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Okuda, Takanari*; Fujiwara, Masayuki*; Nakai, Tatsuyoshi*; Shibata, Kenichi*; Kimura, Akihiko*; Inoue, Masaki; Ukai, Shigeharu*; Onuki, Somei*; Fujisawa, Toshiharu*; Abe, Fujio*
Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9229_1 - 9229_4, 2009/05
Oxygen content in ODS ferritic steel is the most important element to determine the mechanical properties. The oxygen contamination from the air is perfectly prevented by using new designed ball mill and the subsequent process control. Zr, Hf and Ti added ODS steels with three oxygen levels for the evaluation tests are fabricated.
Uwaba, Tomoyuki; Ukai, Shigeharu; Nakai, Tatsuyoshi*; Fujiwara, Masayuki*
Journal of Nuclear Materials, 367-370(2), p.1213 - 1217, 2007/08
Times Cited Count：16 Percentile：72.04(Materials Science, Multidisciplinary)Friction welding between oxide-dispersion-strengthened-steel (ODS) and ferritic-martensitic 11Cr-0.5Mo-2W, V, Nb steel (PNC-FMS) was examined to investigate the feasibility of the welding of this alloy combination. Forge pressure was varied in the welding test to investigate the effect on the soundness of the weld joint. Post weld heat treatment was necessary for the weld joint because the heat affected zone caused quench hardening in the as-welded condition. The welds were cross-sectioned and examined to determine their metallurgical structure, hardness and tensile strength. Since the heat treatment produced a softening zone near the weld interface, the furnace- cooling rate was investigated at which the softening did not occur. The weld joints were cold rolled and the soundness of the weld interface was determined by the tensile test with the cold rolled weld joints.
Otsuka, Satoshi; Ukai, Shigeharu; Sakasegawa, Hideo; Fujiwara, Masayuki; Kaito, Takeji; Narita, Takeshi
Journal of Nuclear Materials, 367-370(1), p.160 - 165, 2007/08
Times Cited Count：59 Percentile：95.87(Materials Science, Multidisciplinary)This paper describes the effect on creep strength and microstructure of 9Cr-oxide dispersion strengthened martensitic steel (9Cr-ODS steel) brought by the differences in titanium concentration and consolidation temperature. The increase of titanium concentration to 0.30-0.35wt% was shown to provide remarkable improvement of creep strength accompanied by the increase of residual-alpha ferrite. The elevation of hot-extrusion temperature notably degraded the creep strength, however, appeared to increase the volume fraction of residual-alpha ferrite. Creep deformation process of 9Cr-ODS steel was discussed to explain these results based on microstructure observations.
Narita, Takeshi*; Ukai, Shigeharu; Kaito, Takeji; Otsuka, Satoshi; Fujiwara, Masayuki
JAEA-Research 2006-050, 85 Pages, 2006/10
JAEA-Research-2006-050.pdf:133.32MB
In 9Cr ODS martensitic steel, tungsten(W) is a solid solution strengthening element, whose addition increases high-temperature strength by the combined effect with oxide dispersion strengthening. However, its excessive addition results in the increase of ferrite phase causing precipitation of intermetallic compound (Laves phase) under high temperature irradiation condition and thus ductility degradation. The amount of W addition therefore should be as low as possible. In this report, the effects of W on microstructure and high temperature mechanical properties of 9Cr ODS martensitic steels were examined for obtaining insights into optimum W concentration in terms of high-temperature strength and ductility. The results obtained are as follows: (1)In the 9CrODS martensitic steel, addition of W exceeding 2mass% is shown to cause precipitation of Laves phase which degrades the ductility and fracture toughness. It can be said that the current specification of W concentration, i.e. 2mass%W, is appropriate. (2)Hardness and tensile strength is shown to increase with W concentration. This increase is caused by the increase of solid solution strengthening and residual-alpha ferrite. The retainment of residual-alpha ferrite is enhanced by the addition of W (ferrite former element). The improvement of tensile strength at 973K provided by the solid solution strengthening is shown to be equivalent to that provided by the retainment of residual-alpha ferrite. (3)It would be open task to explorer an improved alloy design concept, i.e. decrease of W as low as possible and increase of residual-alpha ferrite. The degradation of high-temperature strength by decreasing W addition can be made up by the increasing fraction of residual-alpha phase that is provided by reduction of austenite former elements and increasing addition of ferrite former elements.
