggirth welds. For projects requiringmiles of tubing, this can result in theneed to make thousands of girthwelds. The production of such largenumbers of girth welds can have anadverse impact on both cost anddelivery schedule. In addition, SDSSsuch as alloy 2507 can formdetrimental intermetallic phases. Thepresence of intermetallic phases hasbeen cited as the cause of industryreported failures of SDSS [ref. 3].

The need for a lower cost alternativeto the SDSS resulted in thedevelopment of zinc-sheathed, highfrequency induction (HFI) seamwelded steel tubing by SeaCATCorporation. The HFI welded tubing ismanufactured from cold rolled Cr-Mosteel strip that is quenched andtempered to produce high strengthafter welding. A continuous zincanode is extruded on the outsidesurface of the tubing. The zinc acts asa barrier and provides cathodicprotection in case the sheath isdamaged. While this tubing has andcontinues to be successfully used forsubsea umbilical projects, theintroduction of scale inhibitors notcompatible with the Cr-Mo steelresulted in the need for a morecorrosion resistant tubing.

Gas tungsten arc (GTA) seam weldedalloy 19D tubing was jointlydeveloped by Gibson Tube, AK Steeland SeaCAT Corporation to meet theneed for lower cost subsea umbilicaltubing with increased corrosionresistance. AK Steel provides the coldrolled strip, Gibson Tubemanufactures the seam weld tubing

and to date SeaCAT Corporation hasprovided the same continuouslyextruded zinc anode on the outsidesurface as used for the HFI weldedCr-Mo steel tubing. However, aspreviously discussed, alloy 19D couldbe used with other external protectionsystems.

The GTA seam welded alloy 19Dtubing has successfully demonstratedcompatibility with hydrate/scaleinhibitors that are corrosive to the Cr-Mo steel tubing. GTA seam weldedalloy 19D tubing provides severaladditional advantages. First, alloy19D tubing contains a forged GTAlongitudinal seam weld. As a result,GTA seam welded alloy 19D tubinghas a more uniform internal surfacethan the HFI weld on the Cr-Mo steeltubing. Alloy 19D requires lesscleaning than the Cr-Mo steel. Theability for alloy 19D to handle a widerrange of internal fluids than the Cr-Mosteel provides more flexibility withregard to umbilical design and insome cases may reduce the numberof tubes required. Alloy 19D may alsooffer a more robust solution for waterbased hydraulic fluids [ref. 3].

As of September 2001, seam weldedalloy 19D has been manufactured foruse as subsea umbilical tubing onseveral projects in the Gulf of Mexico,including Serrano, Oregano, Nakika,Einset, Ladybug, Manatee andCoulomb. This report summarizesmanufacturing and testing activitiesassociated with eleven productionheats of seam welded alloy 19Dtubing produced for these projects.

2. Strip

Tubing was manufactured fromeleven heats of strip supplied by AKSteel. The strip was in accordancewith ASTM A 240, UNS designationS32001 [ref. 4]. The chemicalcompositions of the eleven heats ofstrip are shown in Table 1. Thesevalues are as reported by AK Steel.The requirements of the A 240specification are also listed inTable 1.

The compositions of two duplex (2205and 2507) and two austenitic (304Land 316L) stainless steels arecompared to alloy 19D in Table 2.The pitting resistance equivalents(PRE) have been calculated for eachof these alloys using Equation (1) andthe ranges of chemical compositionsshown in Table 2. The resulting PREranges are shown in Table 3, with thealloys listed in descending order ofPRE range. Calculation of an alloy’sPRE is a commonly used means for

ranking chloride pitting corrosionresistance. Based upon the rangesreported in Table 3, it can be seenthat alloy 19D is ranked betweengrades 304L and 316L, but below2205 and 2507.

PRE = %Cr + 3.3 x %Mo + 16 x %N (1)

Tensile and hardness test data for thestrip are reported in Table 4. Thisdata is as reported by AK Steel.

3. Types of welds infinished Gibson Tubecoils

All welds made by Gibson Tubecurrently use the automatic,autogenous GTA welding process. Inaddition, the longitudinal seam weldfor alloy 19D utilizes plasmapreheating. Gibson Tube has recentlyinstalled a tubing mill that utilizes thelaser welding (LW) process. Weldingtrials using the LW process for alloy19D tubing are currently in progress.

All welded tubing contains alongitudinal seam weld along itsentire length. This weld is made afterthe strip has been roll formed into atubular shape. The strip edges arebrought together to form a squarebutt, longitudinal weld joint. The gapbetween the butted edges is carefullycontrolled to provide a consistentweld. The weld is maintained undercompressive load during solidificationto prevent defects.

The longitudinal seam weld for alloy19D tubing is cold forged. Figure 1shows a typical cross section of theforged longitudinal seam weld from aproduction mill coil. The effect of thecold forging is an improved weldgeometry and microstructure. Aftercold forging, the outside and insidesurfaces of the longitudinal seamweld are very uniform. The uniformgeometry provides several benefitsincluding an improved ability toinspect the weld and elimination ofpotential sites for stress concentrationand corrosion. While the amount ofcold work and subsequent heattreatment is not sufficient to fully re-crystallize the weld, some degree ofgrain refinement does occur. Longcoils of tubing produced by GibsonTube generally contain two additionaltypes of welds: strip splice and orbital.

Strip splice welds join the end of onestrip coil to another. These welds areused to enable continuous feeding ofstrip and thereby continuousproduction of tubing at the mill. Thestrip splice weld is made on the

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butted ends of strip cut at an angle.When the strip is subsequentlyformed and welded into tubing, thestrip splice weld assumes a helicalorientation.Due to this helical orientation, theends of the strip splice weld intersectthe longitudinal seam at twolocations. For the 0.625-in. OD x0.065-in. wall thickness (15.9-mm x1.7-mm) alloy 19D tubing, the stripcoils from AK Steel have ranged inlength from 1,500 to 3,200-ft. (460 to975-m). Depending upon the length ofthe strip coil, two to four coils arejoined with strip splice welds toproduce a 5,000 to 6,400-ft. (1,520 to1,950-m) master strip coil. Themaster strip coil is then converted to atubing mill coil of the same length withone to three strip splice welds.

Orbital welds join two or more shortermill coils of seam welded tubing toproduce a long coil. The orbital weldis made on butted ends of tubing.Strip splice and orbital weldprocedure and performancequalification is in accordance withASME Section IX [ref. 5] plusadditional criteria. Several mill coilsare joined to produce a 30,000-ft.(9,140-m) length reel for shipment.The typical number of orbital welds inthese reels is ten. This number isgreater than the 5 to 6 expectedbased upon the length of the millcoils. This is due to shorter mill coilsand the cut out of strip splice weldsrejected by x-ray examination ortubing sections rejected by eddycurrent examination.

The strip splice and longitudinal seamwelds are heat treated by in-lineinduction heating with a protectiveatmosphere. The orbital weldsreceive local postweld heat treatment(PWHT) by resistance heating with aprotective atmosphere on the insidesurface and air on the outsidesurface. The oxide layer on theoutside surface that results from thelocal PWHT is subsequently removedusing an abrasive pad.

4. Seam welded tubing

All strip heats were converted to0.625-in. OD x 0.065-in. wallthickness (15.9-mm x 1.7-mm) tubing.The tubing was manufactured inaccordance with ASTM A 789 [ref. 6].Alloy 19D was recently added toASTM A 789. Table 5 provides asummary of the tensile, hardness andheat treatment requirements thatwere approved for addition to A 789.

All production tubing wasmanufactured using plasma

preheating, autogenous GTA welding,forging and induction heat treatment.As of September 2001, greater than3.5 million feet (1,067 km) of weldedtubing have been produced.

5. Quality assurance plan

Sections 5.1 to 5.5 describe thetypical quality assurance plan thatwould be used for long coils ofwelded alloy 19D tubing intended forsubsea umbilical applications.Gibson Tube Quality Plans typicallyinclude in-process monitoring of keyvariables. For example, equipmentand/or recording forms are used atthe mill to record welding parameters,heat treatment temperature and otherimportant variables.Specific plans are developed to meetthe requirements of individualcustomers.

5.1 Strip

Incoming strip is assessed for thedesired weight per coil (PIW),dimensions (width and thickness),and chemical composition.Reported compliance by the stripsupplier on the mill test report is usedas the basis for acceptance ofchemical composition and mechanicalproperties. Ferrite point counting ofthe strip is performed by GibsonTube. Positive material identification(PMI), using an x-ray fluorescence(XRF) alloy analyzer, is performed atreceiving and the final reelingoperation. The dimensions of the stripare also monitored at the mill on anin-process inspection basis.

5.2 Testing of mill coils inaccordance with ASTM A789

Dimensional, tensile, flange,hardness, reverse flattening, andeddy current testing are performed inaccordance with the requirements ofASTM A 789. Test specimens areremoved from the ends of mill coilsand evaluated. Tensile tests areperformed on samples from one orboth coil ends and from each coil oran agreed upon frequency,depending upon customerrequirements.

Dual coil eddy current testing isperformed at the mills using a lowfrequency to penetrate through thewall thickness and a high frequencyto examine the outside surface.A second low frequency test isperformed off-line as the tubing isbeing reeled for shipment.

The calibration standard for eddycurrent testing contains the fourartificial flaws described below.1. Through-wall hole, 0.031-in.

(0.79-mm) maximum diameter.2. Transverse notch on the outside

surface, 0.0065-in. (0.17-mm)maximum depth.

3. Longitudinal notch on the outsidesurface, 0.0065-in. (0.17-mm)maximum depth.

4. Transverse notch on the insidesurface, 0.0065-in. (0.17-mm)maximum depth.

5.3 X-ray examination of stripsplice and orbital welds

To date, examination of strip spliceand orbital welds has been performedusing film-based radiographictechniques in accordance with ASMESection V [ref. 7].Examination of strip splice welds isperformed after they have beenformed into a tubular shape, weldedand heat-treated. Examination of theorbital welds is performed after localpostweld heat treatment.Three radiographs imaged 0°, + 60°,and − 60° apart and orientedperpendicular to the tubing are usedto examine the strip splice and orbitalwelds.

Gibson Tube has been attempting toimplement real time digital radioscopyfor x-ray examination of strip spliceand orbital welds. The digital systemutilizes the same orientation andnumber of images as film-basedradiography. An interim system iscurrently available and utilizes the x-ray tube and image intensifierplanned for incorporation in the finalsystem. The interim system hasmanual manipulation and is notshielded. An automated multi-axismanipulation system with a fullyshielded cabinet will be incorporatedin the final system.

Gibson Tube has adopted the use ofa wire image quality indicator (IQI) forx-ray examination. The essential wireis based upon BS EN 462-3 [ref. 8]and BS EN 462-1 [ref. 9]. Europeanstandards provide more completecoverage of the wall thickness rangeassociated with small diametertubing. For example, the first rangefor penetrated thickness, “w”, is “up to1.2 mm” (0.047-in.) in Table 9 of BSEN 462-3. For a double-wallradiographic technique, “w” equals 2t,where “t” is the single wall thickness.The “w” value of 1.2 mm (0.047-in.)corresponds to a single wall thicknessof 0.0235-in. (0.6 mm). In contrast,the first range for single wallthickness in Table T-276 of ASME

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Section V (ref. 7) is 0.25-in. (6.35 m),greater than 10 times larger.

Based upon the requirements of BSEN 462-3, Table 9 and BS EN 462-1,Gibson Tube has adopted Set “A” ofASTM E 747 [ref. 10] as the IQI touse for x-ray examination of alltubing. The essential wire for 0.065-in. (1.7 mm) wall thickness tubing isthe No. 2 and has a diameter of0.004-in. (0.10 mm).

