Numerical Simulation Of Electron Beam Welding In Vacuum Rolling Cladding Process

Metal matrix composite is widely used in petrochemical,pressure vessel and aerospace,because of its excellent comprehensive performance.Vacuum electron beam welding is an essential process to obtain high quality composite sheets.In the process of hot rolling,high pressure acted on the weld line and leaded to large deformation.Hence,enough weld width and penetration are needed to guarantee weld strength to avoid cracks.However,excessive welding not only wastes material but also reduces the efficiency of production and the yield rate of steel.Reasonable electron beam welding process is the prerequisite to avoid cracks and reduce weld penetration.Therefore,carrying out temperature field,residual stress field by numerical simulation analysis helps to provide the theoretical basis for electron beam welding,which has very important significance.In this thesis,the numerical simulation and experiments have been used to analyze welding temperature field,stress/strain field of Q345 and 3Cr2Mo under different process by ABAQUS finite element simulation software.A component type heat source model by Gaussian surface heat source and attenuation body heat source was used to simulate temperature field and stress field of two steels.Temperature measuring experiment has been tested and weld morphology features has been observed to verify the simulated result of temperature field,and the weld strength and elongation of two steels were compared by hot tensile experiment.The simulation results of temperature field showed that temperature around welding center changed sharply and the shape of weld pool is typically oval.The front end of the heat source has a large temperature gradient and dense isotherms,while the back end of the heat source has a small temperature gradient and loose isotherms.Meanwhile,With the same welding power,the weld width and penetration decrease with the increase of welding speed.At the same welding speed,the weld width and penetration increase with the increase of power.There is a positive correlation between welding line energy and weld width and penetration.It was also found that weld width and penetration of 3Cr2Mo is larger than that of Q345 under the same welding parameters.In addition,the measured results of welding thermal cycle curve and weld morphology were in good agreement with the simulation results,which verified the effectiveness and reliability of the numerical computation method.The simulation results of stress/strain field studied by indirect coupling method showed that residual stress was mainly concentrated in a 5mm area around weld line and characterized by tensile stress.Transverse residual stress at the weld center characterized by compressive stress,far from the weld center is smaller compressive stress and it ends up been a tensile stress.The maximum longitudinal residual stress was found at the center of weld.There is a small normal residual stress around the weld and it is almost stable in different location.The maximum Mises residual stress was found at the welding speed of 600mm/min with the same welding power,while the minimum Mises residual stress was found at the welding power of 4000W with the same welding speed.Hot tensile experiment showed that the weld strength of 3Cr2Mo under different welding processes at 1000? is generally higher than that of Q345 and its maximum reached 108.8Mpa.Meanwhile,the elongation of the two steels were close to each other at 1000?,and their maximum values were 8.01%and 8.6%respectively.