Numerical Simulation Of Welding Process For Thin-walled Box Girder Based On SYSWELD

As a modern construction materials, low alloy structural steel because of its high strength, high toughness, strong impact resistance, long service life and other advantages are widely used in all kinds of large-scale engineering structures, heavy machinery, bridge, construction machinery, shipbuilding and other welding structure.Due to the large welding structure welding distortion is difficult to correct, forecasting and reduceing welding deformation is of great significance. This paper aiming at low alloy structural steel thin-walled box beam, using the finite element software SYSWELD to simulate the welding process, analyze the stress distribution and deformation rule of law, to lay the foundation for thin-walled box girder integral control welding deformation.Firstly, the establishment of a thin-walled box girder typical local joint form T type joints of MAG welding finite element model, the reliability of the model was verified by experiment, and analyzes the T-joint welding temperature field, microstructure field,stress field and welding deformation, to provide a basis for the subsequent further accurate analysis of thin walled box girder welding process.Secondly, a simplified model of a two-dimensional grid characteristics of thin-walled box girder based on the analysis of phase change, welding sequence and welding cooling time of thin-walled box beam welding. The simulation results show that the effect of phase change for different parts of the welding temperature field is not significant,which can not be considered, but the transformation for welding residual stress force and influence can not be ignored, the residual deformation of welding to consider; comparing the 16 kinds of welding deformation under the overall order,we can found that the minimum deformation is 1.62 mm, the optimal welding sequence for the first from the double groove side diagonal welding welded again on the other side; the cooling time’s effect of welding residual deformation of thin-walled box girder and the residual stress are not significant, we can choose shorter cooling time to enhance the operational and production efficiency.Finally, the three-dimensional simplified model is established based on the two-dimensional simplified model, and the welding process of thin-walled box girder is analyzed:(1)The microstructure of the heat affected zone of the joint is mainly bainite, the content of martensite is the second, and there is a quiet small amount of retained austenite;(2)Plate width direction along the X axis direction of the transverse residual deformation is mainly concentrated in the upper flange plate vertical to the edge of the weld; height direction of the welding deformation is small relatively. The height direction along the Y axis direction deformation are mainly concentrated on the flange of the left position; all contraction deformation along the weld direction of longitudinal residual deformation, above, the lower flange of the right edge of is most obvious.(3)The equivalent stress distribution in the weld and its vicinity area, decreases rapidly far away from the weld stress; transverse residual stress is concentrated in and near the weld area. The transverse residual stress formation stress in the weld ends which formed in the middle part of the weld tensile stress; residual height direction the stress distribution of the compressive stress appears at the end of the weld(lateral position), and the tensile stress is still concentrated in the weld region; the longitudinal residual stress mainly concentrated in and near the weld area, the tensile stress mainly concentrated in the weld and near weld zone, and the power of the stress distribution was significantly higher than the distribution of regional stress, compressive stress mainly concentrated in the region which is away from the weld.