基于磁脉冲成形技术的新型超导接头焊接方法基础问题研究

With the development of superconducting technology, more and more attentions are paid to the researches and applications of many novel electronic apparatuses such as the superconducting magnet, superconducting cable, superconducting fault current limiter, and superconducting transformer. Superconducting joint welding is one of key technologies to ensure superconducting apparatuses stable operating in the extremely cold environment. Especially for the superconducting magnet used in magnetic resonance imaging, the quality of superconducting joints is vitally important. At present, the applied superconducting joint welding technology exist shortcomings. A novel method applying magnetic pulse forming technology is proposed to weld the superconducting joints. This method which can fabricate the superconducting joint with extremely low resistivity has many advantages such as high production efficiency, automation, precise control of the technics parameters and process and technics performance stability. The main research contents of this project is to study the fundamental problems of the method of superconducting joint welding applying magnetic pulse forming technology. The priorities in the project will be to study the superconductor deformation characteristic, found constitutive equations of the superconductor on high speed deformation, study the mechanism of the microstructure forming on welding interface and influencing on the superconducting joint main performances, found the theory model of the superconducting joint welding system applying magnetic pulse forming technology, search the optimization criterion of main technics parameters. The study is very importance in scientific research and engineering application.

随着超导技术的发展成熟，超导磁体、超导电缆、超导限流器、超导变压器等诸多新型电工装备技术的研究和应用越来越受到关注。超导接头焊接是保证超导装置在极低温环境下稳定运行的一项关键技术，尤其对于磁共振成像超导磁体，超导接头的质量至关重要。现存的多种超导接头焊接技术（如钎焊、冷压焊、扩散焊及熔焊等）都存在不完善的地方。本项目拟研究一种采用磁脉冲成形技术进行超导接头焊接的新方法，此方法可制备出电阻率极低的超导接头，具有生产效率高、可以实现自动化、工艺参数和工艺过程可以精确控制、工艺性能稳定等特点。本项目主要对超导接头磁脉冲焊接方法中的基础问题进行研究，重点研究超导体塑变流动规律，建立超导体在高速变形下的本构模型；研究焊接界面微观形貌形成机制以及焊接界面微观形貌对超导接头主要性能的影响机制，构建超导接头磁脉冲焊接系统理论模型，确定主要工艺参数的优化准则。研究具有重要的科学研究意义和工程应用价值。

超导接头焊接是保证超导装置在极低温环境下稳定运行的一项关键技术，尤其对于磁共振成像超导磁体，超导接头的质量至关重要。现存的多种超导接头焊接技术（如钎焊、冷压焊、扩散焊及熔焊等）都存在不完善的地方。本项目详细研究了一种采用磁脉冲成形技术进行超导接头焊接的新方法，此方法可制备出电阻率极低的超导接头，具有生产效率高、可以实现自动化、工艺参数和工艺过程可以精确控制、工艺性能稳定等特点。. 本项目首先对超导接头磁脉冲焊接方法中的基础理论问题进行研究和分析，然后建立了详细的数值仿真模型，具体分析了系统电容量、放电电压、系统电阻等参数对电磁力的影响。针对铌钛超导丝的材料特性重点研究超导丝的塑变特性，采用ABAQUS/EXPLICIT准静态方法对超导丝在电磁压力下的应变进行了仿真，重点考虑了接触面积和等效塑性应变两个关键因素。根据仿真结果分析总结超导丝的塑性应变与电磁压力的关系以及对超导接头电阻的影响，寻找磁压缩超导接头焊接过程中最佳压力量。本项目还详细分析了焊接界面微观形貌形成原因以及焊接界面微观形貌对超导接头主要性能的影响关系，为寻求最佳工艺参数提供了重要依据。本项目还根据数值模型优化结果设计并搭建一套适用于NbTi超导接头磁脉冲焊接实验系统，完成了多个NbTi超导接头样品的焊接制备，并研制了一套基于电流衰减法测电阻的内插式超导接头电阻测量装置，通过对制备的超导接头样品的低温电学性能测试来验证了系统理论模型与工艺参数优化方法的合理性。