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ISIJ International Vol. 64 (2024), No. 10

ISIJ International
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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559
Publisher: The Iron and Steel Institute of Japan

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  1. Vol. 64 (2024)

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

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  3. Vol. 62 (2022)

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  4. Vol. 61 (2021)

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  5. Vol. 60 (2020)

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  6. Vol. 59 (2019)

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  7. Vol. 58 (2018)

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  8. Vol. 57 (2017)

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  9. Vol. 56 (2016)

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  10. Vol. 55 (2015)

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  11. Vol. 54 (2014)

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  12. Vol. 53 (2013)

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  14. Vol. 51 (2011)

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  16. Vol. 49 (2009)

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  17. Vol. 48 (2008)

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  18. Vol. 47 (2007)

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  19. Vol. 46 (2006)

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ISIJ International Vol. 64 (2024), No. 10

Influence of Water Content on the Kinetics and Mechanisms of Hydrogen Reduction Using Industrial Iron Ore Pellets at 873 K–1173 K

Oscar Hessling, Julia Brännberg Fogelström, Niklas Kojola, Johan Martinsson

pp. 1493-1502

DOI:

10.2355/isijinternational.ISIJINT-2023-443

Abstract

This work aims to study the effect of pH2O in the atmosphere during hydrogen reduction of iron oxide over a temperature range relevant to industrial practice. To further the industrial context, industrially produced hematite iron ore pellets are utilized. A resistance heated furnace was employed to conduct experiments, in the temperature range 873 K–1173 K. A water vapor generator was used to control water vapor partial pressure during hydrogen reduction in the range 0–15% pH2O. The system was carefully designed to ensure precise control of the water content in the reaction gas. Thermal Gravimetric Analysis (TGA) was used to follow the reduction of the iron ore pellets. To understand the reaction mechanisms, Scanning Electron Microscopy (SEM) was used to study the microstructure of partially reduced pellets. Results suggest the reduction rate is profoundly affected by water at 873 K, less so when the temperature is increased. The microstructure is also highly affected by pH2O at 873 K, at higher temperatures the microstructure is less affected. The influences of gas dilution and chemical reaction rate on these aspects are discussed.

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Influence of Water Content on the Kinetics and Mechanisms of Hydrogen Reduction Using Industrial Iron Ore Pellets at 873 K–1173 K

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Non-Isothermal Reduction Kinetics Model of Self-Reducing Iron Ore Pellets

Suporn Kittivinitchnun, Pruet Kowitwarangkul, Elsayed Mousa, Alexander Babich

pp. 1503-1516

DOI:

10.2355/isijinternational.ISIJINT-2024-107

Abstract

In this study, a non-isothermal reduction kinetics model has been developed for a single self-reducing iron ore pellet (SRP) to enhance the understanding of the reduction kinetics especially in the thermal reserve zone (TRZ) of the blast furnace (BF). The model simulates the mass changes and chemical processes during reduction, incorporating the effects of temperature, gas composition, and pellet composition on the reduction kinetics of different iron oxide phases, including Fe2O3, Fe3O4, and FeO. A mathematical model, comprising a comprehensive set of ordinary differential equations (ODEs), has been developed and solved using numerical methods and MATLAB software. The model has been rigorously validated against previous studies, specifically under non-isothermal conditions. It enables the calculation of mass loss and the reduction extent of specific phases of iron oxide, with the rate constant (k-value) curve across different temperatures. Moreover, the model adaptability is highlighted by its effective application in various BF conditions, as demonstrated by its use with data from the reference plants.

