| Project/Area Number |
08455345
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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 |
Metal making engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
HIRASAWA Masahiro Tohoku University Institute for Advanced Materials Processing Professor, 素材工学研究所, 教授 (90126897)
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| Project Period (FY) |
1996 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥7,800,000 (Direct Cost: ¥7,800,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Keywords | aluminum / dehydrogenation / vacuum suction degassing / kinetics |
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| Research Abstract |
In the present study, the kinetic aspects of dehydrogenation of molten aluminum under the conditions of Ar blowing and mechanical stirring are investigated. The fundamental aspects of application of Vacuum Suction Degassing (VSD) method to the dehydrogenation are also investigated. The results are summarized as follows. (1) The rate of dehydrogenation from the free surface of the molten metal covered by oxide film follows a first order rate equation in which the metal side mass transfer of hydrogen and the mass transfer of hydrogen in the oxide film are considered as the rate controlling steps. The metal side mass transfer coefficient, k_H, and the mass transfer coefficient in the oxide film, k_<OH,H>, are evaluated from the rate data. (2) The relation between k_H and the stirring power density, epsilon, agrees qualitatively with a correlation obtained from the turbulent mass transfer theory in which a zone of damped turbulence is considered in the liquid side in the vicinity of the interface between the molten metal and the solid oxide film. (3) The flow rate of Ar blown to the bath surface does not affect the dehydrogenation rate, and hence the gas side mass transfer is not a rate controlling step. (4) The dehydrogenation rate increases with increasing temperature, which fact is explained by the decrease in terms of the decrease in the hydrogen mass transfer resistance in the solid oxide film. (5) The dehydrogenation rate is enhanced in several VSD experiments with magnesia immersion tube. (6) It is supposed that a characteristic change in the oxide film due to the reaction between Al and the material of the immersion tube affects the mass transfer of H+ in the oxide film which exists at the interface between the molten Al and the immersion tube.
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