Gibson Tube and TWI Ltd. have justcompleted a joint project to determineacceptance criteria for porosity inalloy 19D girth welds (strip splice andorbital).Cut out production orbital welds withporosity were tested. First, theporosity size was characterized bydigital radioscopy. Before testing,each weld was plastically strained (15cycles) at the location of themaximum diameter pore to simulatethe worst expected strain duringtubing manufacturing, zinc sheathing,umbilical bundling, and installation.Each sample was then burst tested.TWI examined the fracture surfacesto determine the involvement, if any,of the porosity and whether acorrelation existed between burstpressure and porosity size.TWI has concluded that a maximumsingle pore size acceptance limit of0.4 mm (0.016-in.) was reasonable.Gibson Tube has adopted anacceptance criteria based upon thesize of the essential wire in the IQI.For the 0.065-in. (1.7 mm) wallthickness tubing, a single,subsurface, isolated pore with adiameter less than 0.004-in.(0.10 mm) would be allowed.Note that the acceptance criteriaadopted by Gibson Tube allows apore size less than 25% of themaximum recommended by TWI.

5.4 Hydrostatic testing of millcoils

An in-process hydrostatic test of eachmill coil is performed by Gibson Tube.The alloy 19D mill coils for subseaumbilical applications are 5,000 to6,400-ft. (1,525 to 1,950-m) long. Sixto eight of the mill coils are joined byorbital welding to produce 30,000-ft.(9,140-m) long reels. These reels arethen shipped to off-site customerfacilities. Two or more GibsonTube reels are combined to produce+60,000-ft. (18,300-m) zinc-sheathedreels to be used for umbilicalbundling. The final acceptance test(FAT) of these zinc-sheathed reelsincludes a hydrostatic test.It was deemed to be more efficient forGibson Tube to perform only an in-

process hydrostatic test on the millcoils and rely on the customer FAT totest the reels.The in-process hydrostatic test of themill coils consists of holding at yieldpressure for 1 ½ hours. The last thirtyminutes of the test must demonstratepressure stability or the test cycle isrepeated. At the end of the test, thecoil and cardboard placed under it arechecked for leaks.For the 0.625-in. OD x 0.065-in. wallthickness (15.9-mm x 1.7-mm) tubing,the coils are pressurized to 17,500 to18,000 psi (121 to 124 MPa). Thispressure range was establishedbased upon an evaluation in whichdimensional measurements weremade on coils before and aftertesting. The pressure range isexpected to cause minimaldimensional change.During the test, a transducer is usedto read pressure and a digital videorecorder captures the pressureversus time data. Pressure versustime plots are then produced from thedigital data.

5.5 Additional testing of millcoils and orbital welds

The frequency of testing of samplesfrom mill coils is based uponcustomer requirements. Specimensare mounted, polished, etched, andexamined to assess the condition ofthe longitudinal seam weld. Theferrite content of the longitudinalseam and strip splice welds arecurrently determined once at the startof each new heat as described inSection 7.1.

The frequency of testing of orbitalweld samples is based uponcustomer requirements. Tensile testsand ferrite point counting, asdescribed in Section 7.1, have beenperformed.

6. Dimensional and surfaceroughnesscharacterization

Dimensional measurements takenfrom the beginning and end of eachmill coil are reported for all heats andadditional measurement data isprovided for samples from heat301000. In addition, surfaceroughness data are reported forsamples from heat 301000.

The tubing samples used for theadditional testing of heat 301000were as follows. The samplescontained only the longitudinal seamweld (LSW). Three samples, each 12-in. (305 mm) long, were removed

from the ends of 8-ft. (2.4 m) longsections of tubing. The 8-ft. (2.4 m)lengths were randomly selected fromapproximately 1,000-ft. of tubingmanufactured for a specialqualification program.The dimensional analysis and surfaceroughness measurements describedbelow were performed on one end ofthese 12-in. (305 mm) long samples.

6.1 Dimensionalmeasurements

Table 6 provides the results ofdimensional measurements made atthe start and end of each mill coil.The samples used to perform thesemeasurements were removed afterthe tubing was coiled.The maximum and minimum outsidediameters as well as the wallthickness of the base metal and weldwere measured. The average, 95%confidence interval, maximum, andminimum values for each of the fourdimensional characteristics arereported for 950+ mill coils. Therequirements of ASTM A 789 are alsoshown in the table. The datademonstrate excellent control ofdimensions, well within the variationallowed by ASTM A 789.

For the additional samples from heat301000, the outside diameter wasmeasured at the LSW and three otherlocations at 45° increments aroundthe circumference using a 1-in.(25.4 mm) micrometer with a flat anvil.The wall thickness was measured atthe LSW and seven other locations at45° increments around thecircumference using a 9/16-in. (14.3mm) micrometer with a ball anvil.

The outside diameter and wallthickness measurements werecompared to the permissiblevariations in dimensions allowed byASTM A 789. The results of thedimensional analysis andASTM A 789 requirements arereported in Table 7. The data againdemonstrate excellent control ofdimensions, well within the variationallowed by ASTM A 789.

6.2 Surface roughnessmeasurements

Surface roughness parameters weredetermined using a Mitutoyo SJ-201surface roughness tester. ANSI B46.1[ref. 11] classifies this tester as aType V skidded instrumentparameters only, stylus withpiezoelectric transducer. The detectoris described by Mitutoyo as shownbelow:

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Detecting method:differential inductanceStylus:tip radius 5 µm (200 µin), 90° conical,diamondSkid:radius of curvature 40 mm (1.6 in)Measuring force:4 mN (0.9 x 10-3 lbf)

The parameters were determined inaccordance with ANSI B46.1, usingthe phase correct Gaussian filter (PC50). The sampling length was 0.03-in.(0.76 mm) and the evaluation lengthwas 0.15-in. (3.8 mm), i.e., fivesampling lengths of 0.03-in. (0.76mm). The parameters weredetermined with the detector movingin the axial direction of the tubing.Determinations were made on theoutside and inside surfaces at theLSW and three other locations at 90°increments around the circumference.The surface roughness parametersthat were determined are listed belowand are reported in Table 8.

Arithmetic mean deviation of profile, Ra

Maximum height of profile, Ry

Ten-point height of irregularities, Rz

Root-mean-square deviation of theprofile, Rq

As expected, all parameters showedthe roughness of the longitudinalseam weld (orientation weld 0°) onthe outside surface to be less thanthat at the inside surface. ANSIB46.1, Figure B1 provides acomparison of the surface roughness,reported by Ra, for various commonproduction methods. The longitudinalseam weld roughness for both theoutside (Ra 15 to 25 µ in.) and insidesurfaces (Ra 21 to 43 µ in.)corresponds to the range reported forgrinding, thereby indicating a uniformsurface.

The surface roughnessmeasurements provide a directcharacterization of the effectivenessof the forging and sizing operations inachieving uniform weld surfaces. Aspreviously stated, the uniformsurfaces provide several benefitsincluding an improved ability toinspect the longitudinal seam weld,elimination of potential sites for stressconcentration and corrosion, andimproved fluid flow characteristics.

7. Microstructuralcharacterization

Microstructural evaluations wereperformed on the following: strip, strip

splice weld, longitudinal seam weld,and orbital weld samples.The evaluations consisted ofassessment of the ferrite content. Inaddition, photomicrographs wereprepared to represent the typicalmicrostructure.

Strip specimens consisted of asection oriented transverse to thestrip length or rolling direction.Specimens from strip splice,longitudinal seam and orbital weldsconsisted of sections orientedtransverse to the welding direction.Evaluation of the tubing base metalwas performed on the samespecimen as that used for the welds(i.e., a section oriented transverse tothe welding direction).

It should be noted that based uponpreviously reported evaluations byboth Gibson Tube and AK Steel [ref.2], it was determined that noassessment for the presence ofintermetallic phases was necessary.

7.1 Ferrite content

Point counting was in accordancewith ASTM E 562 [ref. 12]. A 5 x 5 (25point) counting grid applied to 32fields (resulting in 800 points counted)was used. The 32 fields consisted oftwo 16-field scans moving from theoutside to the inside surface.The aim was to have a relativeaccuracy of 10% or less. The relativeaccuracy is defined as the 95%confidence interval divided by theaverage ferrite content. The ferritecontent was determined in the basemetal for the strip and in both thebase and weld metal for strip splice,longitudinal seam and orbital welds.The arithmetic average (% Ferrite),the 95% confidence interval (± 95%CI) and the relative accuracy (% RA)are reported for the strip, strip splicewelds, longitudinal seam welds andorbital welds in Tables 9, 10, 11 and12 respectively.

The data shown in Table 9 are basedupon one sample for each strip heat.The data for the strip splice andlongitudinal seam welds shown inTables 10 and 11 are based uponone sample taken at the start of eachnew heat. The data for the orbitalwelds shown in Table 12 are basedupon one sample for each reel. Thedata for the orbital welds represent100+ reels. For the orbital weld data,the range of % ferrite is reportedalong with the ± 95% CI and % RAcorresponding to the limits of therange.

Tables 9 through 12 show that the

ferrite content of the strip, tubing basemetal and weld metal for the threewelds in all production heats was wellwithin the acceptable range (35 to60%) and mainly within the aim range(45 to 50%).

7.2 Photomicrographs

Figures 2 to 6 showphotomicrographs representing thetypical microstructure found in thestrip, strip splice weld metal,longitudinal seam weld metal, tubebase metal and orbital weld metalrespectively. Thesephotomicrographs reveal a relativelyconsistent microstructure for both thewelds and base metal.

8. Physical properties

The following physical properties datahave been provided by AK Steel. Thetesting required for the density,thermal expansion coefficient andmodulus of elasticity data wereperformed by AK Steel. The testingfor the specific heat and thermalconductivity data were performed byHolometrix Micromet. The testing fordensity, specific heat, thermalconductivity, and coefficient ofthermal expansion was performed on0.065-in. (1.7 mm) thick mill annealedstrip from heat number 301000. Thetesting for modulus of elasticity wasperformed on 0.625-in. OD x 0.065-in.wall thickness (15.9-mm x 1.7-mm)tubing samples from heat 301000containing a longitudinal seam weld.

8.1 Density

Testing to determine density at roomtemperature was performed inaccordance with ASTM B 311 [ref.13]. AK Steel reports the density to be7.766 gm/cm3.

8.2 Specific heat

Testing to determine the specific heatwas performed at 25, 260 and 538°C(77, 500 and 1000°F) using laserflash thermal conductivity techniquesin accordance with ASTM E 1461 [ref.14]. Holometrix reports the resultsshown in Table 13.

8.3 Thermal conductivity

Testing to determine the thermalconductivity was performed attemperatures of 25, 260 and 538°C(77, 500 and 1000°F) using laserflash thermal conductivity techniquesin accordance with ASTM E 1461.Holometrix reports the results shown

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in Table 14.

8.4 Coefficient of thermalexpansion

Testing to determine the coefficient ofthermal expansion was performedover the range +20 to 650°C (68 to1200°F) in accordance with ASTM E228 [ref. 15]. The data below +25°Cwas disregarded due to test scatter inthis region. A regression analysis wasperformed on the data and theinstantaneous coefficients weredetermined at – 20, + 20 and 100°C(– 4, 68, and 212°F). AK Steel reportsthe results shown in Table 15. Thecomplete set of data (+20 to 650°C) isavailable from AK Steel if informationregarding higher temperatures isneeded.

