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ISIJ International Vol. 65 (2025), No. 1

ISIJ International
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Grid List Abstracts
オンライン版ISSN: 1347-5460
冊子版ISSN: 0915-1559
発行機関: The Iron and Steel Institute of Japan

Backnumber

  1. Vol. 65 (2025)

    1. No.1

  2. Vol. 64 (2024)

    1. No.15
    2. No.14
    3. No.13
    4. No.12
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  3. Vol. 63 (2023)

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  4. Vol. 62 (2022)

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  5. Vol. 61 (2021)

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  6. Vol. 60 (2020)

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  7. Vol. 59 (2019)

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  8. Vol. 58 (2018)

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  9. Vol. 57 (2017)

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  10. Vol. 56 (2016)

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  11. Vol. 55 (2015)

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  12. Vol. 54 (2014)

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  13. Vol. 53 (2013)

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  14. Vol. 52 (2012)

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  15. Vol. 51 (2011)

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  16. Vol. 50 (2010)

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  17. Vol. 49 (2009)

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  18. Vol. 48 (2008)

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  19. Vol. 47 (2007)

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  20. Vol. 46 (2006)

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  21. Vol. 45 (2005)

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  22. Vol. 44 (2004)

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  23. Vol. 43 (2003)

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  25. Vol. 41 (2001)

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キーワードランキング

15 Jan. (Last 30 Days)

ISIJ International Vol. 65 (2025), No. 1

Ductile Fracture Prediction During Metal Forming Using an Ellipsoidal Void Model and Some Other Models

Kazutake Komori

pp. 1-19

DOI:

10.2355/isijinternational.ISIJINT-2024-250

抄録

This paper reviews studies on the prediction of ductile fracture during metal forming using an ellipsoidal void model and some other models proposed by the author and some relevant studies. Section 2 discusses the research on the theory of voids for predicting ductile fracture during metal forming. Section 3 summarizes the simulation method for predicting ductile fracture during metal forming using the ellipsoidal void model, and Section 4 summarizes the simulation result on the ductile fracture prediction during metal forming using the ellipsoidal void model. Section 5 shows the applicability of the ellipsoidal void model and the simulation result on the ductile fracture prediction during metal forming using some other models.

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Enhanced Resistance to Delayed Fracture in 0.09 mass% P-Doped High-Strength Steel Processed by Warm Tempforming

Yuuji Kimura, Taku Moronaga, Kaneaki Tsuzaki

pp. 20-25

DOI:

10.2355/isijinternational.ISIJINT-2024-189

抄録

From the viewpoint of expanding the allowable P limit, the effect of warm tempforming on delayed fracture resistance was evaluated for 0.09% P-doped 0.4%C–1%Cr–0.7%Mn–0.2%Mo steel (mass%). The P-doped steel was warm tempformed at 500°C with a caliber-rolling reduction of 78% and annealed at 550°C for 1 h. This thermomechanical treatment created an ultrafine elongated grain structure with a strong <110>//rolling direction fiber texture, in which P definitely cosegregated with Mn and Mo at grain boundaries. The slow-strain-rate-test and immersion test demonstrated that warm tempforming markedly enhanced the delayed fracture resistance of the P-doped steel at a tensile strength of 1100 MPa level, in contrast to conventional quenching and tempering treatment.

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Effect of Intercritical Annealing on Microstructure and Toughness of Medium-Mn Steel with Elongated Prior-austenite Grains Formed via Two-step Hot Rolling Process

Kyosuke Matsuda, Takuro Masumura, Toshihiro Tsuchiyama, Misa Takanashi, Takuya Maeda, Shuichi Nakamura, Ryuji Uemori

pp. 26-37

DOI:

10.2355/isijinternational.ISIJINT-2024-180

抄録

Fe-9 mass%Ni alloy is widely used as a cryogenic steel owing to its excellent low-temperature strength and toughness. However, Ni is an expensive element, with medium-Mn steel considered an inexpensive alternative. Considering the Fe-10%Mn-0.1%C alloy is brittle at low temperatures, the application of intercritical annealing with two-step hot rolling could lead to toughening. Herein, the effect of intercritical annealing on the toughness of a Fe-10%Mn-0.1%C alloy with elongated prior-austenite grains (PAGs) formed via a two-step hot-rolling process was investigated. Intercritical annealing was performed on the specimens with and without two-step hot rolling. For both specimens, intercritical annealing resulted in softening of α’-martensite and an increase in the amount of retained austenite. In the specimen not subjected to the two-step hot rolling process, the fracture morphology transitioned from ductile to intergranular with a decrease in the temperature. Intercritical annealing improved the toughness when ductile fracture occurred. In the case of intergranular fracture, the effect of intercritical annealing on the toughness was negligible. In the two-step hot-rolled specimen with elongated PAGs, the fracture morphology transitioned from ductile to separation fracture with ductile fracture, and intercritical annealing improved the toughness at all temperature ranges. The improvement in toughness during separation fracture is attributed to the expansion of the plastic zone owing to ductile crack progression and the formation of sub-cracks, which promote the strain-induced transformation of retained austenite and ε-martensite.

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Constitutive Description of Flow Curve for Duplex Titanium Alloy for Hot Forming under Elevated Temperature

Yuki Shimomura, Hyung-Won Park, Hyeon-Woo Park, Yuji Sato, Jun Yanagimoto

pp. 38-49

DOI:

10.2355/isijinternational.ISIJINT-2024-014

抄録

A novel integrated constitutive equation of the flow curve for Ti–6Al–4V alloys is proposed by incorporating the effects of phase fraction in the hot-forging temperature range. The flow curve was obtained using hot-compression tests in the temperature range of 750–1050°C and strain rate range of 1–25 s−1. The effects of friction and deformation heat generated during compression were corrected using the inverse analysis method to identify the ideal uniaxial flow curve. The obtained stress parameters were satisfactorily regressed using the rule of mixtures on the α and β phases considering changes in the phase fraction. The integrated flow curve equation incorporating the rule of mixtures of the two phases effectively expressed the flow curve throughout the investigated temperature range. The internal microstructural observation showed that the continuous dynamic recrystallization of the α phase is dominant in the α+β two-phase region, while the deformation of the β phase becomes dominant just below the β transus. The constitutive equation presented here is in good agreement with the temperature dependence of the microstructure.

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Measurement of Oil Film Thickness Distribution in Roll Bite during Cold Rolling Using Quantum Dots

Masahiro Shimura, Daisuke Kasai, Takayuki Otsuka, Naoki Yamashita, Tomoko Hirayama

pp. 50-61

DOI:

10.2355/isijinternational.ISIJINT-2024-310

抄録

Lubrication is critical to achieve stable rolling during the cold rolling of flat steel products. However, the oil film thickness distribution in the roll bite and its effect on the friction between the work roll and strip has not yet been clarified. This study aims to elucidate the relationship between the oil film thickness distribution and friction by focusing on the rolling oil viscosity and steel grades because they significantly affect the friction between the work roll and the strip. Rolling oil was prepared with quantum dots (QDs) as the fluorescent additive and used in rolling experiments to determine its distribution. Furthermore, cold rolling experiments were conducted using two types of oils with different viscosities and three steel grades: low-carbon steel (LCS), high-strength steel (HSS), and advanced high-strength steel (AHSS) with tensile strengths of 270, 590, and 1180 MPa, respectively. Subsequently, the oil film thickness distribution on the steel strip surface was visualized by fluorescence microscopy using QDs. The idea that the higher the tensile strength of the steel or the higher the oil viscosity, the wider the rolling oil distribution on the strip surface was demonstrated. The numerical analyses revealed that the rolling oil distribution on the steel sheet surface was wider for AHSS and HSS than that for LCS. The high surface pressure between the roll and the steel plate may have increased the oil leaching area by increasing the oil viscosity. These findings demonstrate that rolling oil permeation from oil pits reduces the friction between the work rolls and the strip.

