DOI： 10.1143/JJAP.49.065802

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記述言語：英語  

In space exploration including the utilization of materials and energy outside the earth, construction of a moon base is one of considerable measures to develop the front line. Due to the huge cost of transportation from the earth, structural materials such as iron should be in-situ produced on the moon. Fortunately, the Apollo 14 mission has reported that the lunar soil contains about 10mass% of iron oxides. When considering ironmaking from lunar soils by graphite on the moon, understanding the reduction behaviour should come first but has not yet been attempted for iron resources whose concentration of iron oxides is as low as 10mass%. Thus, the present work has focused on reduction kinetics of iron oxides in molten lunar soil simulant by graphite, and apparent rate constants for reduction reactions have been derived from experiments with systematic variation in reduction conditions for comprehensive discussion about the reaction mechanism. The apparent rate constant derived is 2.0X10 -4cm/s at 1 803 K and the corresponding activation energy estimated is about 360 kJ/mol. The use of a graphite rod rotation mechanism enabled the stirring condition to be changed, resulting in a finding that stronger stirring shifts the rate-determining step from reduction of FeO by CO gas to direct reduction of FeO by graphite. On the basis of all these kinetic findings, it is likely that ironmaking from lunar soils by graphite on the moon is possible in that high vacuum and low gravity conditions would probably promote the removal of CO gas film from the graphite surface.

DOI： 10.2355/isijinternational.50.35

Scopus

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出版者・発行元：IOP Publishing  

DOI： 10.1143/JJAP.49.065802

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記述言語：日本語   出版者・発行元：JAPAN INST METALS  

Copper is one of the main residual elements in steel, especially in recycled scrap steel. Sulfur and phosphorus are two of the main impurities in steel, and it may result in a large emission of slag and CO2 to remove them from steel. Utilization of these elements; has been an important and difficult matter for metallurgist. In the present paper, the as-cast steels containing different concentrations of copper, sulfur and phosphorus are prepared by strip casting process or laboratory rapid solidification process. The effect of phosphorus addition on sulfide precipitation is investigated and discussed with respect to the morphology, size, and composition of sulfide. Both experimental results and mathematical calculation showed that the addition of phosphorus retards the sulfide precipitation at high temperature, promotes more copper hearings and smaller sulfides precipitation at low temperature. On the other hand, sulfide precipitates are shown to reduce the micro-segregation degree of phosphorus in steel, which may be because some phosphorus dissolves in sulfide and sulfide particles provide more interfaces for phosphorus to distribute.

DOI： 10.2320/jinstmet.73.312

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

To suggest a guideline for designing a mould flux for mild cooling, the radiative heat transfer characteristic of mould fluxes has been investigated using apparent reflectivity and transmissivity data on the basis of an optical-process model. The apparent reflectivities and transmissivities of mould fluxes were measured systematically as functions of the degree of crystallinity and the concentration of iron oxides, where the degree of crystallinity ranged between 0% and about 60%, and the concentration of iron oxides ranged between 0% and 2.0% on a mass basis. The apparent reflectivities and transmissivities were measured over the wavelength range 300-2 600 nm using a spectrophotometer with an integrating sphere. It has been found that crystallisation for mould fluxes increases the apparent reflectivity and decreases the apparent transmissivity, and that additions of iron oxides increase the apparent absorptivity of crystallised mould fluxes and instead decrease the apparent reflectivity. The radiative heat transfer characteristic has been evaluated using apparent reflectivity and transmissivity data on the basis of an optical-process model, which has suggested that crystallisation of mould fluxes leads to mild cooling due to increased apparent reflectivities and decreased apparent transmissivities. Furthermore, it has also been suggested that crystallised mould fluxes with no iron oxides can reduce radiative heat transfer even more by decreasing the apparent absorptivity and increasing the apparent reflectivity.

