Research On Design Of Electron Beam Welding System For Large Complex Heavy-load Vacuum Vessel Port Stub

Vacuum vessel port stub is used to connect the inside vacuum vessel and outside port of China Fusion Engineering Test Reactor.It can't be straightened,after welding with vacuum vessel port,so the port stubs are of higher pricision.In order to ensure the construction quality of the vacuum vessel,the split welding structure is adopted in using Electron Beam Welding which is a kind of high energy beam welding with micro deformation.This thesis concerns two main parts,one of which is designing and researching the electron beam welding system,another one is welding technique analysis of port stub.First of all,the vacuum chamber wall thickness,rib size of Vacuum EBW Machine are calculated through the empirical formulas,structures of welding vacuum chamber are designed,and a finite element model for vacuum chamber is built with its strength and stiffness analyzed.The application of ANSYS finite-element software to optimum design of vacuum chamber.The buckling analysis has also been carried out to prove the good stability of the structure.According to the welding seam of vacuum vessel port stub,The welding scheme is made.Motion platform is designed to meet the welding scheme.The motion platform mainly includes the lower XY translational motion device and upper XY tilting device.Detailed design for the mechanism of the motion platform and static load analysis for key components are presented,which provides a reference for the manufacture of motion platform.According to the vacuum requirements for EBW Machine,The vacuum system utilizes two vacuum pumps,one booster pump and one diffusion pump.A detailed calculation of pumping time was carried out.The main pipe is designed,the wall thickness of the pipe is calculated,and the critical pressure is checked by the empirical formula.According to weld profile in electron beam welding,based upon double-ellipsoidal volumetric heat source model and 3D conical Gaussian volumetric heat-source was established.The experiment of electron beam butt welding for stainless steel plate verified the feasibility of the heat source model in the numerical simulation of temperature field.According to the inherent strain theory,the welding process of vacuum vessel port stub is simulated.Simulation of welding deformation of four different welding programs without clamp shows that port stub with a different welding sequence results in different welding deformation.Welding clamps are set on the basis of simulation reasult.Then the best program is selected.Using the two different welding methods of electron beam welding and narrow gap TIG welding,weld seam shrinkage measurement and tensile strength test are performed on welded joints of 304L sheet.The following conclusions can be drawn.The joints obtained by the two welding methods have good microstructure and have good stability.However,the electron beam welding shrinkage is much smaller than that of the narrow gap TIG.It can be seen that the electron beam welding produces less deformation and has great advantages in controlling the deformation of the welded joint.