What are the letters and numbers after the alloy number, like -O, -H19, and -T6?
These are the temper designations, which are based on the sequence of basic treatments applied to the alloy. The temper designation follows the alloy designation, separated by a hyphen. Basic temper designations consist of a letter- F, O, H, W, or T -that indicates a type of processing, with one or more subsequent digits used to indicate subdivisions of the basic temper. A detailed listing of tempers that have been registered can be obtained from the Aluminum Association.