DOI： 10.2355/isijinternational.49.1722

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DOI： 10.2355/tetsutohagane.95.289

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DOI： 10.2355/tetsutohagane.95.289

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DOI： 10.2320/jinstmet.73.312

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記述言語：英語  

DOI： 10.2355/isijinternational.48.344

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

The evolution of as-cast gamma grain in low carbon steel has been investigated using thin slab cast simulator developed in NIMS (National Institute for Materials Science). Fine columnar gamma grain evolved from the surface to the center of the ingot was obtained, and second dendrite arm spacing and gamma grain size of the ingot along with the distance from the surface showed a good agreement with those of commercially produced 50 mm thick slab by a thin slab caster. Thus, we succeeded to simulate the macro-structure and micro-structure of the thin slab produced by practical thin slab continuous casting process. The gamma grain size for the present cooling rate of approximately 4 K/s showed a relatively good agreement with the estimated value by the previously predicted line of d(gamma)=1.52T(-1) for low carbon steels based on the Classical Grain Growth Model (CGGM).
Phosphorus, one of the typical impurities in steel, well known as the strong b.c.c. stabilizer, was added to low carbon steel aiming at the refinement of gamma grain by the suppression of its growth. The gamma grain size was drastically reduced to about a half of normally cast one even with a little addition of phosphorus lower than 0.05 mass%. It was probably caused by the retardation of gamma phase birth by the phosphorus segregation in the inter-dendritic region and the retardation of completion of delta/gamma transformation which leads to pinning of the gamma grain growth.
Moreover, tin, one of the typical impurities in steel scrap, also known as a b.c.c. stabilizer, was tried for addition. In spite of weaker b.c.c. stabilizing ability than phosphorus judging from the shape of iron binary phase diagram, a compatible gamma grain refining effect was observed with addition of 0.1 mass% tin. According to these results, b.c.c. stabilizing elements such as phosphorus and tin are found quite useful to microstructure control during solidification and cooling process.

DOI： 10.2355/isijinternational.48.344

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

A fine-grained microstructure yields the optimum combination of strength and toughness of steel. Refinement of the ferrite microstructure by formation of fine intra-granular acicular ferrite nucleated on inclusion has been caused wide interesting in weld metallurgy and other metallurgy fields. It is also important to refine the as-cast microstructure during strip casting and thin slab casting process in which the possibility of refining microstructure by rolling technology decreases. In present paper, the possibility to nucleate intra-granular acicular ferrite by sulfide inclusion in steel without special alloy elements during rapid solidification process has been investigated by optical microscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The orientation of the acicular ferrite clusters are also investigated by Electron BackScattered Diffraction (EBSD) analysis. Oxide inclusion and sulfide inclusion are popular in the sample and only sulfide inclusions are observed effective to assistant acicular ferrite nucleation. The possible mechanisms of formation of acicular ferrite in present sample, those are manganese depleted zone and phosphorus rich zone around inclusion in matrix, are discussed in detail.

DOI： 10.2355/isijinternational.47.1781

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DOI： 10.2355/tetsutohagane.93.655

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記述言語：英語   出版者・発行元：JAPAN INST METALS  

Copper is one of the main residual elements in steel, especially in recycled scrap steel, whereas sulfur is one of the main impurities in steel. A large quantity of slag and CO, is produced during the process of removing the sulfur from the steel. However, copper and sulfur may combine to form copper sulfide, especially during the rapid cooling process. In this paper samples containing and not containing fine copper sulfide are prepared by the rapid solidification process. The microstructure, sulfide precipitates, and the mechanical properties of the samples are investigated by optical microscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and the tensile testing. A large difference in the yield strength between the samples containing and not containing copper sulfides is observed. Each contribution of solid solution strengthening, grain refining strengthening, and sulfide precipitates strengthening in the samples with and without copper sulfide has been discussed. Particular attention has been paid to effect of the nano-scale copper sulfides, that is, main factor contributing to the alloy strengthening. Contribution of reduction of the copper sulfide particle size has also been discussed by comparing the results of two rapid solidification processes with different cooling rates.