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Relationship between the Agitation Torque of the Wet Iron Ore Powder and Pellet Properties

Kensuke Kumeda, Hideya Nakamura, Shuji Ohsaki, Satoru Watano, Shohei Fujiwara, Yuji Iwami, Akinori Murao

pp. 62-69

DOI:

10.2355/isijinternational.ISIJINT-2024-281

抄録

Handling dephosphorized iron-ore powders with varying sizes and degrees of reduction is a pivotal issue in the iron-making process. A wet granulation process is employed for using dephosphorised fine ore powders as raw materials; however, it is difficult to determine the optimum water content to produce green pellets with the required physical properties because of the significant variation in the physicochemical properties of the dephosphorized ore powders. Thus, developing a method to determine the optimum water content for producing green pellets from fine ore powders with various degrees of reduction is necessary. In this study, we propose a method to estimate the optimum water content using agitation torque, which is a rheological property of wet ore powders. To this end, we investigated the effects of the hematite/magnetite fraction in the raw ore powder mixture on the agitation torque and green pellet properties. The characteristics of the agitation torque profile and green pellet properties (density and compressive strength) changed significantly depending on the hematite/magnetite fraction. Subsequently, we investigated the relationship between the agitation torque and green pellet properties, which revealed that the density and compressive strength of the gre en pellets correlated well when the product of the agitation torque and tumbling time was employed as the explanatory variable, regardless of the hematite/magnetite fraction. Thus, the properties of green pellets produced from fine ore powders with various degrees of reduction can be estimated based on the rheological properties measured by the agitation torque.

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Effects of Quasi-particles Structure on the Combustion Behaviors and CO and NO Emissions in the Iron Ore Sintering

Tao Han, Changqing Hu, Xuefeng Shi, Yan Shi

pp. 70-79

DOI:

10.2355/isijinternational.ISIJINT-2024-236

抄録

To investigate the influences of quasi-particles structure in the sintering bed on combustion behaviors and CO and NO emission, the non-isothermal combustion experiments and gas analysis were carried out by using coke breeze and sintering raw materials to prepare different types of quasi-particles. The results show that the four types of quasi-particles combustion processes were consistent with the unreacted nuclei model. The adhering layer had positive catalytic effects on coke breeze combustion and the reduction of NO by CO. Compared with S´−0.25, the apparent activation energies of the C71% and P15%(2) combustion decreased by 1.85 kJ/mol and 27.34 kJ/mol, the CO emission reductions were 47.75% and 50.07%, and the NO emissions were reduced by 67.50% and 6.95%, respectively. Compared with S´2~3, the apparent activation energies of the S33%(2~3) decreased by 18.66 kJ/mol, and the emissions of CO and NO were decreased by 87.99% and 75.29%, respectively. Additionally, the structural changes of the four types of quasi-particles significantly affected the combustion and emission behaviors. The adhering fines of S-type, C-type and P-type had abundant porous structure, which provided active sites for the adsorption of CO and NO, promoted the reduction of NO by CO. In contrast, the emissions of S´-type gases were higher, and the emissions increased with increasing of size. Therefore, increasing the S-type content and reducing the S´-type content in the sintering bed will not only effectively improve the solid fuel combustion efficiency, ensure sufficient combustion zone temperature, but also greatly reduce emissions in the sintering flue gas.

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A Volume Expansion Kinetic Model of Decarburization of Liquid Fe-1wt%C Alloy by Ar–CO2 Blowing

Junho Lee, Yongsug Chung

pp. 80-86

DOI:

10.2355/isijinternational.ISIJINT-2024-167

抄録

The decarburization kinetics according to the Ar–CO2 ratio with a liquid Fe-1wt%C alloy was studied using a high-frequency induction furnace at 1873 K. The carbon content in the liquid alloy decreased linearly with time, and as the CO2 ratio increased, the decarburization rate of the liquid alloy increased. The main reaction turned out to be CO2 + C = 2CO based on thermodynamic calculation. Comparing the amount of CO2 gas blown into the liquid alloy and the carbon content in the liquid alloy, it was found that all CO2 gas reacted with dissolved carbon when present as bubbles. A volume expansion model is proposed that takes into account the change in the partial pressure of gases due to the decarburization reaction and the resulting volume expansion of gases. Upon applying this model when S was low (50 ppm) and when S was high (0.1 wt%), no differences were found in the three possible rate-controlling steps (gas phase mass transfer, dissociation&adsorption, and mixed control) when S was low, but Mixed control behavior was observed when S was high.

