Determine the heating rate of aluminum foil should consider the following factors:
(1) The larger the width and diameter of the foil roll, the worse the thermal uniformity of the foil roll. If the heating speed is too fast, the temperature of the surface of the aluminum foil roll and the center of the foil roll may be too different. Due to thermal expansion and contraction, the roll is curled. There will be a large difference in the volume change between the surface and the heart, which will cause a great thermal stress and cause the surface of the wave roll to rise and rise. The effect on the heating speed of the aluminum foil of 0.02mm or more is not obvious, but the heating speed of the thin foil less than 0.02mm should be appropriately reduced, and the low-speed heating is also conducive to preventing the adhesion of the aluminum foil.
(2) Rapid heating makes it easy to obtain a fine uniform structure and improve its performance. For example, in 3A21 alloy foils, rapid heating methods are generally used to prevent local grain coarsening and non-uniform grain appearance that are likely to occur during annealing.
(3) In actual production, the heating rate should be increased as much as possible under the premise of ensuring quality.
(4) An annealing furnace with an axial-flow circulation fan can appropriately increase the heating rate due to the fast circulation of air and the uniform temperature. At present, the vast majority of aluminum foil annealing furnace is a gas circulation type resistance furnace with a charging capacity of 10-30t, with automatic temperature control, over-temperature alarm and other functions. The uniformity of furnace gas temperature is below ±5°C.
(1) The larger the width and diameter of the foil roll, the worse the thermal uniformity of the foil roll. If the heating speed is too fast, the temperature of the surface of the aluminum foil roll and the center of the foil roll may be too different. Due to thermal expansion and contraction, the roll is curled. There will be a large difference in the volume change between the surface and the heart, which will cause a great thermal stress and cause the surface of the wave roll to rise and rise. The effect on the heating speed of the aluminum foil of 0.02mm or more is not obvious, but the heating speed of the thin foil less than 0.02mm should be appropriately reduced, and the low-speed heating is also conducive to preventing the adhesion of the aluminum foil.
(2) Rapid heating makes it easy to obtain a fine uniform structure and improve its performance. For example, in 3A21 alloy foils, rapid heating methods are generally used to prevent local grain coarsening and non-uniform grain appearance that are likely to occur during annealing.
(3) In actual production, the heating rate should be increased as much as possible under the premise of ensuring quality.
(4) An annealing furnace with an axial-flow circulation fan can appropriately increase the heating rate due to the fast circulation of air and the uniform temperature. At present, the vast majority of aluminum foil annealing furnace is a gas circulation type resistance furnace with a charging capacity of 10-30t, with automatic temperature control, over-temperature alarm and other functions. The uniformity of furnace gas temperature is below ±5°C.
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