development of welding and testing technique/s for · pdf filetesting (rt) weld+buttering...

By

Khalid Mahmood Pakistan Welding Institute (PWI)

PAKISTAN ATOMIC ENERGY COMMISSION (PAEC)

PAKISTAN

Development of Welding And Testing

Technique/s For Dissimilar Metal Welding Of

SA-508 Gr-3,class-1 Material With SS-316L.

• Introduction

• Objectives of development work

• Scheme of execution

• Experimental work

• Results and analysis

• Conclusions

2

Scheme of Presentation

Introduction

3

• Dissimilar metal welding: is a specific requirement where a transition in

metallurgical interfaces is attained in such a way that

the intended mechanical properties are achieved.

• Dissimilar metal welding presents a number of

engineering challenges such as: complex configurations,

control of weld microstructure,

difference in chemical, physical, mechanical properties,

difficulties in testing & inspection techniques etc.

Introduction

• SA-508 Cl. 1 Gr-3 is a constructional steel used mainly

in the form of forgings for the manufacture of:

Reactor Pressure Vessel (RPV),

Steam Generator (SG),

Pressurizer (PZ) and

Reactor Coolant Pump (RCP) in nuclear power plants.

• It is specifically needed to weld the safe ends of

SS-316 with SA-508 Gr-3, Cl. 1, material during NPP

construction phase which in term of welding is called

the dissimilar metal welding and is difficult to achieve.

4

Introduction

Introduction

5

Objective The primary objectives were:

Development of welded coupons (for calibration and with known defects) for training/certifications of UT personnel.

Development of welding procedure and performance qualifications for dissimilar welds repair and maintenance, if required and allowed.

To assess and enhance the capability level for testing and examination of dissimilar welds at PAEC level.

6

Objectives of Development Work

Objective Total NPPs = 07 Nos.

Operational = 04 Nos.

Under-construction = 03Nos.

7

Present status of NPPs in Pakistan

• PHASE 1: Collection of relevant information and

selection of variables

• PHASE 2: Preparation of welded coupons.

• PHASE 3: DT and NDT scheme for prepared coupons

and interpretation, discussion and analysis of the obtained results.

8

Scheme of Execution for Development

Work

9

PHASE 1: Collection of relevant information and selection of variables

Welding Coupons:

• Material And Dimensions: – Two (02) coupons were prepared.

– Plates of SA508 Cl-1, Gr-3 and SA-240 TP 316L were used.

– Dimensions (each)= 300mm x 300mm x 50mm

• Welding: – Process: Shielded Metal Arc Welding (SMAW)

– Filler metal: ASME SFA5.11, ENiCrFe-3 (for coupon only)

• Testing Of Produced Welds: – Available information of SNERDI , China (being designer)

was taken as reference for all testing and their acceptance criteria.

10

PHASE 2 : Preparation of Welded Coupons (Process Chart)

Chemical analysis of base materials

Chemical analysis of SA-508 Chemical analysis of SS-316L

Cutting of SA-508 and

SS-316L plates

Inspection of prepared edges

of Plates

Buttering of SA-508

Plate

Applying buttering up to 5-8mm

PT+UT of Buttered

plate In process hydrogen relievment

Completion of buttering up to 30mm

Machining for edge preparation of

buttered SA-508 and 316L Plates for

welding

Stress relieving after buttering

PT of edge/bevel of

buttered plate PT of edge/bevel of SS-316L

plate

Welding of plates to produce

coupons

11

SA-508 SS-316L Joint design used for the latest NPPs i-e C-3/C-4.

Joint design for the old NPP i-e C-1.