Ukai, Shigeharu; Kaito, Takeji; Otsuka, Satoshi; Fujiwara, Masayuki*; Kobayashi, Toshimi*
Materia, 45(1), p.48 - 50, 2006/01
Development of 9Cr-ODS ferritic/martensitic steel cladding was introduced as a new technology applied onece a year by Japan Institute of Metal. This cladding was developed by JAEA, and manufacturing of cladding was originally attained by controlling microstructure. Its high temperature strength is the most superior in the world as a heat resistance ferritic steels.
Otsuka, Satoshi; Ukai, Shigeharu; Fujiwara, Masayuki; Kaito, Takeji; Narita, Takeshi
JNC TN9400 2005-034, 197 Pages, 2005/08
JNC-TN9400-2005-034.pdf:28.06MB
Oxide dispersion strengthened(ODS) martensitic steel (9CrODS steel) has been identified as an attractive candidate for advanced fast reactor (FR) fuel cladding tube because of its superior high-temperature strength and radiation resistance. Our recent activities revealed that high-temperature strength of different lots of the cladding tubes is inconsistent each other, even though the same manufacturing process was applied to these tubes. This inconsistency means a critical problem that high-strength 9CrODS steel cladding tubes can not be manufactured reliably and consistently. In this report, a microstructure control technique for consistently and reliably manufacturing high-strength 9CrODS steel cladding tubes are examined based on a series of data concerning effect of excess oxygen concentration on high temperature strength and microstructure of 9CrODS steel.
Otsuka, Satoshi; Ukai, Shigeharu; Kaito, Takeji; Narita, Takeshi; Fujiwara, Masayuki
Materials Transactions, 46(3), 487 Pages, 2005/00
Times Cited Count：45 Percentile：87.63(Materials Science, Multidisciplinary)None
Narita, Takeshi; Ukai, Shigeharu; Kaito, Takeji; Otsuka, Satoshi; Fujiwara, Masayuki
JNC TN9400 2004-011, 141 Pages, 2004/04
JNC-TN9400-2004-011.pdf:12.79MB
Mass production capability of ODS martensitic steel claddinghas been evaluated in the feasibility studies on commercialized fast reactor cycle system. In this study, Manufacturing the large scale mother tube which has a high degree of accuracy in size, has been successfully carried out using large scale hollow capsule. For reducing the manufacturing cost of the ODS steel claddings, manufacturing process of the mother tubes using a large scale hollow capsules is promising.
Narita, Takeshi; Ukai, Shigeharu; Kaito, Takeji; Otsuka, Satoshi; Fujiwara, Masayuki
JNC TN9400 2003-103, 150 Pages, 2004/01
JNC-TN9400-2003-103.pdf:16.4MB
In order to apply to the real wrapper tube of "Joyo", PNC/FMS/SUS316 complex wrapper tube, which are welded at round tubes condition before cold drawing, were developped. In this study, the mechanical properties of complex tube were evaluated. As aresults, the mechanical properties of welded PNC-FMS/SUS316 is equivalent to base metal or more.
Otsuka, Satoshi; Ukai, Shigeharu; Fujiwara, Masayuki; Kaito, Takeji; Narita, Takeshi
Journal of Nuclear Materials, 329-333(Part A), p.372 - 376, 2004/00
Times Cited Count：99 Percentile：98.22(Materials Science, Multidisciplinary)The effects of different percentages of excess oxygen and titanium on the mechanical property and microstructure of 9Cr-ODS steel were investigated in the wide range of excess oxygen from 0.03wt% to 0.18wt%. It was shown that the controlling of the atomic ratio between excess oxygen and titanium (x in TiOx) around 1.0 is indispensable for the high-temperature strength improvement.
