Anode Oxidation Process And Performance Study Of Insulation Aluminum Core Winding Wire

Compared with the traditional copper core winding line, aluminum winding wire can better meet the requirements of the rapid development of aerospace because of such advantages of it as light weight, high strength etc. Meanwhile, alumina ceramic has many advantages such as high hardness, resistivity, good corrosion resistance and wear resistance. Compared with other ceramic insulating film materials, the preparation method is more simple, thus it is a very potential winding wire insulating materials. The winding wires that based on the above-mentioned advantages can be obtained through the preparation of alumina film on the surface of aluminium wire, thus possessing broad application foreground.The purpose of this topic is: preparing the anodizing film that has such advantages of it as good corrosion resistance, insulation and puncture-withstand performance etc. The alumina film is prepared on the surface of aluminium wire with the anodic oxidation technique that being simple to operate and has lower requirement for equipment, and then the insulation aluminum core winding wire is obtained. Firstly, exploreing the effects of different electrolyte proportion on the microstructure and properties of anodizing film, and the optimal electrolyte ratio of mixed acid is: the optimum parameters were confirmed as the concentrations of H2SO4 is 153.3 g/L, H2C2O4 is 20 g/L, H3BO3 is 33.3 g/L, C3H8O3 is 16.7 g/L. Secondly, taking the oxide film thickness and weight gain as the evaluation index, and optimizing the anodic oxidation process parameter by orthogonal experiment. The optimal preparation process parameters are preliminarily determined as follows :the temperature is 10 oC the current density is 7 A/dm2, the time is 60 min.The composite evaluation index of film(G) under this condition is the largest.On the basis of this analysis,the temperature and current density are changed separately to fine characterize the structure and properties of the oxide film by single-factor variable analysis.Through eddy current thickness, X-ray diffraction(XRD), scanning electron microscope, transmission electron microscope, polarization curve measurement,ac impedance methods and so on,,the main conclusions are as follows:At the same current density, the thickness of the film decreases with the increase of temperature, while the size of pore increases with the increase of temperature. At the same temperature, the thickness of the film and the size of pore both increase when current density increases. After boiling in water and then sealing process, the surface of oxide film was like a network structure, and the micro hole was disappeared. After sealing and heat treatment, the corrosion resistance of the most samples was decreased, and the resistance was also decreased.The ceramic layer obtained under the oxidation process of 30 oC,1 A/dm2 has excellent corrosion resistance before or after oxidation treatment. The oxide film has the best corrosion resistance and the corrosion resistance performance under parameters of 7 A/dm2.The puncture-withstand value of anodic oxide ceramic layer that has been treated by sealing treatment is good, and the value can reach up to 0.99 k V under the conditions that the temperature is 10 oC and the current density is 5 A/dm2. The tolerable voltage of ceramic layer has slightly decreased after heat treatment,the minimum decreasing proportion is 10.3%, and the maximum decreasing proportion is 94%, the average decreasing proportion is the least when the temperature is 30 oC. The nano-hardness of anodic oxide film gradually increases in the range from the interface between the matrix and the oxide film to the surface. At the range of the testing parameters, the higher the temperature,the higher the nano-hardness is at the same current density; the higher the current density,the higher the nano-hardness is at the same temperature. The surface nano-hardness under the conditions that the temperature is 35 oC and the current density is 7 A/dm2 reaches the maximum level of 2.15 GPa. It is found that anodic oxidation have negative effect on the tensile strength of aluminium wire, strengthening effect can be achieved in the case of specific parameters, the tensile strength of aluminium wire under the conditions that the temperature is 35 oC and the current density is 5 A/dm2 reaches the maximum level of 113.4 MPa. The tensile strength of aluminium wire under certain temperature increases and then decreases with the increase of current density.The tensile strength of aluminium wire has reached more than 70 MPa at the range of the testing parameters, and it accords with the standards of actual application. Testing the flexibility of Aluminum wire by winding method. At the same temperature, the film thickness increases with the increase of current density, the surface cracks of the film increases, and the flexibility decreases. The flexibility of the film that has small thickness is good.In this paper, a new mixed acid electrolyte solution was developed and the optimal process parameter was obtained, which made it possible to achieve the goal of improving the corrosion resistance, hardness and tensile strength of insulated aluminum core winding wire. This research provided the technical support for promoting application of aluminum core insulated winding wire in the field of aeronautics and astronautics.