MECHANICAL PROPERTIES OF Zr 2.5Nb PRESSU
MECHANICAL PROPERTIES OF Zr-2.5Nb PRESSURE TUBE
MATERIAL MANUFACTURED EMPLOYING FORGING ROUTES
FOR PHWR700 - PART I: TENSILE BEHAVIOR
by
A.K. Bind, R.N. Singh, Saurav Sunil, J.K. Chakravartty
Mechanical Metallurgy Division
and
A. Ghosh, P. Dhandharia, N.S. More, S. Vijayakumar, A.G. Chhatre
Engineering Directorate, Nuclear Power Corporation of India Ltd.
2012
BARC/2012/E/002
BARC/2012/E/002
BARC/2012/E/002
BARC/2012/E/002
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
MECHANICAL PROPERTIES OF Zr-2.5Nb PRESSURE TUBE
MATERIAL MANUFACTURED EMPLOYING FORGING ROUTES
FOR PHWR700 - PART I: TENSILE BEHAVIOR
by
A.K. Bind, R.N. Singh, Saurav Sunil, J.K. Chakravartty
Mechanical Metallurgy Division
and
A. Ghosh, P. Dhandharia, N.S. More, S. Vijayakumar, A.G. Chhatre
Engineering Directorate, Nuclear Power Corporation of India Ltd.
BHABHA ATOMIC RESEARCH CENTRE
MUMBAI, INDIA
2012
BARC/2012/E/002
BIBLIOGRAPHIC
DESCRIPTION SHEET FOR
(as per IS : 9400 - 1980)
TECHNICAL REPORT
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Security classification :
Unclassified
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Distribution :
External
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Report status :
New
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Series :
BARC External
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Report type :
Technical Report
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Report No. :
BARC/2012/E/002
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Part No. or Volume No. :
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Contract No. :
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Title and subtitle :
Mechanical properties of Zr-2.5Nb pressure tube material
manufactured employing forging routes for PHWR700 - Part 1: tensile
behavior
11
Collation :
45 p., 23 figs., 3 tabs.
13
Project No. :
20
Personal author(s) :
1) A.K. Bind; R.N. Singh; Saurav Sunil; J.K. Chakravartty
2) Agnish Ghosh; Priyesh Dhandharia; Nitin S. More; S.
Vijayakumar; A.G. Chhatre
21
Affiliation of author(s) :
1) Mechanical Metallurgy Division, Bhabha Atomic Research Centre,
Mumbai
2) Engineering Directorate, Nuclear Power Corporation of India
Limited, Mumbai
22
Corporate author(s) :
Bhabha Atomic Research Centre,
Mumbai - 400 085
23
Originating unit :
Mechanical Metallurgy Division,
BARC, Mumbai
24
Sponsor(s) Name :
Department of Atomic Energy
Type :
Government
Contd...
BARC/2012/E/002
30
Date of submission :
December 2011
31
Publication/Issue date :
January 2012
40
Publisher/Distributor :
Head, Scientific Information Resource Division,
Bhabha Atomic Research Centre, Mumbai
42
Form of distribution :
Hard copy
50
Language of text :
English
51
Language of summary :
English
52
No. of references :
15 refs.
53
Gives data on :
60
Abstract :
Tensile properties of Zr-2.5Nb alloy tubes produced employing forging to break the
cast structure were evaluated by carrying out uni-axial tension test at temperatures between 25
and 325 0C and under strain-rate of 1.075 x 10-4/s for both longitudinal and transverse specimens.
Both strength and elongation values were comparable for the samples obtained from front and
back end of the tube. Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples. The yield strength of double forged material at 25 0C
is higher than the PHWR700 specification of a maximum value of 586 MPa.
70
Keywords/Descriptors :
PHWR TYPE REACTORS; PRESSURE TUBES; ZIRCONIUM ALLOYS;
NIOBIUM ALLOYS; YIELD STRENGTH; COLD WORKING; ELONGATION; STRAIN RATE; TENSILE
PROPERTIES
71
INIS Subject Category :
99
Supplementary elements :
S21
Content
Abstract
Page
No.
1
Nomenclature
2
1. Introduction
3
2. Experimental
5
3. Results and Discussion
5
4. Conclusions
10
Acknowledgements
10
Reference
11
List of tables
13
List of figures
13
Tables
17
Figures
19
v
Tensile behavior of Zr-2.5Nb pressure tube material
manufactured employing forging routes
A. K. Bind1, R.N. Singh1, Saurabh Sunil1, J.K. Chakravartty1,
Agnish Ghosh2, Priyesh Dhandharia2, Nitin S. More2, S. Vijayakumar2, A. G. Chhatre2
1
Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai400085.