DOI： 10.2320/matertrans.47.2312

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記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The effects of phosphorus addition on the phase transformation behavior of low-carbon steels were analyzed using a computational simulation focusing on the micro-segregation behavior of phosphorus during solidification and subsequent cooling processes. Based on the results of the simulation, a fully theoretical approach to modeling austenite grain growth was suggested for the continuous cooling processes. A previous model [Yoshida N, Umezawa O, Nagai K. ISIJ Int 2004:44:547; Yoshida N, Kobayashi Y, Nagai K. Tetsu-to-Hagane 2004;90:198] for the prior austenite grain size prediction was also refined based on the newly suggested approach by considering the liquid/solid interfacial energy reduction due to phosphorus addition. The prior austenite grain size that was predicted with the refined model showed good agreement with experimental data in the range 0-0.2% phosphorus. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2006.01.024

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記述言語：日本語   出版者・発行元：コンパス社  

CiNii Books

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DOI： 10.2355/isijinternational.46.854

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

In this paper, the solid delta/gamma phase transformation is observed "in-situ" on the surface of low carbon steels containing different phosphorus concentrations by the Confocal Scanning Laser Microscope (CSLM) at various cooling rates. The effects of phosphorus and cooling rate on the delta/gamma phase transformation are discussed based on the experimental results and mathematical calculation. Phosphorus is shown to decrease the T-A4 temperature and to increase the T-A3 temperature at various cooling rates. This effect is enhanced by the redistribution of phosphorus from the gamma phase to the delta phase during the transformation. Some retained delta phase is kept until the gamma/alpha phase transformation in steel containing high phosphorus (0.2 % P). The retained delta phase could retard the gamma grain growth and promote the alpha phase precipitation. At the slow cooling rate, the gamma cells appear first from the triple points or delta grain boundaries and then spread with finger-like patterns. While at the rapid cooling rate, the gamma cells appear first from the delta grain boundaries with sword-like patterns, and spread sharply into both sides of initial delta grain boundary.

DOI： 10.2355/isijinternational.46.847

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Copper and sulfur are the typical residual elements and impurities in steel. Previously, we reported the precipitation of very fine particles of Cu2S in copper and sulfur containing steel by strip casting process. In the present paper, the morphologies of copper sulfides in strip casting low carbon steels were distinguishably investigated by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM).
Four kinds of copper sulfide with different morphology were observed, namely duplex inclusion of oxide and sulfide (OS), plate-like copper sulfide (PS), shell-like copper sulfide surrounding the inclusions (SS), and nano-scale copper sulfide (NS), and their formation mechanisms were discussed.
The OS is considered to firstly form as molten manganese silicate in molten steel, and grow up with the formation of sulfide inside of the silicate after the solidification of steel. The PS is considered to precipitate from the gamma-Fe phase with plate-like shape due to semicoherency with the gamma-Fe matrix. The SS is considered to precipitate in lower temperature ranges on the other pre-formed inclusions such as MnS, oxide and also Cu2-xS. The NS is considered to form in the low temperature range of gamma-Fe and especially in alpha-Fe phase as very fine particles due to the high supersaturation, low diffusivity of component elements and the coherency with the alpha-Fe matrix.
Based on this classification, formation stage of oxide, MnS and Cu2S was clarified and described as like TTT diagram.

DOI： 10.2355/isijinternational.46.744

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DOI： 10.2320/jinstmet.70.440

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DOI： 10.1557/jmr.2006.0171

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DOI： 10.1557/jmr.2006.0171

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DOI： 10.2355/isijinternational.46.854

