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Influence of purity on aluminium foil roll quality

June 12, 2019

Most aluminium foil rolls are made from 99.0%-99.5% industrial pure aluminum. Generally, the higher the purity, the lower the tensile strength and the higher the elongation. Increasing the impurity content can increase the tensile strength and decrease the elongation. However, when the purity of aluminum is too low, the brittleness of the material increases and the calendering performance deteriorates, in which case pinholes are easily generated, thus aluminium of low purity is not suitable to be rolled into an aluminium foil roll.

aluminum foil roll

Excessively high purity, however, is not conducive to processing, either. Although the elongation of aluminium is improved, the first pass of rolling, especially that after intermediate annealing, is prone to a more serious sticking phenomenon, resulting in blushing of the roll surface and deterioration of lubrication which increases the coefficient of friction between the rolls and the rolled parts, and leads to the creation of pinholes. Therefore, in rolling high-purity aluminum foil, it is not necessary to perform intermediate annealing on the aluminum foil blank, and directly process to the finished product thickness (0.05 mm).

Impurities also impacts purity of the aluminium foil roll. Industrial pure aluminum usually contains impurities such as Fe, Si, Cu, Mn, Ti, B, C, etc. Some impurities are inherently intrinsic, and some are deliberately added as grain refiners, such as Ti and B. Although the content of these impurities is relatively small, it has a very important influence on the mechanical properties and processing properties of the aluminum foil roll.

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