Kinetic Studies on Dehydrogenation of Molten Aluminum by Vacuum Suction Degassing Method

真空抽吸脱气法铝液脱氢动力学研究

• 批准号: 08455345
• 负责人: HIRASAWA Masahiro
• 金额: $ 4.99万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08455345/
• 关键词: aluminum; dehydrogenation; vacuum suction degassing; kinetics

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.

在本研究中，研究了吹氩和机械搅拌条件下铝液脱氢的动力学。还研究了真空抽吸脱气（VSD）方法在脱氢中应用的基本方面。结果总结如下。 (1)被氧化膜覆盖的熔融金属自由表面的脱氢速率遵循一级速率方程，其中氢的金属侧传质和氧化膜中氢的传质被视为速率控制步骤。根据速率数据评估金属侧传质系数k_H和氧化膜中的传质系数k_<OH,H>。 (2) k_H 与搅拌功率密度 epsilon 之间的关系与由湍流传质理论获得的相关性定性一致，在该理论中，在熔融金属与固体氧化膜之间的界面附近的液体侧考虑了阻尼湍流区域。 (3)吹入浴表面的Ar流量不影响脱氢速率，因此气体侧传质不是速率控制步骤。 (4)脱氢速率随着温度的升高而增加，这一事实是通过固体氧化物膜中氢传质阻力的降低来解释的。 (5)在使用氧化镁浸管进行的多次VSD实验中，脱氢率得到提高。 (6)推测由于Al与浸没管的材料之间的反应而导致的氧化膜的特性变化影响存在于熔融Al与浸没管之间的界面处的氧化膜中的H+的传质。