Narita, Takeshi; Ukai, Shigeharu; Kaito, Takeji; Otsuka, Satoshi; Fujiwara, Masayuki
JNC TN9400 2003-076, 81 Pages, 2003/09
JNC-TN9400-2003-076.pdf:13.27MB
Mass production capability of Oxide Dispersion Strengthened (ODS) ferritic claddings are evaluated in the PhaseII of Feasibility Studies on Commercialized Fast Reactor Cycle System. The cost for manufacturing mother tube has a dominant factor in the total cost for manufacturing ODS ferritic cladding. In this study, the large scale 9Cr-ODS martensitic mother tube were produced by overseas supplier with mass production equipments for commercialized ODS steels. The process of manufacturing the ODS mother tube consists of production of raw material powder, mechanical alloying by high energy ball mill, hot isostatic pressing (HIP), and hot extrusion. Following results were obtained in this study. (1) Micro structure of the ODS steels is equivalent to that of domestic products, and fine oxides are uniformly distributed. The mechanical alloying by large capacity (1 ton) ball mill can be satisfactorily carried out. (2) A large scale mother tube (65OD
48ID10,000L), which can produce about 60pieces of 3m length ODS ferritic claddings by four times cold rolling, have been successfully manufactured through HIP and Hot Extrusion process.(3) Rough surface of the mother tubes produced in this study can be improved by selecting the reasonable hot extrusion condition. (4) Hardness and tensile strength of the manufactured ODS steels are lower than domestic products with same chemical composition. This is owing to the high aluminum content in the product, and those properties could be improved by decreasing the aluminum content in the raw material powder.
Fujiwara, Masayuki; Otsuka, Satoshi; Kaito, Takeji; Narita, Takeshi; Ukai, Shigeharu
JNC TN9400 2003-008, 32 Pages, 2003/03
JNC-TN9400-2003-008.pdf:4.73MB
ODS martensitic steel is a prospective candidate cladding matenal for the advanced Fast Breeder Reactor (FBR) core components. A previous result showed that the high temperature strengths were deteriorated by the oxide particle coarsening and the reduction of the residual-alpha grains as excess oxygen (EX.O) increased. In this study, the manufacturing conditions for reducing excess oxygen were examined in order to obtain the target strength. High excess oxygen steels with higher Y
O
addition were also manufactured with the intention of manufacturing the steel which has both fully martensitic microstructure and enough high temperature strength. The derived results can be summarized as follows. (1)It was shown that 0.04wt% excess oxygen was brought from the pre-alloyed raw powders, and 0.04-O.l wt% excess oxygen was mixed in the powders during the Mechanical Alloying(MA). (2)It was shown that excess oxygen could be reduced less than 0.1wt% by applying an ultra high purity Ar gas (99.9999wt%Ar) to MA atmosphere as well as reducing the agitating energy by using pin agitator with shorter length. (3)Residual alpha-grains and transformed alpha-grains were mixed in the furnace-cooled low excess oxygen steels (
0.1wt%EX.O). These steels are expected to have the equal high temperature strength to Mm11 because their Vickers hardness is approximately the same Mm11. (3)Full martensitic microstructure was obtained in the higher YO and excess oxygen-added steels (E1,E2). However enough high temperature strength are not expected in these steels because the Vickers hardness of these steels after the furnace-cooling(FC) or normalizing and tempering (NT) are apparently low.
Otsuka, Satoshi; Ukai, Shigeharu; Kaito, Takeji; Narita, Takeshi; Fujiwara, Masayuki
P121,2003, 121 Pages, 2003/00
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Phase TransformationKaito, Takeji; Ukai, Shigeharu; ; Fujiwara, Masayuki
International Symposium on Material Chemistry in Nuclear Environment(MC02), 0 Pages, 2002/00
None
Hatakeyama, Koichi; Mizuta, Shunji; Fujiwara, Masayuki;
JNC TN9400 2001-110, 87 Pages, 2001/12
JNC-TN9400-2001-110.pdf:9.35MB
For the purpose of urgently discerning the applicability of ODS cladding tube to the long life core of the fast reactors, the irradiation test using Russian fast reactor BOR-60 is planned. In this irradiation test, TIG welding or laser welding will be applied as welding method of ODS cladding with end plug. In this report, applicability of alternative weldin9 method, i.e., TIG welding, laser welding, and also electron beam welding and 3 kinds of brazing diffusion bonding technique was evaluated. In addition, bending test and internal creep rupture test of the samples which were welded by laser and TIG welding were carried out. Following results were obtained in this study. (1) Tensile strength of laser welding test specimens with the highest energy density is most excellent in the welding process (over 90% of the base metal strength). (2) In the brazing filler metal, the tensile strength of the nickel brazing was most excellent (over 84% of the base metal strength). (3) In the bending test of laser and TIG welded test specimens, the crack was generated in circumferential direction of weld zone, which relatively corresponds to small bending angle. (4) As result of internal creep rupture test at 700
C, cladding itself was ruptured in the high stress region, whereas, weld zone was ruptured in the low stress level.
