Vacuum brazing of austenitic stainless steel (SS) under stress with copper-based filler was carried out to assess the susceptibility of liquid metal embrittlement (LME) on stress. Dipping of the SS pipe into molten copper and CuSi3 was performed for comparison. The mechanisms of stress on Cu-SS LME and the effect of Si during cracking were discussed. Test results indicated that microcracks caused by stress concentration increase the possibility of LME. Furthermore, LME was suppressed by the Fe3Si layer between copper and SS. However, the melting range of the filler extended by the addition of Si increases the probability of LME for longer contacting. Accordingly, the addition of Si into copper-based filler should be avoided for most joining methods of SS with high stress concentration.

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As one of the key components to support all the magnet coils, the GS faces engineering challenge to its operational safety throughout the design, qualification and manufacturing process as a result of extreme loading condition. The structural safety of GS was confirmed by both the FEM analysis and the semi-prototype engineering test after a long time of design, qualification, manufacture and assembly. Welding the cooling pipe to the flexible plate without obvious deformation as well as tightening uniformly and precisely all the tie rods to clamp the plates were carried out successfully during manufacturing. The result of final vacuum leakage test indicates that the GS can not only meet the ITER vacuum requirement but also have no slow out-gassing. The first set of GS which has passed the ITER acceptance test is to be delivered to ITER construction site soon.

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