2
Engineering Directorate, Nuclear power Corporation of India Ltd., NUB, Anushaktinagar,
Mumbai-400094
Abstract
In order to obtain improved in-reactor performance NFC, Hyderabad had produced few tubes of Zr2.5Nb alloy by employing forging to break the cast structure. To break the cast structure and to obtain
more homogeneous microstructure both double forging and single forging were employed.
Subsequently the forged material was used to manufacture pressure tube by employing hot extrusion,
cold pilgering and autoclaving. The material was received in the form of spools of length of about 100
mm each. The tubes were slit at 120 degree and then cold flattened. The plates were stress relieved at
400 °C for 24 hour. The both longitudinal (L) and transverse (T) tensile samples were machined from
these plates. Tensile properties were evaluated by carrying out uniaxial tension tests at temperatures
between 25 and 325 °C and under strain-rate of 1.075 x 10-4 /s. Analysis of tensile results showed that
both yield and ultimate tensile strengths of this alloy decreased monotonically with increasing test
temperatures. Both strength and elongation values were comparable for the samples (L & T) obtained
from front and back end of the tube manufactured by single and double forging routes. Transverse
samples showed higher strength and lower uniform elongation values as compared to longitudinal
samples. Double forged material showed higher strength but comparable elongation values as
compared single forged material for L & T samples obtained from front end and back end of the tube.
The yield strength of double forged material at 25 °C is higher than the PHWR700 specification of a
maximum value of ~586 MPa. The observed deviation from specification can be corrected by
changing thermo-mechanical processing parameters appropriately.
Keywords: Zr-2.5Nb alloy, Tensile properties, Yield strength, Ultimate Tensile Strength,
elongation, forging, β-quenching, extrusion, pilgering, autoclaving
1
Nomenclature
ACR
Advanced CANDU Reactor
AERB
Atomic Energy Regulatory Board
ASME
American Society of Mechanical Engineers
BARC
Bhabha Atomic Research Centre
CANDU reactor
Canada Deuterium Uranium reactor
CWSR
Cold Worked and Stress Relieved
DBLA
Double forged back end longitudinal orientation
DBTA
Double forged back end transverse orientation
DFLA
Double forged front end longitudinal orientation
DFTA
Double forged front end transverse orientation
e
Plastic strain
eu
Uniform plastic strain
et
Total plastic strain
EDM
Electro Discharge Machining
IPHWR
Indian Pressurized Heavy Water Reactor
L
Longitudinal orientation
LE
Leading end
mm
millimeter
MPa
Megapascal
MWe
Megawatt electrical
Nb
Niobium
NFC
Nuclear Fuel Complex
NPCIL
Nuclear Power Corporation of India Ltd.
O
Oxygen
PHWR
Pressurized Heavy Water Reactor
ppm
Parts per million
2
PT
Pressure Tube
s
second
S
Engineering stress
SBLA
Single forged back end longitudinal orientation
SBTA
Single forged back end transverse orientation
SFLA
Single forged front end longitudinal orientation
SFTA
Single forged front end transverse orientation
T
Transverse orientation
TE
Trailing end
UTS
Ultimate Tensile Strength
wppm
Weight in parts per million
YS
Yield Strength
Zr
Zirconium
α-Zr
Alpha zirconium having HCP crystal structure
β-Zr
Beta zirconium having BCC crystal structure
°C
Degree Celsius
εpl
True plastic strain
σ
True stress
1. Introduction
Cold-worked and stress relieved (CWSR) Zr-2.5Nb tubes is being used as pressure
tubes for Indian Pressurized Heavy Water Reactors (IPHWR) [1-5]. The pressure tubes serve
as miniature pressure vessels operating at about 300 °C with a coolant pressure of ~ 10 MPa.
The design of the pressure tube is based on section III of the ASME pressure vessel code,
which specifies the criteria of maximum design stress on the basis of ultimate tensile strength,
yield strength, creep and stress-rupture strengths at the operating temperature. For pressure
tube alloys (both Zircaloy-2 and Zr-2.5Nb alloy) one third of the ultimate tensile strength has
been found to be the limiting property [6].
Recent in-reactor dimensional changes measurement by NPCIL in IPHWR220 MWe
has revealed that the diametral creep rate exhibited by some of the tubes is significantly
3
greater than design value. Also, large variability in the axial elongation and diametral creep
rates of the pressure tubes across the reactor core were observed. In order to achieve the
design life of 30 years for Zr-2.5Nb pressure tubes, several discussion and meetings were held
between the BARC scientists, NPCIL engineers, NFC engineers and AERB safety regulators.
A series of investigations were initiated by reactor operators and safety engineers to evaluate
the effect of relaxing the diametral creep limit form present 3 % to 4.5% on thermal
hydraulics of the coolant channels and structural integrity of coolant channel assembly.
