CEFDA04-1202 Task Title: TW5-TVV … using TIG narrow gap process. This mock-up is 486mm length, 60...

- 44 - EFDA Technology / Vessel-In Vessel / Vessel-Blanket and Materials

CEFDA04-1202

Task Title: TW5-TVV-RFUT: COMPARATIVE ASSESSMENT OFULTRASONIC INSPECTION SYSTEMS FOR THE NARROW GAPAUSTENITIC WELDS IN THE ITER VACUUM VESSEL

INTRODUCTION

This work is carried out in co-operation with PHOENIX,SINTEZ/ECHO and EURATOM-CEA Association [1].The main objective of the global project is to prepare threemethods for acceptance by manufacturing code and theFrench Certification Authorities so that they may be usedsuccessfully during the ITER Vacuum Vessel fabrication.This project officially started in September 2005 and it willin operation until October 2007. The kick-off meeting ofthe project was held in Paris in February 2006.This report presents the status of the project up to 2006 [2]and in particular the mock-ups manufacturing and thebeginning of the round trials ultrasonic inspections.

2006 ACTIVITIES

The main activities during 2006 were the following:- The manufacturing of four mock-ups following the related

technical specifications- The beginning of the round robin trials of the mock-ups

manufactured.

MOCK-UPS MANUFACTURING

Four mock-ups have been designed in the frame of thisproject. Two mock-ups were designed and paid for ourAssociation. The other two were designed and paid forPhoenix. The Finland Company TRUEFLAWmanufactured all of these mock-ups. The technicalspecification of the mock-ups are presented in reference [3]Figure 1 presents a picture of mock-up A. This mock-up ismanufactured with ITER Grade steel and the coupon waswelded using TIG narrow gap process. This mock-up is486mm length, 60 mm thick and 475 mm wide.

Figure 1: Mock-up A designed by CEA

Figure 2 presents a schema of the T-joint mock-up D. Thisis the T-shape adaptor of the poloidal rib with one joint ofweld. The material of this mock-up is not ITER Grade steelbut a 316L steel. The dimensions of this mock-up are500mm length, 60 mm thick and 496 mm wide. Thepoloidal rib is 10 mm high along the coupon.

Figure 2: Mock-up D designed by CEA

Figure 3 shows a scheme of mock-up B designed byPHOENIX and manufactured by TRUEFLAW Company.The material of this mock-up is ITER grade steel and theplanar faces of this mock-up have an angle of 10°, which isone situation of actual vacuum vessel design.

Figure 3: Mock-up B designed by Phoenix

Figure 4 shows a mock-up partial welded designed byPhoenix. This sample will be manufactured to inspectdefects, which could appear in realistic situation, inparticular when the weld pass are stopped and startedduring the welding process.

Figure 4: Mock-up C designed by Phoenix


CALIBRATED DEFECTS INCLUDED

In all of these mock-ups were included calibrated flaws.Different types of defects were chosen in order to simulateseveral realistic situations:

- To detect defects immediately after production of weldjoint;

- To test the inspections UT systems near the limits ofdetect ability;

- To compare abilities of systems to detect different types offlaws (lack of fusion in the line of chamfer, centrelinecracks, and incomplete groove weld (crow area).

The location of the flaws was distributed across the weldand in the heat affected zone (HAZ). In particular at rootarea of the weld were included several flaws since this zoneis considered a more HAZ critical weld area.

Thus inner breaking defects, embedded flaws and outerbreaking defect at surface were included. To carry out thesedefects, different fabrication methods were applied, thermalfatigue cracks, solidification cracks and electro-dischargecracks.

In order to maximise the benefits of this project a blind isrequired in terms of inspection of flaws. Thus, partners insightless approach carried out the specification of the flawsrelated to the dimension and location.

The sizes of flaws vary between 1x25 mm and 10x20 mmlocated across the HAZ area.

PROGRESS OF INSPECTION

SINTEZ/ECHO

- SINTEZ/ECHO has optimized his inspection UT system.For this ECHO manufactured several new transducersand carried out inspection on existing mock-ups;

- SINTEZ/ECHO has described his system in the report inreference [4]. This task has been selected in order tofacilitate the information exchange between partners;

- SINTEZ/ECHO started the inspection of the mock-upssent by CEA;

- The assessment of results will be published in nextmonths.

PHOENIX

- Phoenix designed and manufactured a mechanical probepan for transducers carrying. This device will be used forsimultaneously driving several UT transducers.

- The round robin trials of Phoenix will be started in April.

INSPECTION

Our Association started the inspection of both mock-ups.

The phased array technique is used for the presentmeasurements. The configuration was already described inreferences [5], [6] and [7].

