| Oxygen free copper is widely used in various fields of copper due to its excellent thermal conductivity and conductivity.TU2 oxygen free copper,as a high-purity copper material,has attracted much attention in welding performance due to its good corrosion,processing and weldability.Superconducting magnet feeder system(feeder)provides power supply,cooling,measurement,control and diagnosis for ITER magnet systems such as TF,PF and CS.It is a complex system composed of a whole sleeve,cable and wire.HTS current lead is one of the core components of feeder system.Between the room temperature terminal in the HTS current lead and the fin heat exchanger,the fin heat exchanger and the HTS section need to be connected by welding.The room temperature terminal,fin heat exchanger and HTS section are made of TU2 oxygen free copper.This paper first analyzes the basic theoretical knowledge of welding simulation analysis,then carries out the finite element simulation of electron beam welding of TU2 oxygen free copper,carries out the electron beam welding test of TU2 oxygen free copper butt joint according to the process parameters obtained from the simulation results,and carries out the experimental analysis of welding quality detection of the welded joint.The main contents of this paper are summarized as follows;(1)Firstly,this paper introduces the application of welding technology in copper and copper alloys and the current situation of numerical simulation of electron beam welding.Secondly,the basic theoretical knowledge of welding analysis is introduced.According to the "nail" weld pool morphology of electron beam welding,the combined heat source of double ellipsoid heat source and 3D Gaussian heat source is used to simulate the electron beam welding of TU2 oxygen free copper.Obtain the heat source verification parameters that meet the project requirements and the molten pool depth reaches 30mm.(2)According to the actual situation of electron beam welding,the initial conditions and boundary conditions are set.The welding temperature field,stress field and deformation are analyzed.The welding temperature field drops below 100? after cooling for one hour.The welding residual stress is mainly concentrated at the weld and boundary support,and the peak value is about 100MPa.The welding deformation increases with the increase of heat input.(3)Referring to the heat source verification data,three groups of welding process parameters of 100mA,120mA and 140mA are proposed for electron beam welding test.The welding temperature field and the shrinkage in the width direction of butt joint are measured by temperature measuring test paper and vernier caliper.The temperature measured at 50mm away from the weld is 130?,and the deformation in X direction is consistent with the simulation results,both of which are about 0.2mm.(4)Carry out post weld quality inspection for three groups of welded joints.The metallographic structure of the welded joint was observed,and the mechanical properties such as tensile,bending,impact and hardness of the welded joint were tested.The low power metallographic results show that the weld pool morphology is basically consistent with the simulated weld pool morphology.The high power metallographic results show that the heat affected area of oxygen free copper electron beam welding is very small.The test results of mechanical properties show that the mechanical properties of welded joints are better when the acceleration voltage is 150kV and the electron beam current is 120mA. |
PDF Full Text Request