ISIJ International

卓越論文賞

公開日: 2025/05/21 更新日: 2025/05/21

「卓越論文賞」は、「鉄と鋼」または「ISIJ International」に掲載された論文のうち、原則として前10±1カ年にわたって、学術上、技術上最も有益で影響力のある論文を寄稿した者に授与される。

6件中1～6件の論文を表示しています

54 巻 (2014) 1 号 p. 212-221 公開日: 2025/05/21
Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation
Naoya Kamikawa, Yoshihisa Abe, Goro Miyamoto, Yoshimasa Funakawa, Tadashi Furuhara

Tensile behavior and structure-property relationship of ferritic steels with nano-sized carbide dispersion were invesigated using Ti-added steel and Ti,Mo-added low carbon steels. By austenitizing followed by isothermal heat treatment at 700°C, polygonal ferrites containing very fine carbides of TiC and (Ti,Mo)C were obtained in the Ti-added and the Ti,Mo-added steels, respectively. The size of such carbides was finer in the Ti,Mo-added steel than in the Ti-added steel at the same isothermal holding. The results of tensile tests for these samples showed that the strength is higher as the carbide size is smaller. The structure-based strength calculation led to a good agreement with the experiments, when it was assumed that the Ashby-Orowan mechanism is dominant for precipitation strengthening of nano-sized alloy carbides. It was also suggested that a relatively large tensile ductility is related to enhanced recovery during the tensile deformation, accompanied with promotion of secondary slips or cross slips in a finer scale due to the nano-sized particles.
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53 巻 (2013) 12 号 p. 2110-2117 公開日: 2025/05/21
A Kinetic Model to Predict the Compositions of Metal, Slag and Inclusions during Ladle Refining: Part 1. Basic Concept and Application
Akifumi Harada, Nobuhiro Maruoka, Hiroyuki Shibata, Shin-ya Kitamura

A kinetic model to predict chemical composition changes in molten steel, slag, and inclusions in ladle refining was developed and used to elucidate the mechanism underlying the change in the chemical composition of the inclusions. The coupled reaction model was applied to estimate the reaction between molten steel/slag and molten steel/inclusion originating from the slag. The thermodynamic calculation software, FactSage6.3, was employed to obtain the activity of each component in the slag phase. Empirical equations were applied to the reaction between the slag and the refractory. The resulting model can calculate changes in (1) the composition of each element in the molten steel, slag, and the inclusion originating from the slag, (2) the amount of inclusion originating from the slag and the deoxidation products, and (3) the ratio of the inclusion originating from the slag and the deoxidation products to the total inclusion. The calculated results were found to agree with the operational results of a 165 t ladle refining process reported in the literature. The deoxidation products altered from alumina to a MgO·Al₂O₃ spinel-type inclusion due to an increase in the Mg content of steel. In the average composition changes of each element in the total inclusions, calculated results for the MgO and Al₂O₃ contents were also found to agree with the operational results.
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53 巻 (2013) 7 号 p. 1224-1230 公開日: 2025/05/21
Effect of Grain Size on Thermal and Mechanical Stability of Austenite in Metastable Austenitic Stainless Steel
Yoshikazu Matsuoka, Tatsuya Iwasaki, Nobuo Nakada, Toshihiro Tsuchiyama, Setsuo Takaki

In order to clarify the grain size dependence of mechanical stability of austenite, deformation-induced martensitic transformation behavior was investigated on uniaxial tensile deformation in a metastable austenitic stainless steel (Fe–16%Cr–10%Ni) with the grain size controlled from 1 to 80 μm. In addition, crystallographic characteristics of deformation-induced martensite were analyzed by means of the EBSD (electron backscattering diffraction) method to discuss the variant selection rule. It was found that mechanical stability of austenite is independent of its grain size, although thermal stability of austenite is remarkably increased by grain refinement. Some special martensite variants tend to be selected in an austenite grain on the deformation-induced martensitic transformation (near single-variant transformation), and this results in the formation of a texture along tensile direction. This suggests that the most advantageous variants are selected in the deformation-induced martensitic transformation to release tensile strain and leads to the grain size independence of mechanical stability of austenite.
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50 巻 (2010) 6 号 p. 893-899 公開日: 2025/05/21
High-strength Fe–20Mn–Al–C-based Alloys with Low Density
Yuji Sutou, Naohide Kamiya, Reiko Umino, Ikuo Ohnuma, Kiyohito Ishida

