Influence Of Heat Treatment On Microstructure And Property Of 3003 Aluminum Foil For Cathode By Direct Cast-Rolling Of Electrolysis Aluminum Liquid

3003A1-Mn alloy, because of its good corrosion resistance, mechanical processing properties, local corrosion characteristics and mechanical properties, are widely used in manufacture of electrolytic capacitor cathode foil. The production of traditional cathode aluminum foil is hot-rolled metal ingot re-melting and other multi-channel order process, but this production process was complicated and caused energy consumption. In recent years, as technology advanced, the using of high-temperature direct cast-rolling in electrolytic aluminum cathode foil production with short casting production process is replacing the traditional method. Compared with the traditional method, the production of 3003 cathode foil with direct casting by liquid aluminum has several advantages:eliminates the aluminum ingot casting and re-melting processes; reducing the aluminum loss in the process of molten aluminum cast to aluminum ingot and aluminum ingot re-melting; increases the productivity; save a lot of energy; and less investment in equipment and product cost.However, the direct cast-rolling of electrolyte aluminum liquid still have some technical problems:the temperature of aluminum liquid is too high; the low rate of effective crystal nucleation. Because of the fast cooling rate in cast-rolling, the Mn element in 3003 aluminum alloy was too late to precipitation and remained in solid solution as supersaturated, causing the coarse of second phases and the grains. The large number of coarse second phase particles will cause non-uniform corrosion morphology, resulting in lower specific capacitance. Coarse grains will also cause corrosion stratification when surface erosion corrosion, which would lead to lower specific capacitance. To solve the above problems, this paper attempts to study and optimize the heat treatment process of direct cast-rolling aluminum cathode foil to improve the internal organization of aluminum foil, improve the performance of aluminum foil so that to achieve or even exceed the traditional process of cathode foil in specific capacitance. In this paper, polarization optical microscope, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and other analysis methods were used and the mechanical properties, corrosion properties were also tested. The influences of tissue and properties by homogenization annealing and re-crystallization annealing of the 3003 aluminum cathode, which produced by direct cast-rolling production and of aluminum foil were also investigatedThe results show that, due to the high temperature of molten aluminum and high casting speed, Mn element in the 7.2mm aluminum slab, which direct casting by liquid, is too late to precipitation and remain in solid solution as supersaturated, resulting in intragranular segregation. Therefore, there is a lot of needle like FeAl3 phase in the size of 3-4μm; the short rod MnAl6 and (Fe, Mn) Al6 phase, in the size of 2-3μm; small round granular Al (Fe, Mn) Si phase in the size of 1μm.After two times rolling, the thickness of cold-rolled sheet is 4.0mm. Compared with the casting slab, some second phases were crushed, coarse flake needle phases significantly reduced, however, some second phase were angular forms, reducing the mechanical properties of cold-rolled sheet. Grains are elongated along the rolling direction rendered as fibrous completely. After the homogenization annealing, Mn element precipitated from supersaturated solid solution, formed a large number of small and dispersed granular Al (Fe, Mn) Si phase, short rod MnAl6 phase. At the same time, Mn and Fe are easily replacement in the formation process, so precipitated Mn element has a pin replacement in part of the sheet FeAl3 phase, and formed a large number of short rod (Fe, Mn) Al6 phase.When the cold-rolled plate rolling to a thickness of 0.4mm for re-crystallization annealing, and found that compared the plate after homogenization annealing and re-crystallization to the plate after re-crystallization annealing without homogenization annealing, the complete re-crystallization temperature decreased to 300℃from 430℃; the size of fully re-crystallized grains reduced to 150μm from 170μm; re-crystallization temperature range changed from 410-430℃to 260-300℃; the tensile strength of plates after complete re-crystallization changed from 130Mpa to 120Mpa, elongation rate increased from 20.9% to 29.2%. Mn element precipitated from supersaturated solid solution after homogenization annealing, forming a large number of small and uniform second phases, which can promote the nucleation of re-crystallization and increase the nucleation rate and act as pinning effect in grain growth to refine the grain size. Mn atomic can significantly increased re-crystallization temperature of aluminum alloy. Mn element precipitated after homogenization annealing, reduced the re-crystallization temperature and the re-crystallization range expanded because of the low temperature re-crystallization rate. Homogenization Mn atoms precipitated from solid solution, reduce the slip resistance of the alloy, which reduces the strength and increases the plasticity.After homogenization and re-crystallization annealing, the specific capacitance is 500μF/cm2, which reaches the standard of cathode foil produced by traditional method. The tensile strength of cathode aluminum foil are also not less than the traditional one.