Mizuta, Shunji; Fujiwara, Masayuki;
JNC TN9400 2001-103, 139 Pages, 2001/09
JNC-TN9400-2001-103.pdf:7.93MB
Oxide dispersion strengthened (ODS) ferritic steels have been developing as a long life fuel claddings, because they are expected to be superior structure stability and high temperature strength up to high neutron dose. In order to improve a strength anisotropy induced by an elongated grain structure along rolling direction, the effects of manufacturing process and added elements have been studied by means of recrystallization technique. The feasibility study was also conducted for economical manufacturing process with capable of large scale production. Following results were obtained in this study. (1)From cold rolling manufacturing study as a parameter of Ti and YO contents, claddings have been successfully manufactured through softening by recrystallization heat treatment. The grains tend to elongate along rolling direction with increasing Ti and YO contents. (2)The ring tensile tests show the improved strength with increasing Ti and YO contents: 0.3Ti-0.23YO has the highest strength. The uniform elongation and ductility in circumferential direction is maintained at entire temperature range. (3)The internal creep rupture strength is also improved by finely distributed YO-TiO complex oxides. The manufactured cladding with 0.3Ti-0.23YO is expected to attain the target strength (120MPa at 700C for 10,000h). (4)At the cladding manufacturing test with four times rolling, recrystallization structure was realized at the final heat treatment by suppressing heat treatment temperature up to recovery stage at intermediate heat treatment.
; Fujiwara, Masayuki;
JNC TN9400 2001-082, 79 Pages, 2001/08
JNC-TN9400-2001-082.pdf:9.26MB
It is necessary to carry out the welding with the austenitic stainless steel in order to apply the high strength ferritic/Martensitic steel(PNC-FMS) with superior resistance to swelling as wrapper tube in "Joyo" and "Monju". If the 
ferrite phase would be formed at heat affected zone(HAZ) in welding between PNC-FMS wrapper tube and SUS316 steel, toughness degradation would be suspected. In this study, as the method in which ferrite was not formed at the weld zone, the elimination of ferrite by the heat treatment was examined, and the heat treatment condition was optimized. The possibility and realization of manufacturing the PNC-FMS wrapper tube with joint structure to SUS316 short length tube were also evaluated. The results obtained are summarized as follows. (1) ferrite phase in welding part is successfully eliminated by carryjng out the normalizing processing over 1050C 10min as a post-welding heat treatment. (2)As a fabrication process, the following process was selected from the viewpoint of practical application. TIG welding of PNC-FMS round tube and SUS316 round tube 
Post-welding heat treatment Cold drawing(hexagonal tube) Normalizing, tempering The dimension adjustment by the cold drawing (3)As a result of investigation of microstructure and mechanical properties of the weld zone of produced wrapper tube, the satisfied performance of the joint was confirmed.
Fujiwara, Masayuki; Mizuta, Shunji;
JNC TN9400 2000-050, 19 Pages, 2000/04
JNC-TN9400-2000-050.pdf:0.82MB
For evaluating the fast reactor system technology, it is important to evaluate the practical feasibility of ODS ferritic cdaddings, which is the most promising matelials to attain the goal of high coolant temperature and more than 150 GWd/t. Based on the results of their technology development, mass production process with highly economically benefit as well as manufacturing cost estimation of ODS ferritic claddings were preliminarily conducted. From the view point of future utility scale, the cost for manufacturig mother tubes has a dominant factor in the total manufacturing cost. The method to reduce the cost of mother tube manufacturing was also preliminarily investigated.
*; Fujiwara, Masayuki*
JNC TJ8430 2000-001, 55 Pages, 2000/03
JNC-TJ8430-2000-001.pdf:4.82MB
no abstracts in English
Fujiwara, Masayuki*; Harada, Makoto*; Okuda, Takanari*; Nakamura, Shigeharu*; Mizoguchi, Mitsuru*
PNC TJ9058 97-001, 110 Pages, 1995/10
None