This experimental configuration consists in an angularscanning associated with an in-depth focusing. Two linearphased arrays are configured as a dual-element transducer.This probe is composed of two linear arrays of 32 elements(1.2x20 mm² for each element) with a 2 MHz frequency.Dual element configuration is efficient to reduce back-scattering noise in coarse-grained material as in TIG weld.Delay laws are calculated to generate longitudinal waves inthe area of the joint, using two configurations: Zone 1)vertical scanning focusing the beam along the axis (betweenz=1mm and z= 20 mm) of the weld joint, 2) angularscanning between 25° and 70° focusing along a constantradius of curvature (figure 5).

Figure 5: Phased array technique for inspection for a) 1<Z<20mm, b) 20<Z<60mm

Calibration Mock-ups

For the inspection of both mock-ups, the calibration wasperformed using a ITER grade planar mock-up containingthe following flaws:- Nine drilled holes produced by EDM of 90 cm and = 2

mm. The first hole is at 10 mm from the surface at 130mm from the side plane.

Figure 6: Calibration mock-up

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning

Zone 1Vertical scanning

1<Z<20 mm

Z

a)

b)

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

Z

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

VerticalscanningVerticalscanning


1<Z<20 mm

Z

a)

b)


- Two notchs produce by EDM ( 0.2mm opening) of 3 mmand 10 mm high and 20 mm long placed at 120 mm and200 mm from the opposite side plane (figure 6).

The results of the inspection will be present in next report.

NEXT MEETING

The next meeting is planned to be held in June 21 and 22,2007. The objective of this meeting is to exchangeinformation about the inspection of four mock-ups. Theconclusion of this meeting will be useful for the finalassessment of inspection.

SCHEDULE OF THE PROJECT

REPORTS AND PUBLICATIONS

[1] EFDA Contract TW5-TVV-RFUT, EFDAORDER/04-1202 “Comparative assessment ofultrasonic inspection systems for the narrow gapaustenitic welds in the ITER vacuum vessel”

[2] Progress report RFUT N°1; technical specification forRFUT tasks. S§YSSC/06 RT0231/Rev.0 October2006

[3] Flaws technical specification -CEA/DETECS/SYSSC/05-385

[4] Automatic ultrasonic system AUGUR –SINTEZ/ECHO Report. 2007

[5] Development of ultrasonic non destructive testingmethod for the vessel inter-sector weld of ITER:development of dynamic phased array techniques»,SISC/03-RT0096/Rev. 0, September 2003.

[6] Development of phased array techniques for theinspection of one sided welds in ITER vacuumvessel», SYSSC/04-RT0143/Rev. 0 September 2004.

[7] Simulation of phased array technique for qualificationof UT methods for one sided welds during VVmanufacture. SYSSC/05 RT0167/Rev 0, October 2005

TASK LEADER

Jorge TIRIRA

DRT/DeTECS/SYSSC/LMCCEA-SaclayF-91191 Gif-sur-Yvette Cedex

Tel. : 33 1 69 08 40 02Fax : 33 1 69 08 75 97

e-mail : [email protected]


CEFDA05-1226

Task Title: TW5-TVM-LIP: MODIFICATION OF ITER MATERIALSDOCUMENTS, ASSESSMENT OF MATERIALS DATA ANDMAINTENANCE OF A DATABASE

INTRODUCTION

The properties of materials used in fusion components needto be known in detail by designers, by licensing authoritiesand the materials specialists. ITER Materials PropertiesHandbook is a document that provides such information inan internationally accepted format.

Euratom-CEA contribution to MPH, in addition tosupporting ITER-IT, EFDA-CSU, and ITER databasegroups, is to provide MPH files for Type 316L(N) steelweld metals and joints. In 2005, the work was focussed onlow temperature (316L) and high temperature (19-12-2,OKR3U) weld metals. In 2006 work is extended to 16-8-2weld metal, see table 1 for compositions.

Table 1: Weld metal compositions used for welding Type 316L(N) steel (FWC= Flux Wire Couple, C.E.= Coated Electrode,MA= Manual Arc, AC= Automatic Covered)

RCC-MR

WELD METAL

FILLER

METAL

Range C Mn Si P S Cr Ni Mo Nb* Cu B

(ppm)

Co N2 d ferrite

Calculated

Wire for TIG Min

Max 0.030

1.00

2.50 0.60 0.30 0.020

18.00

20.00

12.00

14.00

2.00

3.00

5

15*

RS 2915

ER 316L (Z2

CND 19-13) In weld deposit

C.E.RS 2925

E 316L (Z 19-

12-3 L)

