2005 Fiscal Year Final Research Report Summary
Development of Next-generation Steels combined with High-density Oxide Particles assisted by Interfacing
| Project/Area Number |
16360358
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOSEKI Toshihiko The University of Tokyo, School of Eng, Dept of Mat Eng, Professor, 大学院・工学系研究科, 教授 (70361532)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Toshio The University of Tokyo, School of Eng, Dept of Mat Eng, Professor, 大学院・工学系研究科, 教授 (70115111)
ASAKURA Kentaro The University of Tokyo, School of Eng, Dept of Mat Eng, Research Associate, 大学院・工学系研究科, 助手 (10111460)
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| Project Period (FY) |
2004 – 2005
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| Keywords | interfacing / steel / particle dispersion / wettability / intragranular ferrite / nucleation / simulation / grain growth |
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| Research Abstract |
To achieve new steels combined with high-density oxide particles, this study focuses on the following three subjects : (a)improvement of the wettability between steel melts and oxide particles which is necessary for the oxide particle dispersion through liquid phase processing, (b)development of numerical simulation techniques to give quantitative guideline for oxide particle dispersion to achieve fine grain steels, and (c)investigation of the mechanism of fine ferrite nucleation from oxide particles to achieve fine microstructure steels. As for the wettability, it was found that the addition of Ti to steel melts improved the melt-oxide wettability by forming Ti-rich nano-scale oxide on the original oxide. For the simulation of the effect of oxide dispersion on grain refinement in steels, a hybrid numerical model combining finite difference method and Monte Carlo method was developed, where the finite difference method is used for heat and mass transfer and the Monte Carlo method for n
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ucleation and growth simulation. Using the model, the pinning effect of oxide particles against austenite grain growth during various thermal cycles in steels was made quantitatively clear, which indicated that the pinning force of the dispersed oxide particles was the same as what the modified Zener theory predicted and suggested necessary amount of the dispersion to achieve desired grain size in steels used for welded structure. In the third research subject, a thin oxide film was deposited on a steel plate using electron-beam physical vapor deposition technique, and austenite-to-ferrite transformation behavior from the oxide-steel interface was investigated. It was found that ferrite was preferentially formed from the NaCl-type oxide such as TiO and MgO and this was attributed to good lattice matching between the oxide and ferrite. The investigation also suggested that the interface composition also exerted an influence on the formation and growth of ferrite from the oxide. Both findings would be the basis of the microstructure control in oxide-dispersed steels. Less
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