Test And Analysis Of Temperature Field And Stress Field Of Multi-layer Multi-pass Welding Of Q345 Thick Plate

For a long time,the detection of welding temperature field and stress field mainly relied on a large number of experiments.If the temperature field and stress field are simulated by computer,it can overcome the shortcomings of high measurement cost,large data dispersion and long construction period,etc,and it is the most economical and effective way to describe the distribution of temperature field and stress field.In recent years,the studies of temperature field and stress field by finite element method had focused on heat source and thin plate,and the researches on thick plate were relatively rare.In this paper,the method of combining experimental measurement and simulation calculation was used to study and analyze the welding temperature field,post-weld residual stress,metallographic structure and mechanical properties.The distributions of temperature field and stress field of multi-layer and multi-pass welding were obtained,in order to provide a reliable basis for the welding construction of thick steel structure.The results show that as follows:The simulation results from the butt joint and the actual experiment could be found that the overall error between the simulated temperature and the measured temperature was less than 10%.The simulated average stress was 236 MPa,and the measured average stress after electropolishing was 229.4MPa,and the error was only 3%.The rationality of the mathematical model established before welding and the selected double ellipsoid heat source parameters,meshing method and boundary conditions were verified.In the three-layer and four-pass continuous welding state,the maximum interlayer temperature reached 456.9°C,which exceeded the standard value.However,the subsequent mechanical property tests showed that the average hardness of the first to third weld zone was between 201.1HV and 237.7HV,and the average tensile strength was 544 MPa,512MPa,523 MPa,respectively,there was no obvious crack on the bending specimen,and the mechanical properties generally met the standard requirements.The simulation of the T-joint showed that the temperature of the third weld at 90.5s reached300°C-600°C,and the subsequent temperature was basically stable at this temperature,but there was temperature hysteresis away from the heat source.The maximum stress of the T-joint was moving forward in synchronization with the heat source,and the maximum stress of the featurepoint was 339.1MPa.The stress of each point fluctuated with time,and the stress was maintained at a relatively stable value about 4000 s during the cooling process.Comparing the stress maximum curves of points 8 and 13,since the positions of the two points were symmetrical,the tendency of change was diametrically opposite.