In weld deposit Min

Max 0035 2.50 0.90 0.025 0.025

18.00

20.00

12.00

14.00

2.00

3.00

5

15*

Flux Wire

Couple

Min

Max 0.025

1.00

2.50 0.60 0.020 0.020

18.00

20.00

10.00

13.00

2.00

3.00

5

15*

RS 2945

316L (SA 19-12-

2L) In deposit Min

Max 0030

1.00

2.50 1.00 0.030 0.030

17.00

20.00

10.00

13.00

2.00

3.00

5

15

RS 9513.1

19-12-2

C.E. for MA Min

Max

0.045

0.055

1.20

1.80

0.40

0.70

-

0.025

-

0.020

18.0

19.0

11.0

12.0

1.90

2.2

- - - - - 3

7

RS 9513.2

16-8-2

C.E. for MA Min

Max

0.045

0.055

1.80

2.5 0.5 0.025 0.020

15.5

16.5

7.5

9.0

1.8

2.5

-

0.30

- -

0.25

- 3

7

RS 9523.1

19-12-2

Wire for TIG Min

Max

3

7

RS 9523.2

16-8-2

Wire for TIG Min

Max

0.030

0.045

1.8

2.5 0.5 0.025 0.020

16.0

17.0

8.0

9.0

1.8

2.2

-

0.1

- - - 3

7

RS 9543.1

19-12_2

FWC for AC Min

Max

0.030

0.055

1.20

2.0 0.70

-

0.025

-

0.020

18.0

19.0

11.0

12.0

2.0

2.20

-

0.10-

-

0.25-

- 3

7

RS 9543.2

16-8-2

Submerged Arc Min

Max

0.030

0.045

1.8

2.5

-

0.5

-

0.025

-

0.020

16.0

17.0

8.0

9.0

1.80

2.50

- -

0.10

- -

0.25

- 3

7


2006 ACTIVITES

All deliverables of the task agreement have been met bytheir due dates. The full report is too large to be reportedhere. Only, an example of the many file codes preparedfor MPH will be given, namely the file code for tensilestrength of 16-8-2 weld metal. Even there, several figuresand tables will be left out to reduce the length of the paper.

For more information the reader is referred to ITER MPHfiles.

File Code: ITER-AA09-2101 Tensile Strength

CODE RECOMMENDATIONS

The 16-8-2 weld metal given in the File Code ITER-AA09-1100 is an RCC-MR Code qualified material [1].This metal is also used in other international codes [2 , 3].

ITER MPH recommends the code data, wheneveravailable, for ITER Structural Design Criteria. For weldmetals, these are often in the form of knock down factorsapplied to the base metal properties values [4], accordingto the type and category of welds (see File Code:ITER-AA09-1100).

RS 9513.2: Covered Electrode / Manual Arc WeldingProcessSheet Number RS 9513.2 of RCC-MR [1] gives therequirements for 16-8-2 covered electrodes / manual arcprocess (111). Tests performed on weld metal in flatposition (as-welded) with specimens taken in longitudinalweld orientation should satisfy:

Su (RT) 550 MPa

Su (550 °C) 380 MPa

Tests on qualification test coupons (RS 3334) shouldsatisfy the same Su value at RT. For materials subjected todimensional stabilization heat treatment, 50 h at 650 °C, alower Su limit is allowed (500 MPa).For transverse tests, the specification is given according tothe type of base metal. For the type Z2 CND 17-12 withcontrolled nitrogen addition (similar to ITER 316 L(N)-IG) and Z2 CND 18-12 with controlled nitrogen addition,in the as-welded condition, the values are:

Su (RT) 525 MPa

Su (550 °C) 380 MPa

Specified values are the same following a stabilization heattreatment (longitudinal orientation).

For base metal without controlled nitrogen addition (Z2CND 17-12, similar to 316L) the values in transverseorientation are slightly lower:

Su (RT) 490 MPa

Su (550 °C) 350 MPa

Other recommendations are given in RS 9523.2 for wirefor TIG process (141) and in RS 9543.2 for wireassociated with flux for automatic arc process (121).

ADDITIONAL ANALYSES

General

Codebooks such as RCC-MR do not give materialsproperties data that are at the origin of theirrecommendations. These are usually available in thesupporting documents, such as the Appendix A (see e.g.Appendix A for 316L(N)-IG), [5].

In the additional analysis that follows, we will compare thematerials properties data available for 16-18-2 weld metalwith the code recommendations. The main purpose of thiscomparison is to see if the safety margins incorporated inthe code recommendations are still valid when thesematerials are used under present ITER operatingconditions and the anticipated future evolutions. We shallpay a particular attention to the effects of irradiation thatare not currently fully covered by the international codes.

Mechanical Properties

Tensile properties of Type 316L(N) weld metals have beeninvestigated by ITER partners [6 , 15].

