A Study on the Angular Distortion Control for the Multi-Pass Butt Weldment of STS 316LN

The purpose of this study is to establish the proper control method of angular distortion of multi-pass STS 316LN weldment in the vacuum and cryostat vessel of the fusion reactor. To achieve it, the predictive equation of angular distortion in the multi-pass STS 316LN weldment with reference to welding heat input and effective bending rigidity of weldment was established using FEA and experiment. The bending restraint degree of each weldment in the the vacuum vessels of the fusion reactor was evaluated using FEA. Based on the prediction equation of distortion, both proper welding deposit sequence of double sided butt weldment of STS 316LN for cryostat vessel and proper welding sequence for the vacuum vessel were established and verified by the measured distortion of actual welded structure.