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Non-Isothermal Reduction Kinetics Model of Self-Reducing Iron Ore Pellets

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Reduction Degradation of Lump, Sinter, and Pellets in Blast Furnace with Hydrogen Injection

Muhammad Irfan Ahadian Barustan, Evan Copland, Thi Bang Tuyen Nguyen, Damien O’Dea, Tom Honeyands

pp. 1517-1527

DOI:

10.2355/isijinternational.ISIJINT-2024-114

Abstract

The increase of hydrogen usage in a blast furnace is expected to affect the reduction degradation of ferrous burden materials and influence the gas permeability inside the furnace. Previous studies show a disagreement on the effect of H2 on reduction degradation, with the extent of degradation depending on the H2 content and type of ferrous burden materials. In this study, the reduction degradation of sinter, lump, and pellet was compared using the reduction degradation test under different gas mixtures containing CO and H2, covering the gas composition of conventional and H2 injection blast furnaces. Lump (Newman Blend Lump NBLL) and pellets show a lower RDI-2.8 than sinter under all the gas compositions tested. Higher RDI-2.8 values were obtained for all burden materials with a reducing gas containing both CO and H2 compared to CO or H2 only. The addition of H2 to CO increases the pore diffusion rate allowing reducing gas to reach the centre part of the particles, leading to the reduction of hematite to magnetite and subsequent crack formation across the whole particles. Compared to the conventional blast furnace case, NBLL lump and sinter show a lower degradation for the H2 injection case while it was the opposite for the pellet, suggesting the necessity of reviewing overall burden materials to optimise the hydrogen injection in the blast furnace.

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Reduction Degradation of Lump, Sinter, and Pellets in Blast Furnace with Hydrogen Injection

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Application of Online Automated Segmentation and Evaluation Method in Anomaly Detection at Rail Profile Based on Pattern Matching and Complex Networks

Lingling Tong, Zhimin Lv, Jing Guo

pp. 1528-1537

DOI:

10.2355/isijinternational.ISIJINT-2024-003

Abstract

In steel rail production, complex deformations can induce non-uniform changes in cross-sectional profiles along the rail’s length, resulting in unevenness and safety implications. It is essential to perform dimensional testing to ascertain compliance with standard requirements. Currently, profile inspection results are manually evaluated, posing efficiency challenges and a lack of standardized criteria. To address this challenge, this paper proposes an online automatic steel rail segmentation and evaluation method (online-ASE) based on pattern matching and complex networks to enable automatic rail profile assessment. This method initially utilizes offline high-dimensional time series data for conducting Toeplitz Inverse Covariance-based Clustering (TICC) training and constructs a standard quality characterization pattern library through distinct inverse covariance structures between abnormal and normal high-dimensional quality characterization indicators of steel rails. When applied online, the Viterbi shortest path dynamic programming algorithm is utilized to match steel rail data with the pattern library, swiftly identifying anomalous rail segments. Additionally, the algorithm computes the contribution of steel rail quality parameters to the segmentation results using complex network betweenness centrality, thereby explaining the reasons for segment formation. These explanations provide a reference basis for subsequent steel rail repairs. Finally, the effectiveness of the proposed method is validated using real-world steel rail data from a specific steel factory in China.

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Application of Online Automated Segmentation and Evaluation Method in Anomaly Detection at Rail Profile Based on Pattern Matching and Complex Networks

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Investigation of the Effects of Mechanical Properties and Carbon Content on Cold Cracking in Laser Welds of High-strength Thin Steel Sheets

Hajime Ashida, Hiroki Fujimoto

pp. 1538-1547

DOI:

10.2355/isijinternational.ISIJINT-2024-144

Abstract

This study reports a case of cold cracking along welds, which arises from solidification cracking within the crater during the laser welding of high-strength steel sheets. In this investigation, we aimed to delineate the factors influencing cold cracking that originates from solidification cracking in the crater. This was achieved by using steel sheets whose mechanical properties (tensile strength: 0.6 to 1.5 GPa) and chemical composition (carbon content: 0.20 to 0.55%) were individually adjusted. The evaluation method involved performing laser welding in a stitch pattern on an oiled steel sheet, with variations in welding length. The evaluation focused on the maximum welding length at which cold cracking occurred (LMAX). The results indicated that while a high tensile strength of the steel sheet marginally increased the LMAX, the impact remained limited. Conversely, the carbon content of the steel sheet significantly influenced cold cracking; the LMAX for carbon contents of 0.30% and 0.45% was substantially greater than that for 0.20%. However, an unusual behavior was observed at a carbon content of 0.55%, where the LMAX was smaller than that for 0.45%, despite the significant hardening of the weld metal. This phenomenon was hypothesized to occur because the tensile residual stresses in the welds decreased as martensitic transformation starting temperature lowered and the expansion strain during the transformation increased with higher carbon content.

