Numerical Simulation And Process Analysis Of Temperature And Stress Field Of Thick Wall Pipe In Girth Welds Welding

Thick-walled pipe welding is a very important technology in the long-distance pipeline, the quality of the weld formation directly affect the efficiency of pipeline transportation. Poor weld could fracture and the distribution of residual stress in thick wall pipe weld is also very important for the analysis of each part of weldment. Simulation of the analysis of temperature field provide a basis for the stress field.In this paper, we analyse the thick wall temperature field and stress field finite element numerical simulation with ANSYS simulation software, On the basic theory of thermodynamics, selecting gaussian heat source model and using the command flow of APDL language in ANSYS to establish the finite element model considering latent heat of phase change process and selecting the reasonable grid size, choosing reasonable boundary conditions for constraints. After pretreatment process analysis of load, setting all kinds of boundary conditions and step length, handling the most important part of post-processing after loading process.In radial post-processing analysis, the last layer of the welding thermal cycle curve shows that the temperature of welding node at 20mm rises rapidly affected by a layer of waste heat temperature; The cooling rate of welding node increases in extreme around the period of 72s, by organization changing, comprehensive factors, such as air convection. As the radial movement along the pipe from the center of weld, the maximum temperature of the weld center that the heat source point reached gradually reduce. In this paper, using the generated. rth load file in hot-force coupling analysis, cloud images show that thermal coupling simulation process changed obviously with weldment deformation, and node by the tangential stress effect is more apparent than the radial stress. With the increase of welding time, the equivalent stress of the weld center increase nonlinear and slowly, reaching maximum point for more than a few seconds with the formation of molten pool, the equivalent stress to achieve the minimum point, the equivalent stress increased dramatically after the formation of molten pool, the formation of a stable value is less than the maximum equivalent stress of the welding process before. Sharply as far away from the weld center, the time of various points along the radius gradually increase with the form of the maximum equivalent stress increases gradually, and the equivalent stress increases the formation of molten pool, the node is mainly affected by the compressive stress in the heating process, and the formation of molten pool cooling process was mainly affected by tension stress.In shaft backward processing analysis, through the comparative study on the different process parameters, the post-processing results show that the maximum temperature of heat source of the center increases with the increase of welding voltage and welding current; The maximum temperature increases with as the welding speed slow down, The increase of speed slow down, leading to phase change residence time; The maximum temperature decreases with the increase of the radius of the welding heat source, double seal welding in the welding of the second welding of maximum temperature decreases, hence the phase transformation time; The welding of double seal welding thermal cycle curve indicates that the name of the second welding thermal cycle of maximum temperature increases and makes the time duration of the above phase transition state less.