Another initiative was to reexamine the alloy chemistry and microstructure based on the
experience gained both nationally and internationally with the objective of improving inreactor performance of the pressure tubes. Causey et al. [7] has reviewed the relationship
between alloy chemistry and in-reactor performance of CANDU pressure tubes. The
evolution of alloy chemistry for Zr-2.5Nb pressure tube material is shown in table 1 [7]. It
may be noted that initially Nb content range was between 2.4-2.8 wt percent which has been
narrowed down since 1987 to 2.5-2.8 wt percent. Carbon content has been reduced from 270
wppm in 1976 to a range between 40-60 wppm to reduce deuterium intake. Over the years
oxygen concentration has been increased from 900-1300 to 1200-1500 wppm because of its
beneficial effect in reducing diametral creep. Initially iron content was specified to be less
than 1500 wppm, which was reduced to less than 650 wppm as it was expected to promote
deuterium pick up.
However, recent irradiation studies have suggested role of iron in
reducing diametral creep and axial elongation and hence iron content specified for ACR700 is
900-1300 wppm. Another notable improvement is the specification for chlorine (469MPa, YS at 300°C > 324 MPa and YS at
25 °C < 586 MPa. The deviations from PHWR700 have been indicated in bold font.
List of figures
Fig. 1 Fabrication flow sheets for manufacture of Zr-2.5Nb pressure tube material using
conventional, single forged and double forged routes.
Fig. 2: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 3: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 4: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 5: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
13
Fig. 6: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
Fig. 7: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 8: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 9: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 10: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 11: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
Fig. 12: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the longitudinal
samples obtained from front and back end of the tube manufactured by Double forging route.
Fig. 13: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
14
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Double forging route.
Fig. 14: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Double forging route.
Fig. 15: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from back end of the tube manufactured
by Double forging route.
Fig. 16: Influence of test temperature and sample location (front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Strength was higher and elongation values were lower for samples obtained
from front end as compared to that obtained from back end for the longitudinal samples of the
tube manufactured by single forging route.
Fig. 17: Influence of test temperature and sample location (front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Single forging route.
Fig. 18: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
15
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Single forging route.
Fig. 19: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower elongation values as
compared to longitudinal samples obtained from back end of the tube manufactured by Single
forging route.
Fig. 20: Influence of test temperature and forging (SFLA & DFLA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength and higher total elongation values as compared single forged material for
longitudinal samples obtained from front end of the tubes.
Fig. 21: Influence of test temperature and forging (SFTA & DFTA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
transverse samples obtained from front end of the tubes.
Fig. 22: Influence of test temperature and forging (SFLA & DFLA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
longitudinal samples obtained from back end of the tubes.
Fig. 23: Influence of test temperature and forging (SFTA & DFTA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
transverse samples obtained from back end of the tubes.
16
Table 1: Changes in Alloying/Impurity Element Specifications (in ppm by weight except Nb)
for Zr-2.5Nb PTs [9]
Elements
Nb(wt%)
Carbon
Oxygen
Iron
Aluminium
Antimony
Boron
Cadmium
Chromium
Chlorine
Cobalt
Copper
Hafnium
Hydrogen
Lead
Magnesium
Manganese
Molybdenum
Nickel
Nitrogen
Phosphorus
Silicon
Tantalum
Tin
Titanium
Tungsten
Uranium
Vanadium
Zirconium
(1976)
(1987)
2.4‐2.8
270
900‐1300
1500
75
‐
0.5
0.5
200
‐
20
50
50
20
130
20
50
50
70
65
‐
120
200
100
50
100
3.5
50
Balance
2.5‐2.8
150
1000‐1300
650
75
‐
0.5
0.5
100
‐
20
50
50
20
50
20
50
50
35
65
‐
120
100
100
50
50
3.5
50
Balance
Wolsong
3&4
2.5‐2.8
125
1000‐1300
650
75
‐
0.5
0.5
100
0.5
20
50
50
5
50
10
50
50
35
65
10
100
100
100
50
50
3.5
50
Balance
Qinshan
ACR
Retube
2.5‐2.8
125
1000‐1300
650
75
‐
0.5
0.5
100
*
20
50
50
5
50
1
50
50
35
65
12
100
100
100
50
50
3.5
50
Balance
2.5‐2.8
40‐80
1200‐1500
900‐1300
75
‐
0.5
0.5
100
*
20
50
50
5
50
20
50
50
35
65
12
100
100
50
50
50
3.5
50
Balance
2.5‐2.8
40‐80
900‐1200
900‐1300
75
‐
0.5
0.5
100
0.5*
20
50
50
5
50
20
50
50
35
65
12
100
100
50
50
50
3.5
50
Balance
* It is expected that the ingot processing will maintain the chlorine concentration < 0.2 wppm.
- Not specified
17
Table 2: Details of fabrication route, tube number, test temperatures and sample orientation
used in this work.
Routes
Double
forged
Single
Forged
Conventional
Spool No.
