Study Of Controlling Welding Residual And Strain By Electromagnetic Impact

A new method of controlling welding residual stress and strain by electromagnetic forces is put forward, in order to solve the deformation of welding with thin plates, which based on the theory of electromagnetic and the formation mechanism of welding residual stress and strain. The energy is easy to control and the impact equipment is more of flexibility by this kind of method. The method avoids surface flaws which reduce mechanical performances, as the coil do not contact with welding applying the electromagnetic force.A pulse electromagnetic impact equipment and convenient clamping fixture are developed. The impact equipment can give enough electromagnetic force to welding to meet the experiment, with charging voltage, charging capacitor and frequency alternating randomly in measuring range.Finite element method is used to give theoretical direction and feasibility of experiment. Some inclusions are obtained by using ANSYS software, establishing electromagnetic-Circuit coupled finite element model and electromagnetic-welding construction coupled model. Electromagnetic-Circuit finite element model, simulating the changes of welding residual stress and strain after impact. The result shows that welding residual stress and strain decrease after electromagnetic impact, which reaches the prospection.The effects of parameters on experiment are investigated by single impact and multiple impacts, and the parameters are optimized. The result shows that when the turn number of coil is increasing or the gap distance between coil and workpiece is decreasing, the electromagnetic impact force will become increase. The welding residual stress and strain will decrease with charging voltage, charging capacitor and impact frequency increased. When charging voltage is 2150V, charging capacitor is l000μF, the gap distance between coil and workpiece is lmm and impact frequency is 20, the deformation flexibility decreases from 5.46mm to 0.46mm. The effect is obvious. In comparison of the mechanical properties of welding with and without impacts, the result shows that welding residual stress decreases sharply after electromagnetic impact, the hardness of the center of weld bead increases a little, but hardness of fusion zone are not obviously. The effects of electromagnetic impact on tensile strength and elongation are also not obvious.