8.5 Modulus of elasticity

The modulus of elasticity wasdetermined in accordance with ASTME 111 [ref. 16] at test temperatures of– 20, + 21 and + 100°C (– 4, 70, and212°F). The test temperaturetolerance was ± 5°C (± 9°F). Theresults are reported in Table 16. Eachspecimen was pre-strained threetimes to approximately 7,000 lbf (31MN) to remove the hysteresis. Theaverage 0.2% offset yield strengthwas estimated to be 85,000 psi (586MPa). By multiplying the crosssectional area of each tube by 85,000psi (586 MPa) and taking 75% of thevalue, it was determined that 7,000 lbf(31 MN) would be sufficient to removethe hysteresis. After pre-straining thespecimens, the gages were appliedand testing proceeded. Each reportedmodulus of elasticity represents theaverage of three tests.

8.6 Comparison of physicalproperties to otherstainless steels

Table 17 provides a comparison ofphysical properties reported inSections 8.1 to 8.5 for alloy 19D totypes 304/304L, 316/316L, 2205 and2507 stainless steels. The data forthe other stainless steels wereobtained from the product data sheetsof various strip suppliers. Asdiscussed in Section 1.1 thecoefficient of expansion is lower andthe thermal conductivity is higher forduplex stainless steels as comparedto the austenitic stainless steels. Thisoffers design advantages.

9. Mechanical properties

The mechanical properties of stripsplice, longitudinal seam, and orbitalweld samples were evaluated. Theevaluations consisted of tensile,hardness, rotational fatigue and bursttests. Tensile tests at ambienttemperature were performed on allweld types from each of the heats.Additional tensile tests at varioustemperatures were performed on allthree weld types from heat 301000.Hardness testing was performed onthe longitudinal seam weld from eachof the heats. Additional hardnesstests, including weld cross sectiontraverses, were performed on allthree weld types for heat 301000.Burst testing was performed on allweld types for each of the heats.Rotational fatigue testing wasperformed on all weld types for heat301000.

All testing was performed on 0.625-in.OD x 0.065-in. wall thickness (15.9-mm x 1.7-mm) tubing. Testspecimens generally consisted of 12-in. (304.8 mm) long sections for thetensile, hardness and burst tests. Thespecimens used for tensile testing atvarious temperatures were 8-in.(203.2 mm) long, with 4-in. (101.6mm) between the grips and a 2-in.(50.8 mm) gage length. Thespecimens for rotational fatiguetesting were 33.5 in. (850 mm) long.For specimens with a strip splice ororbital weld, the weld was located atapproximately the center of the testspecimen.

9.1 Tensile test data forproduction heats

Tensile testing was performed inaccordance with ASTM A 370 [ref.17]. The ultimate tensile strength(UTS), 0.2% yield strength (YS) andelongation (E) in 2-in. (50.8-mm) weredetermined. Tensile test data arereported in Tables 18 to 20.

Table 18 reports data for strip splicewelds and is based upon the averageof two samples produced at the startof each new heat. Tables 19 and 20provide data from a larger populationof seam welded tubing and orbitalweld samples. The data for the tubingwas generally taken from a sample atthe start of every fourth mill coil. Thedata for the orbital welds represents asample taken from the end of eachreel. The average, 95% confidenceinterval, maximum, and minimumvalues for each of the tensileproperties are reported for the tubingand orbital welds in Tables 19 and 20.

It should be noted that therequirements listed for alloy 19D inthese tables are based upon subseaumbilical specifications in effect whenthe tubing was manufactured.Changes have recently been made tosubsea umbilical specifications withregard to the minimum UTS and themaximum hardness. The minimumUTS has been changed from 100,000to 110,000 psi (690 to 758 MPa). Themaximum hardness has beenchanged from 25 to 30 HRC.

Prior to discussing the tensile testdata, it is important to consider theissue of appropriate design minimumUTS, YS and E values for alloy 19Dtubing containing all three weld types.As will be discussed in detail, theautogenous orbital weld, when testedin uniaxial tension transverse to theweld, exhibits the lowest tensileproperties. Since prudent designmethodology dictates the use ofproperties reflective of the “weakestlink”, it would seem appropriate tobase the design minimum values forsubsea umbilical tubing upon theorbital weld. From this perspective,certain current minimum requirementsand the recent increase in UTS do notappear to be appropriate. Based uponthe orbital weld, appropriate designminimum values would be:UTS: 100,000 psi (690 MPa)YS: 70,000 psi (483 MPa)E: 10%.

All samples representing the threeweld types exceeded the minimumUTS requirement in effect at the timeof manufacture. All tests for stripsplice and longitudinal seam weldsamples also exceeded the new UTSrequirement. The orbital welds for sixof the heats had UTS values belowthe new requirement. The averageUTS values for all orbital weld heatswere above the new requirement.

All strip splice and longitudinal seamweld samples exceeded the minimumYS requirement. Orbital weld YS metthe minimum requirements for someheats and did not for others. For sixheats (391666, 201595, 410111,410434, 310426 and 410754), allsamples exceeded the minimum YSrequirement. For three of the fiveheats with samples below theminimum YS (301000, 201596 and310106), the average value exceededthe minimum requirement, with atleast one sample below the minimum.Two heats (410078 and 201694) hadaverage YS values below theminimum requirement.

The elongation for all longitudinalseam weld samples exceeded the

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minimum requirement. The elongationfor the strip splice and orbital weldsgenerally did not meet the minimumrequirement.

The reasons for the low yield strengthof the orbital welds and the lowelongation of strip splice and orbitalwelds are related to the lowerstrength of the autogenous weldmetal and the orientation betweenthese welds and the applied tensilestress. Autogenous girth welds aregenerally expected to experiencestrain accumulation within the weldmetal during tensile loadingtransverse to the weld. Such loadingis applied to these girth welds duringa uniaxial tensile test.

The strip splice weld, due to its helicalorientation, is expected to exhibitbehaviour that represents acomposite of base metal and weldmetal properties. As a result, the yieldstrength for the strip splice weldsexceeded the minimum, while that forthe orbital welds did not. Specifically,the yield strength of the as-cast weldstructure of the autogenous weld isexpected to be lower than that of thebase metal. The strain for the orbitalweld concentrates solely in the weldmetal, while that for the strip spliceweld is shared between base metaland weld metal. As a result, the yieldstrength for the strip splice weld tendsto be higher.

The same concept applies to theelongation. However, the elongationdata for the strip splice welds alsoexhibited low values. This is due tothe nature of how the strip splice weldfails and the operationalcharacteristics of the tensile testequipment. When the strip splice weldfails during a uniaxial tensile test, itfirst separates in the center of thehelical shaped weld. The failure thenpropagates through the strip spliceweld metal in two directions followinga helical orientation towards the twopoints of intersection with thelongitudinal seam weld. In someinstances, the tensile test equipmentwill terminate the test shortly after theinitial rupture, but before the finalligament fails at the intersection withthe longitudinal seam weld. In thesesituations, the elongation may belower than those cases where thesample has separated into twopieces.

When considering the reduced yieldstrength and elongation associatedwith the strip splice and orbital welds,it is important to recognize that theyresult from the fact that the welds areautogenous. In Section 9.7 thesuperior rotational fatigue behaviour

of these welds is attributed to theiruniform geometry which resultsdirectly from the fact that the weldsare autogenous. One can thereforeview the reduced yield strength andelongation as a trade-off for improvedfatigue performance.

9.2 Tensile test data as afunction of temperature

Tensile tests at various temperatureswere performed on tubing samplescontaining each of the three weldtypes. The yield strength (0.2% and1% offset methods), ultimate tensilestrength, and elongation in 2 in. (50.8mm) were determined in accordancewith ASTM A 370 [ref. 17], E 8 [ref.18] and E 646 [ref. 19] for testtemperatures of – 20, + 22 and +100°C (– 4, 72, and 212°F). The testtemperature tolerance was ± 5°C (±9°F). The results are reported inTable 21 along with the ambienttemperature requirements of subseaumbilical tubing specifications ineffect when the tubing wasmanufactured. The testing wasperformed by AK Steel.

The test results reflect the expectedchanges in tensile behaviour as thetest temperature is varied above andbelow ambient conditions. The dataappear relatively consistent except forone orbital weld tested at – 20°C (–4°F). No explanation is offered for theapparent low UTS and elongationassociated with this test.

9.3 Assessment of the degreeof cold work during tubingmanufacturing

Table 22 provides a comparison oftensile test data for tubing fromvarious stages in the manufacturingprocess at Gibson Tube. Data forthree of the four process stages arebased upon only one test, while thatfor one stage was based upon 22samples. All data is from one heat,number 310106. The purpose of thistesting was to identify the degree ofcold working/strain hardeningresulting from the Gibson Tubemanufacturing process. It should benoted that the data for the strip is asreported by AK Steel, while the datafor the tubing was based upon testingby Gibson Tube. When comparing thetubing after final reeling with the strip,the data show an increase ofapproximately 9,300 psi (64 MPa) inultimate tensile strength, no increasein yield strength and a 3 percentagepoint decrease in elongation. Oncethe tubing is coiled at the mill, thetensile behaviour remained relatively

constant throughout the remainingmanufacturing stages.

It should be noted that Gibson Tubehas made a conscious effort tominimize the degree of cold workingof the tubing during the manufacturingstages. Two strategies were used toaccomplish this objective. First, thetubing is coiled off the mill to adiameter ranging from 5 to 7-ft. (1.5 to2.1 m) to minimize strain. Second, bycombining the final eddy current testwith the final reeling operation, themill coil is only uncoiled andstraightened once before final reeling.

Table 23 compares tensile test datarepresenting manufacturing stages atGibson Tube and SeaCAT. The datafor Gibson Tube are based upon 20tests while that for SeaCAT are basedupon two tests. The data are againfrom one heat, number 201595. Thepurpose of this data was to identifythe degree of cold work resulting fromthe SeaCAT manufacturing process.When comparing tubing after theGibson Tube mill coiler with that afterthe SeaCAT final acceptance test, thedata show an increase ofapproximately 3,400 psi (23 MPa) inultimate tensile strength, an 800 psi(5.5 MPa) increase in yield strengthand a 2.6 percentage point decreasein elongation.

9.4 Hardness data forproduction tubing

Hardness measurements were madeat both ends of all mill coils inaccordance with ASTM A 370 [ref.17]. The average hardness, 95%confidence interval, maximum, andminimum values were determined foreach heat.

The data are summarized by heat for950+ mill coils in Table 24. As shown,the average hardness for all heats isslightly below the maximumrequirement for subsea umbilicaltubing in effect at the time ofmanufacturing. However, themaximum values for eight of theeleven heats exceed the limit of HRC25. As previously discussed, themaximum hardness requirement inthe specification for subsea umbilicaltubing is being increased to HRC 30.None of the tubing exceeds thisvalue.

9.5 Additional hardnesstesting and traverses

Five Vickers hardness HV 10(nominal test force = 98.97 N [22.25lbf]) test measurements were made

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on the outside surface of the sampleslisted below from heat 301000 inaccordance with ASTM E 92 [ref. 20].

Base metal region ~ 180° away fromthe LSW on two LSW samples

LSW weld metal region on two LSWsamples

SSW weld metal region on two SSWsamples

OW weld metal region on two OWsamples

This testing was performed by AKSteel. The average, minimum andmaximum values for the fivemeasurements are reported inTable 25. Conversion of the HV 10hardness measurements to HRCresults in all values being less thanthe maximum hardness requirementof HRC 25 in effect at the time thetubing was manufactured.

A series of Vickers hardness HV 0.5(nominal test force = 4.903 N [1.10lbf]) test measurements were madeon cross sections of all three weldtypes from heat 301000 inaccordance with ASTM E 384 [ref.21]. Each traverse was perpendicularto the axis (direction of travel) of theweld. The traverses were performedat approximately mid-thickness andconsisted of 26 measurementsspaced at approximately 0.020-in.(0.5 mm) arc distance increments.These traverses started in the basemetal on one side of the weld 0.25-in.(6.35 mm) from the weld centerlineand terminated at the same distanceon the opposite side of the weld. Thistesting was performed by AK Steel.The results are reported in Tables 26,27 and 28. In addition, the data fromTables 26 to 28 are plotted in Figures7, 8, and 9.

