Research On Cathode Optimization Design And Inter-electrode Gap Detection Method For Electrolytic Machining Of M42 High-speed Steel For Roller

High speed steel rolls have excellent properties such as wear resistance,fatigue resistance and oxidation resistance,and are gradually replacing traditional high chromium cast iron rolls,high chromium cast steel rolls and infinite chilled cast iron rolls.However,during the hot rolling process,the rolls are operated at high temperature,high speed and high load for a long time.The rolling conditions are complex and harsh,and the roll surface will inevitably have serious wear and fatigue.With the increase of the number of roll cycles,the development of roll surface wear and fatigue will cause roll failure.Therefore,after a period of time,the roll needs to be repaired to eliminate the roll body defects and surface deterioration layer.At present,the roll repair mostly adopts the traditional grinding method.Due to the influence of various external factors,a series of processing defects such as chatter marks,roll surface scratches and grinding burns often occur during the grinding process of the roll body.In addition,due to the high speed steel material has good wear resistance,hardenability and red hardness,to the traditional grinding roll body poses a major challenge,and even the impossibility of grinding.In this paper,M42 high-speed steel for roller as the research object,to explore an effective way for the repair of roller surface defects.Compared with other traditional processing technologies,electrochemical machining technology has many processing advantages,such as ignoring the mechanical properties of the processed material,no tool loss,high material removal rate,wide processing range and good surface quality.Therefore,in this paper,the electrochemical machining of M42 high-speed steel based on forming cathode is proposed.The electrochemical machining process is affected by many factors such as electric field,flow field and temperature field,and the physical fields are coupled and interacted with each other.It is an extremely complex and changeable electrochemical process.For a long time,the optimization design of high-precision cathode and the detection of uniform and stable small gap machining state have not found effective solutions to the two core process problems of electrochemical machining.In view of this,it is of great significance to carry out the research on the optimization design method of cathode and the detection method of interelectrode gap in electrochemical machining of M42 high speed steel.The main research contents are as follows:(1)Based on the mathematical model of the actual electric field distribution in electrochemical machining,the finite element numerical method is used to analyze the actual electric field distribution of the inter-electrode gap and its influence on the electrochemical machining process of M42 high-speed steel.On this basis,the profile of the cathode is obtained by linear interpolation method,and the flow channel structure of the cathode is determined by combining the principle of flow field uniformity.In this way,the design of cathode surface and flow channel structure of M42 high speed steel electrochemical machining is realized,and the initial structural surface is provided for the subsequent optimization design of cathode.(2)A cathode optimization design method based on multi-physics coupling analysis is proposed.According to the principle of electrochemical machining and multi-physics coupling theory,the multi-physics coupling mechanism of interelectrode gap is analyzed.On this basis,the cathode optimization design model is established,and the contour boundary of the cathode surface is iteratively modified according to the change of conductivity by using the multi-physics coupling analysis method and the idea of iterative adjustment to obtain a more accurate cathode surface.At the same time,an electrochemical machining experimental platform was built to test the electrochemical machining process of M42 high-speed steel to verify the feasibility,rationality and scientificity of the proposed cathode optimization design method.Thus the design accuracy of M42 high speed steel electrochemical machining cathode is improved and the digital design of cathode is realized.(3)Based on the theory of non-imaging optics,the optical model of LED light source and the optimal design model of uniformity illumination optical system are established.On this basis,the illumination optical system of inter-electrode gap is studied based on the principle of illumination uniformity design and orthogonal experimental design method,so as to obtain the optimal illumination scheme of inter-electrode gap.Thereby,the problem of obtaining the best lighting parameters affecting the uniformity of illumination is solved,which provides theoretical support for the construction of machine vision detection system of M42 high speed steel electrochemical machining interelectrode gap.(4)Based on the analysis of image imaging and image edge positioning mechanism of machine vision detection system,the key technologies such as low contrast image preprocessing,image sub-pixel edge detection and positioning,and image detection system calibration that affect the accuracy of machine vision detection of inter-electrode gap in M42 high-speed steel electrochemical machining are deeply studied.A sub-pixel edge composite detection algorithm based on polynomial interpolation-curve fitting is proposed to explore the high-precision machine vision detection method of inter-electrode gap in M42 high-speed steel electrochemical machining.At the same time,the machine vision detection system is used to detect the gap between the poles to verify the feasibility,rationality and scientificity of the proposed detection theory and method.Thus,the machine vision detection accuracy of M42 high speed steel electrochemical machining interelectrode gap is improved,which lays a theoretical foundation for the effective measurement and control of interelectrode gap in the future.Through the research of this subject,the technical problems of cathode optimization design and interelectrode gap detection in electrochemical machining are solved,and the electrochemical machining of M42 high speed steel with high efficiency,high precision and high stability is realized.