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Journal Articles

Improvement of neutron diffraction at compact accelerator-driven neutron source RANS using peak profile deconvolution and delayed neutron reduction for stress measurements

Iwamoto, Chihiro*; Takamura, Masato*; Ueno, Kota*; Kataoka, Minami*; Kurihara, Ryo*; Xu, P. G.; Otake, Yoshie*

ISIJ International, 62(5), p.1013 - 1022, 2022/05

Journal Articles

Dynamic accommodation of internal stress and selection of crystallographic orientation relationship in pearlite

Amemiya, Yutaro*; Nakada, Nobuo*; Morooka, Satoshi; Kosaka, Makoto*; Kato, Masaharu*

ISIJ International, 62(2), p.282 - 290, 2022/02

Journal Articles

Characterization of deformation by cold rolling in ferritic steel containing Cu particles using neutron transmission analysis

Oba, Yojiro; Morooka, Satoshi; Oishi, Kazuki*; Suzuki, Junichi*; Tsuchiyama, Toshihiro*

ISIJ International, 62(1), p.173 - 178, 2022/01

Journal Articles

Evaluation of multiaxial low cycle creep-fatigue life for Mod.9Cr-1Mo steel under non-proportional loading

Nakayama, Yuta*; Ogawa, Fumio*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*

ISIJ International, 61(8), p.2299 - 2304, 2021/08

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

This study discusses the creep-fatigue strength for Mod.9Cr-1Mo steel at a high temperature under multiaxial loading. A low-cycle fatigue tests in various strain waveforms were performed with a hollow cylindrical specimen. The low cycle fatigue test was conducted under a proportional loading with a fixed axial strain and a non-proportional loading with a 90-degree phase difference between axial and shear strains. The low cycle fatigue tests at different strain rates and the creep-fatigue tests at different holding times were also conducted to discuss the effects of stress relaxation and strain holding on the failure life. In this study, two types of multiaxial creep-fatigue life evaluation methods were proposed: the first method is to calculate the strain range using Manson's universal slope method with considering a non-proportional loading factor and creep damage; the second method is to calculate the fatigue damage by considering the non-proportional loading factor using the linear damage law and to calculate the creep damage from the improved ductility exhaustion law. The accuracy of the evaluation methods is much better than that of the methods used in the evaluation of actual machines such as time fraction rule.

Journal Articles

Hydrogen permeation property of bulk cementite

Adachi, Nozomu*; Ueno, Haruki*; Onoe, Katsuhiko*; Morooka, Satoshi; Todaka, Yoshikazu*

ISIJ International, 61(8), p.2320 - 2322, 2021/08

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

Journal Articles

Hydrogen absorption mechanism into iron in aqueous solution including metal cations by laser ablation tests and first-principles calculations

Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki; Sakairi, Masatoshi*; Togashi, Yusuke*; Baba, Kazuhiko*; Takagi, Shusaku*

ISIJ International, 61(4), p.1085 - 1090, 2021/04

In order to clarify the effect of metal cations (Zn$$^{2+}$$, Mg$$^{2+}$$, Na$$^{+}$$) in aqueous solution on hydrogen permeation into iron, the amount of hydrogen permeation from iron surface was measured by electrochemical tests with a laser ablation. Moreover, in order to obtain the basic mechanism of hydrogen permeation with metal cation, first-principles calculations were used to acquire the adsorption potential of the metal cation and the electronic state around iron surface. By Zn$$^{2+}$$ in solution, anodic reaction on ablated surface by laser irradiation was suppressed. Also, by quantum analysis Zn atoms were chemically bonded stronger than Na and Mg atoms to iron surface. It was suggested that the dissolution reaction of iron was suppressed by the formation of the Zn layer, and that lead suppression of hydrogen permeation into iron.