As expected, the hardness of theweld metal was lower than that of thebase metal. The orbital welds had thelowest and most consistent hardnessvalues. The higher and lessconsistent hardness values of thestrip splice and longitudinal seamwelds is attributed to the effects offorging and roll sizing.

9.6 Comparison of tensile andhardness properties toother stainless steels

The tensile and hardnessrequirements for alloy 19D seamwelded tubing are compared to thoseof two duplex (2507 and 2205) andtwo austenitic (304L and 316L)stainless steels in Table 29. Note that

for alloy 19D both the requirements ofASTM A 789 and the recommendeddesign requirements for subseaumbilical tubing based upon theorbital weld are included. Also notethat two UNS designations for alloy2205 (S32205 and S31803) arelisted. As shown in the table, theminimum required tensile strength foralloy 19D umbilical tubing issomewhat less than that of alloy 2507and greater than alloy 2205, UNSdesignation S32005. However, basedupon Gibson Tube’s extensiveexperience manufacturing S32205seam welded tubing, the tensilestrength, yield strength and hardnessare expected to be slightly higherthan those for alloy 19D, while itselongation would be slightly lower.The significant strength advantage ofalloy 19D tubing over the twoaustenitic grades is readily apparent.

9.7 Rotational fatigue testing

Rotational fatigue testing wasperformed on all three weld typesfrom heat 301000. Thirty tests wereplanned for each of the three weldtypes, with ninety total tests. To date,sixty tests have been completed,twenty-four longitudinal seam,eighteen strip splice and eighteenorbital welds.

Duco Ltd. performed the testing.During a test, the tubing is bent toproduce the desired stress level onthe outside surface of the tubing. Astrain gauged sample was bent tovarious diameters and used to directlymeasure the stress on the outsidesurface. From this data, a calibrationcurve was determined and used toset the degree of bending needed toachieve the desired stress duringtesting. For all tests, the tubing wasrotated at a maximum rate (RPM)such that the temperature of the testspecimen remained below 25°C(77°F) during the test. The rotation ofthe tubing produces fully reversedfatigue loading.

The stress range versus number ofcycles to failure (SN) curves areplotted in Figures 10, 11, and 12 forthe longitudinal seam (LSW), stripsplice (SSW), and orbital welds (OW)respectively. Only a linear regressionfit of the data and the upper and lower95% confidence limits (CL) areplotted in each of these figures. Theregression analysis and subsequentplotting of the linear fit and confidencelimits were performed usingOriginLabTM version 6.1 software. Theconfidence limit represents a centralconfidence interval on the meannumber of cycles to failure at

particular values along the fit line. Ineffect, the width of the intervalprovides an indication of how goodthe estimate of the mean was atparticular points along the fit line. Thelinear regression analysis includedonly data points where failureoccurred. The number of data points,by weld type, used in each of thethree separate regression analyseswas as follows: LSW: 24, SSW: 13,OW: 12. Data points where the testwas stopped before failure were notincluded in the regression analysis.

The B-curve from Table 8.4.1.b inNorwegian Standard NS 3742 E [ref.22] has also been plotted in Figures10 through 12. The B-curve isdescribed by Equation (2) andprovides a characteristic SN curve forstructures in sea-water with cathodicprotection. The B-curve allows thehighest stress range and is basedupon a constant stress range of 48MPa (7,000 psi) beyond 2 x 108

cycles to failure. This curve isapplicable to full penetration buttwelds with the weld finished flush withthe surface. The weld is assumed tobe free of significant defects basedupon the use of non-destructiveexamination. The B-curve is thereforeapplicable to the three types of weldsfound in alloy 19D seam weldedtubing.

N = 10(15.01 – 4 log (∆σ)) (2)

Where:N = number of cycles to failure∆σ = fully reversed stress range

All alloy 19D data points (failed andstopped) and fit lines were well abovethe B-curve indicating that all threeweld types exceeded the moststringent design criteria. In addition,the rotational fatigue performance ofall three weld types is very similar.The current fit suggests that at highstress the strip splice weld may havethe limiting lower bound while at lowstress the orbital weld may have thelimiting bound. This relativepositioning of the linear data fit isrelated to the number of failure datapoints at low stress. Specifically, onlythe strip splice weld has a failure datapoint greater than 106 cycles. Thedata also suggest that the endurancelimit for the strip splice and orbitalwelds may be as high as 400 MPa(58,000 psi). Note that this comparesto an endurance limit of 48 MPa(7,000 psi) for the design curve. It isplanned to continue the stopped teststo help establish the endurance limit.The remaining thirty tests (6 LSW, 12SSW and 12 OW) are planned to bothdevelop more data in the range of 104

to 107 cycles to failure and establish

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the endurance limit.

Current specifications for alloy 19Dsubsea umbilical tubing do not allowthe use of orbital welds in thedynamic section. Based upon thesimilar performance of all three weldtypes, it appears appropriate to useboth alloy 19D strip splice and orbitalwelds in the dynamic section.

It would be desirable to compare thefatigue performance of orbital weldsin seamless super duplex stainlesssteel (SDSS) umbilical tubing to thoseof alloy 19D. Unfortunately, no openliterature data for representativeautomatic orbital welds in SDSStubing were available for comparison.A significant number of orbital welds,one every 30 to 40 m (98 to 131 ft.),must be present in the dynamicsection for any seamless SDSSumbilical tubing. Since these weldsare likely to use added filler metal,their fatigue performance may beadversely influenced by the geometryof the weld. While specific data werenot available, it was reported [ref. 23]that two curves describe a region ofdesign SN curves for orbital welds inseamless SDSS. The differencesbetween the curves in the regionreportedly [ref. 23] relate to differenttubing dimensions (diameter and wallthickness) and testing methods.The curves are based upon Equation(3) and represent the minus twostandard deviation (– 2SD) limit forthe “best” (upper curve) and “worst”(lower curve) sets of data within theregion.

Log (N) = Log (a) – 2SD – 4Log (?s) (3)

Where:N = number of cycles to failureLog (a) = mean value of interceptSD = standard deviation of Log (a)?s = fully reversed stress range

The lower curve (worst) is the B-Curve (intercept 15.01, slope – 4) andthe upper curve (best) has anintercept of 16.5 and slope – 4. Thesecurves were determined by a linearregression analysis in which the slopeof the fit was forced to use – 4. Inorder to compare the alloy 19D weldsto these bounds, linear regressionanalyses were performed using theforced slope of – 4.Using the intercept and standarddeviation from this regressionanalysis and Equation (3), the – 2SDlimits were determined and areplotted in Figure 13 for each of thethree alloy 19D weld types. Theresulting intercepts for the three alloy19D welds were LSW: 16.33, SSW:16.51, and OW: 16.30. The upper andlower bound curves for the 2507

orbital welds have also been plottedin Figure 13 and identified as – 2SDLimit 2507 OW “Worst” and “Best”Data Set respectively.

Figure 13 demonstrates that the –2SD limit curves for all three alloy19D welds fall within the upper 15%of the region of design SN curves forthe 2507 orbital welds.The – 2SD limit curve for the alloy19D strip splice weld was the highestand slightly above that for the upper2507 orbital weld curve.The – 2SD limit curves for the alloy19D longitudinal seam and orbitalwelds were slightly below the upper2507 orbital weld curve.This relative positioning is related tothe effect of both forcing the slope to– 4 and the standard deviation.It should be noted that this treatmentof the data provides a differentrelative comparison than thestatistical treatment used in Figures10 through 12.Observing where actual data pointslie (both for alloy 19D and 2507) isalso illuminating.

Although the actual data points arenot plotted, below approximately 590MPa (85,500 psi) all alloy 19D stripsplice and orbital weld data (bothfailed and stopped tests) exhibithigher fatigue strength than the2507 orbital weld upper – 2SD limitcurve.It should be noted that the lowercurve cut-off for the 2507 data was200 MPa (29,000 psi) and the uppercurve cut-off was 400 MPa(58,000 psi). Although alloy 19D stripsplice and orbital welds above590 MPa (85,500 psi) were slightlybelow the 2507 orbital weld upper –2SD limit curve, it reasonable toexpect that they exceed comparableSDSS orbital weld data. The higherfatigue strength of the autogenousalloy 19D girth welds (strip splice andorbital) results from their uniformgeometry.

Regrettably, the inability to directlycompare data points has hindered thecomparison between alloy 19D and2507. In addition, it is recognized thatgood engineering practice suggestsproceeding with caution regarding thedesign of the dynamic section of anumbilical. However, on the basis ofthe available comparison it isreasonable to conclude that the alloy19D girth welds (strip splice andorbital) exhibit similar if not superiorfatigue performance compared to the2507 orbital welds. It therefore doesnot appear reasonable to allow alarger number of welds with similar orpotentially lower fatigue performance(orbital welds in SDSS) while

excluding a smaller number of weldswith demonstrated similar if not higherfatigue performance (orbital welds inalloy 19D). Fatigue testing is currentlybeing performed on an umbilicalmock-up with autogenous alloy 19Dorbital welds. The results of thistesting should provide additionalinsight.

9.8 Burst testing

Two samples for each of the threeweld types were burst tested for eachproduction heat. The samples wereremoved prior to the coiling operationat the tube mill.Tap water was used as the testmedia. Beginning at 0 psig, thepressure was increased in incrementsof 5,000 psig (34.5 GPa), held for oneminute and then increased until thepressure reached approximately 80%of the calculated burst pressure(CBP).The pressure was then increased inincrements of 1,000 psig (6.9 GPa)until the sample burst. The burstpressure and the region of the samplewhere the failure occurred weredetermined. A pressure versus timeplot was recorded for each sampleusing a digital video recorder.

The CBP was based upon Equation(4). This equation is derived from adraft ISO standard for subsea controlumbilicals [ref. 24]. It is specificallyderived from an equation in thisstandard used to calculate themaximum hoop stress at the bore fortubing with Do/tnom ≤ 20, where Do isthe nominal outside diameter and tnomis the nominal wall thickness. Thisequation provides a conservativerepresentation of the stress conditionin comparison to the von Misesequivalent stress. Since the vonMises equivalent stress is still basedupon the maximum stress at theinside surface, the actual burstpressure will be higher due to thelower average stress across the wallthickness.

CBP = (UTSmin x [(ODnom)2 –(IDnom)2])/[(ODnom)2 + (IDnom)2] (4)

Where:UTSmin = minimum ultimate tensilestrength (psi)ODnom = nominal outside diameter (in.)IDnom = nominal inside diameter (in.)

The results of the burst testing areshown in Table 30. Using theminimum UTS in effect at the timethat the tubing was manufactured andthe nominal tubing dimensions, theCBP for the tubing is 22,906 psi (158MPa) based upon Equation (4) and20,088 psi (139 MPa) based upon the

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von Mises equivalent stress.It is important to note that the CBPdoes not represent a minimumrequired burst pressure. It is simplyan estimate of the burst pressuresubject to the limitations of the threeinputs: predicted stress state, ultimatetensile strength and tubingdimensions. While each customerestablishes specific minimumrequired burst pressures, it isexpected that these minimumrequired values will be less than theCBP by a desired safety margin.

The results shown in Table 30indicate that the burst pressure for allof the tubing tested was in excess ofthe CBP using the minimum UTS ineffect at the time of manufacture.Using the recently increasedminimum UTS, the CBP for the tubingis 25,196 psi (174 MPa) based uponEquation (4) and 22,097 psi (152MPa) based upon the von Misesequivalent stress. Only one of thesixty-six burst tests did not exceedthe CBP calculated using Equation(4). Considering that the minimumrequired burst pressure will besignificantly less than the CBP(calculated by either method), theburst pressure for all tubing tested isexpected to readily exceed anyminimum requirements.