Temperature, °C
Orientation
# 2849-1 LE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
OE 2849- 2 TE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
# 2845-2 LE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
OE 2845-2 TE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
19-2557-2
25, 70, 150, 250, 300 and 325
Longitudinal
Table 3: Comparison of tensile properties of the Zr-2.5Nb alloy investigated in this work with
PHWR700 specification, viz., UTS at 300°C >469MPa, YS at 300°C > 324 MPa and YS at
25 °C < 586 MPa. The deviations from PHWR700 have been indicated in bold font.
Fabrication
Route
Tube
Position
Direction
Single Forged
Single Forged
Double
Forged
Double
Forged
Front End
Back End
YS (25 YS (300 UTS (300 Ductility
°C), MPa °C), MPa °C), MPa
(300 °C),
%
Longitudinal
574
398
509
13.1
Longitudinal
546
380
487
16.3
Front End
Longitudinal
610
412
550
17. 3
Back End
Longitudinal
596
406
547
16.1
18
Melted ingot (350 mm Dia)
Extrusion (230 mm
Melted ingot (350 mm Dia)
Melted ingot (550 mm Dia)
Forging (230 mm dia)
Forging (350 mm dia)
dia)
Forging (230 mm dia)
β quenching
β quenching
β quenching
(1000°C/30 min)
(1000°C/30 min)
(1000°C/30 min)
Extrusion (133 mm OD x 9
Extrusion (133 mm OD x 9
Extrusion (119 mm OD x 6
mm WT and Temp‐800°C)
mm WT and Temp‐800°C)
mm WT and Temp‐815°C)
Stress Relieving (480°C / 3
Stress Relieving (480°C / 3
Stress Relieving (480°C / 3
hrs)
hrs)
hrs)
Pilgering (112.8 mm OD –
Pilgering (112.8 mm OD –
Pilgering (112.8 mm OD –
103.4 mm ID)
103.4 mm ID)
103.4 mm ID)
Autoclaving (400°C / 36 hrs)
Autoclaving (400°C / 36 hrs)
Autoclaving (400°C / 36 hrs)
Pilgering
(119 mm x 6 mm WT)
Annealing
(550°C / 6 hrs)
Fig. 1 Fabrication flow sheets for manufacture of Zr-2.5Nb pressure tube material using
conventional, single forged and double forged routes.
19
(a)
(b)
Fig. 2: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
20
(a)
(b)
Fig. 3: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
21
(a)
(b)
Fig. 4: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
22
(a)
(b)
Fig. 5: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
23
e
Fig. 6: Engineering stress vs. plastic strain curves
pl for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
24
(a)
(b)
Fig. 7: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
25
(a)
(b)
Fig. 8: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
26
(a)
(b)
Fig. 9: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
27
(a)
(b)
Fig. 10: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
28
Fig. 11: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
29
900
DBLA-YS
DFLA-YS
NFC DF-YS
DBLA-UTS
DFLA-UTS
NFC-DF-UTS
Strength, MPa
800
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBLA-et
DFLA-et
NFC DF-et
DBLA-eu
DFLA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 12: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the longitudinal
samples obtained from front and back end of the tube manufactured by Double forging route.
30
1000
DBTA-YS
DFTA-YS
DBTA-UTS
DFTA-UTS
900
Strength, MPa
800
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBTA-et
DFTA-et
DBTA-eu
DFTA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 13: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Double forging route.
31
900
DFLA -YS
DFTA-YS
DFLA -UTS
DFTA -UTS
Strength, MPa
800
700
600
500
(a)
400
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DFLA -et
DFTA -et
DFLA -eu
DFTA -eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 14: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Double forging route.
32
900
DBLA-YS
DBTA-YS
DBLA-UTS
DBTA-UTS
Strength, MPa
800
700
600
500
400
300
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBLA-et
DBTA -et
DBLA-eu
DBTA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 15: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from back end of the tube manufactured
by Double forging route.
33
800
SBLA-YS
SFLA-YS
NFC SF-YS
SBLA-UTS
SFLA-UTS
NFC-SF-UTS
Strength, MPa
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
SBLA-et
SFLA-et
NFC SF.et
SBLA-eu
SFLA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperatu
MATERIAL MANUFACTURED EMPLOYING FORGING ROUTES
FOR PHWR700 - PART I: TENSILE BEHAVIOR
by
A.K. Bind, R.N. Singh, Saurav Sunil, J.K. Chakravartty
Mechanical Metallurgy Division
and
A. Ghosh, P. Dhandharia, N.S. More, S. Vijayakumar, A.G. Chhatre
Engineering Directorate, Nuclear Power Corporation of India Ltd.
