overview of the strands production for iter in wsticec26-icmc2016.org/downloads/8-o-1c-1.pdf ·...

Overview of the Strands Production

for ITER in WST

8th, Mar. 2016 New Delhi, India

J.F. Lia,b, Y.H.Lia,b,W.T. Liua,b, K. Zhanga,b, J. W. Liu a,b, S.J. Dua,b, G. Yan a,b, X.H. Liua,b, Y. Fenga,b, P.X. Zhanga,b,c, S. Liud

a. Western Superconducting Technologies Co.,Ltd., Xi’an 710018, China b National Engineering Laboratory for Superconducting Materials Preparation, Xi’an 710018, Chinac. Northwest Institute for Nonferrous Metal Research, P.O. Box 51, Xi’an 710016, Chinad. China International Nuclear Fusion Energy Program Execution Center, Beijing,100862

西部超导西部超导

Western Superconducting Technologies Co., Ltd.

Brief Introduction of WST1

Outline

2

3

Production status for ITER

Summary



NIN = Northwest institute for nonferrous metal

1. History Introduction

Baoji Xi’an

NIN = Northwest institute for nonferrous metal

1965: R&D of NbTi materials (Ingot and wire) started.

1967: The first mono-filamentary NbTi wires were fabricated .

1972: The first multi-filamentary NbTi wires were prepared .

1980: Jc of NbTi wire reached 3450 A/mm2 (4.2 K,5 T), the World Record.

1987: The first NbTi/CuNi wires for AC applications were made .

1995: The large size NbTi multi-filamentary wire with weight of 80 kg were prepared .

1999: Ф20 mm NbTi bars to IGC (MRI wires)

2001: Ф193.5 mm X 760mm NbTi billets to Alstom

2002: Ф29.4 mm NbTi bars to OXFORD for MRI wires

2003: WST was founded and the main aim was ITER project (NIN is the largest share holder)



Company Scale- Area and Location

Area 3Area 2Area 1

The 1st Area The 2nd Area Location: Xi’an Economic-

The 3rd Area

Place: Xi’an Jing Wei Location: Xi’an Economic-Technological Development Area

Area: 82000 square meter

Location: Xi’an Economic-Technological Development Area

Area: 110000 square meter

Place: Xi’an Jing Wei

Industrial Park

Area:208000 square meter

Melting Free forgingMRI wire Swaging

SuperconductorRolling line

Storage R&D buildingStorage

Area 1&2Capability6000 ton ingots of Ti alloy, 3000 ton rods of Ti alloy 500 ton Monolith superconducting wire 300 ton WIC superconducting conductor



Products and Applications

Aviation andNavigation Field

Ti alloy

IndustrialField

New

Energy

Field

Medical Field

Ti alloy

ITER PROJECT

MRISC

SC



Certification

ISO9001B AS9001C ISO14001

Nadcap Heat treatment

Nondestructive testing certificate

ROHS level: Level 4




Outline

2

3

Production Status for ITER

Summary



International Thermonuclear Experimental Reactor (ITER)

China (WST):

170 t NbTi strand

30 t Nb3Sn strand

Coils Superconducting wire Weight (t)Proportion (%）

CN EU JA KO RF US

TF Nb3Sn 420 7.5 20.2 25 20 19.3 7.8

CS Nb3Sn 122 100

PF NbTi 224 65 35

CC/Feeder NbTi 21 100

Overview of NbTi and Nb3Sn Strands for ITER

WST launched mass production of NbTi and Nb3Sn strands for ITER in 2009 and

finished 174t NbTi and 35t Nb3Sn strands production until 2015.

TF conductor

Nb3Sn strand

TF coil

CS coil

CS conductor

Cabling and Jacketing

ITER Magnet Structure

PF conductor

NbTi strand

PF and CC coil

Feeder

CC conductor

MB conductor

CB conductor

Cabling and Jacketing

The distribution of energy in the Nb element in electrode is the key issue for homogeneity.