Journal Articles

Relation between intergranular stress of austenite and martensitic transformation in TRIP steels revealed by neutron diffraction

Harjo, S.; Kawasaki, Takuro; Tsuchida, Noriyuki*; Morooka, Satoshi; Gong, W.*

ISIJ International, 61(2), p.648 - 656, 2021/02

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

Journal Articles

Mechanism of improved ductility of 1500 MPa-class ultra-high strength cold-rolled steel sheet produced by rolling and partitioning method

Hosoya, Yoshihiro*; Matsumura, Yuta*; Tomota, Yo*; Onuki, Yusuke*; Harjo, S.

ISIJ International, 60(9), p.2097 - 2106, 2020/09

 Times Cited Count:1 Percentile:26.63(Metallurgy & Metallurgical Engineering)

Journal Articles

Role of metal cations on corrosion of coated steel substrate in model aqueous layer

Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*

ISIJ International, 58(9), p.1616 - 1622, 2018/09

 Times Cited Count:3 Percentile:28.45(Metallurgy & Metallurgical Engineering)

To elucidate the role of Zn$$^{2+}$$ on corrosion of coated steel, the effects of metal cations on the corrosion of carbon steel in the concentrated Cl$$^{-}$$ aqueous solutions were studied by immersion tests, surface analysis and electrochemical tests. Among the examined metal cations, Zn$$^{2+}$$ showed the significant effect on corrosion inhibition of carbon steel in the Cl$$^{-}$$ aqueous solution at high concentration. XPS analysis results elucidated that Zn$$^{2+}$$ can remain on the steel surface after immersed in the solutions with Zn$$^{2+}$$. EIS measurements showed higher impedance in the solution with Zn$$^{2+}$$ than other solutions, and the results suggested that Zn$$^{2+}$$ reduced the defect points in the thin oxide film by forming a metal cation layer. Based on the experimental results, Zn$$^{2+}$$ may form a layer on the oxide film that protects the Cl$$^{-}$$ attack in the solution. The findings demonstrated that the formation of Zn layer on the oxide film is one of the main reason for showing high and longtime corrosion resistance of Zn coated steel substrate.

Journal Articles

Distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires analyzed using micro-beam X-ray diffraction

Sato, Shigeo*; Shobu, Takahisa; Sato, Kozue*; Ogawa, Hiromi*; Wagatsuma, Kazuaki*; Kumagai, Masayoshi*; Imafuku, Muneyuki*; Tashiro, Hitoshi*; Suzuki, Shigeru*

ISIJ International, 55(7), p.1432 - 1438, 2015/07

 Times Cited Count:9 Percentile:51.23(Metallurgy & Metallurgical Engineering)

To characterize the distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires, X-ray diffraction line-profile analysis was performed using synchrotron radiation micro-beams. The plastic shear strain was generally more severe near the surface than the center of the wire, whereas the dislocation density distribution was almost constant from the center to the surface. On the other hand, the dislocation rearrangement, which evolves the dislocation cell structure, progressed closer to the surface. It was also revealed that a difference between the hardness in axial and transverse wire directions could be explained by anisotropic dislocation density. Line-profile analysis based on diffraction data at elevated temperatures was performed. Whereas the cementite recovery progressed at a constant rate, the ferrite phase recovery rate was temperature-dependent, suggesting that the ferrite phase recovery was less related to that of the cementite phase.

Journal Articles

Process evaluation of use of High Temperature Gas-cooled Reactors to an ironmaking system based on Active Carbon Recycling Energy System

Hayashi, Kentaro*; Kasahara, Seiji; Kurihara, Kohei*; Nakagaki, Takao*; Yan, X.; Inagaki, Yoshiyuki; Ogawa, Masuro

ISIJ International, 55(2), p.348 - 358, 2015/02

 Times Cited Count:5 Percentile:34.67(Metallurgy & Metallurgical Engineering)

