It is important that the material used to produce high-integrity pressure vessels has homogeneous properties which are reproducible and within specification. Most heavy pressure vessels comprise large forgings derived from ingots, and are consequently affected by the chemical segregation that occurs during ingot casting. Of particular concern are the compositional variations that arise from macrosegregation, such as the channels of enriched material commonly referred to as A-segregates. By causing corresponding variations in microstructure, the segregation may be detrimental to mechanical properties. It also cannot be removed by any practically feasible heat treatments because of the large scale on which it forms. Here we describe an investigation on the consequences of macrosegregation on the development of microstructure in a pressure-vessel steel, SA508 Grade 3. It is demonstrated that the kinetics of transformation are sensitive to the segregation, resulting in a dramatic spatial variations in microstructure. It is likely therefore that some of the scatter in mechanical properties as observed for such pressure vessels can be attributed to macroscopic casting-induced chemical segregation.

References

References
1.
Flemings
,
M.
,
1974
,
Solidification Processing
,
McGraw-Hill
,
New York
.
2.
Dantzig
,
J.
, and
Rappaz
,
M.
,
2009
,
Solidification
,
EPFL Press
,
Switzerland
.
3.
Taylor
,
H.
,
Flemings
,
M.
, and
Wulff
,
J.
,
1959
,
Foundry Engineering
,
Wiley
,
New York
.
4.
Marburg
,
E.
,
1953
, “
Accelerated Solidification in Ingots: Its Influence on Ingot Soundness
,”
J. Metals, pp.
157
172
.
5.
Maidorn
,
C.
, and
Blind
,
B.
,
1985
, “
Solidification and Segregation in Heavy Forging Ingots
,”
Nucl. Eng. Des.
,
84
, pp.
285
296
.10.1016/0029-5493(85)90199-2
6.
Druce
,
S.
,
1979
, “
Investigation of the Homogeneity of Chemical Composition and Mechanical Properties in a Large A508 Class 3 Steel Pressure Vessel Forging
,” Report No. AERE-R9581, Sept. 1979.
7.
Kim
,
S.
,
Im
,
Y.
,
Lee
,
S.
,
Lee
,
H.
,
Oh
,
Y.
, and
Hong
,
J.
,
2001
, “
Effects of Alloying Elements on Mechanical and Fracture Properties of Base Metals and Simulated Heat-Affected Zones of SA 508 Steels
,”
Metall. Mater. Trans. A
,
32A
, pp.
903
911
.10.1007/s11661-001-0347-8
8.
Im
,
Y.
,
Oh
,
Y.
,
Lee
,
B.
,
Hong
,
J.
, and
Lee
,
H.
,
2001
, “
Effects of Carbide Precipitation on the Strength and Charpy Impact Properties of Low Carbon Mn–Ni–Mo Bainitic Steels
,”
J. Nucl. Mater.
,
297
, pp.
138
148
.10.1016/S0022-3115(01)00610-9
9.
Wang
,
G.
, and
Chen
,
J.
,
1996
, “
A Comparison of Fracture Behavior of Low Alloy Steel with Different Sizes of Carbide Particles
,”
Metall. Mater. Trans. A
,
27A
, pp.
1909
1917
.10.1007/BF02651940
10.
Kim
,
S.
,
Kang
,
S.
,
Oh
,
S.
,
Kwon
,
S.
,
Lee
,
S.
,
Kim
,
J.
, and
Hong
,
J.
,
2000
, “
Correlation of the Microstructure and Fracture Toughness of the Heat-Affected Zones of an SA 508 Steel
,”
Metall. Mater. Trans. A
,
31A
, pp.
1107
1119
.10.1007/s11661-000-0106-2
11.
Bowen
,
P.
,
Druce
,
S.
, and
Knott
,
J.
,
1986
. “
Effects of Microstructure on Cleavage Fracture in Pressure Vessel Steel
,”
Acta Metall.
,
34
, pp.
1121
1131
.10.1016/0001-6160(86)90222-1
12.
Lee
,
S.
,
Kim
,
S.
,
Hwang
,
B.
,
Lee
,
B.
, and
Lee
,
C.
,
2002
, “
Effect of Carbide Distribution on the Fracture Toughness in the Transition Temperature Region of an SA 508 Steel
,”
Acta Mater.
,
50
, pp.
4755
4762
.10.1016/S1359-6454(02)00313-0
13.
Im
,
Y.
,
Lee
,
B.
,
Oh
,
Y.
,
Hong
,
J.
, and
Lee
,
H.
,
2004
, “
Effect of Microstructure on the Cleavage Fracture Strength of Low Carbon Mn–Ni–Mo Bainitic Steels
,”
J. Nucl. Mater.
,
324
, pp.
33
40
.10.1016/j.jnucmat.2003.09.003
14.
Kim
,
S.
,
Lee
,
S.
,
Im
,
Y.
,
Lee
,
H.
,
Kim
,
S.
, and
Hong
,
J.
,
2004
, “
Effects of Alloying Elements on Fracture Toughness in the Transition Temperature Region of Base Metals and Simulated Heat-Affected Zones of Mn–Mo–Ni Low-Alloy Steels
,”
Metall. Mater. Trans. A
,
35A
, pp.
2027
2037
.10.1007/s11661-004-0151-3
15.
Lee
,
B.
,
Hong
,
J.
,
Yang
,
W.
,
Huh
,
M.
, and
Chi
,
S.
,
2000
, “
Master Curve Characterisation of the Fracture Toughness in Unirradiated and Irradiated RPV Steels Using Full and 1/3-Size Pre-Cracked Charpy Specimens
,”
Int. J. Pressure Vessels Piping
,
77
, pp.
