Mechanism Analysis of Electrochemical Micro-machining Behavior Assisted by Magnetic Field with Local Magnetic Induction Lines Deformation

Grade 404C stainless steel was prepared with high precision by electrochemical micro-machining with or without magnetic field assistance. The surface roughness distributions were detected and their micro-morphologies were analyzed by scanning electron microscopy. Compared with traditional electrochemical micro-machining, the processing efficiency and final surface quality were improved by introducing an external magnet with the north pole directly under the machining gap. However, when dual magnets with the alignment of opposite north–north poles were employed, the variation of surface roughness with processing time was almost consistent with the magnetic field-free case. The mechanism of the effect of magnetic field on electrochemical micro-machining was elaborated. The advantage of magnetic field assistance was the generation of magnetohydrodynamic convection, which facilitated mass transport and accelerated anodic dissolution. Due to the magnetic induction lines in the machining gap being heavily deformed by the repulsion between the magnetic poles, the magnetohydrodynamic force was impaired and the gradient magnetic force was enhanced, which weakened the mass transfer and inhibited the anodic dissolution. In the process of magnetic field assistance electrochemical micro-machining, the magnetohydrodynamic force and the gradient magnetic force will affect the processing effect and enough attention should be paid to the deformation of the magnetic induction lines.