铝热还原电渣精炼法制备铜铬合金触头材料的组织调控的研究

The quality of CuCr alloy depends on the uniformity of the second phase dispersed in the matrix and without macrosegregation, and the regulation of the second phase depends on the preparation method. Aluminum thermal reduction - electroslag refining new methods rose in the present subject, aiming at the instability of the alloy composition and the coarsening and segregation of the second phase of CuCr alloy prepared by aluminum thermal reduction, regulation of composition and organization of copper-chromium alloy will be implemented by adjusting the alloy composition and control of the cooling conditions in ESR process. Using non-equilibrium physical and chemical theory of aluminothermic reduction, the modern theory of the structure of matter and modern detection methods, the present subject will make systematic researches on a series of scientific issues such as composition distribution and morphology and its distribution pattern of inclusions in CuCr alloy prepared by aluminum thermal reduction-electromagnetic casting; regulation mechanism of the cooling rate in ESR process on the CuCr alloy matrix organization and the second phase nucleation and growth process during the cooling process from the high-temperature molten state; formation of solidified structure. Thue, this research provides the scientific theory and test basis for the preparation of high quality CuCr alloy by the aluminum thermal-reduction and Electro-slag Remelting method.

CuCr难混溶合金性能的好坏取决于第二相在基体中均匀弥散分布、无宏观偏析，而第二相的控制又取决适宜的制备方法。本课题提出的铝热还原-电渣精炼新方法，针对自蔓延熔铸法的铜铬合金成分不稳定、第二相粗化偏析等，通过在电渣精炼过程调整合金成分和控制冷却条件实现对铜铬合金组成和组织的调控。课题应用铝热还原的非平衡物理化学理论、现代物质结构理论和现代检测手段，系统研究铝热还原-电磁铸造的铜铬合金 成分组成及分布，夹杂物形貌及其分布规律；电渣精炼过程中CuCr合金添加组元通过改变合金熔体内温度场和流场等传输特性影响第二相析出及粗化过程；合金熔体与夹杂物、结晶器壁与熔体的润湿性对液-液形核过程的影响；电渣重熔过程冷却速率对CuCr合金从高温熔融状态冷却过程中基体组织与第二相形核及其长大过程的调控机理，凝固组织形成等科学问题，从而为制备铝热还原-电渣精炼高品质CuCr合金中提供理论和实验依据。

Cu-Cr合金触头具有耐电压高、分断容量大、耐损蚀特性好、有很强的吸气能力及寿命长等综合优点,目前已成为公认的最佳中压真空断路器触头材料，CuCr合金触头材料的优点源于Cu和Cr 600℃以下几乎不互溶,CuCr合金实际上是机械混合的两相假合金，Cu和Cr都充分保留各自良好的性能。铝热还原-电磁铸造法是一种低成本有可能实现大尺寸近终成形的方法,但目前制备的CuCr合金还存在着夹杂和孔洞等缺陷，还需要对其进行深入研究。. 研究发现添加剂的配比、Cu和Cr元素添加的含量、冷却方式以及坩埚材质都对CuCr合金的熔炼效果有一定的影响。. 经过研究发现在熔炼Cu-Cr合金的过程中，石墨坩埚与合金熔体中的Cr反应，氧化钙和氧化锆坩埚不与合金熔体反应，但是氧化钙耐温较低，易于坩埚支座反应，最终选择氧化锆坩埚熔炼Cu-Cr合金。CuCr25在加热温度为1850℃保温60min所获得合金样品组织均匀，微观气孔较少，电导率和硬度较大；CuCr40在保温温度为1850℃保温90min所获得合金样品组织更加均匀，微观气孔较少。. 通过与工业产品和国家标准相比较，本实验室所制备的CuCr25和CuCr40合金的成分满足国家标准，微观组织的均匀程度优于工业产品。