2012
BARC/2012/E/002
BARC/2012/E/002
BARC/2012/E/002
BARC/2012/E/002
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
MECHANICAL PROPERTIES OF Zr-2.5Nb PRESSURE TUBE
MATERIAL MANUFACTURED EMPLOYING FORGING ROUTES
FOR PHWR700 - PART I: TENSILE BEHAVIOR
by
A.K. Bind, R.N. Singh, Saurav Sunil, J.K. Chakravartty
Mechanical Metallurgy Division
and
A. Ghosh, P. Dhandharia, N.S. More, S. Vijayakumar, A.G. Chhatre
Engineering Directorate, Nuclear Power Corporation of India Ltd.
BHABHA ATOMIC RESEARCH CENTRE
MUMBAI, INDIA
2012
BARC/2012/E/002
BIBLIOGRAPHIC
DESCRIPTION SHEET FOR
(as per IS : 9400 - 1980)
TECHNICAL REPORT
01
Security classification :
Unclassified
02
Distribution :
External
03
Report status :
New
04
Series :
BARC External
05
Report type :
Technical Report
06
Report No. :
BARC/2012/E/002
07
Part No. or Volume No. :
08
Contract No. :
10
Title and subtitle :
Mechanical properties of Zr-2.5Nb pressure tube material
manufactured employing forging routes for PHWR700 - Part 1: tensile
behavior
11
Collation :
45 p., 23 figs., 3 tabs.
13
Project No. :
20
Personal author(s) :
1) A.K. Bind; R.N. Singh; Saurav Sunil; J.K. Chakravartty
2) Agnish Ghosh; Priyesh Dhandharia; Nitin S. More; S.
Vijayakumar; A.G. Chhatre
21
Affiliation of author(s) :
1) Mechanical Metallurgy Division, Bhabha Atomic Research Centre,
Mumbai
2) Engineering Directorate, Nuclear Power Corporation of India
Limited, Mumbai
22
Corporate author(s) :
Bhabha Atomic Research Centre,
Mumbai - 400 085
23
Originating unit :
Mechanical Metallurgy Division,
BARC, Mumbai
24
Sponsor(s) Name :
Department of Atomic Energy
Type :
Government
Contd...
BARC/2012/E/002
30
Date of submission :
December 2011
31
Publication/Issue date :
January 2012
40
Publisher/Distributor :
Head, Scientific Information Resource Division,
Bhabha Atomic Research Centre, Mumbai
42
Form of distribution :
Hard copy
50
Language of text :
English
51
Language of summary :
English
52
No. of references :
15 refs.
53
Gives data on :
60
Abstract :
Tensile properties of Zr-2.5Nb alloy tubes produced employing forging to break the
cast structure were evaluated by carrying out uni-axial tension test at temperatures between 25
and 325 0C and under strain-rate of 1.075 x 10-4/s for both longitudinal and transverse specimens.
Both strength and elongation values were comparable for the samples obtained from front and
back end of the tube. Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples. The yield strength of double forged material at 25 0C
is higher than the PHWR700 specification of a maximum value of 586 MPa.
70
Keywords/Descriptors :
PHWR TYPE REACTORS; PRESSURE TUBES; ZIRCONIUM ALLOYS;
NIOBIUM ALLOYS; YIELD STRENGTH; COLD WORKING; ELONGATION; STRAIN RATE; TENSILE
PROPERTIES
71
INIS Subject Category :
99
Supplementary elements :
S21
Content
Abstract
Page
No.
1
Nomenclature
2
1. Introduction
3
2. Experimental
5
3. Results and Discussion
5
4. Conclusions
10
Acknowledgements
10
Reference
11
List of tables
13
List of figures
13
Tables
17
Figures
19
v
Tensile behavior of Zr-2.5Nb pressure tube material
manufactured employing forging routes
A. K. Bind1, R.N. Singh1, Saurabh Sunil1, J.K. Chakravartty1,
Agnish Ghosh2, Priyesh Dhandharia2, Nitin S. More2, S. Vijayakumar2, A. G. Chhatre2
1
Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai400085.
2
Engineering Directorate, Nuclear power Corporation of India Ltd., NUB, Anushaktinagar,
Mumbai-400094
Abstract
In order to obtain improved in-reactor performance NFC, Hyderabad had produced few tubes of Zr2.5Nb alloy by employing forging to break the cast structure. To break the cast structure and to obtain
more homogeneous microstructure both double forging and single forging were employed.
Subsequently the forged material was used to manufacture pressure tube by employing hot extrusion,
cold pilgering and autoclaving. The material was received in the form of spools of length of about 100
mm each. The tubes were slit at 120 degree and then cold flattened. The plates were stress relieved at
400 °C for 24 hour. The both longitudinal (L) and transverse (T) tensile samples were machined from
these plates. Tensile properties were evaluated by carrying out uniaxial tension tests at temperatures
between 25 and 325 °C and under strain-rate of 1.075 x 10-4 /s. Analysis of tensile results showed that
both yield and ultimate tensile strengths of this alloy decreased monotonically with increasing test
temperatures. Both strength and elongation values were comparable for the samples (L & T) obtained
from front and back end of the tube manufactured by single and double forging routes. Transverse
samples showed higher strength and lower uniform elongation values as compared to longitudinal
samples. Double forged material showed higher strength but comparable elongation values as
compared single forged material for L & T samples obtained from front end and back end of the tube.