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Evolution and Influence of Flow Field Affected by Coupled Swirling Flows in Round Billet Mold

Chunlei Wu, Yanwen Sun, Zhexiao Liu, Qiang Wang, Xiaoming Liu, Dewei Li, Xiaowei Zhu, Chunyang Shi

pp. 87-96

DOI:

10.2355/isijinternational.ISIJINT-2024-252

抄録

The quality of round billet is affected by the flow characteristics of molten steel during continuous casting. The application of nozzle swirling flow combined with electromagnetic stirrer (M-EMS) can increase the number of equiaxed crystal and alleviate macrosegregation, which has been demonstrated in our previous industrial test. However, flow field cannot be visually observed in industrial tests. In this paper, for the first time, the evolution of flow field and its influence on the macrosegregation and liquid level fluctuation under the action of coupled swirling flows were studied. Compared with that by using only mold stirring, the flow field was distributed more symmetrically in the upper part of mold and its impact depth decreased from 350 mm to 246 mm when the rotating speed of stirring propeller was 70 r/min. The centerline segregation level was reduced owing to the inward flow weakened by the outward nozzle swirling flow. Additionally, the tangential velocity at 1/2 radius near the surface was decreased from 0.589 m/s to 0.469 m/s, leading to the reduction of liquid level fluctuation. Consequently, both the internal quality and the surface quality can be improved by coupled swirling flows, provided that the rotating intensities of nozzle swirling flow and M-EMS are selected properly in the actual continuous casting production.

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A Hot Rolling Full Process Rolling Force Prediction Method Based on Transfer Learning and Inception-LSTM Neural Network

Guowei Niu, Ming Zhang, Yanbo Yang, Zihao Huang

pp. 97-103

DOI:

10.2355/isijinternational.ISIJINT-2023-446

抄録

A rolling force prediction method based on transfer learning and Inception-LSTM neural network is proposed to address the problem of low efficiency in predicting rolling forces for individual rolling mill stands due to the complex rolling conditions and distribution differences in the collected process data. The Inception-LSTM neural network combines the spatial feature extraction of the Inception model and the time sequence modeling capability of the LSTM network to comprehensively capture the features in the rolling process, thus establishing a baseline prediction model. Then, the transfer learning method is employed to transfer part of the parameters and structure of the baseline prediction model to the new prediction model. Simultaneously, the model is fine-tuned to establish a new transferred model for rolling force prediction, which is compared and analyzed against the neural network prediction model without using transfer learning. Experimental results show that the model built with transfer learning is higher fitting accuracy than the model built directly for rolling force prediction, and the training time of the model is significantly reduced. It can be used for steel shape and thickness control and digital twin simulation of rolling process.

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SOKD: A Soft Optimization Knowledge Distillation Scheme for Surface Defects Identification of Hot-Rolled Strip

Wenyan Wang, Zheng Ren, Cheng Wang, Kun Lu, Tao Tao, Xuejuan Pan, Bing Wang

pp. 104-110

DOI:

10.2355/isijinternational.ISIJINT-2024-159

抄録

The surface defect of hot-rolled strip is a significant factor that impacts the performance of strip products. In recent years, convolutional neural networks (CNNs) have been extensively used in strip surface defect recognition to ensure product quality. However, the existing CNNs-based methods confront the challenges of high complexity, difficult deployment and slow inference speed. Accordingly, this work proposes a soft optimization knowledge distillation (SOKD) scheme to distill the ResNet-152 large model and extract a compact strip surface recognition model. The SOKD scheme utilizes Kullback-Leibler (KL) divergence to minimize the error between the soft probability distributions of the student network and the teacher network, and gradually reduces the weight of “Hard loss” during the training process. The operation significantly reduces the learning constraints that the prior knowledge of the teacher network on the student network in the original KD, which improves the recognition performance of the model. Additionally, SOKD is applicable to most CNNs for identify surface defect of hot-rolled strip. The experimental results on NEU-CLS dataset show that the SOKD outperforms state-of-the-art methods.

