| Magnetic pulse welding is a new type of welding technology,which can realize the welding of dissimilar and lightweight metals,make up for the shortage of traditional welding.And there is no waste generated in the whole welding process.It is friendly to the environment and there is no secondary pollution problem,which can meet the needs of national intelligent manufacturing and environmental protection.However,the working efficiency of magnetic pulse welding is low now,and the welding effect is not ideal,which limits the industrial application of magnetic pulse welding technology.The working principle of the magnetic pulse welding can be summarized as follows: the pulse current flows through the working coil,the flyer strike the substrates caused by the Lorentz force generated by the magnetic field,then the welding is formed.The shape of the working coil determines the collision angle of the flyer and the substrates and the discharge current determines the speed and acceleration of the flyer,both of which have an important influence on the welding effect.Therefore,in order to improve the working efficiency and welding effect of magnetic pulse welding and expand its application range,this paper studies the working coil and discharge current.This paper first introduces the welding mechanism and influence factor of magnetic pulse welding,and then analyzes and optimizes the influence factor in the magnetic pulse welding electrical system.Firstly,the simplified numerical analysis of the common field shaper is carried out,the magnetic flux density and eddy current of the internal pipe are calculated.A concave magnetic collector has been proposed to improve efficiency.Then the ANSOFT MAXWELL software is used to compare the concave field shaper with the common field shaper.It is found that the concave field shaper improves the magnetic flux density of the welding area.And the concave field shaper has higher shape parameters.The simulation results have been verified by experiments.Secondly,the E-shaped coil used in sheet connection is optimized.The quasi-static analysis model of the E-shaped coil is established.The influence of the current return path is analyzed.The simulation results show that the optimal coil gap of the E-shaped coil is three times the width of middle coil arm,and it is verified by the tensile shear test and metallographic analysis of the sample.The coil thickness has no direct influence on the optimal coil gap.In order to solve the problem that the welding gap is too wide,the cross section of the coil ischanged from a rectangle to a circle.It is concluded from the simulation and the experiment results that the width of the welding gap is reduced by the E-shaped coil with a circular cross section.However,due to the increased distance between flyer and coil or the excessive collision angle,the E-shaped coil with a circular cross section needs to input higher energy during the magnetic pulse welding process,that is,the working efficiency of the system is lowered.Finally,the switch synchronization of the system is studied.The reason for the difference in discharge delay of vacuum trigger switches is analyzed,then the parallel operation of the switch is analyzed and simulated.The results suggest that the larger the difference of the discharge delay of switches,the smaller the peak current,which makes the initial velocity of the flyer lower and the deformation of the flyer smaller,that is,the efficiency of the system lower.So this paper proposes a scheme to compensate for the switch discharge delay.By adjusting the delay time of the signal to compensate for the discharge delay of the switch itself,the switch can be turned on synchronously... |
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