The following factors should be considered in determining the heating rate of aluminum foil:
(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, it is easy to cause the temperature difference between the surface of the aluminum foil roll and the core. The volume change of the surface and the core will have a large difference, which will cause a large thermal stress, which will cause the wave surface to bulge and ridge. The effect on the heating speed of aluminum foil above 0.02mm is not obvious, and the heating speed of thin foil below 0.02mm should be appropriately reduced. Low-speed heating is also beneficial to prevent the aluminum foil from blocking.
(2) Rapid heating is easy to obtain a fine and uniform structure and improve its performance. For example, 3A21 alloy aluminum foil, in order to prevent the local coarse grains and uneven grains that are prone to occur during annealing, fast heating is usually used.
(3) In actual production, the heating speed should be increased as much as possible on the premise of ensuring quality.
(4) An annealing furnace with an axial-flow circulating fan can increase the heating speed properly due to the fast air circulation and uniform temperature. At present, most of the aluminum foil annealing furnaces are air-flow circulating resistance furnaces with a furnace capacity of 10-30t, with automatic temperature control and over-temperature alarm functions. The uniformity of the furnace gas temperature is below ± 5 ° C.