Discussion on the Characteristics of the Isolated Aluminum Foil Pinhole Defect and Its Formation Mechanism

In this paper, we investigated the micro-morphology of the isolated aluminum foil pinhole by using metallographic microscopes and SEM. The pinhole formation mechanism has been discussed. The oil pit area was measured by optical microscope scale statistics. Ansys finite element simulation analysis. The results show that, it is subsequently demonstrated that, the isolated aluminum foil pinhole is often tends to be encircled by the pit, and the little oil pits randomly distributed over the smooth surface of the foil, and some little pits in the matte surface too. After initial rolling pass, the direction of these pinhole are consistent with the rolling direction. SEM analysis of the pinhole micro regions indicates that the isolated aluminum foil pinhole does not exists foreign matter. During the rolling process, the maximum equivalent stress exists in the bottom of the oil pit. Due to the two-sided rolling tension, the weakest area of aluminum foil exists in the connected parts between the oil pit site and the matte side pit, thus these connected parts are likely being ripped apart, and the aluminum foil structure continuity is destroyed with the advent of the isolated aluminum foil pinhole. As the number of rolling pass increases, the area ratio of the pinhole decreases. However, the area ratio of the pinhole increases with the rolling speed rising. With the foil matte side roughness reducing appropriately, and controlling the oil pit ratio of the foil smooth surface, the pinhole ratio will be effectively controlled.