PHASE 2 : Preparation of Welded Coupons (JOINT DESIGN )

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PHASE 2 : Preparation of Welded Coupons

SA-508 Cl.1, Gr-3 Plate Dimensions =300mmx150mmx50mm

Applying Buttering Process: SMAW Filler metal: ASME SFA5.11, ENiCrFe-3,

ɸ3.2/4.0mm Currents: 130-140 amps Pre- heating: (min) 150°C Inter-pass temperature: (max) 250°C PWHT: Hydrogen and Stress relieving

13

PHASE 2 : Preparation of Welded Coupon

SA-508 Buttered Plate

Prepared edge of buttered SA-508 Plate

Inconel Buttering

SA-508 plate

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PHASE 2 : Preparation of Welded Coupon

SS-316L Beveled Plate

Fit up of buttered SA-508 and SS-316L Plate

SA-508 plate

SS-316L plate

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PHASE 2 : Preparation of Welded Coupons

With single-U joint design (for NDT+DT)

With Double-U joint design (for UT reference block)

• Non-Destructive Testing (NDT)

• Destructive Testing (DT)

16

PHASE 3 : Testing Scheme* for welded Coupons

Description

100% PT, 100%RT, 100%UT

Description

•Chemical Analysis

•Tensile Testing (02 specimens at each Temperature) At RT At 350°C

•Guided Bend Testing (04 specimens)

•Impact testing (03 specimens each from SA508 and weld regions) At RT At -10°C

•IGC Testing (specimens from buttering and inconel weld/SS-316L interface region) •Metallographic Examination

Micro-examination

*Available information of SNERDI , China was taken as reference for all testing and their acceptance.

• Both tests were performed at NCNDT, PAEC.

17

PHASE 3 : Non Destructive Testing (NDT) Results

Test Area of interest Results Remarks

Dye Penetrant Testing (PT)

Weld+buttering +HAZs

Acceptable Facility available

at PAEC Radiography Testing (RT)

Weld+buttering +HAZs

Acceptable

Dye Penetrate Test Radiography Test

• Ultrasonic Testing (UT)

• Manual Pulsed echo technique

was adopted for calibration

and scanning of produced

DMWs by using:

45° and 60° Longitudinal probes

with frequency 2MHz.

Calibration work has been

completed with required

sensitivity.

Weld was scanned and two

acceptable discontinuities (slag

inclusions) were found.

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PHASE 3 : Non Destructive Testing (NDT) Results

• Specimens slicing of welded coupon:

– Slicing to obtain samples for different tests was carried out at PWI with band saw.

– Diagram shows the location of different samples and their locations are according to SNERDI designer specifications & ASME section IX code QW-463.1 (b).

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PHASE 3 : Destructive Testing (DT)

Chemical Analysis: – Chemical analysis of buttering and weld was done by technique called spark emission

method at PWI, PAEC.

All elements were found in acceptable range.

20

PHASE 3 : Results of Destructive Testing (DT)

Elements C Si Mn P S Cr Fe Nb Ni Others

weld 0.027 0.60 5.60 0.0055 0.011 16.51 7.82 1.84 67.1 Bal.

Buttering 0.027 0.61 6.29 0.0047 0.011 15.11 6.93 1.51 69.0 Bal.

Acceptance

criteria

≤ 0.10

≤ 1.0

5-9.5

≤ 0.03

≤ 0.015

13-17

≤ 10

1-2.5

Bal.

≤ 0.50

Tensile Test: – At Room Temperature (RT/20°C) .

– At 350°C.

• Two samples for each case were tested.

• Tensile test samples were machined according to ASME section IX code QW 462.1 (c) for room temperature and QW 462.1 (d) for 350°C.

• Samples were tested as per ASME section IX code QW-150.

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Reduced Section Flat Tensile Samples Reduced Section Rounded Tensile Samples

Tensile Test:

22


Tested flat reduced section samples

UTM with tensile flat sample

Tested rounded reduced section samples

Tensile Test Results:

Acceptance criteria: The samples were in acceptable range.

23


Temperature

(°C)

Sample

No

Sample Description Ultimate

Tensile

Strength

(MPa)

Yield

Strength

(MPa)

Remarks Dimensions

(mm)

Area

(mm)2

Room temp.

TT-3 19*19 361 585 350 Broken from

SS316L

TT-2 21*19 399 595 355 Broken from

SS316L

350°C

TT-1 ǿ 12.7 126.7 450 260 Broken from

SS316L

TT-4 ǿ 12.6 124.7 495 295 Broken from

SS316L

Filler type Testing

temp.

