The development of the welding process for the long length CICC jacket production

The jacket of ITER superconducting cable-in-conduit conductors (CICC) for TF coil insert is made by butt welding of short length (6-10 m) thin walled circular tubes. The outer diameters of tubes are 41-51 mm. Material of tubes - Incoloy-908 and titanium BT1-0. Method of welding - orbital gas tungsten arc welding. The special complex program of investigation was prepared. The influences of the different technological factors (tube edge preparing, compaction, bending, heat treatment) and operating conditions (temperature from 273 to 4.2 K, pressure up to 2 MPa) upon the welding joint properties were investigated. The samples were produced using different technological parameters. It is desirable to receive the welding joints properties close to the properties of base material of tubes. The microstructure of welding joints and their mechanical properties were investigated. The quality of welding joints was evaluated by dimensional, X-rays, ultrasonic, pressure and leak testing methods. Incoloy-908 and titanium are strong gas getters and elaborate methods of protection were used.