Numerical Simulation Research On Arc Ultra-narrow Gap Welding Of Thick-walled Steam Turbine Valve Body Material

With the rapid development of metal structures such as modern industrial equipment and engineering structures,large-scale and thick-plate metal structures have become more and more widely used,and the welding problems of large and thick plates have become more and more prominent.Traditional welding methods cannot meet their welding quality and efficiency requirements anymore.Ultra-narrow gap thick plate welding with flux strips constraining arc technology has the characteristics of small welding groove,high welding efficiency,and high welding quality,which can solve many problems of traditional welding methods when welding thick-walled parts.This article takes the valve body produced by Sharing Cast Steel Co.,Ltd as the research object.First,using the flux sheet constrained arc ultra-narrow gap welding technology,the welding experiment was carried out on the 60mm thickness of the steam turbine valve body material ZG13Cr9Mo2Co1NiVNbNB casting steel test block.The welding voltage is 22V,the welding current is 185A～195A,the welding speed is 9mm/s,the width of the lower groove is 4.5mm,the width of the upper groove is 6mm,and a total of 15 layers of welding bead are filled.A thermocouple was used to measure the temperature field during the welding process.Then,use ANSYS software to establish a finite element model of the welding temperature field by writing APDL commands,select a uniform body heat source model suitable for multi-pass welding,carry out the numerical simulation of the welding temperature field.The life and death element method is used to simulate the filling of weld metal more accurately during the welding process.On this basis,the sequential method is used to apply the nodal temperature results of the welding temperature field as a load to the finite element model of the stress field to further analyze the welding stress field.The results show that the thermal cycle curve obtained by the simulation is basically consistent with the thermal cycle curve measured during the experiment.The simulation results of the molten pool morphology are consistent with the actual weld macroscopic morphology.When the current is 185A,the area with a temperature higher than 1400℃ can represent the entire weld area.There is no non-fusion phenomenon at the bottom of the sidewall.Through the analysis of the stress and deformation results,it is found that the fixed constraint position and the size of the heat source are the main factors affecting the residual stress and deformation.The maximum tensile stress is 655MPa,the maximum compressive stress is 474MPa,and the maximum welding deformation is 0.474mm.These research results have important guiding significance for the formulation of subsequent welding process standards.