(°C)

Tensile

Strength

(MPa)

Yield

strength

(MPa)

%

Elongation

(A)

ENiCrFe-3 RT ≥ 550 ≥ 314 ≥30

ENiCrFe-3 350 ≥ 425 ≥ 167 ≥30

Guided Bend Test:

– Bend test samples were machined according to ASME section IX code QW 462.2.

– Four samples were tested as per ASME section IX code QW 160.

– The type of bend was transverse side bend.

24


Side bend test samples

Guided Bend Test:

25


UTM with side bend sample

Side bend tested samples Side bend tested samples

Guided Bend Test: Acceptance criteria for Bend test is:

Results of bend test are shown below.

26


Sample

No

Type of

Bend

Size

(mm)

Angle of

Bend

Observation Status

SB-1 Side

Bend

240*45*10 180° Opening ≤ 3mm Accepted

SB-2 Side

Bend

240*45*10 180° Opening ≤ 3mm

Accepted

SB-3 Side

Bend

240*45*9.5 180° Opening ≤ 3mm

Accepted

SB-4 Side

Bend

240*45*10 180° Opening ≤ 3mm

Accepted

Type of Bend Angle of Bend Max. opening no. Max. opening

length

Side Bend 180° 2 3mm

Impact Test: • Impact test samples were machined according to ASTM E23.

• Six samples were taken from HAZ of SA-508 and weld regions.

• Three samples form each region were tested at:

Room temperature

-10 °C.

• The acceptance criteria was that energy absorbed should be ≥ 71J and lateral expansion should be ≥ 0.8mm.

27


Impact test samples (for Ref.)

Impact Test:

28


Impact tested samples at room temp. Impact tested samples at -10°C.

Impact Test Results:

All samples were in acceptable range of absorbed energy and lateral expansion at

RT and -10°C.

29


Temperature

(°C)

Sample No Region Notch Type

Energy Absorbed

(J)

Lateral Exp.

(mm)

Room temp.

1 weld V 120 3.91

2 weld V 116 4.16

3 weld V 115 3.53

11 HAZ (SA-508) V 164 4.24

12 HAZ (SA-508) V 126 4.4

13 HAZ (SA-508) V 129 4.3

-10°C

4 weld V 131 3.91

5 weld V 120 3.78

6 weld V 130 4.11

14 HAZ (SA-508) V 128 4.54

15 HAZ (SA-508) V 124 4.24

16 HAZ (SA-508) V 127 4.54

• IGC Results:

– ASTM A262 Practice-E was used for testing. No cracking/opening was observed at required magnification even

after bending of sensitized samples.

30


Metallographic examination:

• Metallographic examination was performed at NCNDT, PAEC.

• Regions of interest were

– weld,

– buttering,

– HAZ (SA-508),

– HAZ (SS-316L)

– Base metal SA-508 and SS-316L.

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• Metallographic examination: The acceptance criteria and results for metallographic examination are:

32

Type of Region Type of structure Result

Base Metal SA-508 Tempered Bainite No abnormality was

observed against the

required microstructure.

Base Metal SS-316L Austenite + few carbide

HAZ (SA-508) Tempered Bainite

HAZ (SS-316L) Austenite + few carbide

Weld Austenite + few carbide

Buttering Austenite + few carbide


Problems faced: • Non-availability of material/s, particularly SA508, for development on DMWs.

• Very limited access to technology for development of welding coupons and training of NDT personnel on DMWs (SA508/SS316).

• Specific UT procedure and probes were not available at local level for scanning of these welds.

Positive outcomes: • Acceptable results of Destructive testing (DT) proved that weld produced was of

required quality from strength, ductility, toughness and corrosion resistance point of view. Same variables can be adopted for welding qualifications in future.

• After confidence in manual scanning of these welds using pulse echo technique, a dedicated team of NCNDT personnel is still working for skill enhancement by using TOFD and PAUT techniques.

Future course of action: • More welded coupons even with known welding defects will be prepared for training of

welding and NDT teams by PWI.

33

Conclusions

development of welding and testing technique/s for · pdf filetesting (rt) weld+buttering...

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