Mechanical properties of Fe–20Mn–(10–14)Al–(0–1.8)C (mass%) quaternary and Fe–20Mn–(10–14)Al–(0.75–1.8)C–5Cr (mass%) quinary alloys were investigated by hardness, cold-workability and tensile tests at room temperature. The γ(fcc) alloys in both quaternary and quinary systems with a low density of less than 7.0 g/cm³ showed an excellent ductility and their hardness and tensile strength increased with increasing Al and C contents. The γ+α(bcc) duplex alloys also exhibited a high tensile strength by controlling the α volume fraction. TEM observation confirmed that high hardness and tensile strength of the alloys with high Al and C contents are caused by the precipitation of nano-size κ-carbide with perovskite structure during cooling from the annealing temperature. Fe–20Mn–11Al–1.8C–5Cr alloy with a density of 6.51 g/cm³ showed a high specific strength of more than 180 MPa·cm³/g with a good tensile elongation of 40%. The present Fe–20Mn–Al–C(–5Cr) alloys showed a higher specific strength than conventional steels.
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49 巻 (2009) 12 号 p. 1952-1959 公開日: 2025/05/21
Hydrogen Delayed Fracture Properties and Internal Hydrogen Behavior of a Fe–18Mn–1.5Al–0.6C TWIP Steel
Kyoung Ho So, Ji Soo Kim, Young Soo Chun, Kyung-Tae Park, Young-Kook Lee, Chong Soo Lee

The hydrogen delayed fracture (HDF) properties and internal hydrogen behavior were investigated in a Fe–18Mn–1.5Al–0.6C steel, a representative twinning induced plasticity (TWIP) aided steel. Slow strain rate tests (SSRT) were employed on both smooth and notched specimens to evaluate the effects of diffusible hydrogen on the HDF properties of the steel. Results showed that the fracture stress, fracture strain and time to fracture of the hydrogen pre-charged specimens were relatively insensitive to the amount of diffusible hydrogen. Fracture surface exhibited a ductile dimple fracture mode regardless of the diffusible hydrogen concentration. It was found that most hydrogen became non-diffusible after SSRT. The major trapping sites of hydrogen were dislocations, grain boundaries and twins. The activation energies for detrapping of hydrogen were estimated 35 kJ/mol for dislocations or grain boundaries, and 62 kJ/mol for twins. A comparison of the HDF properties of the present steel with those of other high strength steels revealed that the TWIP steel appeared to be relatively immune to hydrogen delayed fracture. This was due to the combined effects of (a) higher hydrogen solubility of austenite matrix (b) negligible portion of diffusible hydrogen to the total hydrogen, (c) decrease of diffusible hydrogen content during the deformation, and (d) no transformation of austenite to either ε or α′ martensite.
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49 巻 (2009) 6 号 p. 783-787 公開日: 2025/05/21
Removal of Boron from Molten Silicon Using CaO–SiO₂ Based Slags
Leandro Augusto Viana Teixeira, Kazuki Morita

The global shortage of solar grade silicon for the production of photovoltaic cells has motivated many researches on the refining of silicon, especially the refining of metallurgical-grade silicon. In order to obtain better control of the removal process of boron from molten silicon using silicate slags, precise thermodynamic data are required. In the present study the partition ratio of boron (L_B) between the slag and silicon phases and the activity coefficient of boron oxide in CaO–SiO₂, CaO–SiO₂–25%CaF₂, and CaO–SiO₂–40%CaF₂ slags were evaluated at 1823 K. The activity coefficient of BO_1.5 was investigated for slags of CaO/SiO₂ ratio varying from 0.3–7.0; further, the borate capacity of the slag is defined in this study as:
[Equation]
The addition of Na₂O to CaO–SiO₂ slags was found to increase the partition ratio of boron between the slag and the silicon phase.
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