Study On Welding Deformation Of Large Module Of Nuclear SC Structure

CAP1400 nuclear power plant,at the international leading level,is a third-generation nuclear power plant independently developed in China based on AP1000 technology.For the first time,it adopts Steel plate concrete Structure(SC structure)shielding wall,which can better protect against external impact.Because the SC structure is very complex.,which can only conduct single-sided multi-pass welding,the welding deformation is large and difficult to predict and control.In this paper,combined with the welding test and the thermal elastic-plastic finite element method,the welding deformation of the small size test plate of the typical joint of SC structure is studied,and the inherent strain database of the typical joint of SC structure is established.The inherent strain method is used to predict the welding deformation of the large module of SC structure effectively.The influence of the backing plate,clamping mode,welding sequence and back welding process on the welding deformation is analyzed.When the first two weld passes of Q345 B small size thick test plates are welded,the angular deformation is small;when the filling height of transverse welding is within the range of about10mm-25 mm,the angular distortion will increase rapidly,and the final angular distortion of vertical test plate with the same thickness is smaller than that of horizontal test plate,and the final angular distortion will be reduced by using the backing plate,and the welding angular distortion of short test plate with the same thickness is smaller than that of the long test plate.The calculation results of thermal elastic-plastic finite element analysis of Q345 B thick plate are in good agreement with the welding test results.The inherent strain database of the SC Structure typical welded joints was established by the results of the test and the calculation of the thermal elastic-plastic finite element analysis.The results of deformation calculation of small test plate by inherent strain method are in good agreement with those by thermal elastic-plastic method.The results of welding deformation of large module of SC structure calculated by inherent strain method show that: Priority welding vertical seam is conducive to reducing the welding deformation of each module;The welding deformation of the double-layer whole circle module and the 18-19 layer module is obviously reduced when the backing plate is used.The use of backing plate is conducive to reducing the secondary deformation of the module during welding with other modules;Radial deformation is the main deformation mode of each module during welding,and the radial shrinkage deformation is larger than the radial expansion deformation;The effect of back welding process and reserved weld non-welding on reducing the peak value of deformation is small;The deformation of the vertical weld and the cross plate area of the double-layer full circle module and its welding module is large.