Simulation Analysis And Realization Of Gap Field In ECM Of Valve Cooling Hole

Electrochemical machining(ECM)is a technological method that changes the valence of metal elements according to the electron transfer between different metals,so as to make the anode surface materials undergo electrochemical reaction,so as to remove the surface materials.During machining,there is a machining gap between the anode and the cathode,and the anode is etched away by ion dissolution,so there is no stress and deformation,cold work hardening layer.In this paper,COMSOL Multiphysics software is used to simulate and analyze the flow field,electric field and dilute material transfer field in the gap of cooling hole electrochemical machining,which provides some basic data for designing cathode morphology reasonably and determining machining parameters,and lays a foundation for further numerical simulation research of the whole process of electrochemical machining.Specific research contents are as follows:(1)Three cathode tools with different bottom shapes were designed,namely,cylindrical cathode,hemispherical cathode and truncated cone cathode.The flow field and electric field distribution in the machining gap were obtained by simulation analysis.The results show that the overall flow rate and electrolyte current density are higher when using cylindrical cathode than those when using hemispherical cathode and truncated cone cathode,and the flow field distribution is more uniform and the forming profile of cooling hole is more regular.(2)The flow field distribution in the gap during ECM is obtained by COMSOL software,and the effects of different gaps and different inlet pressures on the flow field distribution are mainly studied.the simulation results show that the electrolyte flow rate increases with the decrease of machining gap,but the gap is too small,which may lead to the accumulation of machined products and even short circuit.The higher the inlet pressure is,the higher the electrolyte flow rate in the gap is.When the inlet pressure reaches 2MPa,the flow rate at the control points is all greater than 5m/s,and the flow field characteristics are good.(3)The effects of electrode surface insulation,voltage and machining gap on the gap electric field and cooling hole morphology in electrochemical machining are analyzed by COMSOL software simulation.The results show that cathode surface insulation can make the electric field distribution more concentrated,improve the processing efficiency;The larger the external applied voltage,the higher the electrolyte current density in the gap,the smoother the transition area between the bottom and the side of the cooling hole.With the decrease of machining gap,the maximum electrolyte current density increases,the depth of cooling hole changes obviously,and the lateral expansion trend weakens.In addition,the distribution of hydrogen when the electric field is coupled with the thin material transfer field is analyzed.It is found that the closer to the cathode surface,the higher the hydrogen concentration,and the highest hydrogen concentration in the cathode boundary layer.Hydrogen can flow out of the machining gap along with the flow of electrolyte,so as to ensure that the bubble rate in the gap will not rise continuously and affect the machining effect.(4)The electrochemical machining experiment was carried out with cylindrical head electrode.By comparing the experimental results with the simulation results,it was found that the electrochemical machining can be carried out stably with the selected machining parameters,and the change trend of cooling hole diameter after the electrochemical machining experiment was roughly the same as that after the simulation,which provided a theoretical basis for selecting suitable machining parameters for valve cooling hole electrochemical machining.