Theoretical Calculation And Numerical Analysis Of Electromagnetic Field In High Frequency Longitudinal Welded Pipe

With the rapid development of petroleum,construction,automobile and other industries,there are more requirements about quality of high frequency welded pipe in domestic market.And there are more severe in the market situation at home and abroad.It is an urgent technical problem about how to optimize the welding process parameters and ensure the weld quality of welded pipe.In the research of weld quality of high frequency induction welding,we can not avoid to analyze the electromagnetic-magnetic-thermal coupling produced by induction heating process.At present,the method most widely used to study the physical field coupling of electromagnetic induction is using the finite element software to simulation.The disadvantages of using finite element method to simulate calculation are that the time of setting calculation is too long,and the numerical simulation method only can get the physical change law,but can not study the mechanism of producing law.Compared with the finite element simulation method,the results obtained by the theoretical calculation method are of great reference value,and its changing tendency is usually in accordance with the actual situation within a certain error acceptance range.In order to study the mechanism of electromagnetic field change in induction welding process,the theoretical formula can directly express the influence law of each physical parameter.So the theoretical calculation method has the irreplaceable status and importance of numerical simulation.The purpose of the research is to solve the problem of electromagnetic field in the process of high frequency induction welding by using theoretical calculation method.Starting from the basic principle of electromagnetic induction.Based on the calculation of magnetic field in the induction heating process of V-shaped straight seam welded pipe.The induction magnetic field produced by induction welding process is calculated theoretically.The main content of this article is as following:(1)A mathematical model of the induced magnetic field generated by a charged element at the air-metal interface is established based on the basic electromagnetic theory and the reasonable hypothesis by means of the 3D induction coil in each direction of the coordinate system,the mathematical model of the magnetic field intensity of a circular induction coil at the weld of a straight welded pipe without a V-shaped angle is obtained by transforming the integral variable to push the point and the surface and integrating the pointline-plane-body steps.Using ANSYS software to simulate the induction heating process of the straight welded pipe without V-shaped angle.And it is verified about the accuracy of the mathematical model for calculating the magnetic field intensity variation at the weld in the process of induction heating of straight welded pipe.(2)There was the mathematical model of the magnetic field intensity at the V-shaped fillet weld produced by the induction coil established.On this basis,the mathematical model of induced current distribution in V-shaped angle region is established.Considering the influence of self-induced magnetic field produced by the distribution of induced current in the V-shaped angle region on the induction magnetic field produced by the induction coil,there was a mathematical model of the distribution of total magnetic field intensity at the weld established.Using ANSYS software to simulate the induction welding process of the straight welded pipe.And it is verified about the accuracy of the mathematical model for calculating the magnetic field intensity at the V-shaped angle in the induction welding process of the straight welded pipe.(3)It was tested about the induction heating process in the induction welding of straight welded pipe.And the numerical value of the induction heating process at The Vshaped Angle was measured.Then the numerical simulation and theoretical calculation results are compared and analyzed.The accuracy of the mathematical model of the magnetic field intensity at the V-shaped angle in the induction welding process of the longitudinal welded pipe is further verified by comparing the variation law of the magnetic field intensity at the V-shaped angle.