Numerical Simulation Of Transient Liquid Phase Welding Of X70 Pipeline Steel

Transient liquid phase welding(TLP)is a special connecting measure with advantages as low welding temperature,small residual stress,small weld reinforcement,etc.Numerical simulation of TLP using finite element method can analysis and anticipate the properties of weld joint,also can save materials and manpower.This thesis does numerical simulation analysis of TLP using X70 pipeline steel as base material.Firstly,the theory of electromagnetic induction heating was analyzed,and the mathematical model of electromagnetic field and electromagnetic induction heating were analyzed,then,the magnetic-thermal coupling heat source model was described,the application of the magnetic-thermal coupling model in this experiment was analyzed combined with the actual conditions of the experiment,the conclusion showed that the coupling model cannot be ultimately used in this experiment.Afterwards,by analyzing the actual conditions of the experiment,the induction heating process was simplified and an alternative heat source model was established,which was used to do simulation later showing good agreement between the result of simulation and actual result of temperature field.The geometric model of TLP welding was established,which completed the numerical analysis model.In the process of establishment of the model,the effect of the interlayer and the point impact were considered,a series of assumptions were put forward,which can simplify the calculation process as much as possible and increase the computational efficiency.Using the model of TLP welding,temperature field and residual stress field were analyzed respectively,attaching the change law,by considering holding temperature and holding time as parameters.The result showed that the residual stress increased with higher holding temperature,while the residual stress decreased with longer holding time.The metallurgical structure of the weld seam was analyzed,and the influence on the weld structure was analyzed by considering the holding temperature,holding time and welding pressure as parameters.The results showed that the better welding seam microstructure can be produced by higher holding temperature and longer holding time.