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記述言語：英語  

DOI： 10.2355/isijinternational.46.847

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE SA  

The effect of cooling rate on secondary dendrite arm spacing (SDAS) and prior austenite grain size (PAGS) has been investigated in high-phosphorous steels (0.1% P) subjected to a rapid cooling process of electron-beam (E-beam) surface remelting. A heat flow calculation was carried out to estimate the cooling rates of surface remelting experiments. The measured SDAS values depended on the cooling rate in good accordance with the Suzuki equation up to the cooling rate of 10(5) K s(-1). The classical grain growth modeling (CGM) was employed to clarify the effect of the cooling rates on the PAGS. The growth during the continuous cooling process was calculated for each cooling rate by CGM. With increasing the cooling rate, the growth of the prior austenite grains decreased and the PAGS converged to primary dendrite arm spacing (PDAS) when the cooling rates exceeded 10(3) K s(-1). An analytic model that can be applied to predict the PAGS for cooling rates from 100 to 2 x 10(4) K s(-1) was presented based on the present results. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2005.05.049

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記述言語：日本語   出版者・発行元：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.43.730

CiNii Books

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00242880330?from=CiNii

記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Phosphorus, one of typical impurities in steel, has been traditionally tried to be removed to the refining slag in the conventional steel making process. On the other hand, the inverse-utilization of impurities in steel was introduced recently to provide a resource circulating society. In these processes, phosphorus can be and must be restored in the steel during the deoxidation and solidification. The usage of elements with high deoxidizing and low dephosphorizing abilities such as manganese and silicon will be beneficial for obtaining such kind of steel. However, the thermodynamic behavior of phosphorus in such oxide fluxes has not been established. Therefore, the phosphate capacity as the phosphorus containing ability for the MnO-SiO2-FetO system, one of the typical slags for deoxidation, has been investigated by measuring the phosphorus partition between the slag and solid or molten iron. The phosphate capacities for the present system were determined to be from 8.5x10(14) to 3.8x10(18) at temperatures from 1 673 to 1 923 K. The present system has shown a much smaller phosphate capacity by several orders of magnitude compared to the conventional CaO bearing systems and provides the estimation of a very low phosphorus distribution ratio between the slag and the steel. In addition, the heats of the phosphate formation reaction were derived from the temperature dependence of phosphate capacities.

DOI： 10.2355/isijinternational.44.21

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DOI： 10.2355/tetsutohagane1955.90.4_198

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Copper and sulfur are the major residual elements or impurities in scrap steel. The direct near net shape casting is an attractive process for scrap recycling. In the present paper, the precipitation and orientation relationship with matrix of copper sulfide in a strip casting steel were investigated by transmission electron microscopy. Nano-scale copper sulfides less than 50 nm with a face-centered cubic structure (Digenite) were found precipitating throughout the grains. These tiny copper sulfides have a cube-cube orientation relationship with the body-centered cubic alpha-Fe matrix, which is (001)(Cu2S)//(001)(alpha-Fe) and [110](Cu2S)//[110](alpha-Fe). Thermodynamic and kinetic analysis was conducted to compare the Cu2S precipitation to the MnS precipitation in gamma-Fe and alpha-Fe. The calculation shows the nucleation of Cu2S is dominant in the gamma-Fe at low temperature and in the alpha-Fe compared with that of MnS. The high cooling rate during strip casting and the complete coherent relationship with the matrix result in the present nano-scale copper sulfides.

DOI： 10.2355/isijinternational.44.1560

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記述言語：英語   出版者・発行元：FREUND PUBLISHING HOUSE LTD  

The solubility of oxygen in molten Ti-Al and Zr-Al alloys equilibrated with solid Al2O3 or ZrO2 was measured from 1673 to 1973 K. The standard Gibbs energies for the reactions of Al2O3(s) = 2Al (1, in Ti-Al alloy) + 30 (mass pct, in Ti-Al alloy) and ZrO2(s) = Zr (1, in Zr-Al alloy) + 20 (mass pct, in Zr-Al alloy) were determined as a function of temperature. The standard Gibbs energies of the dissolution of oxygen into molten titanium and zirconium were obtained by applying the regular solution model to the Tt-Al-O and Zr-Al-O systems.

