Study Of Bipolar Pulse Pickling Power Supply And Removal Of Oxide Scales By AC Pulse Pickling

As one type of efficient and clean oxide scale removal technique, electrolytic pickling is suitable for all kinds of steels with different shape and chemical composition, which can remove the oxide scales completely and make steels polished at the same time. Anode and cathode alternate pickling synthesizes advantages both of faster speed with anodic pickling and better effect with cathnodic pickling, using AC or AC pulse for pickling has received more and more attention. Deficiencies in output mode, control accuracy and respond speed of present pickling power supply result in lack of research of pickling process. Thus, it will be of great importance for improving the effect of pickling to develop a type of bipolar pulse pickling power supply with high control accuracy and do research on AC pulse pickling process and its control.According to the overall scheme of the bipolar pulse pickling power supply, design works of each several parts of the main circuit and control system has been done. After installation and debugging process, the bipolar pulse pickling power supply was capable of outputting DC/DC pulse/AC symmetrical pulse/AC asymmetrical pulse current modes, and with high controlling precision and fast response speed, the power supply mentioned above was totally able to meet requirements of various electrolytic pickling process, which has great advantage compared to present pickling power supplies.Study on electrolytic pickling process was carried out. The experimental platform for electrolytic pickling was constructed. By applying the single variable control method, the effect of pulse frequency and current density on electrolytic pickling under AC symmetry pulse mode was studied. With the analysis of electrical characteristic curves during pickling process and observation of surface micro-morphology of workpieces, it was indicated that the pickling effect was better with higher current density when the pulse frequency kept stable, except the too large current over-corrosion condition, which was bad for good surface quality. When the value of current density kept constant, an optimal value of pulse frequency corresponding to the current density was existing, more effective process and nice surface quality were obtained under the optimal frequency, and the optimal frequency-current density curve under AC symmetry pulse mode was obtained by groups of experiments.The removal mechanism of oxide scales under AC pulse pickling and control strategies of pickling process were explored. By analyzing the electrochemical reaction and surface condition change process in anode and cathode electrolysis, the reason for achieving more effective process and nice surface quality under optimal frequency was explained theoretically. The ideals of real-time control and improving the pickling process were put forward, based on studying AC pulse pickling control strategy.