Reducing coking coal consumption and CO$$_{2}$$ emissions by application of iACRES (ironmaking system based on active carbon recycling energy system) was investigated using process flow modeling to show effectiveness of HTGRs (high temperature gas-cooled reactors) adoption to iACRES. Two systems were evaluated: a SOEC (solid oxide electrolysis cell) system using CO$$_{2}$$ electrolysis and a RWGS (reverse water-gas shift reaction) system using RWGS reaction with H$$_{2}$$ produced by IS (iodine-sulfur) process. Both the effects on saving of the coking coal and reduction of CO$$_{2}$$ emissions were greater in the RWGS system. It was the reason of the result that excess H$$_{2}$$ which was not consumed in the RWGS reaction was used as reducing agent in the BF as well as CO. Heat balance in the HTGR, SOEC and RWGS modules were evaluated to clarify process components to be improved. Optimization of the SOEC temperature was desired to reduce Joule heat input for high efficiency operation of the SOEC system. Higher H$$_{2}$$ production thermal efficiency in the IS process for the RWGS system is effective for more efficient HTGR heat utilization. The SOEC system was able to utilize HTGR heat to reduce CO$$_{2}$$ emissions more efficiently by comparing CO$$_{2}$$ emissions reduction per unit heat of HTGR.

Journal Articles

Quantitative evaluation of CO$$_{2}$$ emission reduction of active carbon recycling energy system for ironmaking by modeling with Aspen Plus

Suzuki, Katsuki*; Hayashi, Kentaro*; Kurihara, Kohei*; Nakagaki, Takao*; Kasahara, Seiji

ISIJ International, 55(2), p.340 - 347, 2015/02

 Times Cited Count:7 Percentile:43.85(Metallurgy & Metallurgical Engineering)

Use of the Active Carbon Recycling Energy System in ironmaking (iACRES) has been proposed for reducing CO$$_{2}$$ emissions. To evaluate the performance of iACRES quantitatively, a process flow diagram of a blast furnace model with iACRES was developed using Aspen Plus, a chemical process simulator. CO$$_{2}$$ emission reduction and exergy analysis were performed by using mass and energy balance obtained from simulation results. The following CO$$_{2}$$ reduction methods were evaluated as iACRES: solid oxide electrolysis cells (SOEC) with CO$$_{2}$$ capture and separation (CCS), SOEC without CCS, and a reverse water-gas shift reactor powered by a high-temperature gas-cooled reactor. iACRES enabled CO$$_{2}$$ emission reduction by 3-11% by recycling CO and H$$_{2}$$, whereas effective exergy ratio decreased by 1-7%.

Journal Articles

Numerical analysis of influence of hydrogen charging method on thermal desorption spectra for pre-strained high-strength steel

Ebihara, Kenichi; Iwamoto, Takashi*; Matsubara, Yukio*; Yamada, Hiroki*; Okamura, Tsukasa*; Urushihara, Wataru*; Omura, Tomohiko*

ISIJ International, 54(1), p.153 - 159, 2014/01

 Times Cited Count:10 Percentile:53.03(Metallurgy & Metallurgical Engineering)

For understanding the mechanism of hydrogen embrittlement that is one cause of stress corrosion cracking, it is necessary to identify the location of hydrogen segregation (hydrogen existing state) in steels. The thermal desorption spectrum of hydrogen that is obtained by measuring hydrogen desorbing from specimens heated at a constant rate is a useful data for identifying the hydrogen existing state. In the paper, using the numerical simulation, we examined the difference of the thermal desorption spectra between two specimens of pre-strained high-strength steel, one was charged with hydrogen by the method used widely in laboratories, the other was by the method simulating hydrogen penetration in real environment. As a result, it was found that the difference results from the difference of the initial hydrogen distribution caused by the amount of charged hydrogen. If the amount of charged hydrogen is small, the thermal desorption spectrum is more sensitive to the initial distribution.