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Investigation of the Effects of Mechanical Properties and Carbon Content on Cold Cracking in Laser Welds of High-strength Thin Steel Sheets

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Performance and Structural Analysis of Vanadium Composite Electrogalvanized Steel Sheets

Fumio Shibao, Hiromasa Shoji, Hiroaki Nakano

pp. 1548-1556

DOI:

10.2355/isijinternational.ISIJINT-2024-162

Abstract

Vanadium composite electrogalvanized (Zn–V hydroxide) steel sheets were prepared by electroplating using a horizontal flow cell. The structure of the Zn–V plating layer depended on the flow rate of electrolyte and the current density, and the performance of Zn–V steel sheets depended on the structure of plating films. The Zn–V plating films composed of two-phase structure without cracks showed the high corrosion resistance and high adhesion. The two-phase layer consisted of the field-oriented fiber and non-field oriented texture. The field oriented fiber phase was mainly formed from the amorphous V compound. The V compound in the non-field oriented phase seems to be formed by hydrogen evolution during Zn–V composite plating. The Zn–V steel sheets had a black and low-gloss appearance compared to the conventional electrogalvanized steel sheet (EG). Since the V compound in the non-field oriented texture was black and the field oriented texture formed the surface roughness, the lightness and gloss of the Zn–V steel sheets decreased with increasing V content in plating films.

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Performance and Structural Analysis of Vanadium Composite Electrogalvanized Steel Sheets

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Identification of Precipitate Phases in an 11 Pct Cr Ferritic and Martensitic Steel after Thermomechanical Treatment

Yinzhong Shen, Yajing Guo

pp. 1557-1569

DOI:

10.2355/isijinternational.ISIJINT-2024-042

Abstract

An 11 mass% Cr ferritic/martensitic steel was subjected to a standard heat treatment consisting of normalizing and tempering and subsequently, a thermomechanical treatment (TMT) process involving austenization at 1100°C for 1 hour, warm-rolling with 93% deformation at 650°C and tempering at 650°C for 1 hour. The precipitate phases of the TMT-processed steel were qualitatively analyzed using transmission electron microscopes and energy dispersive X-ray spectrometers in combination of lattice parameter calculation. Nb-rich MC carbides and Nb-rich M(C,N) carbonitrides pre-existing in the normalized-and-tempered steel were also observed in the TMT-processed steel. Eight types of precipitate phases introduced by the TMT were identified in the TMT-processed steel. They are Nd-rich MC carbide with a face-centered cubic crystal structure and lattice parameter a = 1.1408 nm, Cr-rich M2C carbides/Cr-rich M2X (Cr2C type) carbonitrides/Cr-rich M2X (Cr2N type) carbonitride with a hexagonal crystal structure, Cr-rich M7C3 carbides/Cr-rich M3C2 carbide/V-rich M2(C,N) carbonitride with a simple orthorhombic crystal structure, and Mn-rich M5C2 carbide with a base-centered monoclinic crystal structure. Among these identified precipitate phases, Nb-rich MC carbides, Nb-rich M(C,N) carbonitrides, Cr-rich M2C carbides and Cr-rich M2X (Cr2C type) carbonitrides are dominant phases, while the other six precipitate phases are minor phases, in the TMT-processed steel. The identified precipitate phases are also discussed.

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Identification of Precipitate Phases in an 11 Pct Cr Ferritic and Martensitic Steel after Thermomechanical Treatment

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Effect of Deformation-induced α’-martensite and Serrated Grain Boundaries on the Deformation and Fracture Behavior of 201 Austenitic Stainless Steel at Low Temperature

Pham Mai Khanh, Hoang Thi Ngoc Quyen

pp. 1570-1577

DOI:

10.2355/isijinternational.ISIJINT-2024-091

Abstract

This study focuses on the fracture mode of 201 austenitic steel at room temperature (RT) and at −40°C for one hour and three hours. The results reveal that at room temperature, the fracture is dominated by ductile behavior. At −40°C, the fracture mode is a mix of ductile and brittle behavior. Type 201 austenitic stainless steel has a low stacking fault energy value (about 16 mJ.m−2 at RT), leading to the activation of the transformation-induced plasticity (TRIP) effect. When the sample is soaked at −40°C for three hours, deformation-induced martensite transition (DIMT) formation with the volume fraction rises significantly to 19.9%. At −40°C for 3 hours, the alloy’s impact energy absorption is reduced by 39%. The interaction of deformed austenite grains with previous austenite grain boundaries results in the formation of serrated grain boundaries in samples soaked at −40°C. Serrated grain boundaries prevent crack propagation and reduce crack expansion at the grain boundary during the fracture of this alloy. The width of the crack at serrated grain boundaries is 38% less than that of the straight grain boundary.

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Effect of Deformation-induced α’-martensite and Serrated Grain Boundaries on the Deformation and Fracture Behavior of 201 Austenitic Stainless Steel at Low Temperature

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Hydrogen Embrittlement Properties of Rapid Tempered High-Si Steel and Effects of the Carbide and Retained Austenite on Its Properties

Manami Sunako, Masataka Mizumoto, Azusa Ooi, Eiji Tada

pp. 1578-1586

DOI:

10.2355/isijinternational.ISIJINT-2024-181

Abstract

Automotive suspension springs are required to be high-strength and lightweight, and currently have a maximum strength of 2000 MPa. In addition, they must have high resistance to hydrogen embrittlement in the service environment. From previous research, Si addition or rapid tempering improves the hydrogen embrittlement resistance of low alloy steel. In this study, we investigated the hydrogen embrittlement properties of steel samples with different Si contents and tempering rates and the effects of the fine iron carbides and retained austenite on its properties for 2000 MPa suspension spring steel. JISSUP7 (2.0Si) and SAE9254 (1.4Si) spring steels were tempered at different tempering rates by induction (IH) and furnace heating (FH) methods. Four-point bending tests under corrosion cycles were performed on these steels, and the time to failure was measured. The results show that the 2.0Si-IH steel with higher Si content and higher tempering rate has the longest fracture life and highest resistance to hydrogen embrittlement, even with relatively high diffusible hydrogen content. The size and volume fraction of iron carbides and retained austenite were evaluated by TEM, EBSD, and synchrotron XRD, and the 2.0Si-IH steels were found to have the smallest size and the highest volume fraction of fine iron carbides Fe2−3C(ε) and the highest amount of retained austenite. It is considered that the fine iron carbides of Fe2−3C(ε) work as hydrogen trap sites and that their high dispersion suppresses dislocation movement. They suppress hydrogen accumulation in stress concentrated areas and are expected to improve resistance to hydrogen embrittlement.

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Hydrogen Embrittlement Properties of Rapid Tempered High-Si Steel and Effects of the Carbide and Retained Austenite on Its Properties

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Hydrogen Content Dependence of the Contribution of Dislocation-slip Stability and Carbide Precipitation Morphology to the Hydrogen Embrittlement Property of High-strength Martensitic Steels

Kei Saito, Kenichi Takai

pp. 1587-1598

DOI:

10.2355/isijinternational.ISIJINT-2024-156

Abstract

The contribution of dislocation-slip stability and carbide precipitation morphology to the hydrogen embrittlement (HE) property of tempered martensitic steels with low and high silicon contents (L-Si and H-Si) and oil-quenched martensitic steel (As-OQ), was evaluated by conducting slow strain rate tests. The order of dislocation-slip stability was the H-Si specimen > L-Si specimen > As-OQ specimen. The H-Si and As-OQ specimens had finely dispersed carbides inside prior austenite (γ) grains, whereas the L-Si specimen had coarsely dispersed carbides inside prior γ grains and on the boundaries. Notched specimens were charged with hydrogen in a range of low (0.19–0.31 ppm), medium (1.04–1.49 ppm), and high (2.17–2.33 ppm) hydrogen contents. The H-Si specimen had the highest HE property under the three hydrogen charging conditions. With the low and medium hydrogen charging conditions, the HE property of the L-Si specimen was higher than that of the As-OQ specimen, whereas their HE properties markedly declined to a similar level under the high hydrogen charging condition. The HE property of the L-Si specimen with increased dislocation-slip stability by applying stress relaxation was equivalent to that of the L-Si specimen under the high hydrogen charging condition. These results revealed that increasing dislocation-slip stability improved the HE property in the range of low to medium hydrogen charging. Under the high hydrogen charging condition, dislocation-slip stability did not contribute to improving the HE property, but it was found that the carbide precipitation morphology, particularly coarse carbides precipitated on prior γ grain boundaries, influenced the HE property.

