装置内部真空线圈系统 (internal vacuum coil system，IVCS)的内部线圈超导导体接头由于其工作环境恶劣，故对焊缝质量要求较高，接头性能的好坏将直接影响到内部线圈能否正常运行.由于真空室空间受到限制以及对周边环境的要求，最终铜管焊接接头选择采用钨极惰性气体保护焊(tungsten inert gas welding，TIG). 为了验证电弧预热焊接无氧铜铜管的可行性，采用开放式机头，利用机头本身对无氧铜铜管进行电弧预热，以达到铜管焊接时所需要的温度，通过对无氧铜铜管的焊接接头进行无损检测、宏观和显微检查以及焊缝、热影响区和母材的硬度测量，系统地评估了电弧预热对热影响区的影响.结果表明，热影响区与母材硬度无显著差异，焊缝金属硬度稍高，但显微组织有明显差异，在观测范围内电弧预热对热影响区并无显著影响，证明采用电弧预热的方案是可行的.
The superconducting joint of the internal coil in the vacuum coil system of the device has a high requirement on weld quality because of its bad working environment. In order to verify the feasibility of welding oxygen free copper pipe with arc preheating method, the method of arc preheating with open head was adopted to preheat oxygen free copper pipe to reach the temperature required for welding copper pipe . Non-destructive testing, macroscopic and microscopic examination, and hardness measurement of weld, heat-affected zone and base metal are performed on copper welded joints. The influence of arc preheating on the heat-affected zone is evaluated. The analysis shows that there is no significant difference between the hardness of the heat affected zone and the base metal, but there is a significant difference in the microstructure. The hardness of weld metal is slightly higher.In the observation range, arc preheating has no significant effect on the heat-affected zone. The results show that arc preheating is feasible.
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