RCC-MR recommendations are made for specific types of16-8-2 metals and specific welds and welding conditions.Without such constraint a large scatter in results isobserved [6]. For instance, NRG [7] has tested specimenstaken from TIG welds and TIG weld deposits. Specimenstaken from the weld deposit are full weld specimens andshow less scatter, while specimens taken from TIG weldjoins, depending on the orientation of the specimen (T orL) and on the position of the specimen (root weld or bulkweld) show large scatter. The very low yield stress in TIGwelds may be due to failure in the base metal.

The earlier French work on Shielded Manual Arc Welding(SMAW), used as a source for RCC-MR specifications, iscalled here “reference” (see also reference 6).This work covers weld deposits and welded plates inhorizontal and vertical positions (10-20 mm weldthickness) using coated filler metals (with 0.045 to0.055 % C). The results (mainly in L orientation) aresituated in the upper part of the scatter band of 16-8-2 datacollected in reference 6. Figure 1 also shows theestablished trend curves for Su average and Su minimum.RCC-MR min specified values at RT and 550 °C are alsoshown.


0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Type 16-8-2 Weld Metal

Ulti

mat

e Te

nsile

Stre

ngth

, MPa

Test Temperature, °C

Ref (ave)

Ref (min)

RCC-MR

RCC-MR

Figure 1: Dependence of average and minimum Su on testtemperature for 16-8-2 weld metal (SMAW, higher carbon

content, early French work). Experimental data shownare mainly for longitudinal specimens and flat welding

position

Equations describing these trend curves are:

(eq. 1)Su (ave) = 699.2 - 1.2741 + 0.0031629 2 - 3.1193x10-6 3

(eq. 2)Su (min) = 567.3 - 0.91 + 0.00226 2 - 2.23x10-6 3

Figure 2 shows plot of all collected experimental data,independent of the welding type and orientation ofspecimens, on one figure. Clearly most of the datacollected fall below the above reference curves. However,even then the results are mostly above the RCC-MRspecifications.

Equations describing curves for all collected data are:

(eq. 3)Su (ave) = 700.07 - 2.2049 + 0.0060031 2 - 5.3191x10-6 3

(eq. 4)Su (min) = 600.68 – 1.8919 + 0.0051509 2 – 4.564x10-6 3

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700 800

Type 16-8-2 Welds

Ulti

mat

e Te

nsile

Stre

ngth

, MPa


RCC-MR

RCC-MR

Figure 2: Dependence of average and minimum Su ontemperature for 16-8-2 weld metal for a large set of data

(independent of welding type and specimen position)

Effect of Weld Thickness and Welding Position

The effects are expected to be similar to Type 19-12-2.See section 2.3 of the File code AA08-2101.

Structural Stability Tests

Figure 3 shows effects of aging at temperatures rangingfrom 450 to 750 °C on tensile strength of 16-8-2 weldmetal. The large scatter in aged results is mainly due tothe scatter in the initial results. At aging temperatures400-450°C, that are even higher than the operatingconditions of ITER (<300 °C), the effect of aging isnegligible.

The effect of different ITER first wall module fabricationcycles, such as HIPing treatments, remain to beinvestigated but one would expect significant softening, asobserved for Type 19-12-2 welds.

200

300

400

500

600

700

800

900

0 1000 2000 3000 4000 5000 6000

Effect of AgingType 16-8-2 Weld metal

Rp (450-500°C), MPaRm (450-550°C), MPaRp (600°C), MPaRm (600°C), MPaRp (650°C), MPaRm (650°C), MPaRp (750°C), MPaRm (750°C), MPa

Tens

ile S

tress

at 2

0°C

, MP

a

Aging Time, h

Rm (initial)

Rp (Initial)Rm (50h/650 °C min)

Figure 3: Effect of aging on tensile strengths of Type16-8-2 weld metal. Notice that Rm values remain abovelower limit specified for structural stability test of 50h at

650°C

Effect of Irradiation

Unfortunately, weld metals used in some investigations[6 , 15] do not correspond to the RCC-MR specificationsor some results obtained are not fully traceable, others areobtained at temperatures and doses outside the ITERoperating conditions.As a result, only data generated at NRG for TIG depositsand TIG welds for EU fusion programme are retained here[7]. The filler metal used at NRG is Type SMA 16-8-2 SP(from metal FX-456). Its nickel concentration (9%) is nearthe maximum specified level. Its carbon content is in therange of filler metal for TIG welding (0.04%), but lowerthan that of the MMA and filler metal associated with flux.The hardness of the TIG deposit is around 195 HV5 (225in HAZ), while that of the TIG weld is 225 HV5 (195 inHAZ).