Journal Articles

Static tensile deformation behavior of a lean duplex stainless steel studied by in situ neutron diffraction and synchrotron radiation white X-rays

Tsuchida, Noriyuki*; Kawahata, Takuji*; Ishimaru, Eiichiro*; Takahashi, Akihiko*; Suzuki, Hiroshi; Shobu, Takahisa

ISIJ International, 53(7), p.1260 - 1267, 2013/07

 Times Cited Count:17 Percentile:68.86(Metallurgy & Metallurgical Engineering)

To investigate the tensile deformation behavior of a lean duplex stainless steel (S32101) from the viewpoints of plastic deformability among phases or grains, we performed static tensile tests, in situ neutron diffraction, and white X-ray diffraction experiments at room temperature. From the experimental results of synchrotron radiation white X-ray diffraction experiments, the hard phase of S32101 was changed from the ferrite phase to austenite one during tensile deformation. This led to a larger stress partitioning between the phases at the latter stage of deformation. From the experimental results of in situ neutron diffraction, it was found that the stress partitioning of the $$gamma$$ phase in the S32101 was the largest among the present results. Therefore, the larger work hardening rate of S32101 can be explained by the large stress partitioning of the $$gamma$$ phase, that between $$gamma$$ and $$alpha$$ phases and $$gamma$$ volume fraction.

Journal Articles

Development of high chromium steel for fast breeder reactors with high-temperature strength, ductility, and microstructural stabilit

Onizawa, Takashi; Asayama, Tai; Kikuchi, Kenji*

ISIJ International, 53(6), p.1081 - 1088, 2013/06

 Times Cited Count:3 Percentile:26.28(Metallurgy & Metallurgical Engineering)

The applicability of high chromium (Cr) steel as the main structural material in fast breeder reactors (FBR) has been explored to enhance the safety, the credibility and the economic competitiveness of FBR power plants. Vanadium (V) and Niobium (Nb) are believed to improve the high-temperature strength of high Cr steels by precipitating as carbides and/or nitrides, namely fine MX particles, although the long-term efficiency and stability of such precipitation strengthening mechanisms resulting from the fine MX particles have not been clarified yet. The effects of V and Nb on degradation of creep properties were investigated under FBR operating conditions, e.g., at 550 $$^{circ}$$C for 500,000 h, and the relationship between the long-term creep properties and microstructural changes was investigated considering the MX particles and the Z-phase. It was found that the optimal V and Nb contents for excellent high Cr steel of FBR grade are 0.2 mass% and $$<$$0.01 mass%, respectively, under FBR operating conditions.

Journal Articles

Effect of oxidation state of iron ions on the viscosity of alkali silicate melts

Osugi, Takeshi; Sukenaga, Sohei*; Inatomi, Yosuke*; Gonda, Yoshiyuki*; Saito, Noritaka*; Nakashima, Kunihiko*

ISIJ International, 53(2), p.185 - 190, 2013/02

 Times Cited Count:15 Percentile:66.82(Metallurgy & Metallurgical Engineering)

Understanding the changes in viscosity due to the different oxidation states of iron ions is important for simulating phenomena related to molten slags and also for understanding the structure of iron-oxidecontainingsilicate melts. However, these viscosity changes are not well understood. Here, we show the viscosity changes of R$$_{2}$$O-SiO$$_{2}$$-FexO (R = Li, Na, or K) melts due to changes in the oxidation states of the iron ions by systematically varying the oxygen partial pressure using several Ar-based gases at 1773 K. Not only the oxidation state of the iron ions but also the coordination structure of Fe$$^{3+}$$ may be important for understanding the viscosity.

Journal Articles

Flow sheet model evaluation of nuclear hydrogen steelmaking processes with VHTR-IS (Very High Temperature Reactor and Iodine-Sulfur process)

Kasahara, Seiji; Inagaki, Yoshiyuki; Ogawa, Masuro

ISIJ International, 52(8), p.1409 - 1419, 2012/08

 Times Cited Count:4 Percentile:33.38(Metallurgy & Metallurgical Engineering)