The yield strength of double forged material at 25 °C is higher than the PHWR700 specification of a
maximum value of ~586 MPa. The observed deviation from specification can be corrected by
changing thermo-mechanical processing parameters appropriately.
Keywords: Zr-2.5Nb alloy, Tensile properties, Yield strength, Ultimate Tensile Strength,
elongation, forging, β-quenching, extrusion, pilgering, autoclaving
1
Nomenclature
ACR
Advanced CANDU Reactor
AERB
Atomic Energy Regulatory Board
ASME
American Society of Mechanical Engineers
BARC
Bhabha Atomic Research Centre
CANDU reactor
Canada Deuterium Uranium reactor
CWSR
Cold Worked and Stress Relieved
DBLA
Double forged back end longitudinal orientation
DBTA
Double forged back end transverse orientation
DFLA
Double forged front end longitudinal orientation
DFTA
Double forged front end transverse orientation
e
Plastic strain
eu
Uniform plastic strain
et
Total plastic strain
EDM
Electro Discharge Machining
IPHWR
Indian Pressurized Heavy Water Reactor
L
Longitudinal orientation
LE
Leading end
mm
millimeter
MPa
Megapascal
MWe
Megawatt electrical
Nb
Niobium
NFC
Nuclear Fuel Complex
NPCIL
Nuclear Power Corporation of India Ltd.
O
Oxygen
PHWR
Pressurized Heavy Water Reactor
ppm
Parts per million
2
PT
Pressure Tube
s
second
S
Engineering stress
SBLA
Single forged back end longitudinal orientation
SBTA
Single forged back end transverse orientation
SFLA
Single forged front end longitudinal orientation
SFTA
Single forged front end transverse orientation
T
Transverse orientation
TE
Trailing end
UTS
Ultimate Tensile Strength
wppm
Weight in parts per million
YS
Yield Strength
Zr
Zirconium
α-Zr
Alpha zirconium having HCP crystal structure
β-Zr
Beta zirconium having BCC crystal structure
°C
Degree Celsius
εpl
True plastic strain
σ
True stress
1. Introduction
Cold-worked and stress relieved (CWSR) Zr-2.5Nb tubes is being used as pressure
tubes for Indian Pressurized Heavy Water Reactors (IPHWR) [1-5]. The pressure tubes serve
as miniature pressure vessels operating at about 300 °C with a coolant pressure of ~ 10 MPa.
The design of the pressure tube is based on section III of the ASME pressure vessel code,
which specifies the criteria of maximum design stress on the basis of ultimate tensile strength,
yield strength, creep and stress-rupture strengths at the operating temperature. For pressure
tube alloys (both Zircaloy-2 and Zr-2.5Nb alloy) one third of the ultimate tensile strength has
been found to be the limiting property [6].
Recent in-reactor dimensional changes measurement by NPCIL in IPHWR220 MWe
has revealed that the diametral creep rate exhibited by some of the tubes is significantly
3
greater than design value. Also, large variability in the axial elongation and diametral creep
rates of the pressure tubes across the reactor core were observed. In order to achieve the
design life of 30 years for Zr-2.5Nb pressure tubes, several discussion and meetings were held
between the BARC scientists, NPCIL engineers, NFC engineers and AERB safety regulators.
A series of investigations were initiated by reactor operators and safety engineers to evaluate
the effect of relaxing the diametral creep limit form present 3 % to 4.5% on thermal
hydraulics of the coolant channels and structural integrity of coolant channel assembly.
Another initiative was to reexamine the alloy chemistry and microstructure based on the
experience gained both nationally and internationally with the objective of improving inreactor performance of the pressure tubes. Causey et al. [7] has reviewed the relationship
between alloy chemistry and in-reactor performance of CANDU pressure tubes. The
evolution of alloy chemistry for Zr-2.5Nb pressure tube material is shown in table 1 [7]. It
may be noted that initially Nb content range was between 2.4-2.8 wt percent which has been
narrowed down since 1987 to 2.5-2.8 wt percent. Carbon content has been reduced from 270
wppm in 1976 to a range between 40-60 wppm to reduce deuterium intake. Over the years
oxygen concentration has been increased from 900-1300 to 1200-1500 wppm because of its
beneficial effect in reducing diametral creep. Initially iron content was specified to be less
than 1500 wppm, which was reduced to less than 650 wppm as it was expected to promote
deuterium pick up.
However, recent irradiation studies have suggested role of iron in
reducing diametral creep and axial elongation and hence iron content specified for ACR700 is
900-1300 wppm. Another notable improvement is the specification for chlorine (469MPa, YS at 300°C > 324 MPa and YS at
25 °C < 586 MPa. The deviations from PHWR700 have been indicated in bold font.