10. Conclusions

1. Seam welded alloy 19D tubingoffers advantages over otherduplex and austenitic stainlesssteels.

2. The lean composition of alloy19D results in lower cost andessentially no propensity to formdetrimental intermetallic phases.

3. As a duplex stainless steel alloy19D offers both increasedmechanical properties andresistance to chloride stresscorrosion cracking compared toaustenitic stainless steels.

4. Although the corrosion resistanceof alloy 19D is reduced due to itslean composition, a continuousextruded external zinc anode orother means can be used toprovide the required externalcorrosion resistance while itsinternal corrosion resistance isadequate for expected umbilicaltubing service.

5. Extensive testing of seam weldedalloy 19D tubing and allassociated welds from elevenproduction heats demonstrateddesirable dimensional,

microstructural, and mechanicalproperties.

6. It appears appropriate to basedesign minimum tensile testrequirements for subseaumbilical tubing on the orbitalweld.

7. Rotational fatigue testing of thethree weld types in alloy 19Dtubing demonstrated consistentbehaviour, well above thestandard design curve used forumbilical tubing.

8. The rotational fatigue behaviourof alloy 19D orbital welds wascomparable to that of alloy 19Dstrip splice and longitudinal seamwelds and 2507 orbital welds. Asa result, it appears reasonable toallow the use of alloy 19D orbitalwelds in the dynamic section ofumbilical tubing.

9. Seam welded alloy 19D tubingenables the production of longcoils for subsea umbilical tubingapplications with desirableproperties and a greatly reducednumber of girth welds whencompared to seamless tubing.

Acknowledgements

Many personnel at Gibson Tubecontributed to this effort. Phil Lewis ofSeaCAT Corporation was the drivingforce behind the application of seamwelded alloy 19D tubing for subseaumbilical applications. RichardFletcher of TWI Ltd. directed theporosity acceptance criteria program.John Tack directed the various testingperformed by AK Steel. Rotationalfatigue testing was directed by PeterFellows of Duco Ltd. In addition,Peter Fellows graciously shared hisknowledge of umbilical tubing designand provided guidance with regard tovarious issues, especially the designof the porosity acceptance testprogram. Knut Ekeberg, TorfinnOttesen and Stian Karlsen, NexansNorway AS, demonstrated greatpatience and persistence indescribing their design SN curves fororbital welds in alloy 2507 tubing.

References

[1] AK Steel, Product Data BulletinNitronic 19D, October 2000.

[2] J.W. McEnerney, Alloy 19D(UNS S32001) seam welded leanduplex stainless steel tubing,paper number P0117, StainlessSteel World 2001 Conference,The Hague, the Netherlands,

November 13-15, 2001.[3] V.T. Williams and C.M. Ross,

“Technical ImprovementsIncorporated in One Company’sSubsea Umbilical andDistribution Systems”, PaperNumber OTC 13121, presentedat the 2001 Offshore TechnologyConference, Houston, Texas,April 30 to May 3, 2001.

[4] ASTM A 240/A 240M-00,“Standard Specification for Heat-Resisting Chromium andChromium-Nickel Stainless SteelPlate, Sheet, and Strip forPressure Vessels”, 2001 AnnualBook of ASTM Standards, Vol.01.03, Steel- Plate, Sheet, Strip,Wire; Stainless Steel Bar,American Society for Testing andMaterials.

[5] Section IX, Welding and BrazingQualifications, ASME Boiler andPressure Vessel Code, 1998Edition.

[6] ASTM A 789/A 789M-01a,“Standard Specification forSeamless and WeldedFerritic/Austenitic Stainless SteelTubing for General Service”,2001 Annual Book of ASTMStandards, Vol. 01.01, Steel-Piping, Tubing, Fittings,American Society for Testing andMaterials.

[7] Section V, NondestructiveExamination, Article 2,Radiographic Examination,ASME Boiler and PressureVessel Code, 1998 Edition.

[8] BS EN 462-3: 1997, Non-destructive testing – Imagequality of radiographs, Part 3.Image quality classes for ferrousmetals, British StandardsInstitute, 1997.

[9] BS EN 462-1: 1994, Non-destructive testing – Imagequality of radiographs, Part 1.Image quality indicators (wiretype) – Determination of imagequality value, British StandardsInstitute, 1994.

[10] ASTM E 747-97, “StandardPractice for Design, Manufactureand Material GroupingClassification of Wire ImageQuality Indicators (IQI) Used forRadiology”, 2000 Annual Book ofASTM Standards, Section Three,Metals Test Methods andAnalytical Procedures, Volume03.03, Nondestructive Testing,American Society for Testing andMaterials, 2000.

[11] ASME B46.1-1995 (Revision ofANSI/ASME B46.1-1985),Surface Texture (SurfaceRoughness, Waviness, and Lay),The American Society ofMechanical Engineers, 1995.

[12] ASTM 562-99, “Standard Test

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Method for Determining VolumeFraction by Systematic ManualPoint Count”, 2000 Annual Bookof ASTM Standards, Vol. 03.01,Metals- Mechanical Testing;Elevated and Low-TemperatureTests; Metallography, AmericanSociety for Testing and Materials.

[13] ASTM B 311-93 (1997), “TestMethod for DensityDetermination for PowderMetallurgy (P/M) MaterialsContaining Less than TwoPercent Porosity”, 2001 AnnualBook of ASTM Standards, Vol.02.05, American Society forTesting and Materials.

[14] ASTM E 1461-92, “Test Methodfor Thermal Diffusivity of Solidsby the Flash Method”, 2000Annual Book of ASTMStandards, Vol. 14.02, AmericanSociety for Testing and Materials.

[15] ASTM E 228-95, “Test Methodfor Linear Thermal Expansion ofSolid Materials With a VitreousSilica Dilatometer”, 2000 AnnualBook of ASTM Standards, Vol.14.02, American Society forTesting and Materials.

[16] ASTM E 111-97, “Standard TestMethod for Young’s Modulus,Tangent Modulus, and ChordModulus”, 2001 Annual Book ofASTM Standards, Vol. 03.01,Metals – Mechanical Testing;Elevated and Low-TemperatureTests; Metallography, AmericanSociety for Testing and Materials.

[17] ASTM A 370-97a, “Standard TestMethods and Definitions forMechanical Testing of SteelProducts”, 2001 Annual Book ofASTM Standards, Vol. 01.03,Steel- Plate, Sheet, Strip, Wire;Stainless Steel Bar, AmericanSociety for Testing and Materials.

[18] ASTM E 8-00, “Standard TestMethods for Tension Testing ofMetallic Materials”, 2001 AnnualBook of ASTM Standards, Vol.03.01, Metals – MechanicalTesting; Elevated and Low-Temperature Tests;Metallography, American Societyfor Testing and Materials.

[19] ASTM E 646-98, “Standard TestMethod for Tensile Strain-Hardening Exponents (n-Values)of Metallic Sheet Materials”, 2001Annual Book of ASTMStandards, Vol. 03.01, Metals –Mechanical Testing; Elevatedand Low-Temperature Tests;Metallography, American Societyfor Testing and Materials.

[20] ASTM E 92-82, “Standard TestMethod for Vickers Hardness ofMetallic Materials”, 2001 AnnualBook of ASTM Standards, Vol.03.01, Metals – MechanicalTesting; Elevated and Low-

Temperature Tests;Metallography, American Societyfor Testing and Materials.

[21] ASTM E 384-99, “Standard TestMethod for MicroindentationHardness of Materials”, 2001Annual Book of ASTMStandards, Vol. 03.01, Metals –Mechanical Testing; Elevatedand Low-Temperature Tests;Metallography, American Societyfor Testing and Materials.

[22] Norwegian Standard NS 3472 E,Steel structures Design rules, 2nd

edition June 1984.[23] Private communications with

Knut Ekeberg, Torfinn Ottesenand Stian Karlsen, NexansNorway AS, October 3-5, 2001.

[24] ISO/DIS 13628-5, Petroleum andnatural gas industries – Designand operation of subseaproduction systems – Part 5:Subsea control umbilicals, Draft.

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Figures:

Figure 1: Typical forged longitudinal seam weld cross section showing uniformweld geometry on the outside and inside surfaces. The sample wasremoved from one end of a production mill coil of 0.625-in. OD x0.065-in wall thickness(15.7-mm x 1.7-mm) tubing. Electrolyticallyetched in a NaOH solution.

Figure 2: Typical microstructure of strip, electrolytically etched in a NaOHsolution, dark etching phase is ferrite.

Figure 3: Typical microstructure of strip splice weld (weld metal), electrolyticallyetched in a NaOH solution, dark etching phase is ferrite.

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Figure 4: Typical microstructure of longitudinal seam weld (weld metal),electrolytically etched in a NaOH solution, dark etching phase isferrite.

Figure 5: Typical microstructure of welded tubing base metal, electrolyticallyetched in a NaOH solution, dark etching phase is ferrite.

Figure 6: Typical microstructure of orbital weld (weld metal), electrolyticallyetched in a NaOH solution, dark etching phase is ferrite.

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200

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250

260

270

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300

-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25

Position Relative to Weld Centerline (in)

Har

dnes

s (H

V 0

.5)

Base Metal Base MetalLSWHAZ HAZ

Figure 7: Vickers hardness HV 0.5 test measurements at mid-thickness across longitudinal seam weld crosssections.

Figure 8: Vickers hardness HV 0.5 test measurements at mid-thickness across strip splice weld cross sections.

200

210

220

230

240

250

260

270

280

290

300

-0,3 -0,2 -0,1 0 0,1 0,2 0,3


Har

dnes

s (H

V 0

.5)

Base Metal SSW Base MetalHAZ HAZ

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Figure 9: Vickers hardness HV 0.5 test measurements at mid-thickness across orbital weld cross sections.

Figure 10: Stress range versus cycles to failure (SN) for rotational fatigue testing of alloy 19D tubingsamples from heat 301000 with only the longitudinal seam weld (LSW). The B-curve represents acharacteristic SN design curve for structures in sea-water with cathodic protection based upon NS3472E.

200

210

220

230

240

250

260

270

280

290

300

-0,3 -0,2 -0,1 0 0,1 0,2 0,3


Har

dnes

s (H

V 0

.5)

Base Metal Base MetalOWHAZ HAZ

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Figure 11: Stress range versus cycles to failure (SN) for rotational fatigue testing of alloy 19D tubingsamples from heat 301000 with a strip splice weld (SSW) at the center. The B-curve represents acharacteristic SN design curve for structures in sea-water with cathodic protection based upon NS3472E.

Figure 12: Stress range versus cycles to failure (SN) for rotational fatigue testing of alloy 19D tubingsamples from heat 301000 with an orbital weld (OW) at the center. The B-curve represents acharacteristic SN design curve for structures in sea-water with cathodic protection based upon NS3472E.

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Figure 13: Stress range versus cycles to failure (SN) for rotational fatigue testing of alloy 19D tubingsamples from heat 301000. The –2SD limit curves are plotted for all three alloy 19D welds types:samples with only the longitudinal seam weld (LSW), samples with a strip splice weld at thecenter (SSW), and samples with an orbital weld at the center (OW). Upper (best) and lower(worst) –2SD limit curves for a region of design SN curves for 2507 orbital welds are also plotted.

Tables:

Element Weight %Spec. /Heat No. C Cr Mn Mo N Ni P S Si Cu

A 240S32001

0.030max.

19.5 -21.5

4.0 -6.0

0.60max.

0.05 –0.17

1.0 –3.0

0.040max.

0.030max.

1.00max.

1.00max.