Chamber

Electrode

Liquid

Mushy

Arc

High homogeneity NbTi alloy

the key issue for homogeneity.

High-homogeneity NbTi alloy has been explored and produced in large scale for ITER

Solid

Mushy zone

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2040

42

44

46

48

50

top middle bottom

Billet No.

Ti

% R/4 R/2 Center

High homogeneity of componet and microstructure

Fabrication of large size NbTi/Cu composite billet

Subelements

NbTi Nb

Single filament

Cu

WST developed the fabrication technology to make large size

NbTi/Cu billet with high quality and low cost

Subelements

Cu stablizer

Single filament

Cu450kg billlet with 2616 filaments in

one step assembly process. Fill ration

reaches 98%.

400

500

Ic (

A)

4HT-sample 6HT-mass production 4HT-1012-10023 4HT-1012-10024 4HT-1012-10025 6HT-Sultan sample

Enhencement of performance of NbTi by optimization ofHT and additional strain

2500

3000

3500

Jc (

A/m

m2)

8T 7T 6T 5T 4T

The 4 times HT method was developed insteadof traditional 6 times HT method.

4 5 6 7

200

300

ITER Spec.:>339A@5T,4.2KIc (

A)

B (T)

4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.61000

1500

2000

Jc (

A/m

m

f

The Heat treatment times and additional strain have siginificant effect on critical current density of NbTi strands.

Ultrafine filamentary NbTi strands

Cross section of NbTi after extrusion

Distribution of filaments

• One step extrusion

• 65 cold drawing process

• 99.99% deformation ratio

0.73mm final strand

transverse

longitudinal

The maximum unit length of final NbTi strand for ITER with ultrafine filament is 90000m

NbTi

Cu

Nb

SubelementsSurface of filaments

with diameter of 8 µm

longitudinal

Performance of NbTi strands

All the performances of NbTi strands can meet ITER specifications.

Internal-tin Nb3Sn Strand: Design

Ratio of Cu:Nb:Sn=2.97:1.57:1

Key issuesHigh Jc High content of

Nb3Sn pahseHigh ratio of Nb and Sn

Low AC loss Distance of filaments High ratio of Cu

Filaments Number of Nb3Sn strand is 3040.

The subelement in strand

Nb Filament

Low AC loss: (To avoid coupling)The copper surround Nb filamentThe copper surround subelement

The distance of filaments is about 2 µm and of subelements is about 5 µm

The ratio of Cu/Nb/Sn elements and distance ensure high Jc and low AC loss of internal-tin Nb3Sn strands for ITER

Sn2Ti bar

Cu matrix

Step characteristic Size（mm） Drawing rate（%） Purpose

1Low Drawing

rate65-47 7-14

Hardening of all elements synchronously

2High Drawing

rate47-5.85 23-29

Deformation of all elements synchronously

3Middle

Drawing rate5.85-0.82 12-18 Low resistance to deformation

Final billet Final Nb3Sn strand

Internal-tin Nb3Sn Strand: Fabrication

Final billet

Drawing

Final Nb3Sn strand

The special defromation controlling technology ensure the homogenity of all elements in composite to get fine Nb3Sn grains

Assembly

19 subelements

Nb3Sn grains

Strand type Type 1 Type 2 Type 3

Cross section

Internal-tin Nb3Sn Strand: New Structure

New structure strand were fabricated and investigated to improve totalperformance for the future fusion application.

Structure feature

Cu split Cu split Cu split

-- Tin spacer --

-- -- 37 subelements

IC (A) @4.2K,12T >250 >280 >270

n value @4.2K,12T >20 >20 >20

RRR(273K/20K) >100 >100 >100

Qh (mJ/cm3) @4.2K,±3T <300 <340 <320

Qh level is efficiently decreased by Cu split in subelementsIc is increased by tin spacers in final billets

Internal-tin Nb3Sn Strand: Performance

Heat treatment was investgated to understand the intrinsic property of the strand

Duration at reaction temperature Temperature sensitivity

Heat treatment duration has greater impact on Qh

Ic is very sensitive to temperature variation of ± 5 oC at high field

The increase rate of Qh is much more significant than Ic when duration is varied from 55 h to 100 h.