List of figures
Fig. 1 Fabrication flow sheets for manufacture of Zr-2.5Nb pressure tube material using
conventional, single forged and double forged routes.
Fig. 2: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 3: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 4: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 5: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
13
Fig. 6: Engineering stress (S) vs. plastic strain (e) curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
Fig. 7: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 8: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 9: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 10: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
Fig. 11: True stress (σ) vs. true plastic strain (εpl) curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
Fig. 12: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the longitudinal
samples obtained from front and back end of the tube manufactured by Double forging route.
Fig. 13: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
14
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Double forging route.
Fig. 14: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Double forging route.
Fig. 15: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from back end of the tube manufactured
by Double forging route.
Fig. 16: Influence of test temperature and sample location (front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Strength was higher and elongation values were lower for samples obtained
from front end as compared to that obtained from back end for the longitudinal samples of the
tube manufactured by single forging route.
Fig. 17: Influence of test temperature and sample location (front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Single forging route.
Fig. 18: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
15
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Single forging route.
Fig. 19: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by single forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower elongation values as
compared to longitudinal samples obtained from back end of the tube manufactured by Single
forging route.
Fig. 20: Influence of test temperature and forging (SFLA & DFLA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength and higher total elongation values as compared single forged material for
longitudinal samples obtained from front end of the tubes.
Fig. 21: Influence of test temperature and forging (SFTA & DFTA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
transverse samples obtained from front end of the tubes.
Fig. 22: Influence of test temperature and forging (SFLA & DFLA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
longitudinal samples obtained from back end of the tubes.
Fig. 23: Influence of test temperature and forging (SFTA & DFTA) on tensile properties of
Zr-2.5Nb pressure tube material in the temperature range of 25-325°C (a) strength (YS &
UTS) and (b) % uniform (eu) and total tensile elongation (et). Double forged material showed
higher strength but comparable elongation values as compared single forged material for
transverse samples obtained from back end of the tubes.
16
Table 1: Changes in Alloying/Impurity Element Specifications (in ppm by weight except Nb)
for Zr-2.5Nb PTs [9]
Elements
Nb(wt%)
Carbon
Oxygen
Iron
Aluminium
Antimony
Boron
Cadmium
Chromium
Chlorine
Cobalt
Copper
Hafnium
Hydrogen
Lead
Magnesium
Manganese
Molybdenum
Nickel
Nitrogen
Phosphorus
Silicon
Tantalum
Tin
Titanium
Tungsten
Uranium
Vanadium
Zirconium
(1976)
(1987)
2.4‐2.8
270
900‐1300
1500
75
‐
0.5
0.5
200
‐
20
50
50
20
130
20
50
50
70
65
‐
120
200
100
50
100
3.5
50
Balance
2.5‐2.8
150
1000‐1300
650
75
‐
0.5
0.5
100
‐
20
50
50
20
50
20
50
50
35
65
‐
120
100
100
50
50
3.5
50
Balance
Wolsong
3&4
2.5‐2.8
125
1000‐1300
650
75
‐
0.5
0.5
100
0.5
20
50
50
5
50
10
50
50
35
65
10
100
100
100
50
50
3.5
50
Balance
Qinshan
ACR
Retube
2.5‐2.8
125
1000‐1300
650
75
‐
0.5
0.5
100
*
20
50
50
5
50
1
50
50
35
65
12
100
100
100
50
50
3.5
50
Balance
2.5‐2.8
40‐80
1200‐1500
900‐1300
75
‐
0.5
0.5
100
*
20
50
50
5
50
20
50
50
35
65
12
100
100
50
50
50
3.5
50
Balance
2.5‐2.8
40‐80
900‐1200
900‐1300
75
‐
0.5
0.5
100
0.5*
20
50
50
5
50
20
50
50
35
65
12
100
100
50
50
50
3.5
50
Balance
* It is expected that the ingot processing will maintain the chlorine concentration < 0.2 wppm.
- Not specified
17
Table 2: Details of fabrication route, tube number, test temperatures and sample orientation
used in this work.
Routes
Double
forged
Single
Forged
Conventional
Spool No.
Temperature, °C
Orientation
# 2849-1 LE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
OE 2849- 2 TE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
# 2845-2 LE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
OE 2845-2 TE
25, 70, 150, 250, 300 and 325
25, 250 and 325
Transverse
Longitudinal
19-2557-2
25, 70, 150, 250, 300 and 325
Longitudinal
Table 3: Comparison of tensile properties of the Zr-2.5Nb alloy investigated in this work with
PHWR700 specification, viz., UTS at 300°C >469MPa, YS at 300°C > 324 MPa and YS at
25 °C < 586 MPa. The deviations from PHWR700 have been indicated in bold font.
