Research On Jet Electrochemical Machining Technology

In jet electrochemical machining,tube electrodes or other special-shaped electrodes are used as the tool cathodes,and electrolyte flows out of the cathode at a high speed by positive flow method,filling up the machining gap.With the directional movement of the cathode,the workpiece anode dissolves gradually under the action of electrolysis,and holes,planes or surfaces consistent with the cathode shapes are generated.Electrochemical drilling is a process of feeding the cathode into the workpiece,and the hollow metal tube insulated by the side wall is used as the cathode.However,due to the hollow shape of the tube,a spike is often generated at the bottom of the blind hole during processing,reducing the processing stability.Electrochemical milling is a process of cathode scanning along the workpiece surface,and the hollow metal tube or other special-shaped electrode is used as the cathode.Gas pipe in the new liquid-oxygen kerosene rocket engine is made of superalloy GH202,with a curved pipe surface as its structure.The main research contents of this paper are as follows:?1?The shape of the hole bottom in electrochemical drilling is studied.The formation mechanism of the hole bottom in electrochemical drilling is found that the bottom shape is determined by the balance gap,and the balance gap is affected and regulated by the machining parameters(voltage dropbetween the anode and the cathode,electrode feeding speed_?8?.Different balance gaps could be obtained with different machining parameter combinations,and then different bottom shapes could be obtained.The analysis is verified by simulations and experiments,and the method of controlling the hole bottom shape is obtained that before formal machining,orthogonal parameter experiment should be carried out and the experimental results should be summarized as the relationship diagram of machining parameters on the height?depth?of the spike?pit?.Then machining parameters can be chosen according to the diagram to get a required bottom shape.The improvement of machining through holes without spike at the hole bottom is studied.The machining current at the punching through moment is much more stable when there is no spike at the bottom,so the processing stability is higher when there is no spike.The end surface of the tube will be damaged when there is a spike at the bottom,and it will not be damaged when there is no spike,so the electrode durability is also higher when there is no spike.?2?The electrochemical solubility and electrochemical milling characteristics of GH202 in NaNO₃solution and NaCl solution are studied.Electrochemical solubility characteristics shows that the passivation-superpassivation phenomenon exist in GH202 material in NaNO₃ solution,and the current efficiency first increases and then stabilizes with the current density.There is no passivation phenomenon in NaCl solution,and the current efficiency does not change with the current density and is always higher than that in NaNO₃ solution.Electrochemical milling experiments are carried out with metal tube electrodes,and the characteristics of GH202 materials are obtained.Applied voltage is positively related to the grooves'width and depth,scanning speed is negatively related to the grooves'width and depth and the machining gap is positively related to the grooves'width and negatively related to the grooves'depth.NaNO₃ solution has a low processing efficiency but good localization and surface quality,while NaCl solution has a high processing efficiency but poor localization and surface quality.?3?The method of arc cathode electrolytic milling is studied.For the curved pipe with variable radius,the flying electrochemical milling method,which is the curved cathode scanning along the workpiece surface for many times is proposed,and the selection criterion of the curved cathode radius is established and the cathode used for machining is designed.The influence of scanning processing times on the forming precision of curved surface with different initial radius is studied experimentally,which is a foundation for the electrochemical milling of curved pipes with variable radius.The cutting-in electrochemical milling method of cathode feeding into workpiece is studied experimentally.