Figure 4 shows that the unirradiated results are below theaverage reference curve, but once irradiated, even to verylow doses, are higher.Similar results are obtained after 11 dpa irradiation at250°C [8]. Here, the hardening is about the same level as 6dpa irradiation, suggesting a decrease in the rate ofhardening or its saturation. Also, notice that the yield andUTS of irradiated material merge leaving practically noplastic work hardening capability.

0

200

400

600

800

1000

0 100 200 300 400 500 600 700 800

16-8-2 SP TIGNRG data

Su, MPaSu (0.73 dpa), MPaSu (6.1 dpa), MPaRm(ave)Rm(min)

Ulti

mat

e Te

nsile

Stre

ngth

, MP

a


TirrSu (ref)

Figure 4: Comparison of ultimate tensile strengths of Type16-8-2 SP TIG deposit welds, before and after irradiationat 227 °C, with the reference average and minimum curvesderived for 16-8-2 weld metal. Filler metals used in NRGexperiments are for TIG welding and have lower carbon

contents than the Su (ref)

Design Allowable

Sm is governed by base metal properties, see figure 5.Neither aging nor irradiation hardening under ITERconditions modify this situation.

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700 800

16-8-2 Weld

Stre

ss, M

Pa

Temperature, °C

Su (ave)

Sy (ave)

Sm

Base Metal

Su (min)

Sy (min)

Figure 5: Comparison of Sm derived for 316L(N) basemetal with reference average and minimum tensile curves

of 16-8-2 weld metal

CONCLUSIONS

The additional analyses performed here on Type 16-8-2weld metal for ITER application support RCC-MRrecommendations provided filler materials and weldingparameters correspond to those specified in the code.

REFERENCES

1 Design and Construction Rules for Power GeneratingStations, Design and Construction Rules forMechanical Components of the FBR Nuclear Islands,RCC-MR, Section IV Welding, AFCEN, Edition2002.

2 Design and Construction Rules for MechanicalComponents of the LWR Nuclear Islands, RCC-M,AFCEN.

3 ASME "Boiler and Pressure Vessel Code", CodeCases, Nuclear Components N-47-24, Class 1Components in Elevated Temperature Service,Section III Div. 1, 1986.

4 ITER Interim Structural Design Criteria (ISDC), S 74RE 2 97-02-30 W 1.2, IRB/Welds / Revision 3.

5 A-A. F. Tavassoli, "Assessment of AusteniticStainless Steels," N.T. SRMA 94-2061, F.A. 3591-ITER, March 1994. See also Fusion Engineering andDesign 29 (1995) 371-390. See also Appendix A ofISDC for 316L(N)-IG.

6 T. Forgeron (Fr), A-A. F. Tavassoli (Fr), J. Wareing(UK), D. Lehmann (Fr), C. Escaravage (Fr),B. Breitling (D), et C. Picker (UK) "Effect OfThermal Aging on Mechanical Properties of Type316l (N) Base and Weld Metals", CEC StudyContract CT-92-0211-F, CEA Report 94.

7 J.W. Rensman, J.Boskeljon, M.G.Horsten, M.I.DeVries, ”Irradiation Testing of Stainless Steel PlateMaterial and Weldments, Tensile Properties After 0.5and 5 dpa at 350K and 500K”, report ECN-C-97-088,Oct. 97, (ITER Library Number - SS17).

[8 J.L. Puzzolante, M. Scibetta, R. Chaouadi, W.Vandermeulen, “Tensile and Low Cycle FatigueProperties of Solution annealed Type 316L SS Plateand TIG Weld Exposed to 5 dpa at Low Temperature(42°C)”, BLG-821, SCK.CEN, Sept. 1999, (ITERLibrary Number - SS39, SS50).

9 G.L. Tjoa, J Boskeljon, D.S. D'Hulst, M.I.de Vries,”Results of Tensile tests on Type 304 and 316Stainless Steel Plate and Welded joints”, ReportECN-I--94-007, Feb. 1994, (ITER Library Number -SS100).


10 H.Yamada, H.Kawamura, ”Qualification of structuralmaterials and joints”, Final report on ITER task T427JA, Task No G 16 TT fr 97 FJ, May 2001, (ITERLibrary Number - SSCuJ19).

11 W. Vandermeulen, W. Hendrix, V. Massaut, J. Vande Velde, and Ch. Raedt, ”FAFUMA 1 test results”,FT/MOL/90-01, WV/MJW-V, Mol, February 1990,(ITER Library Number - SS87, SS1).

12 Källstrom R., Josefsson B., Haag Y., ”ResultfromTensile Testing of 316L Plate and Weld Material”,Studsvik Nuclear - Report No. Studsvik/M-93/45,April 1993, (ITER Library Number - SS7).