599
604
.10.1016/S0308-0161(00)00032-6
16.
Beremin
,
F.
,
1984
, “
A Local Criterion for Cleavage Fracture of a Nuclear Pressure Vessel Steel
,”
Metall. Trans. A
,
14A
, pp.
2277
2287
.
17.
Kim
,
J.
,
Kwon
,
H.
,
Chang
,
H.
, and
Park
,
Y.
,
1997
, “
Improvement of Impact Toughness of the SA 508 Class 3 Steel for Nuclear Pressure Vessel Through Steel-Making and Heat-Treatment Practices
,”
Nucl. Eng. Des.
,
174
, pp.
51
58
.10.1016/S0029-5493(97)00068-X
18.
Lee
,
K.
,
Kim
,
M.
,
Lee
,
B.
, and
Wee
,
D.
,
2010
, “
Master Curve Characterisation of the Fracture Toughness Behavior in SA508 Gr.4N Low Alloy Steels
,”
J. Nucl. Mater.
,
403
, pp.
68
74
.10.1016/j.jnucmat.2010.05.029
19.
Yang
,
H.-S.
, and
Bhadeshia
,
H.
,
2007
, “
Uncertainties in Dilatometric Determination of Martensite Start Temperature
,”
Mater. Sci. Technol.
,
23
(
5
), pp.
556
560
.10.1179/174328407X176857
20.
Takahashi
,
M.
, and
Bhadeshia
,
H.
,
1989
, “
The Interpretation of Dilatometric Data for Transformations in Steels
,”
J. Mater. Sci. Lett.
,
8
, pp.
477
478
.10.1007/BF00720712
21.
Lee
,
B.
,
Kim
,
M.
,
Yoon
,
J.
, and
Hong
,
J.
,
2010
, “
Characterisation of High Strength and High Toughness Ni–Mo–Cr Low Alloy Steels for Nuclear Application
,”
Int. J. Pressure Vessels Piping
,
87
, pp.
74
80
.10.1016/j.ijpvp.2009.11.001
22.
Curry
,
D.
, and
Knott
,
J.
,
1978
, “
Effects of Microstructure on Cleavage Fracture Stress in Steel
,”
Metal Sci.
,
12
, pp.
511
514
.10.1179/msc.1978.12.11.511
23.
Curry
,
D.
, and
Knott
,
J.
,
1979
, “
Effect of Microstructure on Cleavage Fracture Toughness of Quenched and Tempered Steels
,”
Metal Sci.
,
13
, pp.
341
345
.10.1179/msc.1979.13.6.341
24.
Curry
,
D.
,
1980
, “
Comparison Between Two Models of Cleavage Fracture
,”
Metal Sci.
,
14
, pp.
78
80
.10.1179/030634580790426292
25.
Wallin
,
K.
,
1984
, “
The Scatter in KIC Results
,”
Eng. Fract. Mech.
,
19
, pp.
1085
1093
.10.1016/0013-7944(84)90153-X
26.
Hawthorne
,
J.
,
1985
. “
Composition Influences and Interactions in Radiation Sensitivity of Reactor Vessel Steels
,”
Nucl. Eng. Des.
,
89
, pp.
223
232
.10.1016/0029-5493(85)90156-6
27.
Blondeau
,
R.
,
Maynier
,
P.
,
Dollet
,
J.
, and
Viellard-Baron
,
B.
,
1976
, “
Mathematical Model for the Calculation of Mechanical Properties of Low Alloy Steel Metallurgical Products: A Few Examples of Its Applications
,” In Heat Treatment’76, Metals Society, Proceedings of the 16th International Heat Treatment Conference, Metals Society, Stratford-upon-Avon, May 6–7, 1976, London, UK.
28.
Ion
,
J.
,
Easterling
,
K.
, and
Ashby
,
M.
,
1984
, “
A Second Report on Diagrams of Microstructure and Hardness for Heat-Affected Zones in Welds
,”
Acta Metall.
,
32
, pp.
1949
1962
.10.1016/0001-6160(84)90176-7
29.
Pickering
,
F.
,
1992
, “
Structure–Property Relationships in Steels
,”
Constitution and Properties of Steels
,
R.
Cahn
,
P.
Haasen
,
E.
Kramer
, and
F.
Pickering
, eds., Vol.
7
(Materials Science and Technology: A Comprehensive Treatment),
VCH
,
Weinheim
, pp.
41
94
.
30.
Scheil
,
E.
,
1942
, “
Bemerkungen zur Schichtkristallbildung
,”
Z. Metallkd.
,
34
, pp.
70
72
.
31.
Suzuki
,
K.
, and
Taniguchi
,
K.
,
1981
, “
The Mechanism of Reducing “A” Segregates in Steels Ingots
,”
Trans. ISIJ
,
21
, pp.
235
242
.10.2355/isijinternational1966.21.235
32.
Beckermann
,
C.
, 2012, private communication.
33.
Beckermann
,
C.
,
Gu
,
J.
, and
Boettinger
,
W.
,
2000
, “
Development of a Freckle Predictor via Rayleigh Number Method for Single-Crystal Nickel-Base Superalloy Castings
,”
Metall. Mater. Trans. A
,
31A
, pp.
2545
2557
.10.1007/s11661-000-0199-7
34.
Ramirez
,
J.
, and
Beckermann
,
C.
,
2003
, “
Evaluation of a Rayleigh-Number-Based Freckle Criterion for Pb–Sn Alloys and Ni-Base Superalloys
,”
Metall. Mater. Trans. A
,
34A
, pp.
1525
1536
.10.1007/s11661-003-0264-0
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