| The subway bogie frame is a large welded component with a large number of welds and a large welding heat input.During the welding process,stress and deformation will inevitably occur,which will affect the safety and service life of subway operation.Therefore,an efficient simulation method that can predict the residual stress and deformation of the subway bogie frame after welding has been developed,and the law of residual stress and deformation of the bogie frame has been analyzed.Carrying out research on new welding process of complex frame has very important academic research significance and engineering application value for promoting the "high-precision shape control","high-quality control performance" and "high service safety and reliability" of the bogie frame.In this paper,taking the 80-km B-type subway bogie frame as the research object,the T-joint welding process test of S355J2 W weathering steel was carried out by high-frequency pulse MAG welding and conventional pulse MAG welding.Carry out microstructure observation and mechanical property test as well as actual measurement of welding heat cycle for welds.The SYSWELD numerical simulation software is used to simulate the temperature field and stress field of typical joints,and the side beam and crossbeam of the bogie frame are simulated and analyzed,and their deformation laws are analyzed.The research shows that:1)The welding joints of high-frequency pulse MAG welding and conventional pulse MAG welding are well fused,no welding defects are produced,and the welding seam is beautifully formed.High-frequency pulse MAG welding realizes single-sided welding and double-sided forming,and the welding process is better.2)The microstructures of several working conditions are similar,mainly proeutectoid ferrite,acicular ferrite and pearlite and granular bainite.In the high-frequency pulsed MAG welding process,when the welding gap is 1 mm,the microstructure of the weld is the best,the content of acicular ferrite in this condition is the highest,and no side lath ferrite is formed in the weld zone.3)For the welded joints of several welding conditions,the area with the lowest hardness value is located in the base metal,the hardness of the weld zone is higher than that of the base metal,the area with the highest hardness value is the heat-affected zone,and the Vickers hardness of all areas of the welded joint is less than 380 HV.4)The simulation results of the welding stress field show that the longitudinal residual stress of the crossbeam and the side beam are mainly distributed in the weld area and near-weld area,and the most concentrated part of the side beam stress appears between the bending of the upper and lower cover plates and the vertical plates on both sides.the shape of the part.The simulation results of welding deformation show that the maximum deformation position of the side beam is the bend of the upper and lower cover plates of the side beam,and the maximum deformation position of the beam is located at the center of the last weld of the upper cover plate.5)Under the same welding process conditions,the overall residual welding stress and post-weld deformation of the high-frequency pulse MAG welding joints are significantly lower than those of the conventional pulse MAG welding joints.6)The residual stress of the bogie frame calculated by the inherent strain method is close to the measured value of the stress-strain test system using the indentation method,and the error rate of the side beam and the beam is not more than 15%,indicating that the thermal elastic-plastic method and the inherent strain method are closely related.Combining to predict welding residual stress and deformation has certain accuracy and feasibility. |
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