Study On Pulse Current Assisted Dynamic Medium Frequency Heat Treatment Of Submerged Arc Welded Pipe

With the increasingly depletion of land resources,the exploration of marine resources has become an important field of scientific and technological innovation and energy development.China has rich marine resources,but the development and utilization is still in the early and medium stage.Thick wall submerged arc welded pipe is used as the transportation pipeline of offshore oil and gas resources.The distribution of residual stress in the weld not only affects the service life of submerged arc welded pipe,but also becomes a potential safety hazard in the development and transportation of deep-sea resources.In the heat treatment of submerged arc welded pipe,if the induction heating is only applied to the weld area,the instantaneous heat input at the weld will cause the problem that it is difficult to control the temperature distribution and the circumferential temperature gradient at the weld is too large,resulting in the concentration of residual stress.Aiming at the above problems,this paper adopts pulse current assisted dynamic medium frequency heat treatment process to reduce circumferential temperature difference and residual stress at weld joint.Through the establishment of ANSYS finite element model and relevant experimental verification,this paper explores the influence of pulse current assisted dynamic medium frequency heat treatment process on temperature field and stress field of submerged arc welded pipe.The main contents of this paper are as follows:According to the characteristics of induction heating and pulse current,considering the mutual movement between coil and submerged arc welded pipe,the dynamic four coordinate system co simulation modeling method is proposed by using ANSYS finite element software,the motion electromagnetic thermal stress multi field coupling model is established,and the pulse current assisted dynamic medium frequency heat treatment temperature field is obtained.Taking the circumferential temperature difference between the upper and lower surface of submerged arc welded pipe as the standard,the pulse current is explored The influence of impulse current on temperature field.This paper explores the process of pulse current assisted dynamic medium frequency heat treatment under different parameters,mainly explores the influence of parameters including electric parameters of induction heating,pulse current parameters and coil position parameters on the temperature field of submerged arc welded pipe.The change of stress field after pulse current assisted dynamic medium frequency heat treatment is studied,the influence of pulse current parameters on residual stress is explored,and the influence of coil position parameters on residual stress peak is analyzed.The laboratory induction heating device and pulse current application device are used to verify the pulse current assisted dynamic medium frequency heat treatment,and the temperature measurement experiment and stress experiment are carried out respectively.The experimental data and simulation data are compared and analyzed to verify the feasibility of pulse current assisted dynamic medium frequency heat treatment.