铝的电渣精炼及其净化机制研究

New efficient purification method is one of the important technical basis for developing high quality aluminum and aluminum alloys. A creative idea utilizing the electroslag refining technique is proposed to remove the impurity elements iron and purify the aluminum. Based on thermodynamic analysis, combined with the evaluation of physical and chemical properties of the multicomponent slags, the electroslag refining process and slags to eliminate iron impurity will be optimized. The multi-field coupling simulation will be carried out to reveal the evolution of the temperature field,flow field and concentration filed during aluminum electroslag refining process.Through chemical analysis, microstructure observation and performance testing, the effects of the procedure parameters on the change of the iron impurity content, gas and inclusions in aluminum,as well as the solidification microstructure will be discussed in detail. With the in-situ observation of the electroslag refining process by synchrotron radiation X-imaging technique, a composite model of multiphase reactions and interface processes of the iron removal mechanism will be build based on the kinetics analysis on the local enrichment, reactions and multiphase separation of the iron impurity during the procedure.This proposal will try to estabish an integrated method to remove the gas,inclusions and impurity elements simultaneously and control the solidification structure effectively. It is an attempt to utilize the traditional ferrous metallurgy technology in aluminum research and will promote the development of purifircation principles and techniques,which is believed to be the technical support for developing high-quality aluminum.

探索高效净化新方法是发展优质铝及铝合金的重要技术基础之一。本项目创造性地提出了利用电渣精炼技术去除铝中杂质元素铁的综合净化新思路，将首先通过热力学分析，并结合对多元渣剂理化特性的分析与测试，选择并优化可用于铝电渣精炼处理且具有除铁效果的渣剂；再以多场耦合模拟分析为基础，揭示铝电渣精炼过程的温度场、流场与浓度场的耦合与演变规律；通过化学分析、组织观察与性能测试，探明铝中杂质铁与气体、夹杂含量，以及凝固组织、力学性能等随电渣精炼工艺参数的变化规律；结合电渣精炼过程的同步辐射X成像原位观察分析，在剖析电渣精炼除铁动力学条件的基础上，构建以多相反应与界面过程复合模型为基础的杂质元素的区域富集、反应与多相分离的电渣精炼除铁机制。本项目将探索实现气体、夹杂与杂质元素的同步去除和对凝固组织的有效控制，发展综合纯净化原理与技术，是传统黑色冶金技术在铝纯净化领域的尝试，将为优质铝材的发展提供技术支撑。

铝中杂质元素的控制是高品质铝及高性能铝合金材料制备的关键科学问题。本项目研利用电渣精炼工艺实现了铝合金杂质元素的高效控制，深入研究了电渣精炼的净化化机制。首先对渣系的热物性进行系统研究，提出了可靠的渣系密度预测模型，分析了电导率与温度间的关系。根据电渣精炼熔渣设计原则及系统的实验，首次发现含LiCl或CaCl2的熔渣适用于铝及铝合金的电渣精炼体系。研究结果表明，含LiCl的熔渣有明显的除硅效果和一定的除铁作用。对渣金界面反应的研究，揭示了电场在界面反应中的决定性作用。反应动力学研究表明，除硅反应的界面动力学过程为一级非可逆过程，且硅原子的传质过程为界面反应的限制性环节。 此外，本课题利用电化学工作站研究了铝电极界面处的动力学过程。交流阻抗谱与极化曲线的测试结果均表明，在铝电极与熔渣的界面处形成了双电层结构，且存在明显的极化现象，这些都为界面电化学反应创造了条件。为了从微观上研究铝熔体与熔渣的界面反应，利用经典分子动力学和第一性原理研究了熔渣、铝熔体及熔渣与熔盐的界面结构。计算结果表明，电渣精炼的除硅过程是通过界面处的化学反应完成，而不是熔渣的吸附，并且再次验证了电场在界面反应中有关键作用。