391666 0.026 19.84 5.18 0.09 0.129 1.67 0.026 0.0013 0.38 0.35

301000 0.024 19.83 5.06 0.06 0.140 1.68 0.024 0.0011 0.41 0.32

201595 0.025 19.75 5.07 0.07 0.137 1.70 0.022 0.0005 0.40 0.23

201596 0.027 19.76 5.07 0.05 0.142 1.65 0.022 0.0008 0.38 0.23

410078 0.025 19.76 4.96 0.03 0.134 1.70 0.021 0.0009 0.37 0.29

201694 0.026 19.72 5.11 0.10 0.144 1.71 0.020 0.0008 0.39 0.29

310106 0.026 19.78 5.00 0.08 0.143 1.74 0.023 0.0007 0.38 0.24

410111 0.026 19.80 4.98 0.05 0.134 1.70 0.022 0.0007 0.39 0.26

410434 0.030 19.78 5.15 0.05 0.135 1.70 0.025 0.0005 0.40 0.30

310426 0.027 19.78 5.14 0.05 0.134 1.65 0.023 0.0007 0.38 0.33

410754 0.028 19.90 5.03 0.04 0.139 1.64 0.024 0.0007 0.39 0.21

Table 1: Chemical Composition of Alloy 19D Strip

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ASTM A 240 Element Weight % LimitUNS No.(Alloy) C Cr Mn Mo N Ni P S Si Cu

S32750(2507)

0.030max.

24.0 –26.0

1.2max.

3.0 –5.0

0.24 –0.32

6.0 –8.0

0.035max.

0.020max.

0.8max.

0.5max.

S32205(2205)

0.030max.

22.0 –23.0

2.00max.

3.0 –3.5

0.14 –0.20

4.5 –6.5

0.030max.

0.020max.

1.00max.

-

S32001(19D)

0.030max.

19.5 -21.5

4.0 -6.0

0.60max.

0.05 –0.17

1.0 -3.0

0.040max.

0.030max.

1.00max.

1.00max.

S31603(316L)

0.030max.

16.0 –18.0

2.00max.

2.0 –3.0

0.10max.

10.0 –14.0

0.045max.

0.030max.

0.75max.

-

S30403(304L)

0.030max.

18.0 –20.0

2.00max.

- 0.10max.

8.0 –12.0

0.045max.

0.030max

0.75max.

-

Table 2: Comparison of the Chemical Composition for Various Duplex and Austenitic Stainless Steel Alloys

UNS No. (Alloy) PRE RangeS32750 (2507) 37.74 to 47.62S32205 (2205) 34.14 to 37.75S31603 (316L) 22.60 to 29.50S32001 (19D) 20.30 to 26.20S30403 (304L) 18.00 to 21.60

Table 3: Comparison of the PRE Range for Various Duplex and Austenitic Stainless Steel Alloys

Heat No. UTSa (psi) 0.2 YSa (psi) E (%) HardnessASTM A 240UNS S32001

90,000min.

65,000min.

25min.

HRC 25max.

391666 115,300 87,400 38.3 HRB 99

301000 119,900 79,900 48.7 HRC 22301000 119,800 81,800 46.0 HRC 22301000 120,800 81,800 46.0 HRC 22

201595 113,600 84,000 42.7 HRC 20201595 115,000 85,800 41.7 HRC 20201595 113,800 83,900 41.4 HRC 19201595 113,300 85,100 41.9 HRC 21

201596 115,000 79,100 45.4 HRC 22201596 113,200 78,400 40.6 HRC 20

410078 113,800 79,600 41.8 HRC 20410078 113,600 81,300 41.9 HRC 21

201694 115,000 83,000 41.9 HRC 21201694 116,500 84,700 41.4 HRC 21

310106 115,600 78,400 43.9 HRC 21310106 117,500 85,100 45.1 HRC 20310106 115,000 81,900 41.8 HRC 21

410111 118,900 86,500 42.2 HRC 22410111 115,600 83,400 41.2 HRC 21

410434 123,400 87,600 40.8 HRC 21410434 116,600 82,100 41.0 HRC 21

310426 116,400 83,200 41.0 HRC 21

410754 120,900 92,400 38.8 HRC 22410754 119,900 84,500 41.9 HRC 22

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.

Table 4: Tensile and Hardness Test Data for Alloy 19D Strip

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Property / Heat Treatment Proposed RequirementTensile Strength, min, ksi [MPa] 90 [620]Yield Strength, min, ksi [MPa] 65 [450]Elongation in 2 in., min, % 25Hardness, max, HB 290Hardness, max, HRC 30Heat treatment temperature 1,800 – 1,950°F [982 – 1,066°C]Quench Rapid cooling in air or water

Table 5: Tensile, Hardness and Heat Treatment Requirements for UNS S32001 (Alloy 19D) Recently Added toASTM A 789

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Heat No. /Statistical Quantity

Outside Dia.Min. (in.)

Outside Dia.Max. (in.)

Wall ThicknessBase Metal (in.)

Wall Thicknessat Weld (in.)

ASTM A 789 Requirements 0.620–0.630 0.620–0.630 0.0585–0.0715 0.0585–0.0715Heat 391666 (84 Mill Coils)Average 0.6250 0.6265 0.0650 0.0654± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0001Maximum 0.6260 0.6280 0.0675 0.0685Minimum 0.6230 0.6250 0.0630 0.0630Heat 301000 (107 Mill Coils)Average 0.6243 0.6264 0.0658 0.0656± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0002Maximum 0.6260 0.6280 0.0680 0.0682Minimum 0.6230 0.6240 0.0635 0.0630Heat 201595 (79 Mill Coils)Average 0.6244 0.6264 0.0657 0.0651± 95% Confidence Interval 0.0002 0.0001 0.0001 0.0002Maximum 0.6260 0.6270 0.0674 0.0670Minimum 0.6220 0.6235 0.0648 0.0630Heat 201596 (113 Mill Coils)Average 0.6242 0.6263 0.0656 0.0650± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0001Maximum 0.6260 0.6280 0.0670 0.0675Minimum 0.6220 0.6250 0.0640 0.0628Heat 410078 (100 Mill Coils)Average 0.6242 0.6263 0.0658 0.0655± 95% Confidence Interval 0.0002 0.0001 0.0001 0.0001Maximum 0.6270 0.6280 0.0670 0.0674Minimum 0.6220 0.6250 0.0638 0.0635Heat 201694 (109 Mill Coils)Average 0.6238 0.6263 0.0655 0.0649± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0001Maximum 0.6260 0.6280 0.0680 0.0685Minimum 0.6240 0.6240 0.0630 0.0630Heat 310106 (85 Mill Coils)Average 0.6237 0.6264 0.0658 0.0652± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0001Maximum 0.6250 0.6280 0.0672 0.0686Minimum 0.6230 0.6250 0.0645 0.0635Heat 410111 (100 Mill Coils)Average 0.6244 0.6264 0.0657 0.0653± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0002Maximum 0.6260 0.6290 0.0670 0.0676Minimum 0.6230 0.6250 0.0638 0.0635Heat 410434 (109 Mill Coils)Average 0.6255 0.6273 0.0657 0.0654± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0001Maximum 0.6270 0.6280 0.0680 0.0695Minimum 0.6220 0.6240 0.0600 0.0600Heat 310426 (72 Mill Coils)Average 0.6252 0.6274 0.0657 0.0651± 95% Confidence Interval 0.0001 0.0001 0.0001 0.0002Maximum 0.6270 0.6280 0.0673 0.0670Minimum 0.6240 0.6260 0.0640 0.0627Heat 410754 (14 Mill Coils)Average 0.6250 0.6274 0.0661 0.0654± 95% Confidence Interval 0.0004 0.0002 0.0002 0.0003Maximum 0.6260 0.6280 0.0670 0.0668Minimum 0.6240 0.6260 0.0650 0.0635

To convert from inches to mm, multiply by 25.4.

Table 6: Dimensional Data for Alloy 19D Seam Welded Tubing from Production Mill Coils

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Sample No. Orientation OutsideDiameter (in.)a

WallThickness (in.)a

Variation allowed byASTM A 789

0.620 to 0.630(± 0.005-in.)

0.0585 to 0.0715(± 10%)

LSW-10-114 Weld 0° 0.626 0.064LSW-10-114 45° 0.626 0.067LSW-10-114 90° 0.626 0.067LSW-10-114 135° 0.625 0.065LSW-10-114 180° 0.064LSW-10-114 225° 0.065LSW-10-114 270° 0.065LSW-10-114 315° 0.067

Avg. 0.626 0.066


Avg. 0.626 0.066


Avg. 0.625 0.065Notesa. To convert from inches to mm, multiply by 25.4.

Table 7: Additional Detailed Dimensional Analysis of Alloy 19D Tubing Samples From Heat 301000

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Sample No. Surfacea Orientation Ra

(µ in.)bRy

(µ in.)cRz

(µ in.)dRq

(µ in.)e

LSW-10-114 OD Weld 0° 14.7 129.5 104.2 18.9LSW-10-114 OD 90° 13.2 132.3 81.2 17.9LSW-10-114 OD 180° 3.9 32.7 24.9 5.1LSW-10-114 OD 270° 22.7 258.7 152.6 30.9

OD Avg. 13.6 138.3 90.7 18.2

LSW-10-114 ID Weld 0° 42.2 258.3 222.2 52.3LSW-10-114 ID 90° 9.8 94.1 73.1 12.7LSW-10-114 ID 180° 49.6 304.3 268.6 63.2LSW-10-114 ID 270° 14.1 118.9 93.1 18.0

ID Avg. 28.9 193.9 164.3 36.6


OD Avg. 12.4 149.3 95.3 17.5


ID Avg. 27.9 185.5 149.6 34.9


OD Avg. 15.9 139.6 117.2 22.3


ID Avg. 14.4 120.5 95.8 18.1

NotesOD = outside surface; ID = inside surface.Ra = arithmetic mean deviation of profile.Ry = maximum height of the profile.Rz = ten-point height of irregularities.Rq = root-mean-square deviation of the profile.To convert from inches to mm, multiply by 25.4.

Table 8: Surface Roughness Parameters for Alloy 19D Tubing Samples From Heat 301000

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Heat No. % Ferrite ± 95% CI % RAAima 45 to 50Acceptable Rangea 35 to 60391666 50.3 3.6 7.1301000 46.8 4.0 8.5201595 45.4 4.4 9.6201596 48.3 3.9 8.1410078 45.2 3.4 7.5201694 51.7 4.6 8.9310106 41.6 3.2 7.6410111 51.4 3.2 6.1410434 41.4 3.2 7.7310426 44.4 4.1 9.2410754 51.1 3.2 6.2

Notesa. The requirements are based upon current subsea umbilical tubing specifications.

