CO₂ Gas Shielded Welding Process Of Q235 Thin Plates And Numerical Simulation Research Based On Abaqus Software

The thin-walled parts of metal have a very wide range of applications in modern industry,welding is an important connection method which plays an irreplaceable role in the manufacture of thin-walled parts.Because of poor rigidity,the deformation after welding have not been completely solved for a long time,and the commonly used methods can be summarized as 2aspects:the process design before welding and the post-weld correction after welding.Over the years,many people introduced finite element calculation to help with designing the welding process and post-weld correction process,and achieved remarkable results.However,the commonly used welding heat source model has considerable errors in the consistency and accuracy of the shape and size of the actual welding pool,the combined heat source model composed of Gaussian surface heat source and pyramidal heat source based on the actual shape and size of the welding pool shows higher accuracy in the calculation of temperature field and welding pool shape,it also shows good prospects in the calculation of stress field and deformation after welding which based on the field of temperature.This article takes Q235 thin plates with a thickness of 1mm and 2mm as the research object,and conducts a study on the influence of various process parameters of CO₂ gas shielded welding on the forming quality of the joint.The microstructure and mechanical properties of the joint are evaluated through experimental methods such as metallography,microhardness,and static tension.Based on the actual molten pool,a combined heat source model was established,and the rules and mechanisms of welding temperature field,residual stress and post welding deformation were studied by a method which combine experiments and finite element calculation.Welding experiments were carried out to study the influence of welding process parameters on joint formation.On the premise of making welding samples with joint quality up to industrial application standards,the weld pool image taken by CCD camera was converted into aerial view through Python language Open CV perspective transformation script.It was found that the weld pool surface of thin plate welding was oval with different sizes at every end,and its dimensions were calculated;Through metallographic observation,it was found that the cross-section of the molten pool is conical with wide ends and narrow waist,and its size was measured.Based on the shape and size of the actual weld pool,the combined heat source model composed of Gaussian surface heat source and cone heat source was established.The Abaqus welding subroutine was written by Fortran language and the welding temperature field of two kinds of thickness samples was calculated.It was found that the calculated weld pool was in good agreement with the actual weld pool,with the maximum size difference of 0.8mm;By comparing with the measured temperature of the calibrated thermocouple,it was found that the maximum difference between the calculated temperature and the measured temperature was29.8℃.The residual stress and deformation of the constraint frame after removal were calculated using the sequential coupling method.It was found that there is a certain difference between the calculated and measured values of residual stress.The calculated results of post weld deformation are in good agreement with the actual deformation,and the calculation accuracy for 1mm samples is higher than that for 2mm samples.