Flow sheet model evaluation of nuclear hydrogen steelmaking (NHS) and nuclear hydrogen partial reduction steelmaking (NHPRS) systems applying VHTR-IS (Very high temperature reactor and iodine-sulfur process) was carried out. Heat input and CO$$_{2}$$ emissions of these systems were analyzed. Total net heat input to the NHS system was 28.4 GJ/t-high quality steel (HQS), including material production, material transportation, and power generation. This value was much larger than that of blast furnace steelmaking (BFS) system of 17.6 GJ/t-HQS. Reduction of hydrogen consumption in the shaft furnace and electricity consumption in the electric arc furnace were desired for lowering the heat input. Total net heat input of the NHPRS system was 31.9 GJ/t-HQS. Optimization of operation parameters such as reduction ratio of partial reduced ore (PRO) and PRO input ratio to the blast furnace is desired to decrease the heat input. CO$$_{2}$$ emissions from the NHS and the NHPRS systems were 9% and 50% of that from BFS system. Substitution of hydrogen for coal and reduction of transportation weight contributed to the reduction. Steelmaking cost was also evaluated. When steelmaking scale of each system was unified to one million t-HQS/y, NHS was economically competitive to the BFS and Midrex steelmaking. And NHS was advantageous at higher cost of resources.

Journal Articles

Merit assessment of nuclear hydrogen steelmaking with very high temperature reactor

Inagaki, Yoshiyuki; Kasahara, Seiji; Ogawa, Masuro

ISIJ International, 52(8), p.1420 - 1426, 2012/08

 Times Cited Count:4 Percentile:14.29(Metallurgy & Metallurgical Engineering)

The merit assessment of the nuclear hydrogen steelmaking (NHS) was performed for reduction of CO$$_{2}$$ emissions from the steelmaking process. The NHS process is composed of the steelmaking process by hydrogen reduction and hydrogen production process, namely IS process, using a very high temperature reactor (VHTR). VHTR has the excellent safety features outstanding as compared with the other nuclear reactors that the reactor can be shut down inherently and cooled down passively using natural heat radiation from outside of the reactor pressure vessel even in a loss of coolant flow accident caused by loss of power and so on. Therefore, hydrogen can be supplied directly to a shaft furnace using piping from VHTR installed near the steelmaking plant. The NHS process with VHTR and IS process can decrease the CO$$_{2}$$ emissions by approximately 9% of those of the conventional blast furnace process, and be economically competitive to the blast furnace and the shaft furnace processes.

Journal Articles

Numerical modeling of thermal desorption spectra of hydrogen; A Review of thermal desorption models

Ebihara, Kenichi; Kaburaki, Hideo

ISIJ International, 52(2), p.181 - 186, 2012/02

 Times Cited Count:15 Percentile:41.67(Metallurgy & Metallurgical Engineering)

In the study of hydrogen embrittlement, it is indispensable to identify the hydrogen trapping state in steels. The hydrogen thermal desorption profile, which is obtained from the thermal desorption analysis (TDA) and is the relation between temperature and the amount of desorbed hydrogen of a specimen heated at a constant rate, is effective. Since various factors such as the specimen size, the heating rate, the hydrogen diffusion and the trapping effect of defects affect the desorption profile, however, it is necessary to model the process of the hydrogen desorption from the specimen. This paper reviewed the present model which can simulate the desorption profile by categorizing them according to the rate-determining process of the hydrogen desorption. The historical background and the range of validity of the models were also mentioned.

Journal Articles

Enhanced lattice defect formation associated with hydrogen and hydrogen embrittlement under elastic stress of a tempered martensitic steel

Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Oshima, Nagayasu*; Hirade, Tetsuya

ISIJ International, 52(2), p.198 - 207, 2012/02

 Times Cited Count:45 Percentile:91.61(Metallurgy & Metallurgical Engineering)

Hydrogen behavior and hydrogen-enhanced lattice defect formation under elastic stress of tempered martensitic steel were clarified with respect to dislocations and vacancies by thermal desorption analysis (TDA) using hydrogen as a probe of defects and a positron probe microanalyzer (PPMA). The relationship between hydrogen embrittlement and lattice defects associated with hydrogen was also investigated. The amount of lattice defects increased gradually with increasing time of applied stress. The specimen fractured under elastic stress. The enhanced vacancies due to interactions between dislocations and hydrogen under elastic stress directly caused ductility loss. Even though hydrogen was completely removed by degassing the vacancies remain. Besides hydrogen content and applied stress, the time of formation and accumulation of vacancies are also concluded to be important factors causing hydrogen embrittlement.

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