13 Horsten M.G., Van Hoepen J., de Vries M.I.,”Tensile Tests on Plate and Electron-Beam WeldedType 316L(N) Material”, ECN, Petten, NL - ReportNo. ECN-CX--93-112, November 1993, (ITERLibrary Number - SS9).

14 A.Rowcliffe, ”Irradiation testing of stainless steel andInconel including welding and rewelding of irradiatedmaterials”, Final report on ITER task T214 US TaskNo G 16 TT fr 75 95-07-04 FU, March 1998, (ITERLibrary Number - SS29).

15 H.Sagawa, ”Irradiation testing of stainless steel andInconel including welding and rewelding of irradiatedmaterials”, Final report on ITER task T214 JA, TaskNo G 16 TT fr 73 95-07-04 FJ, June 1998, (ITERLibrary Number - SS30).

TASK LEADER

Farhad TAVASSOLI

DEN/DMN/DIRCEA-SaclayF-91191 Gif-sur-Yvette Cedex

Tel. : 33 1 69 08 60 21Fax : 33 1 69 08 80 70


Not available on line

58 EFDA Technology / Vessel-In Vessel / Vessel-Blanket and Materials

TW5-TVV-MPUT

Task Title: TIG NARROW GAP INFLUENCE OF WELD STRUCTUREAND GEOMETRY ON PHASED ARRAY TECHNIQUEPERFORMANCES

INTRODUCTION

For ITER vacuum vessel inspection, studies wereperformed to investigate the performances of the ultrasonictechniques [1], [2]. It has been shown that phased arraytechnique is a valuable technique for inspection of TIGnarrow gap welds. The techniques used consist indynamical inspection methods based on angular scanningassociated with beam focusing [3], [4], and [5].The objective of this study in the frame ofTW5-TVV-MPUT project is to study the influence of boththe TIG narrow gap weld structure and geometry on theperformances of phased array method for one sided weldsmock-up that may be used during ITER VV manufacture.In particular, this report presents the set of the results of thisproject.

2006 ACTIVITIES

The main activities during this period were the following:

- To carry out the inspections of critical areas (root of weldand near the surface) using an UT phased arraytechnique;

- To synthesize the results in terms of the influence of theweld structure and geometry for detecting defects in theroot weld area and near the surface in the crown area.

MOCK-UP INSPECTED

In order to evaluate the influence of the TIG weld structuretwo mock-ups are used in the present work:

- One existing TIG mock-up is devoted to study theattenuation of the sound through the joint weld; for that,three new flaws are included in the mock-up;

- One new mock-up is dedicated to analyse the role of weldroot geometry on the inspection of flaws in the root area;for that, a new mock-up is designed with two beads tosimulate the deposit of weld metal produced by a fusion-welding process.

Figure 1 presents the TIG narrow gap mock-up which wasalready described in reference [3]. In particular, this mock-up has both breaking surfaces defects and the embeddedflaws. In this mock-up are included for the present studythree new flaws which are used to perform test related tothe weld structure. Two surface breaking flaws are includedoutside of the joint weld. One supplementary notch is

manufactured near the surface. All of these flaws are10 mm high and 20 mm wide.

Figure 1: Mock-up including flaws to analyse the weldstructure

Figure 2 presents the scheme of the new mock-ups in whichwas manufactured a bead to simulate the longitudinaldeposit of weld metal produced by a fusion-weldingprocess and two breaking surface defects of 3mm high and20 mm wide.

Figure 2: Manufactured mock-up for analysing theinfluence of the root weld geometry

Inner breaking flaw (15x20mm)

45mm

Inner breaking flaw (15x20mm)

45mm

r =5 r =3r =5 r =3r =3

Scanning X

Flaws Joint beads

r =5 r =3r =5 r =3r =3

Scanning X

Flaws Joint beads

20

10

218 217

10

80

258

1020

287

500

10

Side drilled holes

View 2

View 1

New Notchesincluded

TIG weld area

415

5

Existing notchembedded

20

1010

218 217

10

80

258

1020

1020

287

500

10

Side drilled holes

View 2

View 1

New Notchesincluded

TIG weld area

415

55

Existing notchembedded


TECHNIQUE USED FOR INSPECTION

The phased array technique [1], [2], and [3] has been usedfor inspection of mock-ups. The probe is composed of twolinear arrays of 32 elements (1.2x20 mm² for each element)with a 2 MHz frequency. Dual element configuration (onein emission and another in reception) is efficient to reduceback-scattering noise in coarse-grained material as in TIGweld. This technique consists in an angular scanningassociated with an in-depth focusing. Delay laws arecalculated to generate longitudinal waves in the area of thejoint, using two configurations:

Zone 1) vertical scanning focusing the beam along the axis(between z = 1mm and z = 20 mm) of the weld joint,

Zone 2) angular scanning between 25° and 70° focusingalong a constant radius of curvature (figure 3).