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Factors Affecting Cathodoluminescence Intensity of Internal α-alumina Scales on Heat-resistant Alloys

Susumu Imashuku, Shun Ito, Makoto Nagasako

pp. 111-116

DOI:

10.2355/isijinternational.ISIJINT-2024-309

抄録

The identification of internal α-alumina (α-Al2O3) scales is crucial because α-Al2O3 determines the performance of heat-resistant alloys. A non-destructive method was recently developed to rapidly identify internal α-Al2O3 scales on the Ni–Cr–Al and Ni–Al alloys by obtaining their surface cathodoluminescence (CL) spectra. However, the peak intensities at 695 nm originating from α-Al2O3 considerably deviated from those estimated from the attenuation rates of overlaid scales (Cr2O3, NiO, and NiAl2O4) and the CL peak intensity at 695 nm for the α-Al2O3 scale on the Fe–Cr–Al alloy surface. In this study, factors causing the deviations in the CL peak intensity at 695 nm for the internal α-Al2O3 scales were investigated by obtaining images of the scales and their CL spectra. The surface Cr2O3 scale on the Ni–25Cr–5Al alloy exhibited a surface with the roughness of ~1 µm, causing the CL peak intensity at 695 nm to be one order of magnitude higher than the estimated value. The CL spectrum and scanning transmission electron microscopy observation revealed that θ-Al2O3 overlaid on α-Al2O3 in the internal Al2O3 scale on the Ni–14Al alloy reduced the CL peak intensity at 695 nm by two orders of magnitude.

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Effects of Welding Factors on Liquid Metal Embrittlement Cracking during Resistance Spot Welding of Zinc-coated High-strength Steel

Yang Yu, Yongqiang Zhang, Tianyue Zhang, Guangxiang Cao, Weixuan Chen

pp. 117-126

DOI:

10.2355/isijinternational.ISIJINT-2024-290

抄録

During resistance spot welding of zinc-coated advanced high-strength steels (AHSS), cracks which are promoted by liquid metal embrittlement (LME) may occur. According to previous researches, welding current, welding time, electrode tip diameter and electrode misalignment angle are significant factors on LME cracking. In this study, the effects of these four factors on LME cracking were compared with an orthogonal design experiment. After welding, numbers and lengths of cracks were measured, and Crack Index (CI) of each experiment group was calculated for comparison. As the result, two types of LME cracks, i.e., Type A cracks located at the indentation of electrode tip and Type B cracks located at the indentation of electrode shoulder were observed. The order of influence degree on CI of Type A crack from high to low was welding current > electrode tip diameter > electrode misalignment angle > welding time. The order of influence degree on CI of Type B crack was electrode tip diameter > electrode misalignment angle > welding time > welding current. The result reveals that modifying welding current is the most effective way to reduce Type A cracks and optimizing the electrode tip diameter is significant for preventing Type B cracks.

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Plasma Nitriding of Austenitic Stainless Steel using Ti–Mo Combination Screen

Yasuhiro Hoshiyama, Yuki Furuta, Tomoki Maruoka

pp. 127-132

DOI:

10.2355/isijinternational.ISIJINT-2024-251

抄録

Austenitic stainless steels such as SUS304 are widely used in various applications due to their excellent corrosion resistance; however, their low hardness and wear resistance limit their structural use. Plasma nitriding was applied using a Ti–Mo combination screen to simultaneously form a Ti–Mo composite nitride layer and a nitrogen diffusion layer in SUS304 stainless steel. The microstructure and mechanical properties of the plasma-nitrided SUS304 were evaluated. XRD analysis revealed peaks of δ-(Ti,Mo)N, which originated from the constituent elements of the screen, indicating the successful formation of a Ti–Mo–N composite nitride layer on the sample surface. The thickness of the Ti–Mo–N layer increased with higher gas pressure and nitrogen content in the gas mixture. The formation of the Ti–Mo–N layer on the nitrogen diffusion layer significantly enhanced the hardness and reduced the kinetic friction coefficient. The results suggest that this surface treatment method could be beneficial for improving the durability and lifespan of stainless steel components in demanding applications.

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Rapid Achievement of High Frequency of CSL Boundaries in Austenitic Stainless Steel via Reduced Stacking Fault Energy

Chikako Takushima, Jun-ichi Hamada, Sadahiro Tsurekawa

pp. 133-141

DOI:

10.2355/isijinternational.ISIJINT-2024-259

抄録

This study identifies a method for shortening the duration of annealing in the grain boundary control process to achieve a high frequency of CSL boundaries in austenitic stainless steel by focusing on decreasing stacking fault energy. Si-added SUSXM15J1, which has significantly lower stacking fault energy, was used to examine the impact of a decreased stacking fault energy on the duration of annealing after cold-rolling, necessary to introduce a high frequency of CSL boundaries, by comparing it with SUS304 austenitic stainless steel. It was found that a decrease in stacking fault energy significantly contributed to shortening annealing duration. The frequency of the CSL boundaries in SUSXM15J1 increased from 55% to 75% through 5% cold rolling and subsequent annealing at 1323 K for only 60 s. Ex-situ and in-situ EBSD observations revealed that the strain-induced grain boundary migration, accompanied by the formation of twin boundaries, likely occurred in SUSXM15J1 compared to SUS304, as the recovery process was hindered by the lower stacking fault energy resulting from Si addition.

