Wrought pure grade aluminum alloy and process for producing same

Abstract

Pure aluminum alloy which has been continuously cast and partially worked to a strip at a gauge of 0.25 inches through use of a Hunter-Caster, is heated to a temperature in a range of about 900.degree. to about 1150.degree. F. and then subjected to slow cooling in a range between cooling at around 600.degree. F./hr. as a maximum, and cooling at a rate of 25.degree. F./hr. as a practical minimum, until ambient temperature or about 100.degree. F. is reached. After cooling, the alloy strip is subjected to cold working and annealing until a desired gauge is reached for a particular product, one typical product being aluminum foil. In one process according to the invention, the strip is heated as it leaves a Hunter-Caster and then coiled, and the cooling is effected by leaving the coil in ambient air. In another process, it is coiled prior to heating which is then effected by placing the coil in a suitable furnace such as in box annealing. The coil is then cooled in the furnace, either as the furnace cools naturally or at a slower, controlled cooling rate. In another preferred process the alloy strip produced by the Hunter-Caster is subjected to conventional cold working until a suitable gauge, for example, 0.050 inches is reached. At this point, rather than subjecting the alloy to a conventional annealing process, it is subjected to the heat treatment and slow cooling described after which it is then cold worked further and subjected to a final stress relieving anneal at approximately 400.degree. F. The heating and slow cooling of the present invention improve the ductility and recrystallization kinetics of wrought pure aliminum produced through continuous casting, cold rolling and annealing.