Fabrication
Route
Tube
Position
Direction
Single Forged
Single Forged
Double
Forged
Double
Forged
Front End
Back End
YS (25 YS (300 UTS (300 Ductility
°C), MPa °C), MPa °C), MPa
(300 °C),
%
Longitudinal
574
398
509
13.1
Longitudinal
546
380
487
16.3
Front End
Longitudinal
610
412
550
17. 3
Back End
Longitudinal
596
406
547
16.1
18
Melted ingot (350 mm Dia)
Extrusion (230 mm
Melted ingot (350 mm Dia)
Melted ingot (550 mm Dia)
Forging (230 mm dia)
Forging (350 mm dia)
dia)
Forging (230 mm dia)
β quenching
β quenching
β quenching
(1000°C/30 min)
(1000°C/30 min)
(1000°C/30 min)
Extrusion (133 mm OD x 9
Extrusion (133 mm OD x 9
Extrusion (119 mm OD x 6
mm WT and Temp‐800°C)
mm WT and Temp‐800°C)
mm WT and Temp‐815°C)
Stress Relieving (480°C / 3
Stress Relieving (480°C / 3
Stress Relieving (480°C / 3
hrs)
hrs)
hrs)
Pilgering (112.8 mm OD –
Pilgering (112.8 mm OD –
Pilgering (112.8 mm OD –
103.4 mm ID)
103.4 mm ID)
103.4 mm ID)
Autoclaving (400°C / 36 hrs)
Autoclaving (400°C / 36 hrs)
Autoclaving (400°C / 36 hrs)
Pilgering
(119 mm x 6 mm WT)
Annealing
(550°C / 6 hrs)
Fig. 1 Fabrication flow sheets for manufacture of Zr-2.5Nb pressure tube material using
conventional, single forged and double forged routes.
19
(a)
(b)
Fig. 2: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
20
(a)
(b)
Fig. 3: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
21
(a)
(b)
Fig. 4: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
22
(a)
(b)
Fig. 5: Engineering stress vs. plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
23
e
Fig. 6: Engineering stress vs. plastic strain curves
pl for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
24
(a)
(b)
Fig. 7: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
25
(a)
(b)
Fig. 8: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by double forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
26
(a)
(b)
Fig. 9: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the front end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
27
(a)
(b)
Fig. 10: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by single forging route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 325 °C. Tensile samples were machined from the back end of the
tube with its axes parallel to (a) longitudinal and (b) transverse direction of the tubes.
28
Fig. 11: True stress vs. true plastic strain curves for Zr-2.5Nb pressure tube material
manufactured by conventional route (fig. 1). The tensile tests were carried out in the
temperature range of 25 – 300 °C.
29
900
DBLA-YS
DFLA-YS
NFC DF-YS
DBLA-UTS
DFLA-UTS
NFC-DF-UTS
Strength, MPa
800
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBLA-et
DFLA-et
NFC DF-et
DBLA-eu
DFLA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 12: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the longitudinal
samples obtained from front and back end of the tube manufactured by Double forging route.
30
1000
DBTA-YS
DFTA-YS
DBTA-UTS
DFTA-UTS
900
Strength, MPa
800
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBTA-et
DFTA-et
DBTA-eu
DFTA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 13: Influence of test temperature and sample location (Front & back) on tensile properties
of Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Both strength and elongation values are comparable for the Transverse
samples obtained from front and back end of the tube manufactured by Double forging route.
31
900
DFLA -YS
DFTA-YS
DFLA -UTS
DFTA -UTS
Strength, MPa
800
700
600
500
(a)
400
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DFLA -et
DFTA -et
DFLA -eu
DFTA -eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 14: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from front end of the tube manufactured
by Double forging route.
32
900
DBLA-YS
DBTA-YS
DBLA-UTS
DBTA-UTS
Strength, MPa
800
700
600
500
400
300
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
DBLA-et
DBTA -et
DBLA-eu
DBTA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperature, °C
Fig. 15: Influence of test temperature and sample orientation (L & T) on tensile properties of
Zr-2.5Nb pressure tube material manufactured by double forging route in the temperature
range of 25-325°C (a) strength (YS & UTS) and (b) % uniform (eu) and total tensile
elongation (et). Transverse samples showed higher strength and lower uniform elongation
values as compared to longitudinal samples obtained from back end of the tube manufactured
by Double forging route.
33
800
SBLA-YS
SFLA-YS
NFC SF-YS
SBLA-UTS
SFLA-UTS
NFC-SF-UTS
Strength, MPa
700
600
500
400
(a)
0
50
100
150
200
250
300
350
Temperature, °C
30
(b)
SBLA-et
SFLA-et
NFC SF.et
SBLA-eu
SFLA-eu
25
% Elongation
20
15
10
5
0
0
50
100
150
200
250
300
350
Temperatu