Table 9: Ferrite Point Count Data for Alloy 19D Strip

Heat No. /Region Evaluated % Ferrite ± 95% CI % RA

Aima 45 to 50Acceptable Rangea 35 to 60Heat 391666Base metal 46.9 3.4 7.2Weld metal 49.9 4.6 9.2Heat 301000Base metal 43.3 3.5 8.1Weld metal 52.1 4.1 7.8Heat 201595Base metal 46.5 3.1 6.6Weld metal 49.5 3.8 7.7Heat 201596Base metal 47.0 3.3 7.1Weld metal 49.3 4.2 8.4Heat 410078Base metal 44.7 4.0 9.0Weld metal 49.8 4.0 8.0Heat 201694Base metal 47.4 2.5 5.3Weld metal 48.6 3.8 7.8Heat 310106Base metal 49.8 3.3 6.7Weld metal 51.0 3.8 7.5Heat 410111Base metal 49.7 3.9 7.9Weld metal 48.8 3.9 7.9Heat 410434Base metal 40.7 4.0 9.8Weld metal 44.6 2.6 5.8Heat 310426Base metal 44.3 3.2 7.2Weld metal 50.9 3.9 7.6Heat 410754Base metal 49.1 2.1 4.3Weld metal 50.6 2.1 4.3


Table 10: Ferrite Point Count Data for Alloy 19D Longitudinal Seam Welds

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Heat No. /Region Evaluated % Ferrite ± 95% CI % RA

Aima 45 to 50Acceptable Rangea 35 to 60Heat 391666Base metal 47.8 3.1 6.6Weld metal 47.3 2.7 5.7Heat 301000Base metal 42.1 3.8 9.2Weld metal 50.9 3.8 7.5Heat 201595Base metal 44.3 3.8 8.5Weld metal 49.8 3.9 7.9Heat 201596Base metal 44.4 3.4 7.7Weld metal 51.4 2.9 5.6Heat 410078Base metal 45.9 3.1 6.8Weld metal 50.0 3.5 7.0Heat 201694Base metal 44.8 4.1 9.2Weld metal 49.8 2.9 5.7Heat 310106Base metal 46.9 3.8 8.2Weld metal 50.5 3.6 7.1Heat 410111Base metal 48.8 2.9 5.9Weld metal 52.0 3.7 7.1Heat 410434Base metal 42.3 3.9 9.2Weld metal 45.2 3.3 7.3Heat 310426Base metal 45.0 3.0 6.6Weld metal 49.4 2.4 4.8Heat 410754Base metal 47.8 2.7 5.6Weld metal 53.6 3.3 6.1


Table 11: Ferrite Point Count Data for Alloy 19D Strip Splice Welds

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Heat No. /Region Evaluated

% FerriteRange ± 95% CIb % RAb

Aima 45 to 50Acceptable Rangea 35 to 60Heat 391666 (7 samples)Base metal 43.3 – 49.6 5.6, 5.1 12.8, 10.2Weld metal 41.1 – 48.6 3.3, 4.4 7.9, 9.0Heat 301000 (10 samples)Base metal 41.8 – 51.0 3.4, 3.5 8.1, 6.8Weld metal 39.1 – 48.0 3.8, 3.6 9.8, 7.5Heat 201595 (6 samples)Base metal 41.4 – 46.4 5.3, 5.0 12.6, 10.8Weld metal 44.1 – 50.6 3.4, 4.2 7.7, 8.3Heat 201596 (9 samples)Base metal 43.3 – 49.3 4.3, 3.7 10.0, 7.5Weld metal 41.0 – 46.6 4.4, 4.9 10.6, 10.4Heat 410078 (13 samples)Base metal 42.2 – 48.7 4.8, 3.2 11.4, 6.6Weld metal 39.0 – 48.9 3.7, 2.6 9.4, 5.3Heat 201694 (16 samples)Base metal 40.4 – 49.6 3.5, 4.6 8.8, 9.3Weld metal 40.9 – 51.6 3.4, 4.9 8.3, 9.4Heat 310106 (12 samples)Base metal 42.8 – 48.9 3.4, 3.3 7.9, 6.8Weld metal 38.9 – 48.1 3.1, 3.3 8.0, 6.9Heat 410111 (9 samples)Base metal 39.9 – 48.8 3.7, 3.5 9.4, 7.1Weld metal 47.6 – 53.9 3.6, 3.9 7.6, 7.1Heat 410434 (12 samples)Base metal 44.3 – 49.3 3.0, 2.5 6.8, 5.1Weld metal 43.7 – 50.4 2.4, 4.4 5.4, 8.7Heat 310426 (10 samples)Base metal 44.8 – 48.0 3.6, 2.9 8.0, 6.1Weld metal 43.9 – 50.5 3.4, 2.8 7.8, 5.5Heat 410754 (2 samples)Base metal 44.3 – 47.3 2.1, 2.4 4.7, 5.0Weld metal 47.2 – 47.6 3.3, 3.1 6.9, 6.5

Notesa. The requirements are based upon current subsea umbilical tubing specifications.b. Values corresponding to limits of % ferrite range.

Table 12: Ferrite Point Count Data for Alloy 19D Orbital Welds

Temperature(°C)

Specific Heat(J/g-K)

25 0.471260 0.548538 0.684

Table 13: Specific Heat Data For Alloy 19D Strip Samples from Heat 301000

Temperature(°C)

Thermal Conductivity(W/m-K)

25 15.9260 18.9538 22.9

Table 14: Thermal Conductivity Data for Alloy 19D Strip Samples from Heat 301000

Temperature(°C)

Coefficientof Thermal Expansion

(∆L/L/°C)− 20 14.11 x 10-6

+ 20 14.42 x 10-6

+ 100 15.04 x 10-6

Table 15: Coefficient of Thermal Expansion Data for Alloy 19D Strip Samples from Heat 301000

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Sample No. TestTemp. (°C)

Modulus ofElasticity (psi)a

LSW-10-108 − 20 30.2 x 106

LSW-10-109 − 20 30.3 x 106

LSW-10-106 + 21 29.1 x 106

LSW-10-107 + 21 31.3 x 106

LSW-10-110 + 100 28.5 x 106

LSW-10-111 + 100 31.9 x 106

Notesa. Average of three tests.

Table 16: Modulus of Elasticity Data For Alloy 19D Tubing Samples from Heat 301000

Alloy / Property 304 /304L

316 /316L 19D 2205 2507

Density(g/cm3) 7.94 8.03 7.77 7.85 7.80

Specific Heat(J/g-K) 0.500 0.450 0.471 0.470 0.470

Thermal Conductivity(W/m-K) 16.3 16.2 15.9 14.0 14.0

Coefficientof Thermal Expansion(∆L/L/°C) x10-6

16.6 16.5 14.4 13.7 13.5

Modulus of Elasticity(GPa) 193 200 208b 200 200

Notesa. Data reported are for a temperature of approximately 20°C.b. Data based upon seam welded tubing samples.

Table 17: Comparison of Physical Properties of Alloy 19D With Various Stainless Steels

Heat No. UTSa,b (psi) YSa,b (psi) Eb (%)

Requirementsc 100,000min.

80,000min.

25min.

391666 110,969 86,245 26.3301000 112,705 85,166 24.2201595 111,800 86,500 17.0201596 112,050 85,200 15.4410078 117,500 87,600 24.2201694 113,900 85,800 20.5310106 113,600 93,950 14.0410111 113,250 92,350 14.3410434 116,800 80,850 25.9310426 114,150 92,400 13.8410754 115,850 93,850 10.6

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. Average of two tests.c. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.

Table 18: Tensile Test Data for Alloy 19D Strip Splice Welds

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Heat / Statistical Quantity UTS (psi)a YS (psi)a E (%)

Requirementsb 100,000min.

80,000min.

25min.

Heat 391666 (71 Samples)Average 121,269 86,923 42.0± 95% Confidence Interval 779 1,053 0.7Maximum 132,173 99,107 47.0Minimum 113,793 80,000 31.0Heat 301000 (45 Samples)Average 123,209 87,832 42.7± 95% Confidence Interval 511 1,093 0.8Maximum 126,956 97,391 47.0Minimum 120,175 80,400 34.0Heat 201595 (20 Samples)Average 123,081 91,076 41.1± 95% Confidence Interval 1,063 1,955 1.2Maximum 128,800 97,413 44.0Minimum 118,803 82,500 34.8Heat 201596 (29 Samples)Average 125,260 86,473 41.6± 95% Confidence Interval 923 1,663 0.7Maximum 130,700 94,500 45.5Minimum 121,551 80,400 38.0Heat 410078 (23 Samples)Average 126,274 84,543 39.3± 95% Confidence Interval 862 1,227 1.1Maximum 129,900 92,500 44.2Minimum 121,800 80,500 33.4Heat 201694 (28 Samples)Average 123,425 85,631 40.4± 95% Confidence Interval 944 2,149 1.0Maximum 131,200 101,709 45.5Minimum 118,900 80,600 35.6Heat 310106 (22 Samples)Average 125,905 83,773 40.2± 95% Confidence Interval 846 1,087 0.9Maximum 130,100 89,000 43.8Minimum 122,200 80,100 34.0Heat 410111 (26 Samples)Average 125,262 83,981 39.2± 95% Confidence Interval 765 812 0.8Maximum 129,100 89,900 43.3Minimum 121,200 81,200 35.5Heat 410434 (28 Samples)Average 126,871 84,354 40.3± 95% Confidence Interval 1,011 1,372 0.8Maximum 132,500 94,600 43.7Minimum 122,000 80,200 34.2Heat 310426 (17 Samples)Average 127,271 83,824 39.5± 95% Confidence Interval 1,336 1,734 1.5Maximum 132,100 94,300 44.6Minimum 123,000 80,000 31.8Heat 410754 4( Samples)Average 125,600 84,500 40.2± 95% Confidence Interval 2,651 3,868 1.8Maximum 128,900 88,700 42.7Minimum 123,100 80,700 38.3

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.

Table 19: Tensile Test Data for Alloy 19D Seam Welded Tubing from Production Mill Coils

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Heat / Statistical Quantity UTS (psi)a YS (psi)a E (%)


80,000min.

25min.

Heat 391666 (4 Reels)Average 110,346 88,168 19.0± 95% Confidence Interval 2,038 4,603 4.8Maximum 113,392 94,642 25.0Minimum 108,695 84,347 13.0Heat 301000 (12 Reels)Average 113,431 85,534 24.4± 95% Confidence Interval 1,210 3,370 2.4Maximum 116,100 94,782 31.0Minimum 109,482 76,700 13.0Heat 201595 (6 Reels)Average 111,709 89,287 22.0± 95% Confidence Interval 1,915 4,334 2.1Maximum 114,782 96,551 25.0Minimum 107,758 83,333 19.0Heat 201596 (10 Reels)Average 113,331 80,842 20.3± 95% Confidence Interval 1,439 3,502 3.7Maximum 116,700 94,736 25.8Minimum 108,800 74,000 11.4Heat 410078 (13 Reels)Average 115,823 79,885 24.8± 95% Confidence Interval 1,378 1,758 1.0Maximum 119,700 84,300 27.6Minimum 110,400 72,200 21.1Heat 201694 (16 Reels)Average 112,100 77,881 16.4± 95% Confidence Interval 845 1,281 2.3Maximum 115,400 83,200 26.1Minimum 109,900 73,500 10.5Heat 310106 (12 Reels)Average 113,667 82,183 21.5± 95% Confidence Interval 1,122 4,126 2.3Maximum 117,100 96,600 25.7Minimum 110,200 74,600 13.0Heat 410111 (10 Reels)Average 113,760 82,080 20.4± 95% Confidence Interval 2,095 2,411 3.2Maximum 121,700 92,700 25.5Minimum 110,100 80,000 12.8Heat 410434 (12 Reels)Average 114,983 82,592 19.7± 95% Confidence Interval 1,055 1,746 1.9Maximum 118,100 90,600 25.3Minimum 112,200 80,100 14.8Heat 310426 (10 Reels)Average 113,270 81,470 21.5± 95% Confidence Interval 1,064 1,033 2.0Maximum 116,500 85,200 25.2Minimum 109,700 80,200 14.9Heat 410754 (2 Reels)Average 113,850 83,100 22.8± 95% Confidence Interval 1,078 5,292 3.4Maximum 114,400 85,800 24.5Minimum 113,300 80,400 21.0

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.

Table 20: Tensile Test Data for Alloy 19D Orbital Welds from Production Reels

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Specification / SampleTest

Temp. (°C)UTS(psi)

0.2% YS(psi)

1% YS(psi)

E(%)

RequirementsaAmbient

(+ 22)100,000

min.80,000min. None

25min.