DOI： 10.1515/HTMP.2000.19.3-4.211

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記述言語：英語   出版者・発行元：SPRINGER  

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記述言語：英語   出版者・発行元：SPRINGER  

The solubility of yttrium and oxygen in molten Ti, Ti3Al, and TiAl equilibrated with solid Y2O3 has been measured from 1793 to 2093 K, The equilibrium constant of reaction Y2O3 (s) = 2 (Y) under bar (mass pct) + 3 (O) under bar (mass pct) and the interaction parameter between yttrium and oxygen in molten metals were determined. The standard Gibbs energy of reaction was also obtained as a function of temperature. The deoxidation of Ti, Ti3Al, and TiAl by using yttrium-based fluxes is discussed and the deoxidation ability of yttrium is compared with that of calcium.

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記述言語：英語   出版者・発行元：SPRINGER  

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記述言語：英語   出版者・発行元：Iron and Steel Institute of Japan  

The activity of chromium in molten Fe-Cr-Csatd alloy has been measured at temperatures ranging from 1 548 to 1 773 K by a chemical equilibrium technique. There is little temperature dependence of the activity of chronium in the region of low chromium contents by weight, and the activity coefficient of chromium decreases as the chromium content increases. The activity coefficient of chromium in silver, which was needed for the foregoing measurement, was predetermined. By thermodynamic discussion in combination with the carbon solubility in molten iron-chromium alloys, the expression for the activity coefficient of chromium in Fe-Cr-Csatd alloy has been obtained as a function of chromium content and temperature as follows. In γCr(s)= -2.52+3880/T+(8.31- 23300/T)XCr+(-4.21+14900/T)XCr2 (1 623 to 1773 K) The standard Gibbs energy of mixing of Fe-Cr-Csatd alloy was also estimated using the Gibbs-Duhem relationship, indicating that chromium and manganese behave similarly in terms of affinity for carbon and iron in molten carbon-saturated iron.

DOI： 10.2355/isijinternational.36.1009

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

The activity of chromium in molten Fe-Cr-C-satd. alloy has been measured at temperatures ranging from 1 548 to 1 773 K by a chemical equilibrium technique. There is little temperature dependence of the activity of chronium in the region of low chromium contents by weight, and the activity coefficient of chromium decreases as the chromium content increases.
The activity coefficient of chromium in silver, which was needed for the foregoing measurement, was predetermined.
By thermodynamic discussion in combination with the carbon solubility in molten iron-chromium alloys, the expression for the activity coefficient of chromium in Fe-Cr-C-satd. alloy has been obtained as a function of chromium content and temperature as follows.
ln gamma(Cr(s))=-2.52+3880/T+(8.31-23300/T)X(Cr)(+)(-4.21+14900/T)X(Cr)(2) (1623 to 1773 K)
The standard Gibbs energy of mixing of Fe-Cr-C-satd. alloy was also estimated using the Gibbs-Duhem relationship, indicating that chromium and manganese behave similarly in terms of affinity for carbon and iron in molten carbon-saturated iron.

DOI： 10.2355/isijinternational.36.1009

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記述言語：英語  

DOI： 10.1007/BF02653874

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記述言語：英語   出版者・発行元：SPRINGER  

The standard Gibbs energy of formation of 3BaO . Cr3O3 has been measured by a
3BaO(s) + 2Cr(s) + 3/2 O-2 (g) = 3BaO . Cr2O3 (s)
Delta G degrees = -1,260,000 (+/-3000) + 282 (+/-24)T (J/mol)
The activity coefficient of chromium in copper, which was needed for the foregoing measurement, may be expressed by the following equation:
log gamma(Cr)degrees = 5790/T - 2.10
The value of standard Gibbs energy at 1573 K was found to be close to that of reaction of formation of CaO . Cr2O3 expressed in the similar form. The BaO saturated BaF2 flux is shown to be far more promising in the oxidative dephosphorization of chromium-containing hot metal in comparison with the CaO-SiO2-CaF2 flux doubly saturated with CaO and 3CaO . Cr2O3.

DOI： 10.1007/BF02653874

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