Figure 3: Phased array technique for inspection for a) 1<Z<20mm, b) 20<Z<60mm

RESULTS OF THE INSPECTION NEAR THESURFACE

The objective of this inspection is to characterise flawslocated near the surface up to 20mm. In order to analysethis area a specific wedge is used which can generates 60°longitudinal waves focused at 10mm. The flaws areinspected in two opposite directions before and through theweld. To optimise the detection of the notch outer breakingthe surface, the transducer drives mechanically in directionsX and Y (figure 4) around defects so that the maximum ofthe amplitude for the bottom diffraction is reached.Afterward, the inspection of all flaws near the surface in theblock is carried out in automatic mode driving thetransducer only in Y direction when the transducer islocated at 60 mm from the axis of the weld.

Figure 4: Configuration of inspection near the surface

Figure 5 presents the detections of the outer surfacebreaking notch 10 mm high. This experimental data showboth signals detected separately; the diffraction at thebottom of the notch and the signal coming from thebreaking surface area.

Figure 5: Experimental vertical scan data for 10 mm highbraking surface notch placed at the inspection surface

(a) before the weld (b) through the weld

Table 1 presents the amplitude ratio for the notch inspectionbefore and through the weld. In particular, the amplitude ofthe bottom diffraction is -13 dB before the weld and -15 dBthrough the weld. The signal to noise ratio is 3dB throughthe weld and 9 dB before the weld. The high of the flaw ismeasured with 2mm.

Table 1: Experimental amplitude ratio for 20x10 mm innernotch breaking at the surface of inspection

ATTENUATION OF THE SOUND DUE TO THEWELD STRUCTURE

The weld structure is analysed in terms of the beamattenuation through the weld area. The sample inspected isthe TIG mock-up shown in figure 1 and the flaw underanalysis is 10 mm high breaking surface notch which islocated at 40 mm from the center line of the weld joint.The inspection has been performed in automatic mode, thetransducer drives mechanically in direction X and Y. The

surface

10mm

Bottom diffraction

60 mm

Through the weldBefore the weld

Signal frombreaking surface

AB

Bottom diffraction

60 mm

surface

10mm

Bottom diffraction

60 mm

Through the weldBefore the weld

Signal frombreaking surface

AB

Bottom diffraction

60 mm

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

Z

a)

b)

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

Z

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

S1 S2

77

25

70°

Focal points

Wedge

TIG weld

Zone 2Angular scan

20<Z<60

Verticalscanning


1<Z<20 mm

VerticalscanningVerticalscanning


1<Z<20 mm

Z

a)

b)

Scanning YScanning X

Breaking surfacenotch Weld

Before the weld

Through the weld

Scanning YScanning X

Breaking surfacenotch Weld

Before the weld

Through the weld


flaw is inspected in two opposite directions before andthrough the weld as displayed in figure below (figure 6).

Figure 6: Inspection of the inner breaking notch before theweld and through the weld

Table 2 presents the amplitude ratio for both the cornerecho and the tip diffraction for the flaw inspected beforeand through the weld. The amplitude of the corner echodecreases through the weld of about 5 dB and thosecorresponding to the tip diffraction decreases of 4 dB. Thefrequency of the signal detected in both cases is 1.55 MHz.The joint weld is relatively thin (~10mm) so than the soundis not filtered in frequency (in the interval of measurementaccuracy) through the weld. The number of shot to detectthe corner echo and the tip diffraction is shifted of about 5shots. It means a deviation of the beam of about 5° when itpasses through the weld joint.

Table 2: Amplitude ratio for inner breaking surface locatedat 40 mm outside the weld axis

INFLUENCE OF THE BEAD WELD GEOMETRY INTHE INSPECTION

The objective of this experimental measurement is toevaluate the influence of the bead of the weld on thedetection of flaws near the weld root area. For thismeasurement the mock-up presented in figure 2 is used.The bead and the block are composed of the steel 316 L.

The mock-up has two beads; one of them has a radius of3 mm and the second a radius of 5mm. In previous annualreport was presented the preliminary measurement. In thepresent paper is given the analytical evaluation.

Figure 7A presents the UT angular B-scan considering adirect inspection of the 3mm high breaking surface notchand for the bead R=5mm. This experimental data showsboth the signals resulting from the geometry of bead andsignals related to the interaction of the ultrasonic beam andthe notch. In this figure the signals of the bead and thenotch (tip diffraction and the corner echo) are detectedapart.

