Study On The Stress Relieving Process And Microstructure Properties Of Q345E Steel MAG Welded Joint

Q345E low-alloy steel is made the structure of the commonly used rail transit vehicle bogie welding materials.According to the requirements of technical specification,the bogie must need for eliminating stress annealing heat treatment after welding(The SR treatment)technology,and the goal is to eliminate the welding residual stress,reduce the deformation,welding process to reduce welding crack sensitivity,which is an important process of bogie welding manufacturing.But the traditional SR treatment not only takes longer,also consume more energy and process complexly.However,Using optimization to stress relieving heat treatment process can reduce the time consuming time and reduce energy consumption.The test for the actual production of the welding process has very important application value and practical significance.This topic research main content is as follows.According to the corresponding standard of Q345E low-alloy steel welding specimen in optimizing the stress relieving heat treatment process,the traditional stress relieving heat treatment process and welding test plate under the original state without heat treatment craft of the welding joint are going to trying out microstructure observation analysis,tensile,bending,impact,hardness and other conventional mechanical property test,the stress relieving heat treatment process test and the measurement of welding residual stress test.The results showed that through the analysis of welding residual stress test results,the optimized stress relieving heat treatment process and the traditional stress annealing process of the welding residual stress in both transverse residual stress value and the longitudinal residual stress values are basically same.Two to stress relieving heat treatment after welding process of the Q345E low-alloy steel welded joint microstructure in the base area are composed of blocky ferrite and a small amount of pearlite;The microstructure of weld area is acicular ferrite and a small amount of pearlite;The microstructure of the fusion area is composed of ferrite and a small amount of pearlite.Under the two stress relieving heat treatment process,Q345E low-alloy steel welding joint in the parent metal,weld and heat affected zone of vickers hardness are similar.Optimization of the stress relieving heat treatment process compared with the traditional stress relieving heat treatment process,Q345E low-alloy steel welding joint tensile,bending,impact test results are basically the same.Comprehensive above,under the MAG welding process of Q345E low-alloy steel,optimization of the stress relieving heat treatment process of comprehensive performance with traditional stress annealing process to the comprehensive performance of basic same,illustrates the feasibility of the optimization process.