Ic is very sensitive to temperature fluctuation specially from 645 oC to 650 oC at field above 12 T.

Performance of Internal-tin Nb3Sn Strands for ITER

All the performances of IT Nb3Sn strands can meet ITER specifications.

High-Sn Bronze Nb rod 37×367=13579 filament

Key issues to fabricate the Nb3Sn wires with High Jc and low AC loss:

• a. High-Sn content in bronze

• b. Enough fine filament

Nb3Sn filament

Bronze Nb3Sn strand: Strand design

First stacking Re-stacking

Our design idea: a) Using the high-Sn Bronze with 15.5 wt.% Sn content as the raw material;b) Increasing the filament number to 13579, make the filament size up to 2 um;c) Using the hetermophous bronze rod to make the filling ratio up to 97.8%.

Final strands

Ta barrierCu

Bronze Nb3Sn strand: Design

Effect of diffusion barrier on hysteresis loss

Sample-1

Sample-2

Sample-3

Number of filaments 13579 13579 11581

Filament material Nb Nb NbTa

Barrier material Nb+Ta Nb Ta

Performance of Nb3Sn wires with different barrier design

The SEM images of bronze processed Nb3Sn strand after heat treatment(a) Nb3Sn strand with combined Nb-Ta diffusion barrier (Sample-1). (b) Nb3Sn strand with single Nb diffusion barrier (Sample-2). (c) Nb3Sn strand with single Ta diffusion barrier (Sample-3).

Barrier material Nb+Ta Nb Ta

Ic (A) @4.2K, 12T 236 244 201

Hysteresis loss(mJ/cm3) @4.2K,±3T

159 309 53

Nb3Sn ring formed by Nb barrier

leads a high loss.

Ta strips interrupt the circular Nb3Sn

layer reacted by Nb barrier which

results a middle loss.

Bronze Nb3Sn strand: Performance

Design 1 Design 2 Design 3

Matrix material Cu15.5Sn0.25Ti

Filament material Nb

Number of filaments 13579

Effect of bronze/Nb ratio on Jcn

Performance of Nb3Sn wires with bronze/Nb ratio

1A-WT-P-051A-WT-P-05

See also:1A-WT-P-05

Bronze/Nb area ratio 2.5 2.2 2.0

Filament spacing(μm) 1.4 1.3 1.2

Ic (A) @4.2K, 12T 236 239 244

Jcn (A/mm2)@4.2K,12T 907 923 930

n value 37 36 40

Jcn increase slowly with the bronze/Nb area ratio reducing for the increase of Nb3Sn

volume fraction.

By optimizing the design, now the Jcn of bronze Nb3Sn superconducting wires

exceeds 900A/mm2 at 4.2K and 12T .

1A-WT-P-051A-WT-P-05

SULTAN Test results

SULTAN Test Facility and Sample in CRPP, Switzerland.

WST strands has passed all the ITER qualification test




Outline

2

3

Production status for ITER

Summary



Summary WST is the only supplier of NbTi and Nb3Sn superconducting strands

in China for ITER project, and 174 tons NbTi strands and 35 tons Nb3Sn strands have been produced until Dec. 2015. All the performance can meet ITER specification.

WST is the only supplier of NbTi bars, mono-bars and NbTi wires in the world.

WST also put forth effort to develop the customized superconductors for High Energy Physics, NMR and High Magnetic Field applications.

overview of the strands production for iter in wsticec26-icmc2016.org/downloads/8-o-1c-1.pdf ·...

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