Patent ID: 7172664

Claim:
A method of making collared aluminum alloy foil for use in heat exchanger fins, which method comprises (a) providing a molten aluminum-based alloy consisting essentially of 0.27% to 0.55% by weight iron, 0.06% to 0.55% silicon, optionally 0.05% to 0.20% copper and the balance aluminum and unavoidable impurities, (b) continuously casting said molten aluminum alloy into an aluminum alloy strip, (c) cold rolling the continuously cast aluminum alloy strip to a final gauge of about 0.076 mm to about 0.152 mm, and (d) forming at least one collar in said strip of final gauge and subjecting said collar to reflaring with radial stretching; characterized by partially annealing the final gauge aluminum alloy strip, prior to said collar formation, at a temperature below about 260Â° C. with a maximum overheat of about 10Â° C. to thereby anneal the aluminum alloy foil while producing no more than 5% of recrystallized grains in the alloy.