Long. Seam WeldsLSW-10-100 − 20 146,100 93,800 104,400 38.1LSW-10-101 − 20 144,900 93,900 103,900 38.3LSW-10-102 + 22 120,900 85,000 93,600 40.6LSW-10-103 + 22 120,300 84,200 93,500 40.4LSW-10-104 + 100 103,300 74,100 81,400 32.6LSW-10-105 + 100 100,900 72,700 79,500 31.7Strip Splice WeldsSSW-7-110 − 20 131,700 93,900 103,500 23.6SSW-7-127 − 20 132,300 94,200 104,100 24.7SSW-7-132 + 22 116,800 85,400 95,400 25.9SSW-7-134 + 22 112,800 84,400 93,900 22.8SSW-7-135 + 100 96,100 73,400 80,700 14.6SSW-7-136 + 100 Sample DestroyedOrbital WeldsOW-82-102 − 20 108,600 83,000 98,400 9.2OW-82-105 − 20 129,500 82,700 96,800 25.2OW-82-127 + 22 110,200 77,500 89,900 19.9OW-82-128 + 22 107,700 77,600 89,400 16.9OW-82-130 + 100 91,400 65,200 75,900 12.2OW-82-134 + 100 92,700 66,300 76,900 12.6

Notesa. Based upon ambient temperature requirements of subsea umbilical tubing specifications in effect when the tubing was

manufactured.

Table 21: Tensile Test Data for Alloy 19D Longitudinal Seam, Strip Splice and Orbital Weld Samples From Heat 301000

Manufacturing Stage UTSa (psi) YSa (psi) E (%)


80,000min.

25min.

Stripc 116,033 81,800 43.6Tubing, after milleddy currentd 122,400 82,800 41.1

Average of 22 samplesafter mill coiler 125,905 83,773 40.2

Tubing, after orbitalweld straightnerd 125,300 82,700 41.5

Tubing, afterfinal reelingd 125,300 81,600 40.8

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.c. As reported by AK Steel.d. Data are from one sample.

Table 22: Comparison of Tensile Test Data for Alloy 19D Tubing Samples from Heat 310106 At Various Stages in the GibsonTube Manufacturing Process

Heat No. /Coil Identification /Manufacturing Stage

UTSa (psi) YSa (psi) E (%)


80,000min.

25min.

Average of 20 samples aftermill coiler at Gibson Tube 123,081 91,076 41.1

SG-382, Mill Coil 66 AfterFAT at SeaCATc 126,500 92,300 38.9

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.c. Average of two tests.

Table 23: Comparison of Tensile Test Data for Alloy 19D Tubing Samples from Heat 201595 Representing ManufacturingStages at Gibson Tube and SeaCAT

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Heat / Statistical Quantity Hardness(HRC)

Requirementsa 25 max.Heat 391666 (84 Mill Coils )Average 24.0± 95% Confidence Interval 0.2Maximum 27.4Minimum 20.0Heat 301000 (107 Mill Coils)Average 24.4± 95% Confidence Interval 0.2Maximum 28.4Minimum 21.4Heat 201595 (79 Mill Coils)Average 24.6± 95% Confidence Interval 0.2Maximum 27.7Minimum 20.2Heat 201596 (113 Mill Coils)Average 24.8± 95% Confidence Interval 0.2Maximum 28.2Minimum 20.0Heat 410078 (100 Mill Coils)Average 24.0± 95% Confidence Interval 0.1Maximum 26.5Minimum 21.2Heat 201694 (109 Mill Coils)Average 24.4± 95% Confidence Interval 0.2Maximum 27.9Minimum 19.4Heat 310106 (85 Mill Coils)Average 24.0± 95% Confidence Interval 0.1Maximum 26.3Minimum 21.8Heat 410111 (100 Mill Coils)Average 23.7± 95% Confidence Interval 0.1Maximum 25.0Minimum 21.6Heat 410434 (109 Mill Coils)Average 23.0± 95% Confidence Interval 0.2Maximum 28.8Minimum 18.2Heat 310426 (72 Mill Coils)Average 21.9± 95% Confidence Interval 0.2Maximum 24.8Minimum 18.8Heat 410754 (14 Mill Coils)Average 22.1± 95% Confidence Interval 0.5Maximum 24.0Minimum 20.0

Notesa. The requirements are based upon subsea umbilical tubing specifications in effect when the tubing was manufactured.

Table 24: Hardness Test Data for Alloy 19D Seam Welded Tubing from Production Mill Coils

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Weld Type /Sample Number

TestLocationa

AverageHV 10

Hardnessb

MinimumHV 10

Hardnessb

MaximumHV 10

Hardnessb

Long. Seam WeldLSW-10-112 BM 258 253 261LSW-10-112 LSW 245 242 251LSW-10-113 BM 247 243 251LSW-10-113 LSW 253 251 254Strip Splice WeldSSW-7-137 SSW 246 242 252SSW-7-138 SSW 243 237 249Orbital WeldOW-82-137 OW 231 211 249OW-82-138 OW 233 227 237

Notesa. Test location key: BM = base metal, LSW = longitudinal seam weld metal, SSW = strip splice weld metal, OW = orbital

weld metal.b. Five Vickers hardness test measurements were made on the outside surface using a Vickers test force HV 10.

Table 25: Vickers Hardness Test Measurements For Alloy 19D Tubing Samples from Heat 301000

TestLocationa

ApproximateArc DistanceFrom Weld

Centerline (in.)

LSW-10-112HV 0.5

Hardnessb

LSW-10-113HV 0.5

Hardnessb

BM 0.25 268 260BM 0.23 258 262BM 0.21 260 258BM 0.19 257 258BM 0.17 258 260BM 0.15 254 252BM 0.13 264 252BM 0.11 263 253

HAZ 0.09 254 261LSW 0.07 247 253LSW 0.05 246 244LSW 0.03 228 236LSW 0.01 252 249LSW 0.01 245 236LSW 0.03 247 233LSW 0.05 252 248LSW 0.07 240 238HAZ 0.09 248 256BM 0.11 264 265BM 0.13 251 260BM 0.15 257 254BM 0.17 264 259BM 0.19 259 263BM 0.21 265 264BM 0.23 267 265BM 0.25 255 254

Notesa. Test location key: BM = base metal, HAZ = heat affected zone, LSW = longitudinal seam weld metal.b. Vickers hardness test measurements were made on a weld cross section at approximately the mid-thickness using a

Vickers test force HV 0.5. The measurements were spaced at increments of 0.020-in. (0.5 mm).

Table 26: Vickers Hardness Test Measurements for Alloy 19D Longitudinal Seam Weld Cross Sections from Heat 301000

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TestLocationa

DistanceFrom Weld

Centerline (in.)

SSW-7-137HV 0.5

Hardnessb

SSW-7-138HV 0.5

Hardnessb


HAZ 0.09 264 267SSW 0.07 248 249SSW 0.05 254 241SSW 0.03 246 249SSW 0.01 260 255SSW 0.01 249 236SSW 0.03 248 261SSW 0.05 245 268SSW 0.07 245 245HAZ 0.09 260 254BM 0.11 266 259BM 0.13 260 265BM 0.15 263 262BM 0.17 260 261BM 0.19 255 265BM 0.21 263 262BM 0.23 263 260BM 0.25 263 271

Notesa. Test location key: BM = base metal, HAZ = heat affected zone, SSW = strip splice weld metal.b. Vickers hardness test measurements were made on a weld cross section at approximately the mid-thickness using a


Table 27: Vickers Hardness Test Measurements for Alloy 19D Strip Splice Weld Cross Sections from Heat 301000

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TestLocationa

DistanceFrom Weld

Centerline (in.)

OW-82-137HV 0.5

Hardnessb

OW-82-138HV 0.5

Hardnessb


HAZ 0.09 250 237OW 0.07 218 232OW 0.05 213 232OW 0.03 227 223OW 0.01 228 224OW 0.01 227 228OW 0.03 222 234OW 0.05 235 228OW 0.07 228 217HAZ 0.09 251 240BM 0.11 253 256BM 0.13 255 260BM 0.15 255 260BM 0.17 252 252BM 0.19 251 249BM 0.21 248 244BM 0.23 253 254BM 0.25 248 253

Notesa. Test location key: BM = base metal, HAZ = heat affected zone, OW = orbital weld metal.b. Vickers hardness test measurements were made on a weld cross section at approximately the mid-thickness using a


Table 28: Vickers Hardness Test Measurements for Alloy 19D Orbital Weld Cross Sections from Heat 301000

ASTM Specification / Grade(UNS Designation))

UTSa, min.(psi)

YSa, min.(psi) E, min. (%) Hardness,

Max.A 789 / 2507 (S32750) 116,000 80,000 15 HRC 32A 789 / 2205 (S32205) 95,000 70,000 25 HRC 30.5A 789 / 2205 (S31803) 90,000 65,000 25 HRC 30.5A 789 / 19D (S32001) 90,000 65,000 25 HRC 30Alloy 19D subsea umbilical tubingb 100,000 70,000 10 HRC 30A 249 / 316L (S31603) 70,000 25,000 35 HRB 90A 249 / 304L (S30403) 70,000 25,000 35 HRB 90

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. Recommended design requirements for subsea umbilical tubing based upon the limiting values of the orbital weld.

Table 29: Comparison of Tensile and Hardness Requirements for Various Duplex and Austenitic Stainless Steel WeldedTubing Specifications

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Heat /Sample

Test 1Burst

Pressurea

(psi)

Test 1Failure

Locationb

Test 2Burst

Pressurea

(psi)

Test 2Failure

Locationb

Heat 391666Strip splice weld 26,000 SSW 26,000 SSWLongitudinal seam weld 26,500 LSW 26,000 LSWOrbital weld 26,000 LSW 26,500 LSWHeat 301000Strip splice weld 26,500 LSW 26,000 LSWLongitudinal seam weld 25,000 LSW 26,000 LSWOrbital weld 26,500 OW 26,500 OWHeat 201595Strip splice weld 27,910 SSW 27,980 SSWLongitudinal seam weld 27,390 LSW 27,200 LSWOrbital weld 27,550 OW 27,630 OWHeat 201596Strip splice weld 25,610 LSW 25,860 LSWLongitudinal seam weld 26,670 LSW 27,340 LSWOrbital weld 27,830 OW 25,670 FittingHeat 410078Strip splice weld 28,150 SSW 28,220 SSWLongitudinal seam weld 26,590 LSW 26,470 LSWOrbital weld 27,500 OW 27,470 LSWHeat 201694Strip splice weld 27,450 SSW 27,640 SSWLongitudinal seam weld 27,100 LSW 27,470 LSWOrbital weld 27,850 OW 27,940 OWHeat 310106Strip splice weld 27,390 SSW 28,330 SSWLongitudinal seam weld 27,740 LSW 28,300 LSWOrbital weld 27,850 OW 27,740 OWHeat 410111Strip splice weld 26,750 SSW 27,060 SSWLongitudinal seam weld 27,140 LSW 27,240 LSWOrbital weld 24,640 OW 27,060 OWHeat 410434Strip splice weld 25,580 SSW 25,850 SSWLongitudinal seam weld 25,540 BM 25,620 LSWOrbital weld 25,410 OW 25,590 LSWHeat 310426Strip splice weld 27,320 SSW 27,480 LSWLongitudinal seam weld 27,640 LSW 27,550 LSWOrbital weld 27,370 OW 27,050 OWHeat 410754Strip splice weld 28,100 SSW 28,330 SSWLongitudinal seam weld 28,510 LSW 28,570 LSWOrbital weld 27,780 OW 27,830 OW

Notesa. To convert from psi to MPa, multiply by 6.895 x 10-3.b. Key to failure location: SSW = strip splice weld, LSW = longitudinal seam weld, OW= orbital weld, Fitting = failure or

disengagement of fitting at indicated pressure.

Table 30: Burst Test Data for Alloy 19D Tubing

duplex mcenerney

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