Influence Of Annealing And Rolling Deformation On Microstructure Of 3003 Cathode Electronic Aluminum Foil

The production of 3003 cathode aluminum foil by direct cast-rolling of electrolysis aluminum liquid is a promising manufacturing method of cathode aluminum foil with the advantages of short process flow, less investment in equipment and low cost in production etc. But it also has disadvantages, such as corrosion stripes and lower specific capacitance which restrict the application of high capacity aluminum electrolytic capacitor's cathode foil. To solve the above problems, the process of rolling and thermal treatment will be optimized, in this paper, to improve the quality of 3003 cathode aluminum foil by direct cast-rolling of electrolysis aluminum liquid.In this paper, polarization microscope, double-arm bridge and LCR digital electric bridge were used to investigate the influence of cold deformation and thermal treatment in microstructure of 3003 cold-rolled sheets by direct cast-rolling of electrolysis aluminum liquid, and the productive technology was optimized according to the specific capacitance of 3003 cathode aluminum foil after corrosion. And it offers some theoretical reference and practical basis for the production of 3003 cathode aluminum foil by direct cast-rolling of electrolysis aluminum liquid.The results show that the grains morphology at the surface layer of the 7.2mm cast-rolled aluminum stock is lamellae, and column in the center layer. And the quantity and size of second-phase particles at surface layer are smaller than center layer.The second-phase particles precipitation speed of 5.1mm,3.9mm,2.9mm and 2.0mm aluminum sheets cold-rolled by 7.2mm cast-rolled aluminum stock respectively reach their maximum at 490℃,470℃,450℃and 450℃homogenization annealing. And when the annealing time is more than 8 hours, there is a intensity quickly decrease in precipitation speed of second-phase particles or no precipitation.With the rolling of aluminum sheet form 5.1mm to 2.0mm, the primary second-phase particles were gradually crushed up, and the number of second-phase particles within 1μm increases. The second-phase particles within 1μm could hinder formation of viable recrystallization nuclei, therefore, the recrystallization grain size increases quickly with the thickness decrease of aluminum sheet.5.1mm aluminum sheet after homogenization annealing were cold rolled to 1.0mm,0.73mm, and 0.55mm, then recrystallization annealing was carry out. The results show that the recrystallizing temperature of 1.0mm aluminum sheet is 320℃at the very start and 340℃at the end, but the recrystallizing temperature of 0.73mm and 0.55mm aluminum sheets are 295℃at the very start and 320℃at the end. And with the increase of recrystallization temperature between 340～460℃, the second-phase particle sizes increase, and the number of second-phase particles more than 1μm increase. The second-phase particles more than 1μm could promote formation of viable recrystallization nuclei, therefore, the recrystallization grain sizes of three thickness aluminum sheets above decrease with the increase of recrystallization temperatures.In alkali cleaning process of 3003 cathode aluminum foil, with the lower temperature and shorter time, the aluminum foil's surface structure is not effectively improved, so that the specific capacitance will be reduced; but when temperature is higher and the time is longer, there will be a over alkali cleaning which also reduce the specific capacitance. In the corrosion process, there will be less and shallow corrosion pits when the corrosion time is not enough, so the specific capacitance is lower; and if the corrosion time is too long, there will be huge amounts of black powder which will fill the pits, at last, the specific capacitance is lower, too.There are recrystallization grains and fibrous tissues in the 0.55mm aluminum sheet after 295℃annealing, so that 0.041mm aluminum foil rolled by 0.55mm aluminum sheet has coarse grain stripes which lead to layered corrosion on the tiny view, corrosion stripes on the macro view and lower specific capacitance. But after 320℃annealing,0.041mm aluminum foil has homogeneous state of corrosion morphology and higher specific capacitance.