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Hydrogen Content Dependence of the Contribution of Dislocation-slip Stability and Carbide Precipitation Morphology to the Hydrogen Embrittlement Property of High-strength Martensitic Steels

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Estimation of True Hardness and Quantitative Evaluation of Auto-Tempering in As-Quenched Martensitic Steels

Osamu Idohara, Youhei Hiyama, Yoshitaka Misaka, Setsuo Takaki, Toshihiro Tsuchiyama

pp. 1599-1606

DOI:

10.2355/isijinternational.ISIJINT-2024-140

Abstract

The hardness of martensitic steels with high Ms temperatures is reduced by auto-tempering after transformation, therefore the true hardness of martensite with carbon in fully solid solution is not known. In this study, we investigated a method to quantitatively evaluate the true hardness of quenched martensite unaffected by auto-tempering and the effect of auto-tempering was quantitatively evaluated by the diffusion area of carbon in bcc iron at temperatures below 400°C. As a result, it was clarified that the effect of auto-tempering is more pronounced in steels with an M50 temperature higher than 300°C and that the softening behavior of martensitic steels can be uniformly evaluated regardless of the carbon content if the activation energy of carbon diffusion is known. Furthermore, it was clarified that the degree of auto-tempering can be quantitatively evaluated by calculating the integral diffusion area S (= ∑Dt) below the M50 temperature during quenching.

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Estimation of True Hardness and Quantitative Evaluation of Auto-Tempering in As-Quenched Martensitic Steels

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Effect of Shape and Composition of Steel Particles on Simultaneous H2 Production and CO2 Fixation

Hayao Yagi, Norika Nakazawa, Naoki Yamamoto, Hiromi Eba

pp. 1607-1614

DOI:

10.2355/isijinternational.ISIJINT-2024-129

Abstract

To develop a H2 production and CO2 fixation process using scrap iron, the characteristics of iron and steel particles that react efficiently were investigated. The reaction of commercial pure iron and alloyed steel powders were compared, and their reactivity was evaluated based on the specific surface area, apparent density, and crystal lattice strain. The efficient reactivity in porous iron powders was attributed to crevice corrosion. To investigate the effect of alloy composition, we added Ni to pure iron powder by pretreatment, which resulted in enhanced H2 production and CO2 fixation. The results indicated that galvanic corrosion contributes to Fe oxidation, because Fe is less noble than Ni based on their electrode potentials. This study provides guidelines for improving the efficiency of reactions that produce H2 while fixing CO2 using steel scrap.

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Effect of Shape and Composition of Steel Particles on Simultaneous H2 Production and CO2 Fixation

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Chlorine-free Microwave Digestion of Stainless Steel for Inductively Coupled Plasma Mass Spectrometric Analysis

Kenichi Nakayama

pp. 1615-1617

DOI:

10.2355/isijinternational.ISIJINT-2024-050

Abstract

This paper reports an improved method for sample preparation of a stainless steel sample for inductively coupled plasma mass spectrometry. Conventional digestion methods using a digestion agent containing hydrochloric acid affect chlorine spectral interference such as that by 35Cl16O+ or 40Ar35Cl+. Alternatively, a microwave digestion method using an acid mixture of nitric acid and hydrofluoric acid can fully eliminate these interferences. The suggested procedure can contribute to more reliable quantification of titanium, vanadium, arsenic, niobium, tin, and antimony in stainless steel samples using a low-resolution quadrupole mass spectrometer.

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Chlorine-free Microwave Digestion of Stainless Steel for Inductively Coupled Plasma Mass Spectrometric Analysis

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Editorial Board, Copyright Page and Announcements

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Editorial Board, Copyright Page and Announcements

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