| Electrofusion blasting processing relies on the high temperature action of thermal plasma to remove materials.It has the advantages of high material removal rate and no significant cutting force.It can effectively solve the serious tool wear in the mechanical drilling of difficult-to-process materials,the insufficient rigidity of the process system and the problem of low processing efficiency.However,electrofusion blasting processing has the problems of serious electrode wear and poor surface quality.In this paper,based on the action characteristics of the arc plasma in the discharge channel formed during the magnetic field and the electric fusion blasting process,the magnetic field is introduced into the electric fusion blasting deep hole processing to achieve the purpose of reducing electrode loss and improving the surface quality of the machining.Firstly,the theoretical study of the plasma motion law under the action of a magnetic field is carried out,and the influence of the arc shape and position distribution law under the action of a uniform transverse magnetic field and a longitudinal magnetic field on the processing effect is analyzed.The research results show that the transverse magnetic field will cause the axis of the formed deep hole to deviate from the geometric center of the workpiece;the longitudinal magnetic field will cause the arc plasma to spirally move in the direction of the jet,and the centrifugal force generated by the rotation will cause the arc to diffuse radially as a whole,which will change the erosion pits.Large and shallow,shorten the arc time on the electrode discharge surface,can reduce the electrode loss.Secondly,based on the role of the electrode in the process of electrofusion blasting deep hole processing,the internal chip removal electrode is designed,and the arrangement of the longitudinal magnetic field generator and the magnetic source are determined according to the direction of the magnetic line of induction that has a significant impact on the processing quality.According to the actual processing conditions,the simulation model under the self-magnetic field including the cathode-arc-anode surface and the simulation model under the external longitudinal magnetic field including the cathode-arc-anode surface-coil are established,and the COMSOL finite element analysis software is used to analyze the self-magnetic field.The physical field distribution of the magnetic field and the arc with an external longitudinal magnetic field is solved,and the comparison shows that:under the action of the external longitudinal magnetic field,the arc plasma flow rate and the overall arc temperature decrease,but the maximum arc temperature is still near z=1.6mm,and the arc temperature The distribution area of the field and current density expands.As the magnetic flux density of the arc area increases,the arc temperature field expands significantly in the radial direction,which makes the anode surface current density distribution more uniform,which is beneficial to reduce the surface roughness of the machining.Finally,a single factor test method is used to compare and analyze the influence of the presence or absence of the longitudinal magnetic field on the processing target.The results show that when the machining current and voltage are 150A-170A and 20V-22V,as the excitation current increases,the machining erosion rate and surface roughness decrease by 8%-29%and 10%-51%,respectively,while the electrode The loss first decreases and then increases.Through range analysis,it is found that the machining current and voltage have a significant impact on the electrode loss,while the excitation current has the least impact on the electrode loss.The primary and secondary order of the process parameters affecting the degree of each machining target is determined,and the matrix analysis method is used to perform optimize and determine the optimal combination of process parameters. |
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