Effect of Ausforming Temperature on the Microstructure of G91 Steel

Vivas, Javier; Capdevila, Carlos; Jiménez, José A.; Benito-Alfonso, Miguel; San-Martín, David

doi:10.3390/met7070236

Cited by 38 publications

(26 citation statements)

References 28 publications

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“…It is believed that the texture changes based on the fraction of austenite phase during intercritical annealing of the two steel types. The texture with a strong {111} component develops by intercritical annealing with a certain amount of γ phase transformed during the α → γ → α transformation [29][30][31]. Therefore, the Alloy B steels with a high phase-transformation temperature did not develop γ-fibers which are components that become parallel to the ND direction as a result of incomplete normalization during the α→ γ → α transformation.…”

Section: Discussionmentioning

confidence: 99%

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

Heo¹,

Kim²,

Kim³

et al. 2019

Preprint

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In this study, the effect of heat treatment was investigated to influence the occurrence of fracture during manufacturing process of Alloy B steel with boron contents as high as 130 ppm. As the content of boron increases, it affects the phase transformation temperature and texture. The development of {111} components in the γ-fiber is affected depending on the austenite fraction after phase transformation. The Alloy B steel indicated that the increase in the boron content increased the α to γ phase transformation temperature such that sufficient transformation did not occur in the normalizing condition. The cracks occurred at the point of the transition from elastic to plastic deformation in the ND direction during the rolling process, thereby resulting in failure.Therefore, it is necessary to avoid the intermediate heat treatment condition in which γ-fiber does not fully develop, i.e., an imperfect normalization. IntroductionNuclear power generation plays a key role in the Korea energy with low costs of raw materials and excellent base load capacity, however its enlargement is limited due to problem of spent nuclear fuel after operation. To solve these problems, it is necessary to develop an innovative nuclear power plant which can contribute to sustainable development, environmental protection and preparation for rapidly increasing energy consumption [1,2].Recently, research has carried out to develop sodium cooled fast reactor (SFR) because it has many advantages in terms of economic efficiency, stability, nuclear non-proliferation and reducing the emission of spent nuclear fuel. It is designed to operate at temperature much higher than those in light water reactors and to improve thermal efficiency [3][4][5][6][7]. Nuclear fuel cladding tube which transfers efficient the fission energy and confines nuclear fuel rod and fissile material is a main component. Hence, the development of fuel cladding tube is essential as it is the most important component directly related to the safety of nuclear reactor.Ferritic-martensitic (FM) steels have been considered as fuel cladding and duct materials for a SFR owing to their high thermal conductivities, low expansion coefficients and superior irradiation swelling compared to austenitic steel [8][9][10]. However, the creep rupture strength of FM steels abruptly decreases during long term creep exposure at high temperature [11]. An advanced FM steel alloy was developed on the basis of Gr.92 steel. Minor alloying elements such as B, N, Nb, Ta, and C Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 16

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Section: Discussionmentioning

confidence: 99%

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

Heo¹,

Kim²,

Kim³

et al. 2019

Preprint

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“…Thermomechanical processing of 9Cr FM steels has been revealed as a promising tool to promote a high number density of MX carbonitrides [30][31][32][33][34][35][36][37][38]. TMT involves different steps that need to be optimized to produce the most favorable precipitate microstructure for elevated-temperature strength.…”

Section: Creep and Microstructural Evolutionmentioning

confidence: 99%

“…The number density and average particle size of these carbides were determined by studying several SEM micrographs to determine values of 6.19 × 10 19 m −3 and 141 ± 3 nm for AR condition, 8.24 × 10 19 m −3 Figure 5. Temperature evolution of phase mole fraction in G91 calculated by Thermocalc® [38].…”

Section: Effect Of Austenitization Temperaturementioning

confidence: 99%

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High-Chromium (9-12Cr) Steels: Creep Enhancement by Conventional Thermomechanical Treatments

Vivas¹,

San-Martín²,

Caballero³

et al. 2021

Welding - Modern Topics

Self Cite

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There is a worldwide need to develop materials for advanced power plants with steam temperatures of 700°C and above which have the capacity to achieve high efficiency and low CO 2 emissions. This request involves the development of new grades of 9-12Cr heat-resistant steels, with a nanostructured martensite, mainly focusing on the long-term creep rupture strength of base metal and welded joints, creep-fatigue properties, and microstructure evolution during exposure at such elevated temperatures. The main shortcomings of actual 9-12Cr high-chromium steels are that the creep resistance is not enough to fulfill the engineering requirements at temperatures higher than 600°C and the material undergoes a cyclic softening. Creep strength at high temperature could be improved by a microstructural optimization through nano-precipitation, guided by computational thermodynamics, and thermomechanical control process optimization.

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“…Numerous alloying elements were added to obtain nano‐structure bainite and achieve ultrahigh strength and toughness, leading to a very long time, sometimes even a few days, transformation at low temperature. Previous studies have proven that ausforming at low to middle temperature range (300–500 °C) can effectively accelerate bainitic transformation in nano‐structured bainite steels . It is necessary to clarify the stress–strain behavior of high‐strength bainite steels at different strain rates in order to calculate the deformation force, setup the deformation schedule, and check the safety of processing equipment.…”

mentioning

confidence: 99%

Effect of Strain Rate on Deformation Resistance during Ausforming in Fe–C–Mn–Si High‐Strength Bainite Steels

Chen

et al. 2018

steel research int.

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Deformation experiments for two bainite steels at different strain rates are conducted to analyze the effects of strain rate on deformation resistance during ausforming of two bainite steels. The results indicate that deformation resistance for medium-carbon steel increases with strain as well as strain rate due to work hardening. However, for low-carbon steel, although deformation resistance increases with strain due to work hardening, maximum flow stress unexpectedly appears in the specimen deformed at the smallest strain rate of 0.001 s À1 instead of the largest strain rate of 5.0 s À1 . Microstructure observation of specimens deformed at 0.001 s À1 and 1.0 s À1 of low-carbon bainite steel confirms that bainitic transformation induced by plastic deformation dominates the flow stress behavior of low-carbon bainite steel at strain rate from 0.001 to 1.0 s À1 . The present work provides the useful reference for the calculating of deformation force, setup of the deformation schedule, and safety check of processing equipment.

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Effect of Ausforming Temperature on the Microstructure of G91 Steel

Cited by 38 publications

References 28 publications

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

High-Chromium (9-12Cr) Steels: Creep Enhancement by Conventional Thermomechanical Treatments

Effect of Strain Rate on Deformation Resistance during Ausforming in Fe–C–Mn–Si High‐Strength Bainite Steels

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