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Impurity removal kinetics of hydrogen plasma arc melting

氢等离子弧熔炼除杂动力学

基本信息

批准号：
08455344
负责人：
ISSHIKI Minoru
金额：
$ 4.86万
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

项目摘要

It has been found that hydrogen plasma arc melting (HPAM) has a strong effect on impurity removal even under an atmospheric pressure. The aim of this study is to clarify the mechanism of impurity elimination during HPAM.The main results are follows.1. The thermodynamic calculations agree with the experimental data on the impurity elimination. This indicates that hydrogen addition to the argon plasma gas allows the system to achieve the equilibrium like state much faster than argon plasma melting.2. It is found that the impurity removal mainly depends on the vapor pressure difference between the impurity and the base metal, although several impurities such as Sb, P and O are eliminated in the form of hydrides.3. Impurity removal obeys the first law reaction and consists of 2 steps with different elimination rates. In the higher concentration range (step 1), elimination rate remarkably increase with the hydrogen concentration of the plasma gas. Hydrogen addition also lowers the impurity concentration at the transition from step 1 to step 2.4. Impurity elimination of step 1 and 2 are found limited by diffusion through boundary layers in gas phase and metal phase, respectively.5. Thermodynamic and mathematical simulations clarify that hydrogen addition gives drastic change of the properties and performance of the plasma arc and increases the temperature in the vicinity of the molten metal surface.6.Finally, HPAM is found to possess an remarkable capability as a new refining method, which is confirmed by applying it to the purification of several metals.

已经发现，即使在大气压下，氢等离子体电弧熔化（HPAM）也对杂质去除具有强效果。本研究旨在阐明HPAM的除杂机理，主要研究结果如下：1.热力学计算结果与实验数据吻合较好。这表明向氩等离子体气体中添加氢允许系统比氩等离子体熔化快得多地实现类平衡状态。研究发现，虽然Sb、P、O等杂质以排杂的形式排出，但排杂主要取决于杂质与母材之间的蒸气压差.杂质去除遵循第一定律反应，由两个不同去除率的步骤组成。在较高浓度范围（步骤1）中，消除速率随等离子体气体的氢浓度显著增加。氢的加入还降低了从步骤1到步骤2.4的过渡中的杂质浓度。发现步骤1和步骤2的杂质去除分别受到通过气相和金属相中的边界层的扩散的限制。热力学和数学模拟表明，氢气的加入使等离子体电弧的性质和性能发生了剧烈的变化，并使金属熔体表面附近的温度升高。6.最后，HPAM作为一种新的精炼方法具有显著的性能，并通过将其应用于几种金属的提纯来证实这一点。