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Crystallite-assisted γ-fiber Texture Formation during Two Stage Cold Rolling of Ferritic Stainless Steel and Its Corresponding Relationship with Formability

Fei Gao, Qiyong Zhu, Jingjing Zhang, Xinyu Liu, Zitong Liang, Jiafu Wang, Jianjun Wang, Zhenyu Liu

pp. 142-154

DOI:

10.2355/isijinternational.ISIJINT-2024-255

抄録

During two stage cold rolling, texture and formability at various reduction distribution coefficients (n) were investigated for ferritic stainless steel for elucidating the evolution of recrystallization texture and leveraging the advantages of this process. The shear band-induced crystallite occurred during cold rolling, and a model of crystallite-assisted γ-fiber texture development was presented during annealing. High cold rolling reduction promoted the crystallite formation and their transformation into more stable {111}<112> components, and the {111}<112> recrystallized nuclei growth, while low cold rolling reduction retarded the phenomenon that the surrounding matrix of deformed grain occurring preferential nucleation was consumed through priority developed γ-fiber recrystallized grain, and promoted the {111}<110> recrystallized nuclei growth during final annealing. Hence, after final annealing, as n decreased (first and second stage cold rolling reductions increased and decreased, respectively), the γ-fiber textures weakened and the fluctuation of intensity along γ-fiber reduced, and the intensity of {110}<001> component displayed a gradual increase followed by reduce. Moreover, as n decreased, the distribution for oriented grain clusters after annealing exhibited gradual uniformity followed by unevenness on account of low degree of microstructure fragmentation and high recovery tendency at lower cold rolling reduction and high nucleation and growth tendency of grains with similar orientations at higher cold rolling reduction. As n decreased, therefore, the ridging resistance and anisotropy of r-value displayed a step-by-step rise followed by a step-by-step reduce, and the difference in r-value was small. The n of 0.405 contributed to realizing optimal matching of r-value and its anisotropy and ridging resistance.

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Anisotropy in Hydrogen Embrittlement Resistance of Drawn Pearlitic Steel Wire Evaluated by in-situ Miniature Test and Scanning Electron Microscopy during Plasma Hydrogen Charging

Kota Tomatsu, Takahiro Chiba, Tetsushi Chida, Takahiro Aoki, Nobuhito Maeda, Tomohiko Omura, Akimitsu Hatta

pp. 155-164

DOI:

10.2355/isijinternational.ISIJINT-2024-294

抄録

In drawn pearlitic steel wire, hydrogen embrittlement cracks are preferentially formed along cementite/ferrite interfaces perpendicular to the tensile stress, predicting an anisotropy in the hydrogen embrittlement resistance of the wire. To validate this prediction, notched miniature tensile test specimens were extracted from the wire with their orientation changed, and in-situ miniature tensile tests were conducted during plasma hydrogen charging in a scanning electron microscope. The fracture process was also investigated from secondary electron images simultaneously obtained during these in-situ miniature tensile tests. As a result, it was revealed that, in accordance with the prediction, the fracture stress is decreased by the plasma hydrogen charging for the specimens with the tensile direction perpendicular to the drawing direction of the wire whereas it is hardly changed for the specimen with the tensile direction parallel to the drawing direction. In the secondary electron images, a stationary subcrack was observed before the fracture only for the specimen with the tensile direction parallel to the drawing direction. Based on finite element method analysis results, the subcrack was found to be formed by the triaxial stress due to the notch. The difference in the presence and absence of the subcrack depending on the specimen orientation was also well explained from the preferential hydrogen embrittlement crack formation along the cementite/ferrite interfaces perpendicular to the tensile stress.

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