Suppressing welding deformation instability of vacuum vessel considering external restraint and welding sequence

The vacuum vessel has a double-layer shell structure with complex ribs and high-density, full-penetration welded joints. Suppression of welding deformation is very critical to the improvement of manufacturing accuracy. In this paper, the welding experiment is studied for a double-layer shell pre-developed part. The welding deformation measured after welding is compared with the simulation results based on the inherent strain theory, which verified the effectiveness of the numerical simulation method. The welding deformation of the vacuum vessel poloidal segment is simulated numerically. The influence of different welding sequences on welding deformation without constraints is analyzed, and the position where large deformation occurs is fixed by multiple constraints to restrain deformation. The influence of several restraint schemes and fixture removal sequences on deformation suppression is compared. The results show that the optimum welding sequence can reduce 13.6 % of the welding deformation, the minimum welding deformation under free conditions is 14.52 mm, and the final deformation is effectively reduced to 3.6 mm by fixed constraints, which can provide technical guidance for engineering manufacturing.