Figure 7B shows the UT angular B-scan considering anindirect inspection. In particular, in this case experimentaldata show that the corner echo and the signal of the beadcan not be detected apart. Nevertheless, the tip diffractionsignal is separately detected. The amplitude ratio ispresented in table 3.

Figure 7: The 3 mm inner breaking notch inspection – theradius of the bead is 5 mm.

A) The notch is inspected before the beadB) the notch is inspected after the bead

Table 3: Amplitude ratio for the 3mm notch – the radius ofthe bead is 5mm

Figure 8A presents the UT angular B-scan considering adirect inspection of the 3mm high breaking surface notchand for the bead of R=3mm. This experimental data showsthe signal of the bead of joint and the notch (tip diffractionand the corner echo) are detected apart. Table 4 presents theamplitude rate.

Figure 8B shows the UT angular B-scan considering anindirect inspection. In particular, experimental data showsthat both signals the bead of joint and the notch are notdetected apart. The signals from the flaw are completelyincluded in the signal coming from the geometry.

R=5mm

Corner echoEchoes fromthe geometryof bead andcorner echo

Signals fromthe notch

Scan direction

3mm

Scan direction

Tip diffraction

3mm

3mm

Echo of thebead joint

A

B

76 76

R=5mm



Scan direction

3mm

Scan direction

Tip diffraction

3mm

3mm


A

B

76 76



Scan direction

3mm

Scan direction

Tip diffraction

3mm3mm

3mm


A

B

76 76


Figure 8: Inspection of 3 mm height inner breaking notch–the radius of the bead is 3 mm.

A) The notch is inspected before the bead B) the notch is inspected after the bead

Table 4: Amplitude ratio for the 3mm notch – the radius ofthe bead is 3 mm

The result of this inspection shows that flaws of 3mm highcan be detected and sized when the flaw is located beforethe bead. In this case the spatial resolution allows us toseparate echoes coming from the flaw and those comingfrom the geometry. In the opposite direction the 3mm highnotch is hidden by the geometrical echoes.

CONCLUSIONS

Results presented in this report and those obtained inprevious experimental data show that phased array is avaluable technique in detecting and sizing embedded andsurface breaking notches in TIG narrow gap welds.

In particular, this report presents the analysis of the effectof the TIG joint weld structure related to the UT inspectionusing phased array techniques. Special effort is paid toanalyse the role of both the root joint weld geometry andthe attenuation through the weld when flaws are inspected.

Near the surface, experimental inspection was carried out toanalyse the detection and sizing performances of flawslocated near the surface. In particular, the results show thatbefore the weld flaws can be detected and sized up to4mm.Through the weld, these flaws can be detected but notsized.

Concerning the weld structure effect, the experimentalresults show a slight attenuation and relatively low level ofnoise in the area of weld. The most important level of noisecomes from the weld backwall.

Regarding the effects of the geometry, the results show thatit is possible to detect apart notch of 3mm high and the

signal coming from the bead of weld for a radius of 3mmand 5mm. Nevertheless, it depends on the configuration ofthe experimental inspection. In general, the inspection ofnotch 3 mm high is difficult to characterise if the inspectionis performed in the direction through the weld. It is due tothe geometrical echo generated by the weld root area.

The final results of this project were presented in thereport [5].

REPORTS AND PUBLICATIONS

[1] Development of ultrasonic non destructive testingmethod for the vessel inter-sector weld of ITER:development of dynamic phased array techniques»,SISC/03-RT0096/Rev. 0, September 2003

[2] Development of ultrasonic non destructive testingmethod for the vessel inter-sector weld of ITER:simulation of welding process»,DECS/SISC/LMUS/02-RT0052, July 2002

[3] Development of phased array techniques for theinspection of one sided welds in ITER vacuumvessel», SYSSC/04-RT0143/ Rev. 0 September 2004

[4] Simulation of phased array technique for qualificationof UT methods for one sided welds during VVmanufacture. SYSSC/05 RT0167/ Rév. 0 October2005

[5] TIG Narrow gap influence of weld structure andgeometry on phased array techniques performances.SYSSC/06 RT0233/ Rév. 0 October 2006

TASK LEADER

Jorge TIRIRA

DRT/DeTECS/SYSSC/LMCCEA-SaclayF-91191 Gif-sur-Yvette Cedex

Tel. : 33 1 69 08 40 02Fax : 33 1 69 08 75 97


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CEFDA04-1202 Task Title: TW5-TVV … using TIG narrow gap process. This mock-up is 486mm length, 60...

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Transcript of CEFDA04-1202 Task Title: TW5-TVV … using TIG narrow gap process. This mock-up is 486mm length, 60...